Рыболовство во внутренних водоемах

Report of the 2011 session of the Joint EIFAAC/ICES Working Group on Eels. Lisbon, Portugal, from 5 to 9 September 2011. EIFAAC Occasional Paper. No. 48.

Managing inland fisheries

Indications are that the eel stock remains at an historical minimum, continues to decline and is outside safe biological limits. Recruitment of both glass eel and young yellow eel continues to decline and shows no sign of recovery. Current levels of anthropogenic mortality, thought to be high on juvenile (glass eel) and older eel (yellow and silver eel), are not sustainable and there is an urgent need to reduce these until there is clear evidence that the stock is increasing. The effect of implemented management actions under the European Union (EU) Regulation initiated in 2009 have not yet led to any discernible changes in recruitment. It is likely that such changes will not be statistically detectable for some years, or even up to a decade or more. The loss of recruitment-series will weaken the power to detect any changes in the overall recruitment pattern or trend. Fisheries on all life stages are found throughout the distribution area. Impacts vary from almost nil to heavy overexploitation. With the implementation of the management plans and the decline in the stock, a progressive restriction or collapse of local small-scale fisheries is foreseen. This change will come to the detriment of culture and heritage (e.g. fishing techniques, skills, gastronomy). There is also an increased risk of illegal fishing. Landings data continues to be unreliable and reporting under the Regulation and Data Collection Framework (DCF) is incomplete. Reported landings data in the Country Reports to WGEEL showed a great heterogeneity. Because landings data were incomplete, with some years missing for some of the countries, missing values were estimated and this shows that landings continue to decline. Scientific reference points have not been previously set for eel. The EU Regulation sets a long-term escapement objective for the biomass of silver eel escaping from each management area at 40% of the pristine biomass (B0) or Blim. However, no explicit limit on anthropogenic impacts Alim was specified, even though current biomass is (far) below B0 and Blim. The biomass reference point of Blim = 40% of B0 corresponds to a lifetime mortality limit of ΣAlim = 0.92, unless strong density-dependence applies. As an initial option, it is recommended to set BMSY-trigger (value which should trigger a mortality reduction) at Blim, and to reduce the mortality target below BMSY-trigger correspondingly. Allowing for natural variation in B0 and for uncertainty in the estimates of status indicators and reference points, the resulting reference points (Blim, BMSY-trigger and Alim) should be considered as somewhat optimistic or unsafe. Noting the relationship between biomass stock reference points Bcurrent, BMSY-trigger and mortality reference point ΣAlim, the actual value for ΣAlim below BMSY-trigger must be determined on a country (or Eel Management Unit) basis. A framework is presented in the report for calculating lifetime anthropogenic mortality (ΣA) at the catchment level. As there are several different types of anthropogenic mortality (e.g. fishing, turbines and pumps, pollution, barriers and obstacles), this total mortality is expressed as the sum of those for all types, ΣA. Where direct estimates are not currently available, mortality information is collated in this report which may be used as alternatives in the interim. With the need for statistical and scientific assessments of the reported management actions in 2012 and subsequent years and post-evaluation of the eel stock at the international level, WGEEL recommends that a (series of) planning workshop(s) be held to provide support and coordination for data collection, analysis and reporting. This should include updating the data reporting requirements for eel in the DCF, to include improved fisheries dependent sampling and fisheries independent surveys. The European Eel Quality Database (EEQD) integrates data on contaminants, diseases and parasites, and fat content and this was updated with 2011 records. There is a need for data standardization across Europe and for the development of sensitivity thresholds in order to assess the impact of different contaminants/infections on the ability of the eel to migrate and breed successfully. The levels of some hazardous substances are so high is some cases that an effect on reproduction is likely to occur, but scientific evidence (dose/response studies) is still not available. Some direct fish kills due to pollution have been observed but the effect on the overall stock is not known. Anguillicoloides crassus continues to spread (e.g. in Scotland and Ireland) and is now quasi-omnipresent over Europe. Fisheries for eel (and other species) have been closed in the south of Belgium in 2006 and in many important rivers of France and the Netherlands in 2010 and 2011, because pollution levels are so high as to be a risk to the health of consumers. The eels protected by these measures are in general of lower quality and hence their contribution to the restoration of the stock might be limited. Declared glass eel total catch from fisheries in 2011 was approximately equal to the current requirements for stocking listed in eel management plans submitted under the EU Regulation. The best estimate is that glass eel fisheries in 2011 distributed 12% of their total catch to restocking, 30% to Aquaculture and the fate of the remainder is unknown. There are insufficient traceability systems in place to improve this analysis making it difficult to provide accurate advice on the fate of glass eel. Giving priority to the recovery of the European stock, the objective of any stocking exercise should be to maximize net benefit to the stock as a whole until clear signs of recovery. However, stocking with an element of fishery support, combined with maintaining some spawner escapement, is not excluded in the EU Regulation. Given the current assessment of the overall stock, stocking, where it occurs, should be in conjunction with reductions in fisheries (yellow and silver) mortality and other direct mortalities (e.g. turbine, pumping stations) affecting the stocked eels. Stocking should not be seen as a substitute for reducing mortality, but as an additional measure. There is an obligation that up to 60% of the catch of eel less than 12 cm is used for stocking. WGEEL makes the management recommendation that this 60% should be stocked in areas where anthropogenic mortality is minimal and environmental quality is high. Those wishing to stock to support fisheries, or to mitigate against other anthropogenic mortalities, should draw on stock from the remaining 40% allocated by management to other uses. The burden of proof that stocking will generate net benefit in terms of spawner escapement rests with those taking the stocking action. Prior to, or for continuing existing, stocking, a risk assessment and net benefit analysis should be conducted. The MSFD requires the development of a marine strategy, specific to its own waters, that reflects the overall perspective of the marine region or subregion concerned. The definition of criteria and the selection of indicators to assess GES is an important step in this directive. As the eel is a diadromous species with a wide distribution and unusual life cycle some caution has to be taken when selecting the life stage (glass eel, yellow or silver eel) to assess the environmental status of marine regions. The descriptors selected relevant to eel by the WG included: D1-Biological Diversity is maintained; D3-Populations of all commercially exploited fish and shellfish are within safe biological limits; D9-Contaminants in fish and other seafood for human consumption do not exceed levels established; and D11- Introduction of energy, including underwater noise, is at levels that do not adversely affect the marine environment.