3. PRESENT STATE OF DATA

3.1 Data of Regional Value
3.2 Major Gaps in Reported Data

3.1 Data of Regional Value

Basic data required for stock assessment purposes fall under four headings:

(a) Nominal catches (yearly summaries) made by various nationally identified fleets fishing the same stocks.

(b) Catch per unit effort - or better, fishing efforts and corresponding catches - year by year, for all homogeneous (in terms of fishing power) groups of vessels for which such data can be compiled.

(c) Length frequency distributions (yearly summaries) of catches landed by the main unit fleets.

(d) Other biological data such as those provided by surveys, growth (age) studies, selectivity, tagging experiments, etc.

Although these three kinds of statistics refer to distinct quantities (i.e., yield, fishing mortality and stock density), only two of them have to be recorded separately, as the third can be easily calculated from the first two. When cpue provides reliable indices of stock abundance (which can be derived from recording the activity of only parts of the fleets), total effort can be raised if total catch is known, or vice versa. In modern fisheries where fish is landed at only a few places, it is usually easier to record these landed quantities and, from these, through conversion factors, establish the liveweight equivalent (nominal catches). In fisheries of highly scattered nature, such as the canoe fisheries, total catches are often raised from records in samples of the whole fleet, the raising factors being based on censuses of the number and size of crafts, i.e., on estimates of total fishing power.

Furthermore, data to be collected should refer to individual stocks. Since it is not feasible, or necessary, to assess all the stocks of the CECAF region, the Working Party on Resources Evaluation selected 17 species and 5 groups of related species¹, taking into account their economic importance and their present or possible exploitation by more than one country. As for other species, information of an economic nature is essentially required at the present time, and national production figures can be collected by larger taxonomic groups. Furthermore, based on information available at present on identity and geographic distribution of stocks belonging to the same species, the Working Party made the assumption that there is a unit stock in each CECAF statistical division². (Their boundaries were drawn taking into account the major ecological units recognized for the region.)

¹ See list in Annex 1
² See nap in Annex 2

(a) by species (for those stocks which have to be assessed separately) and by wider taxonomic groups for the others;

(b) by CECAF statistical divisions;

(c) by main types of fishing (e.g., artisanal, purse seine, bottom trawl - those fishing for finfish and shrimpers separately - mid-water trawl, etc.) or by unit fisheries, since they do not exploit with the same intensity the various stocks and the various population strata in each stock.

(a) fishing power (fishing gear and methods, size and main characteristics of fishing boats) so that fishing effort can be properly quantified;

(b) mesh size used or selectivity corresponding to length frequency distributions collected by types of fishing.

3.2 Major Gaps in Reported Data

3.2.1 Nominal catches
3.2.2 Fishing effort and catch per unit effort
3.2.3 Biological data

Statistics stored by CECAF show typical shortcomings which can be related to particular difficulties not yet overcome by several national statistical systems.

3.2.1 Nominal catches

- By countries

According to the basic rule adopted for reporting country statistics to regional bodies, each country is responsible for collecting and reporting all nominal catches made in each fishing area (corresponding to a fishery body) by all vessels flying its flag. Most serious errors in production statistics by regions and countries result from departure from this rule.

Several countries fishing in the CECAF area fail to record the geographic location of their national catches or provide inadequate estimates. For example, in some countries the origin of catches is derived from the location of landing ports, an improper method when catches from more than one region are likely to be landed in the same places. This occurs in several Mediterranean countries - but by no means only there - so that variable quantities of CECAF catches are included with quantities reported for other fishing areas (Mediterranean, North Atlantic). Similar failures, causing in such case an overestimation of CECAF production figures, are encountered in catch statistics reported by coastal countries fishing also outside the CECAF area (at present only in the ICSEAF area). In the last case, the corresponding quantities are still relatively small but may increase in the future. The netting up of statistical systems for correctly recording the geographic location of catches by CECAF, ICSEAF and other statistical divisions - which is required for stock assessment purposes - will ipso facto eliminate this type of error.

With the development of fishing arrangements (chartered vessels, joint ventures, etc.) between countries or fishing companies from different countries, the risk of errors in national catch statistics increases. When vessels fishing under such agreements are operating for long periods far from their port of registry, home statistical services often cease to monitor their fishing activities, whereas landing countries tend to consider corresponding landings as national production rather than as imports, which they actually are. Transshipments, either at sea or in West African harbours, between fishing vessels of one nationality and factory or cargo ships flying other flags lead to the same errors when the flag of fishing vessels is not properly recorded. It may be difficult to achieve proper identification when, as observed in the CECAF area, vessels supplying a factory vessel are fishing under different flags¹.

¹ These issues have already been identified and discussed, for example, in:

Fisheries Circular No. 174 - The Statistical Treatment of Direct Foreign Landings

Fisheries Circular No. 269 - Notes on Problems in Fishery Statistics Related to Flag and Other Nationality Indicators of Fishing Craft

FAO Fisheries Report No. 3 - Requirements and Improvement of Fishery Statistics in the North Atlantic Region

In addition to such biases, inaccuracies are generated by incorrect statistical procedures used for estimating the quantities caught. In relation to their very scattered nature, proper monitoring of canoe fisheries raise specific difficulties from both the theoretical and practical standpoints. Up to now only a limited number of coastal countries have been able to design and implement statistical schemes leading to correct estimates of the amount and species composition of artisanal landings. Considering the relative importance of small-scale fisheries in some countries - where they can yield more than the modern vessels - it is clear that several national sampling systems applied to canoe fisheries must be rapidly improved.

As regards level of precision, requirements differ depending on the end use of the statistics. For preparing the Yearbook of Fishery Statistics, FAO has until now requested that national catches be submitted in hundred tons (reported on STATLANT NS and 34A forms), whereas for stock assessment purposes (i.e., for species for which separate assessments are justified) catches have to be expressed in tons. It should however be noted that FAO has decided to initiate in 1975 the collection of national productions, in tons for the years of 1974 and onward, and in hundred tons for previous years. As a result, all catch statistics should be reported in the future with a precision suitable to stock assessment requirements. However, a substantial number of historical catch figures stored in the CECAF files are expressed in hundred tons and are of little value for stock assessment.

- By species and species groups

A first list of species and species groups to be used by national statistical offices for centrally reporting their nominal landings caught in the CECAF area was prepared at the initiation of CECAF activities. This list is given in document FAO Fish.Circ. No. 461 and is printed on the STATLANT 34B form (Annex 3). It includes:

(a) a limited number of species and groups of related species for which separate statistics are expected to be gathered for stock assessment purposes;

(b) larger taxonomic groups as required for regional economic analysis.

As a whole, several countries are able to report their catches properly allocated according to the large categories (b) above. A study on the availability of these kinds of statistics was presented at the Fourth Session of CECAF in a document entitled “Eastern Central Atlantic (Area 34 - CECAF) - Availability of Catch Statistics” (Ref. CECAF/74/Inf. 6), However, only very few countries regularly report their annual catches according to the more refined list of species to be assessed. This is partly due to the fact that this new list has not yet been incorporated in STATLANT ITS, 34A and 34B forms as well as in the corresponding notes for completion sent annually by FAO to all countries fishing in the CECAF region.

In addition, CECAF files show that allocation of catches by species or taxonomic groups is particularly deficient for catches which are not, or inadequately, sorted by the industry before marketing. Such is particularly the case for:

(a) industrial catches for reduction purposes;
(b) artisanal landings;
(c) morphologically very similar species (hakes, horse mackerels, octopuses, squids, cuttlefishes).

- By CECAF statistical divisions

Although some countries have substantially improved their reporting in recent years, only a few of them are as yet able to properly allocate their catches by statistical divisions. For coastal countries fishing only off their own shores, no difficulty arises. This is not the case for countries which operate long-distance fleets, i.e., for all non-coastal countries and for a few riparian ones. Clearly assessments of CECAF stocks depend on progress made in recording the actual location of fishing (e.g., through the use of logbooks).

- By fishing methods of unit fisheries

This kind of information is centrally compiled by CECAF on STATLANT 34B forms, each country being requested to fill a separate form for each type of fishing. A review of forms stored in CECAF files revealed that actually only very few countries are able to meet the standard of the regional system in this respect.

The breaking down of catch resulting from midwater and bottom trawl operations is particularly unreliable or non-existent when these two gears are used by the same vessels during the same trips. In this respect, better statistics will be generated by strengthening specific sampling programmes.

3.2.2 Fishing effort and catch per unit effort

For a substantial number of countries no statistics of that kind are available or are only supplied occasionally in inadequate form. Some countries do not yet have the staff and means necessary for designing and implementing systems for proper monitoring of fishing effort. Because of their very scattered nature, canoe fisheries raise particular difficulties in this respect. Still, once a proper sampling scheme has been initiated, estimating fishing effort should raise no major difficulty to the extent that estimates of total landings, usually the prime goal, often require surveys of harvesting means (e.g., number of canoes) and monitoring of their activity in particular samples (e.g., number of trips). However, such information on fishing effort should be properly recorded and processed and riot, as has been observed, discarded once they have been used for estimating the total catches.

In many countries, substantial improvements can be achieved in statistical programmes without requiring comparable increases in staffing and financing. Often central statistical services and national fishery agencies - to whom FAO officially sends requests for statistics-are primarily concerned with compiling figures on yield and harvesting means, whereas statistics on fishing effort (in the stock assessment sense) are usually gathered by research laboratories. Inadequate collaboration between both types of institutions, as well as failures of national laboratories to bring their individual programmes for monitoring performances of various national fleets into line with one another, often cause gaps to be left in national data on fishing effort. During their visits, the consultants also noted that in certain countries substantial amounts of raw material are regularly recorded by fishing companies but such information remains largely unused.

Vessels operating for long periods far from home ports often escape the attention of home statistical networks. As they are usually powerful vessels, the need to improve their monitoring is of prime importance.

3.2.3 Biological data

The need to centralize national data applies first of all to length frequency distribution of fishes from samples of commercial landings. Data of this kind available to CECAF are even more fragmentary than effort statistics. This is partly because CECAF initiated compilation of length data later. However, most of the shortcomings noted in national programmes as regards fishing effort are also affecting biological sampling programmes.

Some coastal countries lack the necessary means for collecting such data. Fortunately, several of them for whom fishery represents an important sector of their economy, have succeeded in implementing programmes covering landings of their main fisheries. Still, as a whole, canoe and trawler landings are less properly sampled than those of purse seiners.

Partly in connexion with difficulties in implementing adequate programmes for sampling landings and monitoring the activity of long-distance fleets, several non-coastal countries are placing emphasis on research cruises (e.g., surveys). However, this type of investigation cannot provide all the necessary information, e.g., on the quantities and species composition of catches, which is normally derived from monitoring the activity of fishing fleets and sampling their catches. Moreover, exploratory surveys are not always conducted with the desired regularity nor with comparable standards so their outcome only imperfectly reflects changes occurring in abundance and composition of stocks.

Some countries fail to report their length composition data in accordance with the standard recommended by CECAF to facilitate their subsequent working out and pooling. Many length frequency distributions are sent without indication of the sample weights, which makes estimation of overall length composition of stocks difficult.

In some countries, both coastal and non-coastal, biological data are not easily released before having been interpreted and published by the collecting laboratories; however, their rapid distribution will be of prime interest to individual scientists who need a series of data as complete as possible for assessing the stocks they are concerned with. In this connexion, it should be noted that with the computer programmes used by the FAO Fishery Data Centre it is possible to not print out any data that it is deemed desirable to keep temporarily confidential.