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Carpentieri, P., Bonanno, A. and Scarcella, G. 2020. Technical guidelines for scientific surveys in the Mediterranean and the Black Sea. FAO Fisheries and Aquaculture Technical Papers No. 641. Rome, FAO. https://doi.org/10.4060/ca8870en

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Preparation of this document

These guidelines have been prepared by the General Fisheries Commission for the Mediterranean (GFCM) of the Food and Agriculture Organization of the United Nations (FAO) to address the priorities identified by Mediterranean and Black Sea countries in the context of existing international commitments and regional strategies. In particular, Target 1 of the mid-term strategy (2017–2020) towards the sustainability of Mediterranean and Black Sea fisheries (mid-term strategy) aims at reversing the declining trend of fish stocks through strengthened scientific advice in support of management. This document contributes to the objective of this strategy aimed at enhancing knowledge on Mediterranean and Black Sea fisheries through regional surveys-at-sea, namely acoustic surveys for pelagic species and bottom and beam trawl surveys for demersal species.

As it is difficult to gather information on the status of fish stocks in the context of multispecies and multigear fisheries in the Mediterranean Sea, fisheries independent data sources obtained through scientific surveys are very useful to acquire direct information on the state and dynamics of fish stocks and ecosystems and to improve the assessments based on the analysis of fishery-dependent data. Standardized time series are essential to provide information on the spatial and temporal variations in the abundance of commercial and non-commercial species as well as on the demographic attributes and other ecological indices of these species.

Within the GFCM, the Scientific Advisory Committee on Fisheries (SAC) and the Working Group on the Black Sea (WGBS) have highlighted the lack of survey data for some areas in the Mediterranean and the Black Sea and the need to harmonize the production and collection of such data across the region. Building upon the protocols already in place in the European Union – namely the Mediterranean International Bottom Trawl Survey (MEDITS), the Solea Monitoring Survey (SoleMon) and the Mediterranean International Acoustic Survey (MEDIAS) – these technical guidelines provide a framework for the implementation of harmonized regional and subregional scientific surveys in the Mediterranean and the Black Sea using a standardized methodology aimed at producing comparable results.

Experts in bottom, beam trawl and acoustic surveys, namely Giuseppe Scarcella and Angelo Bonanno, were tasked with developing these guidelines under the overall coordination of Paolo Carpentieri, GFCM Fishery Resources Monitoring Specialist, who ensured consistency with the methodologies in place and with GFCM priorities as well as applicability across the GFCM area of application.

A coordination meeting for the implementation of scientific surveys in the Mediterranean, organized in 2017 by the GFCM in Slovenia, gathered preliminary elements on acoustic and bottom trawl surveys, based on national experiences and on the outcomes of similar initiatives both in the European Union and at the international level. Technical consultations with experts involved in the BlackSea4Fish project also led to the integration of a section on beam trawl surveys. The draft guidelines were reviewed on the occasion of a workshop on the harmonization of data collection in scientific surveys-at-sea, held in 2019 in Bulgaria. In parallel, they were also presented to the Regional Coordination Group for the Mediterranean and Black Sea of the European Commission and at the MEDITS and MEDIAS Steering Committee meetings. These consultations contributed to the set-up of appropriate coordination mechanisms and helped fine-tune the methodology and align it to current practices so that it could be useful and replicable in different countries and areas. GFCM national focal points in Algeria, Egypt, Lebanon, Morocco and Tunisia already provided technical inputs as they prepared for the launch of their scientific surveys in 2019 and 2020, carried out with the support of the GFCM and the FAO regional projects and based on a standard methodology. Finally, the SAC and the WGBS reviewed and endorsed the final document for publication.

The editing, graphics, layout and publishing were coordinated by Dominique Bourdenet, GFCM Scientific Editor, with the assistance of Julia Pierraccini, GFCM Language and Communications Specialist, Lauriane Palopoli and Ysé Bendjeddou, GFCM Editing/Communications Interns. Barbara Hall served as language editor and Chorouk Benkabbour managed the graphic design and layout. Alberto Gennari produced and modified several illustrations based on existing materials.

This document was produced with the financial support of the European Union. The views expressed herein can in no way be taken to reflect the official opinion of the European Union.

Abstract

There is increasing concern about species diversity, stock status and environmental conditions in ecology and conservation biology. Following investigations carried out in recent years at a local and regional scale, there is a growing need for large and multiscale data to increase knowledge on these aspects and determine how to maintain diversity. This is of particular importance in enclosed and semi-enclosed marine ecosystems such as the Mediterranean and the Black Sea, which are highly sensitive to human impacts.

In the Mediterranean and the Black Sea, demersal stocks are mainly assessed using data obtained through scientific demersal surveys (bottom and beam trawl), while pelagic stocks are assessed using data from acoustic surveys (i.e. using acoustic techniques together with mid-water trawling). These types of routine surveys provide essential information on many stocks and allow monitoring changes in species distribution and estimating annually the total mortality, growth parameters, sex ratios and average length at maturity of species so as to fine-tune assessments on the status of resources and to estimate indicators more precisely at the level of fish populations and communities.

However, scientific survey practices differ across subregions, each one having its own strengths and limitations, and there is still a lack of large-scale, standardized surveys devoted to analysing the diversity and distribution of the main demersal and pelagic species across the Mediterranean and the Black Sea. One solution to tackle this issue is to establish international scientific surveys covering the main demersal and pelagic stocks based on a common methodology.

The General Fisheries Commission for the Mediterranean (GFCM) has identified, among the main priorities of its mid-term strategy (2017–2020) towards the sustainability of Mediterranean and Black Sea fisheries (mid-term strategy), the need to develop a unique framework for the planning and implementation of regional demersal (bottom and beam) trawl and pelagic acoustic surveys based on existing protocols – namely the Mediterranean International Bottom Trawl Survey (MEDITS), the Solea Monitoring Survey (SoleMon) and the Mediterranean International Acoustic Survey (MEDIAS) that are being implemented in the European Union.

These technical guidelines aim at supporting this endeavour. Their use can serve different purposes: i) implementation of new surveys (applicable to areas where demersal trawl and/or pelagic acoustic surveys are not regularly carried out); ii) increasing comparability between existing surveys by standardizing methods, sampling of catches, and recording and analysis of data; and iii) definition of minimum requirements towards sustainability and management objectives (e.g. assessing the status of resources, establishment of management plans) at a regional and subregional scale. The guidelines cover Mediterranean and Black Sea priority species identified by the Scientific Advisory Committee on Fisheries (SAC) and the Working Group on the Black Sea (WGBS), based on the inputs of the Working Groups on Stock Assessment (WGSAs), and are in line with data collection requirements within the GFCM Data Collection Reference Framework (DCRF[1]). They provide a useful tool for the collection of relevant complementary information on the incidental catch of vulnerable species, vulnerable marine ecosystems and non-indigenous species. Furthermore, scientific surveys can represent a valuable source of information on marine litter.

1 As the DCRF is updated on a regular basis, please check the DCRF section of the GFCM website for the latest version.

Contents

Preparation of this document

Abstract

Acknowledgements

Acronyms

Background

1. DEMERSAL BOTTOM TRAWL SURVEYS

1.1 Aim

1.2 Vessel characteristics

1.3 Sampling gear

1.4 Survey design

1.5 Handling of the catch

1.6 Data reporting and exchange formats

2. PELAGIC ACOUSTIC SURVEYS

2.1 Aim

2.2 Vessel characteristics

2.3 Methodology

2.4 Period for and timing of pelagic acoustic surveys

2.5 Pelagic trawl

2.6 Oceanographic data

2.7 Data reporting and exchange formats

3. DEMERSAL BEAM TRAWL SURVEYS

3.1 Aim

3.2 Vessel characteristics

3.3 Sampling gear

3.4 Survey design

3.5 Handling of the catch

3.6 Data reporting and exchange formats

4. ECOSYSTEM DATA

4.1 Macrobenthos

4.2 Vulnerable species

4.3 Marine litter

4.4 Non-indigenous species

5. DATA POLICY

REFERENCES

ANNEXES

Annex 1. GFCM subregions and geographical subareas (GSAs)

Annex 2. List of priority species by subregion

Annex 3. Fishing haul information

Annex 4. Catch composition by fishing haul

Annex 5. Length data by fishing haul

Annex 6. Individual weight by species

Annex 7. Sex and maturity data

Annex 8. Maturity scales

Annex 9. Six-phase maturity stages for anchovies and sardines caught in pelagic surveys

Annex 10. Maturity scale conversion table for anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus)

Annex 11. Reporting templates for bottom and beam trawl demersal surveys

Annex 12. Reporting templates for pelagic acoustic surveys

Annex 13. List of vulnerable species

Annex 14. Data entry sheet for vulnerable species

Annex 15. Data entry sheet for marine macro-litter

Annex 16. Data entry sheet for macrobenthos

Annex 17. Scheme of the rapido trawl

Tables

Table 1. Relationship between depth (m) and warp length (m) for the trawl GOC 73 at different warp length diameters (mm)

Table 2. Depth strata (with surface in km^2) and number of planned hauls per stratum and GSA

Table 3. Proposed minimum number of otoliths by length class per survey

Table 4. Taxonomy of small pelagic species of potential interest in performing a pelagic acoustic survey

Table 5. Priority species of potential interest for which a BTS could provide primary and/or additional data for tuning indices, by GFCM subregion

Table 6. Subsampling of epibenthic and benthic species, and debris fraction

Figures

Figure 1. Main components of a demersal trawl net

Figure 2. GOC 73 trawl used for the MEDITS survey (acronyms specified for each netting)

Figure 3. Gear rigging details adopted for the MEDITS trawl

Figure 4. Main characteristics of the Morgere W horizontal (WH) otter board

Figure 5. Morgere WH S 8

Figure 6. Measurement of total (TL) and standard lengths (SL) in bony fish

Figure 7. Measurement of total (TL) and fork lengths (FL) in elasmobranchs

Figure 8. Measurement of carapace length (CL) for Decapoda crustacean

Figure 9. Measurement of dorsal mantle length (ML) of cephalopods

Figure 10. Example of an echogram acquired by a scientific split-beam echo-sounder (38 kHz)

Figure 11. Screenshots of a possible system for monitoring net sampling on small pelagic fish

Figure 12. Schematic representation and picture of the rapido trawl

Figure 13. Design of the rapido trawl net

Figure 14. Beam trawl scheme

Figure 15. Relationship between depth and warp length

Plates

Plate 1. Catch composition reaching a vessel deck (left) and sorting procedures (right)

Plate 2. Weighting and counting different species in the total catch

Plate 3. Invertebrates in catch composition (forming the megabenthos size > 2 cm)

Plate 4. Collection of total weight by species

Plate 5. Collection of individual weight

Plate 6. Results of a sampling activity by pelagic net

Plate 7. Results of biological sampling by pelagic net: species identification and separation

Plate 8. Measurement phases of biological samples

Plate 9. Catch reaching a vessel deck (left) and sorting procedures (right)

Plate 10. Various species of macroinvertebrates in a catch

Plate 11. Marine litter in catch composition

Boxes

Box 1. Length data to be reported during a pelagic acoustic survey

Box 2. Age data to be reported during a pelagic acoustic survey

Box 3. The SoleMon survey in the northern Adriatic Sea (GSA 17)

Box 4. Mediterranean VME indicator: features (a), habitats (b) and taxa (c)

Box 5. Minimum set of data to be collected regarding the incidental catch of vulnerable species

Acknowledgements

This document was prepared under the general supervision of Abdellah Srour, GFCM Executive Secretary, thanks to the expert guidance of Miguel Bernal, GFCM Senior Fishery Officer, with the support of Elisabetta Betulla Morello, GFCM Fishery Resources Officer, Margherita Sessa, GFCM Fishery Liaison Officer, and with the contribution of the staff of the GFCM Secretariat.

Special gratitude goes to the national focal points involved in the implementation of joint GFCM scientific surveys-at-sea and to the chairs and participants of the MEDITS and MEDIAS steering committees who provided their technical inputs, shared their direct experience and helped fine-tune the methodology. This publication builds upon the experience acquired through MEDITS and MEDIAS over the years and draws elements from their related manuals (in particular as far as gear and gear use are concerned). Warm thanks are due to all the people who have participated, directly or indirectly, in the scientific surveys already carried out and who have contributed to the development and improvement of common knowledge on fisheries ecosystems in the Mediterranean and the Black Sea. Finally, the original illustrations of the rapido trawl used in this document were kindly provided by Emilio Notti.

Acronyms

BTS Beam trawl survey

CL Carapace length

CPCs Contracting parties and cooperating non-contracting parties (GFCM)

CTD Conductivity, temperature and depth

DCRF Data Collection Reference Framework (GFCM)

EDSU Elementary distance sampling unit

FAO Food and Agriculture Organization of the United Nations

FL Fork length

GFCM General Fisheries Commission for the Mediterranean

GSA Geographical subarea (GFCM)

IFREMER Institut Français de Recherche pour l’Exploitation de la Mer

IUCN International Union for Conservation of Nature

MEDIAS MEDiterranean International Acoustic Survey

MEDITS MEDiterranean International bottom Trawl Survey

ML Mantle length

NASC Nautical area scattering coefficient

SAC Scientific Advisory Committee on Fisheries (GFCM)

SL Standard length

SOLEMON SOLEa MONitoring survey

TL Total length

UNCLOS United Nations Convention on the Law of the Sea

VME Vulnerable marine ecosystem

WGBS Working Group on the Black Sea (GFCM)

WGSA Working Group on Stock Assessment (GFCM)

Background

The establishment of pan-Mediterranean and Black Sea surveys has been motivated by the lack of comprehensive studies of the biological status of most demersal and pelagic fish stocks in some Mediterranean areas (GFCM, 2007; GFCM, 2017a, 2017b). To date, scientific surveys in the Mediterranean and the Black Sea have been carried out at an international scale, mainly covering European Union countries (Bertrand et al., 1997, 2002; AdriaMed, 2011; MEDITS, 2017; MEDIAS, 2019), with very few national surveys and varying degrees of comparability among surveys and countries. To effectively use survey information from all sources, the adoption of standard survey methods and stratification schemes is essential. Survey data throughout the Mediterranean and the Black Sea should be harmonized in order to capture the most relevant biological events and to allow for more accurate estimates of life history parameters such as mortality and growth. Since the boundaries of stock units are still not very well known for most Mediterranean species, the need for standardized indices of abundance and demography is a priority. Such data would provide valuable records to better assess the spatial occupation of the diverse components of stocks (e.g. seasonal distribution, spatial segregation, community structure and recruitment areas). This gain in accuracy would, in turn, sharpen the evaluation of variations in population indicators and input data/parameters for population and community modelling.

At a coordination meeting for the implementation of scientific surveys in the Mediterranean, organized by the GFCM in 2017 (GFCM, 2017d), it was decided that the existing manuals already in use among some GFCM countries (MEDIAS, 2015; 2017; 2019; MEDITS, 2016; 2017; SoleMon, 2017; 2019) and covering both demersal (bottom and beam) trawl and pelagic acoustic surveys should be considered as the main references. The proposal was endorsed by the Scientific Advisory Committee on Fisheries (SAC) (GFCM, 2017a) and the Working Group on the Black Sea (WGBS) (GFCM, 2016, 2017b, 2019b). In terms of target species, this document addresses priority species identified by the SAC and the WGBS, on the basis of the work carried out by the GFCM working groups on stock assessment (WGSAs) and in line with existing data collection requirements within the GFCM Data Collection Reference Framework (DCRF). The list of target species, which is based on the existing manuals, may be complemented at a later stage with other species of regional or subregional interest (GFCM, 2017d; 2018a).

1. DEMERSAL BOTTOM TRAWL SURVEYS

1.1 AIM

The aim of a demersal bottom trawl survey is to collect standardized fishery-independent data with a view to improving stock assessments. Demersal bottom trawl surveys should contribute to the characterization of fishery resources in a given area, in terms of population distribution (e.g. relative abundance indices) and demographic structure (e.g. length and sex distributions) as they collect data, including sex, maturity and weight, for the estimation of growth parameters of priority species. Thanks to the data obtained, it should be possible to compare catch composition in different areas, subregions and geographical subareas (GSAs) (GFCM, 2009; Annex 1) and to describe the spatial distribution pattern of all identified GFCM priority species (Annex 2), using the same gear specifications, to the extent possible.

The results of these surveys are crucial for the formulation of science-based advice on sustainable fisheries and conservation of stocks. In addition, the data collected should also be used for modelling the dynamics of the main target species in each GFCM subregion. Finally these surveys are also extremely useful to collect data on ecosystems (e.g. macrobenthos, several vulnerable marine species, and marine litter).

1.2 VESSEL CHARACTERISTICS

For the correct implementation of a standardized demersal bottom trawl survey, commercial and/or research vessels should be equipped with an engine of at least 370 kW (500 hp) to be able to tow the standard sampling gear (traction at ground run: 4.5 tonnes) (Section 1.3).

Trawl speed during each fishing operation should be of about 3 knots. This recommended speed is very important to ensure the best trawl geometry. A speed lower than 2.8 knots can have a negative effect on the vertical opening of the net mouth and the stability of the doors, which can descend and become stuck in the mud. In deep waters, a speed greater than 3.2 knots can cause the gear to lift off the bottom and must be avoided (MEDITS, 2017).

During the survey implementation, the main information on each fishing haul (e.g. latitude, longitude, depth, speed, etc.) should be monitored and reported (see Annexes 3).

1.3 SAMPLING GEAR

The sampling gear for demersal trawl surveys should correspond to the bottom trawl (i.e. GOC 73, see Section 1.3.1) used to carry out the MEDITS, including all its material and rigging from the doors to the codend of the net (Relini, Carpentieri and Murenu, 2008; MEDITS, 2017). This was agreed by the GFCM survey coordination meeting (GFCM, 2017d) and endorsed by the SAC (GFCM, 2017a) and the WGBS (GFCM, 2017b). The adoption of this standard gear would permit comparability of data and results among countries and GSAs.

This gear constitutes a good compromise between different constraints (Bertrand et al., 1997, 2002): it has been planned with a vertical opening that is slightly superior to the most common commercial types of gear used in the Mediterranean and the Black Sea to increase the catch of demersal species (MEDITS, 2017).

Some general requirements and details regarding the mesh size, codend, otter boards and warps are provided in the following sections (a more detailed description of the gear is included in MEDITS, 2017).

For countries/GSAs where no demersal surveys have been previously carried out or where little information on sea bottom is available, it is suggested that exploratory fishing operations (e.g. fishing hauls/transects) should be carried out before the implementation of the standardized scientific survey with a commercial demersal trawl net (Figure 1). The bottom trawl used in this pre-survey should have a conical net bag with a wide mouth fitted with weights on the ground-rope and floats on the headrope.

The use of a commercial trawl net would allow to better explore the bathymetry and the topography of the sea bottom. Based on the results of this pre-survey, the sampling scheme using the GOC 73 trawl gear (Section 1.3.1) designed by the Institut français de recherche pour l’exploitation de la mer (Ifremer) could then be used or modified.

1.3.1 GOC 73 trawl gear

All fishing hauls should be undertaken using a bottom otter trawl net with standard dimensions, i.e. the reference GOC 73 trawl designed for scientific purposes by Ifremer – width 22 m, height of vertical opening 2 m, length 40 m, stretched mesh size at codend 20 mm (Fiorentini and Dremière, 1996; Fiorentini et al., 1999). Figure 2 shows a schematic drawing of the Ifremer GOC 73 trawl gear (MEDITS, 2017).

The most important specifications of this gear, also reported in the MEDITS manual (MEDITS, 2017), are the following:

– It is able to work from 10 to 800 m depth.

– It has low selectivity so as to have good images of the populations sampled, including recruits.

The mesh size of the codend should be 10 mm of mesh side, which corresponds to about 20 mm of mesh opening (stretch). In the International Organization for Standardization (ISO) 1107:2017, ISO defines the mesh side as “the distance between two sequential knots or joints, measured from centre to centre when the yarn between those points is fully extended”.

The nets should be made of good-quality polyamide netting (nylon). The headrope should have around 40 floats, resisting to an immersion of 1 300 m depth. Their diameter should be about 20 cm, their individual buoyancy 2.7 kilograms-force per float (kgf) (± 5 percent), with the total buoyancy of the 40 floats being some 108 kgf (± 5 percent). The floats should be distributed along the headrope as follows:

– from the end of each wing, one float every 1.5 m, five times;

– one pair of floats every 1.5 m on the whole remaining length;

– in the headrope bosom, a small adjustment of the spacing is necessary.

Based on this number of floats, the vertical opening of the trawl should reach from 2.4 m to 2.6 m, being inversely related to the horizontal opening.

A weighting chain (ballast chain) of 120 kg (3 × 40 kg) should be secured to the foot rope at 17 cm intervals (with a hanging height of at most 8 cm).

In addition, a supplementary chain (one only) of 15 kg (about 6.5 m with a diameter of 10 mm) should be secured symmetrically on both parts of the belly bosom in the same way as the first chain (garland of 17 cm in length) (MEDITS, 2017).

1.3.2 Rigging

A general illustration of the rigging is presented in Figure 3 (MEDITS, 2017). The upper bridle length should be 30 m (C); the lower bridle length should be 29 m, plus the adjustment chain of 1 m (the adjustment chain is only found on the lower legs) (D).

In order to maintain the geometry of the trawl as constant as possible, two bridle lengths (MEDITS, 2017) are defined below according to the depth:

1.3.3 Doors

The doors should be of type Morgere W Horizontal: S (WH S, Figures 4 and 5), corresponding to size 8. The length of the backstops (shackles not included) should be as follows (MEDITS, 2017):

– long external backstrops: 1.60 m; and

– short upper and lower backstrops: 0.65 m (± 10 percent).

1.3.4 Warp diameter and length

Taking the characteristics of the trawl and rigging into account, the warps should have a diameter ranging between a minimum of 14 mm and a maximum of 22 mm. The length of warps to be shot should be determined by the operating depth. Table 1 gives, by depth, different warp lengths to be shot at different depth in function of the warp diameter (from 12 to 22 mm). The relationships are calculated based on the specifications of the GOV 73 net and the WS 8 doors (MEDITS, 2017). In addition, it is recommended that the warp length not be less than 200 m, because this would considerably decrease the door spread, increasing door instability.

Although in particular circumstances some adaptations can be made to this relationship, it is recommended that the depth/warp length ratio be respected as far as possible. For vessels not equipped with a device to measure the length of warp shot, it is recommended to put a mark every 50/100 m directly on the warp to know how much cable is dropped.

1.4 SURVEY DESIGN

The aim of a demersal trawl survey is to cover the main distribution area of the target species. Demersal abundance is highly variable and large-scale trends related to habitat features, bathymetric and hydrographic conditions are evident. To exploit these trends to improve the precision of abundance indices, it is important to correctly allocate the trawl stations.

A procedure for the allocation of stations should be established. A fixed grid of stations ensures maximum information on distribution throughout the area, but not necessarily the most precise estimate of biomass (Sparre and Venema, 1998). For an estimation of stock sizes, a completely randomized design or a stratified random sampling design should be preferred. In most cases, a stratified random sampling design should be chosen, because fish are seldom uniformly distributed, and in most cases, species occurrence and abundance is related to depth (Sparre and Venema, 1998).

A stratified random sampling scheme has several advantages over a purely random scheme:

– Sampling is spread out over the entire area of the survey (e.g. GSAs) by assuring the required number of trawl stations in each stratum (e.g. bathymetric range).

– Sampling rates, in terms of stations per unit area, can be varied to improve the precision of estimates for some key species, this being an advantage over systematic sampling.

Trawl station location, depending on the characteristics of each area (see Section 1.4.1), can be randomly selected within an identified bathymetric stratum (e.g. 10–50, 51–100, 101–200 m, etc.) prior to each survey. The number of stations within each stratum should be generally proportional to the area of the stratum and also include consideration of the overall variability in multispecies distribution among strata.

Generally, the use of stratified random sampling enables the size of the contribution of sampling error to be controlled and estimated, and avoids possible biases in station selection.

1.4.1 Survey area

A demersal trawl survey should cover the main geographical and bathymetric range of the main species within a given GSA or a combination of GSAs according to the stock boundaries of the target species. The total covered area should be stratified according to depth and geographical criteria and, if known, fish density. Fishing positions must be chosen randomly in a first survey, but may be maintained as fixed stations during subsequent surveys. Information about depth and type of bottom to point out trawlable areas and strata may be obtained also from a preliminary survey with echo-sounding. Information from local fishers may also be valuable (Sparre and Venema, 1998). Information on seasonal winds, currents and migration patterns of fish stocks are important as well. Preferably, surveys in new areas should involve zones where commercial trawling is performed, using commercial hauls as a guide when deciding on sampling stations. This is essential due to the time constraints on performing the survey and also for safety reasons. Except in the case of particular problems (e.g. damages noted in previous years, etc.), once identified and selected, the same hauls position should be visited every year. According to Hilborn and Walters (1992) resorting the stations in each survey should allow a more accurate estimate of the standing stock in the investigated area, while keeping stations fixed over time should allow for more accurate information on time trends of relative abundance.

For conservation purposes, sensitive habitats (e.g. Posidonia spp. meadows, coralligenous beds), as well as vulnerable marine ecosystems (VMEs) (see Section 4.1) should be excluded from the sampling scheme and should never be trawled. All these aspects must be considered during the process of allocation of hauls to the different strata (Section 1.4.2).

1.4.2 Depth strata and sampling stations

Since bathymetry is the main factor affecting the distribution of demersal species, the trawl stations (or fishing hauls) should be allocated proportionally to the surface of each depth stratum, both over the shelves (0–200 m) and the upper slopes (> 200 m). Then, based on the MEDITS manual (Relini, Carpentieri and Murenu, 2008; MEDITS, 2017), fishing hauls should be allocated among five main depth strata (i.e. 10–50 m, 51–100 m, 101–200 m, 201–500 m, > 501 m). Within each identified stratum, the position of the stations should be then selected randomly in the first survey. Each country performing a new survey will have to adapt the allocation of the fishing hauls based on the morphological and ecological features of the sea bottom.

Generally, the target average sampling rate should be about one station per 60 square nautical miles in all areas (Bertrand et al., 2002). To reduce or avoid covariance between fishing stations in adjacent strata, stations should be separated by at least 5–10 miles (ICES, 2010). Before the survey, it would be fundamental to set the surface area (in km^2) and number of fishing hauls by GSA and for each identified stratum (Table 2).

The following formula should be applied (modified from Sparre and Venema, 1998) and can be used to estimate how many fishing hauls can be carried out in a given period:

– number of fishing hauls per day = T/(t_1+t_2+t_3); and

– total number of fishing hauls during the survey = (N)*(number of fishing hauls per day).

It is important to standardize the length of a fishing haul throughout the survey, because the catchability of species and sizes can be affected by the duration of the haul (Section 1.4.3).

In general, fishing hauls should be performed at constant depth. The depth variations during the haul should not exceed ± 5 percent relative to the initial depth. As far as possible and in respect of the previous constraints, the hauls should be rectilinear.

The gear should stay in good contact with the seabed during the whole haul. This should be checked regularly by observation of chain wear, observation of benthic organisms in catches after the haul, and an acoustic device (if any) during the haul. The systematic use of a device (e.g. Scanmar, Simrad or other catch sensor) to control the trawl geometry (i.e. vertical and horizontal openings, contact with the bottom) is highly recommended.

When a device is not present, a proper contact could be indicated both by inspecting for chain/warp wear and for monitoring of warp widening and vibration. The measurements of the trawl geometry should be taken at various depths on board each vessel at the beginning of the survey to establish the relationship between the horizontal and vertical opening and parameters easy to measure, such as depth and/or warp length.

At deeper waters (i.e. more than 200 m), some difficulties might be encountered in gear setting on the bottom; thus particular attention must be paid to the shooting operations. In order to decrease the setting time, the following recommendations should be considered (MEDITS, 2017):

– After the complete shooting of the warps and once the winch is stopped, a relatively high speed (5–6 knots) should be maintained for about one minute to stretch the gear and open the doors.

– The speed should then be strongly reduced (even to 0), allowing the doors to reach the seabed. The time required varies depending on the vessel and the depth, for example 2–3 minutes at 500 m.

– Once the doors are on the seabed, a speed lower than normal (2.5–2.7 knots) should be maintained to allow the net to reach the bottom.

– Once the net is well stabilized, the speed will be increased towards the standard speed (3 knots); this moment is defined as the real start of the haul.

1.4.3 Survey period and timing of fishing operations

Demersal trawl surveys should be conducted annually, possibly during spring or summer (from 1 May to 30 September). This would permit greater comparability of data among GSAs and GFCM subregions (Annex 1). To properly carry out the survey, and based on the main biological aspects of the selected species (e.g. recruitments and spawning periods), the best month during this period should be selected.

Due to the different catchability of demersal resources according to the diel cycle, it is recommended to conduct trawling operations during daylight hours (i.e. between sunrise and sundown), although it is recognized that some institutes may wish to trawl both during the day and at night. More specifically, the daylight period is defined as the time between 30 minutes after sunrise and 30 minutes before sunset. Fishing hauls should have a duration of 30 minutes on bottoms shallower than 200 m and 60 minutes on bottoms deeper than 200 m. For vessels using a device such as a SCANMAR Trawl Sensor or SIMRAD or other equivalent equipment, the start time of the haul is defined as the moment when vertical net opening and wing spread indicate that the net is in its stable fishing configuration (Engås et al., 2001; ICES, 2009; MEDITS, 2017). For the vessels without such a device, preliminary trials shall be made before the survey to determine the setting time needed to operate correctly for each vessel, taking into consideration the experience of each individual skipper, as well as the best predicting models of the net behaviour (e.g. horizontal and vertical net openings by warp length). Stop time is defined as the start of pull back (ICES, 2011). If the haul should be stopped before completion of the standard duration, it can be considered valid if at least two-thirds of the time or of the distance have been successfully attained (MEDITS, 2017).

It is strongly recommended that the sampling period of the survey is consistent yeartoyear to reduce the time-of-the-survey effect on the time series (ICES, 2012; MEDITS, 2017).

1.5 HANDLING OF THE CATCH

The organisation of work at sea mainly depends on the facilities available on board the vessel. Photos of whole catch should be systematically taken at each fishing haul. Wherever possible, the entire catch should be sorted (Plate 1), with all species (e.g. fish, cephalopods, crustaceans, etc.) identified to the lowest taxonomic level possible. However, as the level of taxonomic expertise on board vessels can be variable, and certain species can be hard to distinguish from one another, those could be reported by genus and/or higher taxonomic group (e.g. Nezumia spp. or Macrouridae).

Data on total catch composition (i.e. number and weight by species) for a single fishing haul can be collected and recorded as in Annex 4. For large catches, a representative subsample should be sorted. In some cases, the sample (e.g. non-identified species, a subsample of huge catch, etc.) can be taken and preserved on board, and the biological analyses carried out at laboratories.

After the catch has been sorted, for each species, the total weight and number of individuals should be recorded (Plate 2). Length measurements and some other biological data (i.e. sex, maturity and weight) should be taken, at least for all identified target species (Section 1.5.1).

With the exception of decapod crustaceans and cephalopods, which should be recorded according to the standard templates[1], the number and the total weight should be recorded for all other macroinvertebrates (Plate 3) (see Annex 16 and Section 4.1). In this sense, attention should be mainly focused on benthic species indicators of VMEs, as defined by the FAO (FAO, 2009; GFCM 2017a, 2017b; GFCM, 2018b, 2019a).

1.5.1 Target species

Although a scientific survey should aim to collect basic information on all species caught, the level of sampling requirements, based on time availability and human resources, will be different for all species observed in the survey. Hence, as a general principle, and in line with the requirements of the SAC and WGBS, the collection of basic data should be ensured to allow estimation of the distribution, abundance and key biological parameters (e.g. length, weight, sex and maturity) at least for all species of group 1 and group 2 (Annex 2) as requested by the DCRF (GFCM, 2018a). For all other sampled species of fish, crustaceans, molluscs and other invertebrates, data collection depends on time availability, but at least the total number and total weight by species should always be collected.

Moreover, since in recent years non-indigenous species have been pointed out as one the most important direct drivers of biodiversity and ecosystem service changes both in the Mediterranean and the Black Sea, particular attention should also be paid to collecting biological data (i.e. length, weight, sex and maturity) on this group of species. Survey information on non-indigenous species could contribute to understanding their roles in the benthic and pelagic ecosystems, their impacts on their new colonised environment, including restructuring established food webs, and competition with native organisms for food and space (see also Section 4.4).

1.5.2 Biological parameters

In order to allow an exhaustive and accurate processing of collected materials, individual biological data (length, weight, sex, maturity and otoliths reading) can be recorded either on board or in laboratory according to the work conditions (e.g. trawl surveys carried out by using an oceanographic vessel or a hired commercial trawler).

1.5.2a Length measurements

After sorting the catch into species, representative length distributions should be recorded for collected species (following the criteria described in Section 1.5.1), from high-priority species (i.e. group 1 and group 2 of Annex 2) to all others if time permits. Where the number of individuals is too high to measure them all, a representative subsample should be selected, from 50 to 100 specimens, depending on the species in each fishing haul. The length measurements to be taken depend on the group of species under study, and a proper representation of the given length distribution is key. Thus, attention must be given to a possible uneven distribution of species and/or size classes in the hold.

The methodology to be used for the collection and reporting of length data should follow the DCRF manual (GFCM, 2018a).

Bony fish and elasmobranchs – For bony fish, sharks, skates and rays, the length to be considered is total length (TL). The fish should be measured from the tip of the snout to the end of the caudal fin (Figures 6 and 7), to the lower half centimetre (e.g. 13.4 = 13 cm; 16.8 = 16.5 cm).

For bony fish, the standard length (SL) could be also recorded, which is defined as the measurement taken from the tip of the lower jaw to the posterior end of the hypural bone (Figure 6). For elasmobranchs, fork length (FL) can be recorded when the caudal fin is damaged and the TL cannot be measured (Figure 7).

Crustaceans – For crustaceans, the cephalothorax (carapace) length in millimetres should be reported to the lowest millimetre (as a whole number, e.g. 1, 2, 3, 4, etc.) (Figure 8).

Cephalopods – For cephalopods, the mantle length in centimetres should be collected and reported to the lower half centimetre (as a whole or half number, e.g. 0.5, 1.0, 1.5, etc.) (Figure 9). For Octopoda, measurement is taken along the median line, passing through the eyes to the apex of the mantle (Figure 9a). For Decapoda, measurement is made along the dorsal midline from the mantle margin to the posterior tip of the body, excluding long tails (Figure 9b).

Length data for different groups of species can be collected and reported using the forms in Annex 5.

1.5.2b Weight

The total weight (in kg) of all species (Plate 4) in the catch should be collected and recorded (Annex 4).

Individual weight should be collected and recorded (Plate 5) for at least all species of group 1 (Annex 6.1). The optimum number for individual weight per length class cannot be given in a universal form, but a minimum of five specimens per length class should be weighed.

The choice of weighing device (e.g. hanging balance, electronic balance) depends on the size of the sampling and working conditions (on board or at laboratory). For fish, elasmobranch and cephalopod species, the total weight of each individual could be reported to the nearest gramme, using an electronic balance. For crustaceans, the weight should be recorded to the nearest 0.1 g.

If it is impossible to measure individual weight, as a possible alternative, the number and total weight of a group of individuals with the same length should be recorded in order to calculate the mean weight of individuals in the length class (Annex 6.2).

Although the weighing of single individuals may prove more complex, depending on prevailing conditions in the workplace, it is important to collect this biological information to the extent possible.

1.5.2c Sex and maturity

The sex is defined following four categories, through macroscopic observation: male (M), female (F), undetermined (U – when, after dissection, it was not possible to determine the sex of different specimens with the naked eye), and not determined (ND – an individual that has not been examined). Sex and maturity data should be collected and reported (Annex 7) for the main priority species.

A large number of macroscopic maturation scales are available in the literature, varying from oversimplified scales comprising three to four stages to highly specific and relatively complicated scales (up to nine stages) (Follesa and Carbonara, 2019). For the purpose of this section, the maturity scales designed for scientific trawl surveys in other contexts should be used (MEDITS, 2017; see Annex 8)[2]. Using common maturity scales would simplify data sharing and data quality checks.

1.5.2d Otoliths

Otolith samples can be collected on a “by need” basis, depending on the countries participating in the survey and on regional and/or subregional working group requirements. However, otoliths of routinely assessed species should always be collected for age estimation.

The technique for cutting otoliths depends on the species. For descriptions of these techniques (i.e. otolith sampling, preparation and reading) it is recommended to consult the literature on the subject (Carbonara and Follesa, 2019). The optimum number of otoliths per species and length class cannot be given in a universal form. A description of the optimum sample size of age readings and length measurements dependent on a universal cost function is given in Oeberst (2000) and in the Manual for Baltic International Trawl Surveys (ICES, 2011). The analyses showed that the necessary number of age readings in a length class depends on:

– the portion of the length class within the length frequency; and

– the maximum variance of the portions of the age groups within the length class.

Table 3 proposes a minimum number of otoliths by length class that must be taken per survey and species, based on length distribution. For the smallest sized groups, which presumably contain only one age group, the number of otoliths per length class may be reduced. Conversely, more otoliths per length are required for the larger length classes.

Otoliths may be sampled during the survey if proper facilities and experienced people are on board and stored in envelopes or other suitable containers. The whole fish or its head can be stored for later processing in laboratory. In both cases, it is important, when otoliths are removed, that each single container be labelled with the identification code of

the species and date. For each specimen, length, individual weight, together with sex and the maturity stage, should be also collected. Annex 6.1 can be used to report these data.

1.5.3 Oceanographic data

As a minimum, the following hydrographical data should be collected at each fishing haul:

– seawater temperature and salinity in the surface layer; and

– seawater temperature, salinity and oxygen content in the bottom layer.

Whenever possible, other parameters (e.g. turbidity, transparency, and current among others) from the surface to the bottom should be recorded. Annex 3.2 can be used to report all these hydrographical data.

1.6 DATA REPORTING AND EXCHANGE FORMATS

The outcomes of demersal trawl surveys should satisfy different data requirements within the GFCM:

– Relevant information should comply with DCRF provisions (GFCM, 2018a).

– Useful information in compliance with existing GFCM recommendations should be reported to the GFCM by its contracting parties and cooperating non-contracting parties (CPCs).

– Information supporting stock assessment should be reported to the different Working Groups on Stock Assessments (WGSAs) through stock assessment forms.

– Other relevant information useful for regional analysis can be examined in dedicated expert groups.

Standard templates[3] are defined for the storage and exchange of data produced by demersal trawl surveys already conducted in some Mediterranean and Black sea countries (see also annexes from X to XIII in MEDITS, 2017). In order to have comparable and harmonized data, basic information on fishing hauls, catch and biological data should be reported, once collected, using these standard templates: i) Fishing hauls data (TA template; Annex 11.1); ii) Catch data by haul (TB template; Annex 11.2); iii) Biological data, length, sex, and maturity at aggregated species level (TC template; Annex 11.3); iv) Biological parameters at individual level (TE template; Annex 11.4) and v) Data on marine litter (TL template; Annex 11.5). The use of these standard templates should facilitate the exchange and analysis of the data produced by the demersal surveys among different countries.

In order to make proper use of the mentioned formats, ad hoc tool should be used and adapted (i.e. some fields should be revised, codifications are needed, among others) to the different needs of Mediterranean and Black Sea countries that are not currently involved in scientific surveys. Therefore, flexible routines for data conversion, from the input structure to the common formats (i.e. TA, TB, TC, TE and TL type formats), together with the complementary codification, will be made available to each country involved in a scientific survey.

This tool (i.e. MEDITS.Web application, COISPA Tecnologia & Ricerca, 2020), is conceived taking into account the long and consolidated experience of the MEDITS trawl survey (MEDITS, 2017), in terms of standardised protocols for data collection and data format. This approach is integrated by introducing a wide flexibility to allow applications in other areas taking into account the specificities at sub-regional level while maintaining a common minimum standard. MEDITS.Web application has been realized for data input, import/export, storage, check and sharing. Besides the needed flexibility other basic concepts associated to the MEDITS.Web application are the data quality control check, data elaboration, data check procedures, which would permit to highlight errors that could compromise further analysis and make them unreliable.

2. PELAGIC ACOUSTIC SURVEYS

2.1 AIM

The main aim of a pelagic acoustic survey is to evaluate biomass and spatial distribution of the small pelagic fish species in given GSAs through the combined use of acoustic methods (Simmonds and MacLennan, 2005) and pelagic trawl. Consequently, data acquired during this survey should provide information on the pelagic fish community and on the pelagic environment.

The main species of the pelagic community, which could be sampled through the implementation of a pelagic acoustic survey in the Mediterranean and the Black Sea, are reported in Table 4.

2.2 VESSEL CHARACTERISTICS

It is highly recommended, whenever possible, that research vessel are used for acoustic surveying at sea. Vessels should be equipped with hull-mounted transducers for both the scientific echo-sounder and the net-sounder. Furthermore, vessels should be equipped with an engine capable of towing the sampling gear (maximum traction about 4.5 tonnes) (see Section 2.5).

2.3 METHODOLOGY

The survey design for acoustic sampling is strongly dependent on both the spatial structures of small pelagic fish and the topographic characteristics of the area to be investigated.

The survey should cover the sea area between the coastline and the limit of the continental shelf. The minimum bottom depth should be 20 m or less, reaching the 10 m isobaths whenever possible. The maximum echo-sounding depth should be 200 m. The intertransect distance to be adopted should be carefully determined based on the continental shelf extension and, if available, on specific knowledge of the ecological characteristics of the area.

2.4 PERIOD FOR AND TIMING OF PELAGIC ACOUSTIC SURVEYS

In the Mediterranean, pelagic acoustic surveys should be conducted annually, possibly during spring or summer (between May and September). In the Black Sea, surveys should be carried out in the period from spring to autumn (between April and November). Each Mediterranean and Black Sea country, based on the main biological aspects of the identified priority species (e.g. recruitments and spawning periods), should select the best month during these periods to carry out the survey. This would permit greater comparability of data among areas and GFCM subregions.

Acoustic surveys should only take place during daytime and should be interrupted at night, when fish schools disperse. This approach would prevent possible bias in the biomass estimation due to the different aggregation status of fish species. If available survey time does not permit acquisition of data only during daytime, echo sampling might be extended. Previous studies had indicated that night estimates can be higher or lower than daytime estimates, largely depending on the area characteristics and, especially, the local plankton and fish densities (Simmonds and MacLennan, 2005; Draštík et al., 2009). However, results showed that correction is possible and advisable when night sampling is inevitable. In this context, and depending on the available vessel time, it is good practice to identify specific test areas where acoustic data are recorded both in the daytime and at night. Test areas should be selected considering:

– the extension of the continental shelf;

– specific geographical characteristics (e.g. the presence of gulfs); and

– oceanographic processes such as the presence of specific enrichment processes driving the productivity of the area (e.g. upwelling events, river runoff, tidal mixing).

2.4.1 Analysis design

For countries/GSAs where acoustic surveys have been performed, the acoustic survey design is already established and, if necessary, could be adjusted to achieve minimization of the coefficient of variation of the acoustic estimates for the priority species in each area.

For countries/GSAs where no acoustic survey has been previously carried out, it is suggested that parallel transects be adopted along the depth gradients (i.e. bottom topography), which are normally perpendicular to the coastline/bathymetry. In cases of topographic complexity, as with semi-closed gulfs, riverine areas or islands, survey design could be decided in another manner (see Simmonds and MacLennan, 2005).

2.4.2 Echo sounder parameters

A scientific split-beam echo-sounder should be used for the acoustic survey (Figure 10). Pulse duration should be 0.5 or 1 millisecond (ms), depending on the technical specifications of each echo-sounder. The frequency for assessment should be 38 kilohertz (kHz), while other split beam transducers can operate as complementary frequencies (e.g. 18, 70, 120 and 200 kHz).

The threshold for assessment should be -70 to -60 dB, depending on the survey and the ecosystem. Background noise should be evaluated and removed. Since the main objective is optimum discrimination between fish and plankton, based on the available frequencies used in each survey, a frequency-response-based mask should be developed to split the acoustic backscattering between fish and plankton. Whenever this cannot apply, the threshold for assessment should be set at -70 to -60 dB, depending on: (a) noise level (-60 dB in the case of high noise); (b) the peculiarities of each area regarding school morphology and plankton density (-60 dB when plankton is dense, but -70 dB when small schools dominate the area); (c) echo-sounder features; and (d) time of day that echo acquisition is carried out.

The elementary distance sampling unit (EDSU) for echo integration should be one nautical mile (NM). The acoustic energy acquired in the inter-transect tracks should not be taken into account for assessment purposes.

At least one calibration of echo-sounder should be held per survey, based on the procedure reported in the manual of each echo-sounder and according to the principles described by Foote et al., (1987) and Demer et al., (2015).

2.5 PELAGIC TRAWL

Implementing acoustic surveys means acquiring both acoustic data and net samplings of small pelagic fish with a pelagic trawl (i.e. pelagic fishing hauls). The details of each pelagic trawl haul (e.g. latitude, longitude, depth, time) should be monitored and reported as in Annex 3.1. Furthermore, temperature, salinity and other parameters from the surface to the bottom should be sampled. Annex 3.2 can be used to report these data.

The main objectives of trawling in an acoustic survey are to obtain a sample from the schools or layers that appear on the echograms and to acquire information on fish species composition and size distribution. Thus, it is important that the trawling gear be suitable for catching a representative sample of the target schools or layers.

In an acoustic survey, the sampling intensity for biological samples depends on the extent of the area covered, the frequency of occurrence of different echo traces on the echograms, and on the spatial characteristics of fish aggregations. The presence of specific behavioural effects, such as the spatial segregation between different age/length classes, should be considered in order to sample the whole fish population. In addition, the geographical coordinates or the sampling depth of the hauls cannot be predetermined, because pelagic species execute extended horizontal and vertical movements. School morphometry and energetic characteristics might change depending on the area, the time interval or even the fishing pressure. Thus, the sampling strategy has to be adaptive, depending on school characteristics per area, time of the survey and year.

It is recommended to use a net monitoring system (a net-sounder) during trawling operations (Figure 11).

Given the fact that different research vessels are expected to be used in the GSAs in the Mediterranean and Black Sea, as a minimum, the following indications should be adopted:

– A standardized pelagic trawl net should be used in all areas for biological sampling.

– Maximum codend mesh size should be equal to 24 mm (mesh size equal to 12 mm).

– The vertical opening during the pelagic fishing hauls should be reported, along with the net-sounder used.

– The duration of fishing hauls should be no less than 30 minutes for unknown echoes and when multispecies scattered echoes are being fished.

– Vessel speed during fishing should be 3.5–4.5 knots.

– Sampling intensity must be adequate to ensure identification of echo traces, to obtain a representative length structure of the population for each small pelagic species, and to evaluate the species composition of the insonified target in the water column.

2.5.1 Handling of the catch

Once on board the vessel, the biological sample collected during each pelagic haul should be divided by species (Plate 6).

All species in the catch should be recorded. Data (i.e. length and weight) on total catch composition for single pelagic haul and by species should be collected and reported as in Annex 4. When the catch of a given species is too abundant, a representative subsample of the whole catch should be randomly selected (Plate 7).

This subsample should be not less than 100 individuals per species. The total length (TL) of each fish should be measured on board immediately, with the tail fully extended to the lower half centimetre. Length data for groups of species can be collected using the forms in Annex 5.

Individual weight (±0.01g) should be collected and recorded (Annex 6.1), at least for all pelagic species of group 1 (Annex 2 and Table 4). If it is impossible to determine individual weight, as a possible alternative, the number and total weight of a group of individuals with the same length should be recorded in order to calculate the mean weight of individuals in the length class (Annex 6.2).

Sex is defined following four categories, through macroscopic observation: male (M), female (F), undetermined (U – when, after dissection, it was not possible to determine the sex of different specimens with the naked eye), not determined (ND – an individual that has not been examined), and the spawning phases (Annexes 7 and 8). Based on the pelagic acoustic protocol in place (MEDIAS, 2017, 2019), for sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus) only, a six-phase maturity scale, which would permit comparability of data among pelagic surveys, should be used (ICES, 2008; Annex 9)[4].

Otoliths of the target species can be collected for age determination at a laboratory (Plate 8) and reported in Annex 6.1.

2.6 OCEANOGRAPHIC DATA

A multiparametric CTD probe should be used to acquire vertical profiles of the main oceanographic variables (e.g. pressure, temperature, and salinity) in the entire water column (MEDIAS, 2015, 2017). Taking into account the great importance of environmental parameters for small pelagic fish, a minimum of three CTD stations should be collected per transect or a grid of stations with density adequate to describe the oceanography of the surveyed area. The hydrographic parameters temperature and salinity should be measured at each station.

2.7 DATA REPORTING AND EXCHANGE FORMATS

The acoustic method for small pelagic fish biomass estimation is structured in two main phases to be performed, respectively, on board the vessel (acoustic data and biological samples collection) and at a ground-based laboratory (post-processing of acoustic data and analysis of biological samples). During the first phase, acoustic data collected both along the survey tracks and during the calibration procedure, should be stored in a specific format (e.g. *.raw or *.hac) in a mass storage unit.

The results of the second phase should be reported in specific tables or maps in terms of nautical area scattering coefficient (NASC) (MacLennan, Fernandes and Dalen, 2002) per EDSU, biomass per EDSU and numbers per EDSU (see Annex 12).

In particular, the following abundance estimates, maps and charts are obtained:

Moreover, total biomass and total abundance (both by age class and by length class) should be estimated.

The minimum length and age data to be collected and reported during the implementation of a pelagic acoustic survey are summarized in Box 1 and Box 2.

3. DEMERSAL BEAM TRAWL SURVEYS

3.1 AIM

The main aims for carrying out a standard and harmonized BTS are similar to those of a bottom trawl survey (Section 1). The main difference is that a BTS can supply fishery-independent indices and estimates of the age/length structure of target stocks that are not effectively sampled during a bottom trawl survey, such as flatfish, shellfish and other commercially-important benthic organisms.

In particular, in the different GSAs and/or GFCM subregions, a BTS can provide accurate information in terms of relative abundance/biomass, population distribution, demographic structure and biological parameters for target species such as common sole (Solea solea), cuttlefish (Sepia officinalis) and mantis shrimp (Squilla mantis), common in the Mediterranean Sea, but also turbot (Scophthalmus maximus) and Rapana whelk (Rapana venosa) common in the Black Sea.

Also, in coastal areas characterized by shallow waters and flat muddy bottoms, such as the Nile Delta, Iskenderun Bay, the inshore areas of the gulf of Lion and the Thracian Sea, a BTS can be a suitable technique for collecting fishery-independent data for different coastal benthic resources. In addition, a BTS can provide additional data for other demersal stocks already sampled during a standard bottom trawl survey (e.g. red mullet). These data can be functional in integrated approaches (e.g. SS3, a widely used statistical catch-at-age model), characterized by the use of more than one tuning index having a different selection pattern.

Similarly to standard bottom trawl surveys, a BTS can collect data on epibenthos assemblages as well as on VMEs (e.g. Pennatulacea). However, while in a standard bottom trawl survey, such data usually provide a qualitative indication of benthos assemblages, in a BTS, they can deliver quantitative data of benthos assemblages. Moreover, during the BTS, data on marine litter distribution and abundance can be collected.

Taking into consideration that, to date, the only BTS carried out regularly in the Mediterranean Sea is the SoleMon survey (SoleMon, 2017, 2019), which has been conducted since 2005 in the Adriatic Sea (see Box 3), it is recommended to use the same gear and methodology to have standard approaches and comparable results in other areas of the Mediterranean and Black Sea.

3.2 VESSEL CHARACTERISTICS

Taking into account the sampling gear characteristics (Section 3.3) as well as the rigging, a BTS should be carried out with commercial and/or research vessels equipped with an engine of at least 298 kW (400 hp) to be able to tow the sampling gear with a correct speed. Trawl speed during each fishing operation should be from 4 to 5.5 knots. This recommended speed range is very important to ensure that the gear is always in contact with the seabed. A speed lower than 4 knots can have a negative influence on the penetration depth of a beam trawl into the seafloor. Therefore, the speed is an important factor determining catch efficiency, particularly for buried species, and also depends on the sediment type. It is recommended to monitor and report the speed of the trawl and to use the same speed every year.

During the survey implementation, details of each fishing haul (e.g. latitude, longitude, depth, speed, direction, etc.) should be monitored and reported as in Annex 3.1. Whenever possible, temperature, salinity and other parameters from the surface to the bottom should be sampled. Annex 3.2 can be used to report these data.

3.3 SAMPLING GEAR

A beam trawl is a kind of trawl characterized by the mouth, or opening of the net, that is kept open by a beam mounted at each end on guides or skids that travel along the seabed. The trawls should be adapted and made more effective by attaching tickler chains (for sand or mud) or heavy chain matting (for rough, rocky ground), depending on the type of ground being fished. These drag along the seabed in front of the net, disturbing the fish in the path of the trawl, causing them to rise from the seabed into the oncoming net. Modern beam trawls range in size from 4 m to 12 m (weighing up to 7.5 tonnes in air) beam width, depending on the size and power of the operating vessel.

In implementing this survey in the Mediterranean and the Black Sea, a modified beam trawl called “rapido” should be used (SoleMon, 2017, 2019). This gear, commonly employed in the Adriatic subregion, was appositely designed to work on different types of soft bottoms. It consists of a modified beam trawl (Giovanardi et al., 1998; Hall-Spencer et al., 1999) with a rigid mouth fitted with 46 iron teeth (6–7 cm long) along the lower part. Joined to the iron frame there are four skids and a reinforced rubber diamond-mesh net in the lower part to protect the polyamide net bag (width: 3.59 m; height: 0.25; weight: around 225 kg; four 120-mm wide skids). The gear is always in contact with the seabed by an inclined wooden board (width: 3.60 m; length: 0.35 m; thickness: 0.03; weight: around 25 kg) fitted to the front of the iron frame, which acts as a spoiler and keeps the skids and the teeth tightly pushed down to the seafloor. The gear is joined to the warp with iron chains (long chain length: 2.10 m, short chain length: 1.00 m). A schematic representation of this gear is given in Figure 12 (drawings in Annex 17 schematize with more details all the different components).

In Figure 13, the mesh sizes are indicated in bar length. The mesh numbers in height correspond to well-finished and joined netting sections; the joining meshes are also shown. The length of the net is around 2.7 m. All fishing hauls should be undertaken using the rapido and the net as specified in the design.

The most important specifications of this gear are as follows:

– It is able to work from 5 to 100 m depth.

– It has a selectivity as low as possible, so as to have good images of the populations sampled, including recruits.

The mesh size of the codend should be 26 mm of mesh side (stretch). The nets should be made of good-quality polyamide netting (nylon).

3.3.1 Rigging

In implementing this survey, it is advisable that a vessel should be able to tow two fishing gear simultaneously, namely “beam A” on the right side of the vessel and “beam D” on the left side. (Figure 14). The gear positioned on the right side of the vessel should have 15 m more warp than the other in order to avoid possible interference between the two gear during the fishing haul.

3.3.2 Warp diameter and length

Taking the characteristics of the rigging and the gear into account, the warps should have a diameter of 14–16 mm. The length of warps to be shot is determined by the depth. The suggested relationship between depth and warp length is given in Figure 15. Although in certain peculiar circumstances some adaptations can be made to this relationship, it is recommended to respect the depth/warp length ratio as far as possible. Gear should be equipped with a DST (depth, salinity, temperature) recorder device. The use of this device, together with the fixed measures of mouth of the gear, should allow to know exactly the area explored by each gear.

3.4 SURVEY DESIGN

Similarly to a standard bottom trawl survey, during a BTS, one of the primary methods for estimating accurate indices reducing the variance of the estimates is to stratify the sampling frame into sets of sampling units with more homogeneous properties (Cochran, 1963). The overall variance is estimated as a weighted average of the within-stratum variances. If the strata have been defined appropriately, the stratified estimate of the variance will be smaller than that obtained from a simple random sample. When a BTS is carried out in the Mediterranean and the Black Sea, the sampling frame can be a GSA or a combination of GSAs according to the stock configuration of the target species, assuming as bathymetric limit the maximum depth beyond which a certain sampling gear (a beam trawl) is no longer efficient in sampling the target species.

For a BTS, a stratified random sampling design should be chosen, because fish and shellfish are seldom uniformly distributed, and in most cases, abundance is related to depth (Sparre and Venema, 1998). Therefore, a stratified random sampling scheme has several advantages over a purely random scheme, also for a BTS:

– sampling is spread out over the whole area of the survey (e.g. GSAs) by assuring the required number of fishing hauls in each stratum (e.g. bathymetric range); and

– sampling rates, in terms of fishing hauls per unit area, can be varied to improve the precision of estimates for some key species, this being an advantage over systematic sampling.

In a BTS, the fishing haul location, depending on the characteristics of each area (see Section 3.4.1), can be randomly selected within identified bathymetric stratum prior to each cruise. Importantly, the rapido trawl is efficient if used only at depths less than 100 m.

3.4.1 Survey area

The total area covered by a BTS should be stratified according to depth and geographical criteria, and if known, fish density. Fishing hauls positions should be chosen randomly in a first survey, but may be used as known and clear tow fishing hauls during subsequent surveys, except in the case of particular problems (e.g. area closures for military reasons). Regarding the standard bottom trawl survey as well as the BTS, it is advisable to control the bottom condition to understand if the area is trawlable. This control can be carried out using an echo-sounder or information gathered from local fishers (Sparre and Venema, 1998).

For conservation purposes, sensitive habitats (e.g. Posidonia spp. meadows, coralligenous beds, etc.) should be excluded from the sampling scheme and should never be trawled. All these aspects should be considered during the process of allocating fishing hauls to the different depths. In particular, in the case of a BTS, it is advisable to carry out an explorative haul of a few minutes (from 2 to 5 minutes) in order to understand the nature of the substratum in term of granulometry and morphology. Should this explorative haul show a significant amount of rhodolite or phanerogams leaves, it is recommended to move away the fishing haul.

3.4.2 Depth strata and sampling stations

Before the survey, the surface area and number of fishing hauls by GSA and for each identified stratum should be identified. In absence of already available information about the density of target species by strata, the fishing hauls should be proportionally distributed over the shelves (from 0 to 100 m) according to the surface of each stratum and should follow a depth-stratified sampling scheme with a random drawing of the positions. For a given amount of sampling effort (e.g. 100 fishing hauls), based on several technical constraints (e.g. availability of funds, vessel), a greater degree of precision can be attained by increasing sampling in areas, or strata, of high abundance of target species.

Stratified sampling involves conducting a preliminary survey to identify different strata in the spatial distribution of the target species. These strata could be identified on the basis of information on biology of the target species. On the other hand, systematic pre-surveys could be carried out positioning the fishing hauls on fixed distances that could be considered the lower limit of the distribution pattern of many target species of the survey.

In order to decide on the number of fishing hauls inside each strata that maximize the precision in the estimate of the abundance of a pool of target species, a standard method based on the Neyman equation (Neyman, 1938) can be applied using the data of abundance and variances from the systematic survey to find a mathematical solution to the allocation problem. To reduce or avoid covariance between fishing hauls in adjacent strata, the distance between fishing hauls should be at least 5–10 miles (ICES, 2010).

Similarly to the standard bottom trawl survey, the length of a haul needs to be standardized, because the catchability of target species and sizes often depends on the duration of the haul. Moreover, fishing hauls should be performed at a constant depth. The depth variations during the haul should not exceed ± 5 percent relative to the initial depth. As far as possible and in respect of the previous constraints, the hauls should be rectilinear. The gear should stay in good contact with the seabed during the entire haul. This can be checked by the depth profile available from the minilog data logger and by observing the skids and teeth wear at the end of the haul.

During a BTS carried out with a rapido trawl, it is recommended to adjust the speed as follow:

– During the shooting of the warps, a relatively high speed (6-6.5 knots) should be maintained.

– The speed should then be reduced (to 3.5-4 knots) just before the rapido touches the sea bottom and is stopped.

– Once the rapido is on the seabed, a speed of 5–5.5 knots should be maintained to allow the gear to be in close contact with the sea bottom; this moment is defined as the real start of the fishing haul.

3.4.3 Survey period and timing of fishing operations

A BTS should be conducted every year during autumn, corresponding to the period of recruitment and/or spawning for most of the identified priority species (see Table 5). Each country, based on the main biological aspects of the selected species (e.g. recruitments and spawning periods), should choose the best month(s) during this period to carry out the survey. This will permit greater comparability of data among areas and GFCM subregions. It is strongly recommended that the sampling period of the survey be consistent year-to-year to reduce the time-of-the-survey effect on the time series (ICES, 2012).

It is also recommended to conduct fishing haul operations during daylight hours. The daylight period is defined as the time between 30 minutes after sunrise and 30 minutes before sunset. A fishing haul consists of 30 minutes of trawling two gear simultaneously during daytime, starting when the gear settles on the bottom and ending when hauling commences. Depending on the circumstances (e.g. great amount of shells and debris), a shorter period is allowed. Should the fishing haul be stopped before completion of the standard duration, it can be considered valid if at least two-thirds of the time or of the distance have been successfully attained.

3.5 HANDLING OF THE CATCH

The catch of the two gear towed simultaneously should be analysed separately for “beam A” and “beam D”. The entire catch of each gear (Plate 9) should be sorted and weighted for all bony fish, rays, sharks, cephalopods and commercially important shellfish and crustaceans’ species (Annex 4). For the whole catch (or a subsample) of the epibenthic/benthic species and debris (see Section 3.5.2), the weight and the total number should be recorded (fresh on board or in the lab) for each species identified to the lowest taxonomic level possible.

Length measurements (Annex 5), weight, otolith (Annex 6), sex and maturity (Annex 7), should be collected and reported for the main target species following the same approach defined for the bottom trawl survey (see also Section 1.5.2).

In Table 5, the priority species (Annex 2) for which a BTS can provide both primary and/or additional data for tuning indices are specified by subregion.

3.5.1 Biological parameters

3.5.1a Length measurements

For fish (both bony fish and elasmobranches), the length is always the total length, the tail being extended following its longer dimension (see also Section 1.5.2a). The measurement unit (in cm) should be reported to the lower half centimetre (e.g. 13.4 = 13 cm; 16.8 = 16.5 cm).

For crustaceans, the length is measured in terms of cephalo-thoracic (carapace) length at the lowest millimetre (mm). For cephalopods, the length is the mantle length at the half centimetre (cm). For commercially important bivalves, the shell length at the lowest millimetre is recorded (Section 1.5.2a).

Subsampling by species may occur for the length measurements when the numbers are extremely high. Length data should be collected and reported as in Annex 5 at least for the main priority species, by GFCM subregion (Annex 2).

3.5.1b Sex and maturity

Also for BTS, sex is defined through macroscopic observation according to four categories: male (M), female (F), undetermined (U – when, after dissection, it was not possible to determine the sex of different specimens with the naked eye), and not determined (ND – an individual that has not been examined). Sex and maturity data should be collected and reported (Annex 7) for the main priority species.

When carrying out a demersal beam trawl, maturity scales designed for scientific trawl surveys with similar data (e.g. SOLEMON data) in other contexts should be used (e.g. MEDITS, 2017; see Annex 8)[5]. Using common maturity scales would simplify data sharing and data quality checks.

3.5.1c Otolith, weight at the individual level

Similar to demersal trawl surveys (see Section 1.5.2d), otoliths should be collected at least for the targets species of fish.

When otoliths are removed, the length, the individual weight, together with the sex and maturity stage of the sampled specimen, should be collected (Annex 6.1). For the target fish species, it is suggested to collect a minimum of ten otoliths per identified length class in each fishing haul.

3.5.2 Analysis of epibenthos, benthos, debris and marine litter

Sorting, counting and weighting epibenthic and benthic species (see Section 4.1), together with debris (i.e. shells, rocks, etc.) and marine litter items (see Section 4.3), should be carried out (whenever possible) directly on board on fresh material. Photos of epibenthic/benthic species, debris fraction and marine litter should be systematically taken at each fishing haul (see Annexes 15 and 16).

The subsampling should be carried out as follows:

– if the catch of epibenthic/benthic species and debris fraction in one rapido is around or less than 30 kg, all the species and debris items should be sorted directly without subsampling.

– If the catch of epibenthic/benthic species and debris fraction in one rapido is more than 30 kg, a subsample varying from 50 to 5 percent of the catches should be taken and sorted directly following the rules in Table 6.

All the items of marine litter should be collected from one randomly chosen rapido and analysed. The fraction of epibenthic/benthic species and debris sorted for the rapido randomly chosen are assumed to correspond to the rapido that hasn’t been analysed. The quantitative amount of the species assumed for the rapido not analysed are standardized on the basis of its overall catch weight, calculating the raising factor (RF) as follows:

3.5.3 Other parameters

During a single fishing haul, depth temperature throughout the tow should be recorded and monitored. A wide range of instruments can be been used to measure temperature and salinity.

At the end of a beam trawl fishing haul, a vertical cast with CTD should be made for temperature, salinity and turbidity.

3.6 DATA REPORTING AND EXCHANGE FORMATS

Similarly to demersal trawl surveys, BTS outcomes should satisfy different data requirements within the GFCM:

– Useful information in compliance with existing GFCM recommendations should be reported to the GFCM by its CPCs.

– Information supporting stock assessment should be reported to the WGSAs through stock assessment forms.

– Other relevant information for regional analysis should be examined in dedicated expert groups.

Standard formats are defined for the storage and exchange of data produced by a BTS. Once collected, the basic information on fishing hauls, catch and biological data should be reported using the templates[6] shown in Annex 11 (see also Section 1.6)

4. ECOSYSTEM DATA

4.1 MACROBENTHOS

Fishing is the most widespread human activity exploiting the marine environment and has a direct impact not only on target species, but also on the entire marine community, including benthic organisms (plate 10) (GFCM, 2018b; FAO 2019a, 2019b). The importance of benthic habitats to ecological processes and as providers of key ecosystem services is unquestionable. In particular, macrobenthos or megabenthos (> 2cm), generally defined as a group of marine invertebrate organisms that live in (infauna) or on (epifauna) the sediment, due to their direct dependency on the sediment, become a valuable part of the ecosystem and are frequently used as bioindicators in ecological assessment (Pinto et al., 2009).

Species distribution, abundance and diversity of benthic macroinvertebrate fauna as well as their relationship to environmental conditions are important in understanding the structure and functions of diverse ecosystems. Macrobenthos form the key element of the food web and serve as primary food source for fish and other higher organisms, also playing a major role in the maintenance, well-being and dynamics of the ecosystem.

Therefore, the collection of data through scientific surveys, such as surveys on the presence and abundance of different macrobenthic species, can provide a unique opportunity to increase knowledge of benthic assemblages and to produce basic information on their distribution within the Mediterranean and Black Sea region.

For the purpose of these guidelines, macrobenthos are considered as all organisms visible to the eye without the aid of a microscope and pertaining to major taxonomic phylum: Porifera (e.g. sponges), Cnidaria (e.g. corals), Briozoa, Echinodermata (e.g. sea stars, sea urchins, sea cucumbers), Crustacea, Mollusca (e.g. bivalves and gastropods), Annelida (e.g. polychaetes), Tunicata (e.g. ascidians) and others.

Ideally, macrobenthic individuals should be identified to the minimum taxonomic level, and species is obviously the basic taxonomic level to which to refer. However, since many species pertaining to the macrobenthos groups are difficult to identify (e.g. due a scarcity of taxonomic expertise on board), aggregation of species to higher taxonomic levels (e.g. family or genus) and/or their assignment to morphological groups according to their growth form (e.g. massive, tubular, globular, arborescent, stalked, fan-shaped, lollipop-shaped, cup-shaped, among others – see FAO, 2017a; 2017b) may at times be unavoidable.

In some cases, for correct identification of the species, biological samples should be collected and brought to the laboratory and/or photographic documentation should be made. Coupled with photographic documentation, it is also highly recommended to report on the colour, consistency (e.g. hard, soft, and cartilaginous) and form of benthic species. A minimum set of parameters, such as the total number of individuals caught per fishing haul and total weight (see Annex 16), should be always reported.

Furthermore, owing to the difficulty of collecting information for all macrobenthic species, attention should focus mainly on vulnerable benthic species that may form VMEs as defined by FAO (FAO, 2009; FAO, 2017a, 2017b; GFCM, 2018b, and 2019a). VMEs are characterized by slow resistance and resilience from environmental short-term or chronic disturbance. They are easily disturbed and very slow to recover, or may never recover from such disturbance. VMEs are therefore highly susceptible to the impact of bottom fishing gear (i.e. significant adverse impact of fisheries) (FAO, 2009). Among VME indicator taxa, corals (phylum Cnidaria) and sponges (phylum Porifera) are known to be the main habitat-forming structures, often with numerous species living within or around their body structures.

The GFCM defined a series of VME indicators such as features, habitats and taxa for the Mediterranean Sea (Box 4), which, whenever possible, should be recorded and reported in Annex 16.

It is important to underline that the presence of individuals of vulnerable benthic species does not necessarily imply the occurrence of a VME, but specific communities, habitats and seabottom features may display characteristics consistent with the possible occurrence of VMEs.

Once collected, all data on macrobenthic species could serve to produce basic information for different ecosystems in terms of species richness (i.e. number of species), abundance (the counts of individuals for every species) and biomass (i.e. weight).

4.2 VULNERABLE SPECIES

The incidental capture or bycatch of vulnerable and protected species (e.g. marine mammals, seabirds, sea turtles, sharks and rays, see Annex 13) has become an increasingly important aspect of fisheries management (FAO, 2019b). Limited or non-existent information from Mediterranean and Black Sea countries regarding bycatch rates for vulnerable species makes it impossible now to assess the likely conservation threat posed by total bycatch levels (FAO, 2016; 2018; GFCM, 2018a; FAO, 2019b). Moreover, the limited data available do not necessarily allow for accurate and realistic assessments of populations and of the impacts of incidental catch on them. More data collection and analyses will be required before it will be possible to produce robust total bycatch estimates for vulnerable species.

Therefore, when carrying out scientific surveys, it is important to collect a minimum set of data (e.g. number of individuals for each vulnerable species; Box 5) that could represent additional/alternative sources of information to provide guidance for any possible revision of incidental catches monitoring programmes. Data should be reported by GSA and by species group and/or family if the detailed information by species is not available (e.g. when an individual could not be identified at the species or genus level, as in the case of recording seabirds, which include a large number of possible species). It is also important to report the total number of individuals caught and whether they have been released alive, dead or in unknown status. When an individual is caught alive, the main goal is to facilitate a prompt release of the specimen through an appropriate handling (FAO and ACCOBAMS, 2018a, 2018b, 2018c, 2018d).

All the available information on vulnerable species should be collected and reported using the template[7] in Annex 14.

4.3 MARINE LITTER

Litter in the marine environment (Plate 11) not only has negative environmental effects, but can also have negative economic and social impacts on fisheries (UNEP/MAP, 2015). So far, data on marine litter have been inconsistent and geographically restricted to some areas in the Mediterranean and the Black Sea, which explains why the understanding of these impacts is still limited. A standardized data collection protocol of marine litter data started within the framework of the MEDITS scientific survey (Fiorentino et al., 2013), allowing to produce over the years a first mapping of marine litter on trawling fishing grounds (Spedicato et al., 2019). Standardized research data for statistical purposes are still needed regarding the problem of litter in the whole region, and also in this case, bottom trawl and beam trawl surveys could be an important source of information on occurrence of litter on the sea bottoms.

During each survey it would be important to give a rough estimation of the quantity (weight) and quality (type) of any macro-litter material brought up by fishing operations (e.g. plastics, wood, metals, glass, rubber, clothing, fishing gear, petrochemicals). An indicative list of relevant data to be provided is reported in Annex 15. Registration of number and weight of items by categories and by subcategory is highly recommendable.

4.4 NON-INDIGENOUS SPECIES

In recent decades, non-indigenous species (i.e. any species introduced, either intentionally or unintentionally, outside its natural past or present distribution, also known as exotic or alien species) have been frequently caught by commercial fishing gear in different areas, accounting for a large share of the catch in some cases. In light of this rapid increase, there is a need to collect information in order to measure their impacts on fisheries and ecosystems. Scientific surveys could therefore offer an opportunity to collect important and standardized data regarding not only the distribution of nonindigenous species as well as their quantitative and qualitative impacts, but also some biological information (e.g. length, weight, sex and maturity). All of this information, once collected, could contribute to an effective management strategy. When performing any kind of scientific survey, it is strongly encouraged to collect and report biological data on non-indigenous species, using the standard templates already provided (Annexes 5, 6 and 7).

5. DATA POLICY

Data from national scientific surveys should remain the property of the country executing the survey, and data and information transmitted by countries should be treated by the GFCM Secretariat in accordance with all necessary measures to comply with GFCM security and confidentiality provisions. People carrying out the work on board should not disclose any information without the permission of the flag country.

Each country will be responsible for the quality and completeness of the data. Collected data should be submitted by countries every year following the DCRF provisions (GFCM, 2018a) and requirements.

Data put at the disposal of dedicated expert groups will be treated in the same manner as data used by different WGSAs: all participants should have access to the data needed to address the objectives of the meeting.

Through its Secretariat, the GFCM will define and maintain high levels of protection for the data transmitted by countries complying with GFCM data submission requirements, as endorsed by the Commission. The use of shared data outside the framework of the GFCM or for purposes other than the agreed objectives should follow the existing GFCM data confidentiality rules.

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ANNEXES

ANNEX 1. GFCM SUBREGIONS AND GEOGRAPHICAL SUBAREAS (GSAS)

ANNEX 2. LIST OF PRIORITY SPECIES BY SUBREGION*

Annex 2.1. Group 1: species that drive the fishery and for which assessment is regularly carried out

Annex 2.2. Group 2: species that are important in terms of landings and/or economic value at the regional and subregional levels and for which assessment is not regularly carried out

Annex 2.3. Group 3: species under international/national management plans and recovery and/or conservation action plans; non-indigenous species with greatest potential impact

ANNEX 3. FISHING HAUL INFORMATION

Annex 3.1. Data entry sheet: main characteristics of each fishing haul

Annex 3.2. Data entry sheet: oceanographic characteristics (when available) by single fishing haul

ANNEX 4. CATCH COMPOSITION BY FISHING HAUL

ANNEX 5. LENGTH DATA BY FISHING HAUL

Annex 5.1. Data entry sheet: length data for fish, cephalopods and elasmobranchs

Annex 5.2. Data entry sheet: length data for crustaceans

ANNEX 6. INDIVIDUAL WEIGHT BY SPECIES

Annex 6.1. Data entry sheet: individual weight by species

Annex 6.2. Data entry sheet: weight by length class

ANNEX 7. SEX AND MATURITY DATA

Annex 7.1. Data entry sheet: sex and maturity data for fish

Annex 7.2. Data entry sheet: sex and maturity data for crustaceans

Annex 7.3. Data entry sheet: sex and maturity data for cephalopods

Annex 7.4. Data entry sheet: sex and maturity data for elasmobranchs

ANNEX 8. MATURITY SCALES

Annex 8.1. Maturity scale for bony fish

Annex 8.2. Maturity scale for cephalopods

Annex 8.3. Maturity scale for crustaceans

Annex 8.4. Maturity scale for oviparous elasmobranchs

Annex 8.5. Maturity scale for viviparous elasmobranchs

Annex 8.6. Maturity scale for stomatopods

ANNEX 9. SIX-PHASE MATURITY STAGES FOR ANCHOVIES AND SARDINES CAUGHT IN PELAGIC SURVEYS

ANNEX 10. MATURITY SCALE CONVERSION TABLE FOR ANCHOVY (ENGRAULIS ENCRASICOLUS) AND SARDINE (SARDINA PILCHARDUS)

ANNEX 11. REPORTING TEMPLATES FOR BOTTOM AND BEAM TRAWL DEMERSAL SURVEYS

Annex 11.1. Demersal surveys: fishing haul data (TA file)

Annex 11.2. Demersal surveys: catch data (TB file)

Annex 11.3. Demersal surveys: biological data (TC file)

Annex 11.4. Demersal surveys: individual biological data (TE file)

Annex 11.5. Demersal surveys: data on marine litter (TL file)

ANNEX 12. REPORTING TEMPLATES FOR PELAGIC ACOUSTIC SURVEYS

Annex 12.1. Pelagic acoustic surveys: length data

Annex 12.2. Pelagic acoustic surveys: age data

ANNEX 13. LIST OF VULNERABLE SPECIES

Annex 13.1. Vulnerable species included in Annex II and Annex III of the Barcelona Convention

List of vulnerable species included in Annex II (endangered or threatened species) and Annex III (species whose exploitation is regulated) of the Convention for the Protection of the Marine Environment and the Coastal Region of the Mediterranean (Barcelona Convention). The list also contains the amendments of Annexes II and III of the Convention’s Protocol Concerning Specially Protected Areas and Biological Diversity in the Mediterranean (2012/510/EU: Council Decision of 10 July 2012, establishing the position to be adopted on behalf of the European Union with regard to the amendments, adopted by the 17th Meeting of the Contracting Parties, Paris, France, 8–10 February 2012).

Annex 13.2 Rare elasmobranch species

This list reports elasmobranchs species that are included in the IUCN Red List of Threatened species (www.iucnredlist.org) or that are considered rare in the Mediterranean and the Black Sea (Bradai et al., 2012; IUCN, 2016). (https://www.iucn.org/sites/dev/files/content/documents/brochure_medredlist_sharks.pdf)

ANNEX 14. DATA ENTRY SHEET FOR VULNERABLE SPECIES

ANNEX 15. DATA ENTRY SHEET FOR MARINE MACRO-LITTER

ANNEX 16. DATA ENTRY SHEET FOR MACROBENTHOS

ANNEX 17. SCHEME OF THE RAPIDO TRAWL

1 All the templates are available for consultation and download in electronic format at: http://www.fao.org/gfcm/data/en/

2 Collected maturity data, only for the purpose of the DCRF (GFCM, 2018a), should be submitted and reported with reference to the maturity scales based on DCRF rules and requirements (Recommendation GFCM/41/2017/6).

3 All the templates are available for consultation and download in electronic format at: http://www.fao.org/gfcm/data/en/

4 Collected maturity data, only for the purpose of the DCRF (GFCM, 2018a), should be submitted and reported with reference to the maturity scales based on DCRF rules and requirements (Recommendation GFCM/41/2017/6) using the conversion table as in Annex 10.

5 Collected maturity data, only for the purpose of the DCRF (GFCM, 2018a), should be submitted and reported with reference to the maturity scales based on DCRF rules and requirements (Recommendation GFCM/41/2017/6).

6 All the templates are available for consultation and download in electronic format at: http://www.fao.org/gfcm/data/en/

7 All the templates are available for consultation and download in electronic format at: http://www.fao.org/gfcm/data/en/