Assessment of the eel stock in Sweden, spring 2012

• Main Author: Dekker, Willem
• Format: Report
• Language: Swedish; English
• Published: 2012
• Subjects: Fish and Aquacultural Science; Anguilla anguilla
• Online Access: https://pub.epsilon.slu.se/10290/; https://pub.epsilon.slu.se/10290/7/dekker_w_130424.pdf

The population of the European eel Anguilla anguilla (L.) is in severe decline. In 2007, the European Union decided on a Regulation establishing measures for the recovery of the stock of European eel, obliging its Member States to implement a national Eel Management Plan by 2009. According to this Regulation, Member States will report to the Commission by July 2012, on the implementation of their Eel Management Plans and the progress achieved in protection and restoration. The current report provides an assessment of the eel stock in Sweden as of spring 2012, intending to feed into the coming Swedish post-evaluation reporting. In this report, the impacts on the stock are assessed - of fishing, restocking and of the mortality related to hydropower generation. Other anthropogenic actions, (climate change, pollution, spread of parasites, disruption of migration by transport, etc) probably have an impact on the stock too, but these factors are hardly quantified and no management targets have been set. For that reason, and because these factors were not included in the EU Eel Regulation, these other factors were excluded from this technical evaluation. In this report, focus is on the quantification of the biomass of silver eel escaping (actual, potential and pristine) and the mortality endured by those eels during their lifetime. The assessment is broken down on a regional basis, with different impacts dominating in different areas. For the yellow eel fishery on the West Coast, the assessment presented in the Eel Management Plan is extrapolated to most recent years. Since 2009, the fishery has been restricted severely, and as of spring 2012, it has been closed. In the coming years, this reduction in fishing mortality will lead to a recovery of the West Coast stock to the best possible status given the depleted state of the whole international stock. For the stock in inland waters, a new assessment is presented, in which the dominant contribution from past restocking is put central. Recent changes (increased quantities, shift to west-ward flowing rivers) will have a delayed effect over the coming 10-20 years. The escapement biomass is expected to decrease until 2020 and then to restore to its current (low) value. Assuming that current conditions (2011) are continued, the impact of the fishery will slowly decline, while the impact of hydropower generation will stabilise/increase, at least until 2030. For the East Coast fishery on silver eel, a new assessment indicates a low mortality on a very large stock of silver eel derived from all over the Baltic. Recent restrictions have reduced the East Coast fishery. Protective actions in the whole Baltic (and their delayed effects) will determine the future trend in the East Coast fishery. Comparing the overall status of the national Swedish eel stock to the management targets, it is concluded that 1. Criteria of the Swedish Eel Management Plan have been fulfilled almost exactly; 2. Biomass escaping is about one-fourth of pristine escapement, below the minimum target of 40% set in the EU Regulation; and 3. The 2011 anthropogenic impacts are about half the allowable maximum (according to the ICES/WGEEL post-evaluation framework, at one-fourth of pristine escapement). Following the current closure of the West Coast fishery, the impacts will reduce to one-quarter of that allowable maximum.