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DocumentReproductive potential of yellowfin tuna (Thunnus albacares) in the western Indian Ocean 2013
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No results found.The reproductive biology of Yellowfin Tu (Thunnus albacares) in the western Indian Ocean was investigated from samples collected in 2009 and 2010. In our study, 1012 female Yellowfin Tu were sampled: 320 fish on board a purse seiner and 692 fish at a Seychelles cannery. We assessed the main biological parameters that describe reproductive potential: maturity, spawning seasolity, fish condition, and fecundity. The length at which 50% of the female Yellowfin Tu population matures (L50) was estimat ed at 75 cm in fork length (FL) when the maturity threshold was established at the cortical alveolar stage of oocyte development. To eble comparison with previous studies, L50 also was estimated with maturity set at the vitellogenic stage of oocyte development; this assessment resulted in a higher value of L50 at 102 cm FL. The main spawning season, during which asynchrony in reproductive timing among sizes was observed, was November–February and a second peak occurred in June. Smaller females ( <100 cm FL) had shorter spawning periods (December to February) than those (November to February and June) of large individuals, and signs of skipspawning periods were observed among small females. The Yellowfin Tu followed a “capital-income” breeder strategy during ovarian development, by mobilizing accumulated energy while using incoming energy from feeding. The mean batch fecundity for females 79–147 cm FL was estimated at 3.1 million oocytes, and the mean relative batch fecundity was 74.4 oo cytes per gram of god-free weight. Our results, obtained with techniques defined more precisely than techniques used in previous studies in this region, provide an improved understanding of the reproductive cycle of Yellowfin Tu in the western Indian Ocean. -
Book (series)Handbook on fish age determination: a Mediterranean experience 2019
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No results found.Fish age, among other biological parameters, is one of the most relevant pieces of data in reaching sustainable exploitation of fishery resources. Indeed, most analytical methods used in stock assessment require knowledge of demographic structure according to the age of stocks, as well as to recruitment, growth, maturity, natural mortality, etc., which are strictly linked to information on age and age structure. The literature on ageing analysis shows some gaps regarding ageing schemes, criteria and methodologies used in preparing calcified structures. These aspects affect both the precision and accuracy of age estimation. One action that could be taken to overcome this gap was to formalize a handbook that clarified approaches to ageing schemes, criteria and preparation methods. Having a common protocol is fundamental to decreasing relative/absolute bias associated with the activities of age determination and to improving the precision (reproducibility and reduction of the coefficient of variation) of age readers from the various laboratories. In the light of these considerations, this handbook aims to be a guideline to standardizing the methods used in fish ageing studies. The document is focused on a description of the general principles on which age analysis relies (assignment of birth date, preparation methods, aging scheme reading and identification of true and false rings). Moreover, common shared analysis methods can enable a high level of calibration among the diverse institutes involved, thus improving the quality and reliability of results. The volume is subdivided into five main sections: Small Pelagic Species, Demersal Species, Cartilaginous Species, Large Pelagic Species and the European Eel. For each section, information on extraction and storage, preparation method, interpretation of age (age scheme) and ageing criteria are provided by species. In total, 30 species were analysed: 6 small pelagic, 12 demersal, 5 cartilaginous, 6 large pelagic and the European eel. These species represent some of the most important fish from an economic and ecological point of view. Thus this volume represents one of the most complete outlooks for fish ageing analysis in the Mediterranean context. -
Book (stand-alone)Assessment of IUU activities on Lake Victoria 2012
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No results found.Fishing all over the world is a major source of food for humanity and a provider of employment and economic benefits to those engaged in the activity. However, with increased knowledge and the dynamic development of fisheries, it should be known that world living aquatic resources, although renewable, are not infinite and need proper management, if their continued contribution to the nutritional, economic and social well-being of the growing world’s population is to be sustained. Lake Victoria i s Africa’s largest and most important inland water body with a total water surface area of 68,800km2. Lake Victoria contributes significantly through its fishery and generation of electricity to the economic benefits of not only the riparian states, Kenya, Tanzania and Uganda, but also to the neighboring countries and the world at large. Lake Victoria is arguably the most important single source of freshwater fish on the African continent, contributing significantly to national and regional econ omies and livelihoods of the regions inhabitants. Although not often associated with inland fisheries, Illegal, Unreported and Unregulated (IUU) fishing and the trade of illegal fish has threatened the biological, social, financial and cultural integrity of the lakes resources and those that depend on them. Given that Lake Victoria’s living resources are shared amongst the three riparian states, a regional fisheries body, the Lake Victoria Fisheries Organization (LVFO) was formed in 1994 though the technical assistance of the FAO to manage the fisheries resources in Lake Victoria as a single ecological entity. Within the LVFO mandate, the identified areas of IUU fishing are considered in the form of: Illegal or misuse of fishing gears; illegal fishing, fish landing, processing and trading; unregulated fishing number of boats, fishers and gears (capacity); unregulated, unreported or undocumented domestic and regional fish trade; fishing and landing undersize fish in undesignated landing sites; and fishing during closed seasons or in the closed breeding areas or critical habitats. The decline of Nile perch stocks suggest that fisheries management and compliance structures within the three riparian states and at LVFO at the moment are at various levels of disarray, hence allowing IUU fishing to continue thriving unabated. Since the introduction of Nile perch into Lake Victoria in the 1950’s it has been the focus of an intensifying commercial fishery. In 1980, a total of 4 439 to ns of Nile perch were harvested, a decade later over 338 115 tons of Nile perch were landed annually. From 2000 to 2010, and average of 253 404 tons of Nile perch are caught. Despite relatively consistent landings reported by the LVFO, total biomass of Nile perch decreased from 1.4 million tons (92% of total biomass in Lake Victoria) in 1999 to it lowest recorded estimate of 298 394 tons in 2008 (14.9% of total biomass in Lake Victoria). Currently, as of 2010, the Nile perch biomass was estimate d at 18% of total biomass in Lake Victoria, which equates to 367 800 tons. Although a slight increase in biomass between 2008 and 2010 was observed, Nile perch biological indicators suggest that the fish is in a critical survival state. The average size of Nile perch has decreased from 51.7 cm TL to 26.6 cm TL, according to hydro acoustic surveys suggesting that a significant portion of total Nile perch biomass is less than 50 cm TL (legal size for export). It was reported by the LVFO stock asse ssment team that in 2006 and 2008, less than 2% of the Nile perch biomass was in fact greater than 50 cm TL. The size at first maturity of male and female Nile perch is also decreasing, this common amongst fish populations that are stressed (or overexploited). Despite the biological indicators, which suggest legal size Nile perch are less than 2% of total Nile perch biomass, the average number of fishermen increased by 33% between 2000 and 2008. During the same period, Frame survey and MCS compl iance missions noted a marked increase in the number of illegal gears being deployed to target undersize Nile perch. The number of vessels increased by 37% and the use of outboard engines increased by approximately 50%. It has been reported that motorized boats are more efficient, catching about 25 kg of fish per day, compared to 10 kg caught by non-motorized vessels. The increase in use of illegal gears, motorized vessels and fishermen suggests that fishing for Nile perch is still profitable. P reviously driven by lucrative export prices for Nile perch, fishers now target undersize illegal Nile perch for the lucrative domestic and regional trade, which is estimated to exceed the export trade by volume and value. This shift in fishing for undersize Nile perch will effect government revenues earned from the export fishery. The Nile perch fishery over the last decade contributed 0.6% less to the Tanzanian GDP, similarly, a decrease in export trade of Nile perch from Uganda of 14% occurred between 2007 and 2008, resulting in a 0.1% decrease in GDP contribution. By not controlling fishing effort targeting illegal, undersized and immature Nile perch, economic and social hardships will worsen. Current fisheries management both regionally through the LVFO, and nationally amongst the riparian states is inadequate, with respect to Monitoring, Control and Surveillance (MCS). MCS is a collection of activities and tools intended to support fisheries management in fighting IUU fishing, and forms the framework on which accurate, informative and dynamic fisheries management decisions can be made. MCS is critical at all levels of fisheries management. Within the Lake Victoria region, co-management has been implemented through the establishment of Beach Management Units (BMU’s). A BMU is a community-based organization, which is legally accepted as a representative of a fishing community and is mandated on a voluntary basis to engage in MCS initiatives. Lake Victoria has 1 087 registe red BMU’s according to the harmonized BMU guidelines, agreed upon amongst the member states and the LFVO. Although the inclusion of community based management and MCS is critical in contributing to effective management of Lake Victoria’s fisheries resources, many challenges exist, including amongst others; geographical isolation of fishing communities, social issues (families of BMU members may partake in illicit activities), political interference (revenue collections, or election voting), corr uption, conflict of interests (BMU members are often fishmongers and fish traders) and lack of representation in higher management committees. Although advances in MCS technology have revolutionized fisheries management amongst many ESA-IO countries, the sharing of regional resources and capacity is fragmented and not effectively harnessed by the LVFO. Database management systems are not working effectively, data collecting, analyzing and dissemination are unreliable and time inefficient, respec tively and appropriate MCS tools for example net gauges are not available. The RWG-MCS reported that between 2004 and the end of 2008, a total of 4 605 suspects were apprehended, 12 126 beach seines, 9 550 small seine nets, 27 703 monofilament nets, 248 843 kilograms of immature Nile perch (249 tons) and 254 589 illegal gillnets were confiscated. These data are unreliable; furthermore they were not quantified in terms of definition of the item (how long were the nets that were confiscated 80 met er, or one kilometer, this has a profound effect on CPUE), of financial loss to fishers and traders versus the opportunity costs of MCS. The valve of court fines are insignificant especially if one considers the amount of uncontrolled fishing effort, uncontrolled illegal gears used in Lake Victoria, and the increasing value in the trade of immature fish on domestic markets. Also, there is no indication as to whether the court penalties and fines imposed on the same offences in the three partner states have any reference to the same severity across the region, or are recycled back into MCS initiatives. It is therefore difficult to determine whether the RWG-MCS interventions from 2004 to the end of 2008 were beneficial, as little to no comparative data exists. The LVFO depends highly on donor funds to support MCS and management initiatives, including training, capacity building and technical expertise. When donor funds are not available, regional MCS stagnates, which is a major concern. Operation Save the Nile perch is one such example. The EAC Council of Ministers in 2009 launched the ‘Operation Save the Nile Perch’ (OSNP), which required each of the three member states to contribute US$ 600 000. The goal of the initiative was to target illegal fishing and to curb the trade in undersize Nile perch currently threatening the economic integrity of Lake Victoria. The target of OSNP, as ratified by the Council of Ministers was to have fisheries illegalities in the lake, based on th e 2008 frame survey data as bench mark, reduced by 50% in June and 100% by December 2009. Currently as of 2011, Kenya has paid the required funds, with Tanzania only contributing 31% and Uganda zero resulting in less than half of the required funds paid in by from the member states. This undermines the legitimacy of ‘Operation Save the Nile Perch’ and political will and MCS operational capacity. The aim of this report was to assess the state of IUU in Lake Victoria, and to support the SMARTFISH programme in assisting the LVFO and established MCS committees to implement joint regional MCS trainings, by conducting a short cost benefit analysis of enhancing existing regional MCS initiatives and by evaluating past and present regional action plans to deter IUU fishing on Lake Victoria. An action plan was developed through a participatory workshop between the LVFO, national states and the MCS-RWG, held in Jinja, Uganda from the 5th to the 7th of October 2011.
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