Original publication: February 2019
Thünen Institute of Fisheries Ecology: Reinhold HANEL, Lasse MAROHN, Klaus WYSUJACK, Marko FREESE, Jan-Dag POHLMANN, Nicholas WAIDMANN
Thünen Institute of Sea Fisheries: Ralf DÖRING
Profundo: Ward WARMERDAM, Melina van SCHARRENBURG, Jeroen WALSTRA, Mara WERKMAN, Joeri de WILDE, Anya MARCELIS
EPTB Vilaine: Cédric BRIAND
AZTI-Tecnalia: Estibaliz DIAZ, Margarita ANDRÉS,
Fisheries Research Institute of the Hellenic Agricultural Organization: Argyrios SAPOUNIDIS
Design of cover artwork: Pieter Frank de Jong
Short link to this post: http://bit.ly/2TNbZlg
Within the last 50 years the European eel (Anguilla anguilla) has turned from one of the largest freshwater fishery resources in many areas of Europe and northern Africa to an endangered species. While the reasons for this tremendous decline of the eel population are still not fully understood, three anthropogenic causes of mortality are thought to have a significant impact at least in specific habitats. Together with the unpredictable risks caused by water and sediment pollution, intensive fisheries on all continental life stages as well as habitat fragmentation and destruction play a major role.
The European eel has a complex life cycle, which is characterised by distant oceanic and freshwater migrations between its spawning area in the Sargasso Sea and the coastal and freshwater feeding habitats. The different phases in the life cycle are related to several metamorphoses and distinct life stages: After their oceanic journey as leptocephalus larvae they reach the continental shelf areas and metamorphose to glass eels, which aggregate in river estuaries before colonising freshwater and coastal habitats for their growth and feeding yellow eel life stage. Yellow eels spend 4 to more than 20 years in fresh and coastal waters before they metamorphose again to silver eels and start their unique migration back to the spawning area in the Sargasso Sea. As a result, eels colonize and migrate through a great variety of habitats in the ocean, in brackish water and of course a variety of different inland waters. Furthermore, all life stages from glass eel to silver eel are fished in coastal and freshwater habitats by commercial and recreational fisheries. European eel aquaculture is exclusively capture-based, depending totally on wild caught glass eels, since artificial reproduction of the species is still not possible.
Despite the lack of a quantified assessment of the impact of fisheries on the whole stock and a decrease in the number of fishers targeting eels in the four focus countries since 2006, it is noteworthy that any further mortality caused by fisheries contributes to losses in silver eel escapement and therefore spawning stock biomass. During the 2015-2017 period, 193 million glass eels were caught annually compared to roughly 6.1 million yellow and silver eels. In many areas yellow and silver eel fishing is only sustained through extensive stocking activities. Stocking of wild caught glass eels, carried out usually by regional authorities, commercial or recreational fishing associations or even individual fishers without scientific evaluation, is still continued under the premise of a potential net benefit for the recovery of the overall eel population, but effectively may even further increase the pressure on the panmictic stock.
The introduction of barriers represents one of the major factors affecting riverine fish populations, in particular of migratory species. With regard to eels, different types of obstacles and barriers, including culverts, weirs, bridge aprons, dams, hydropower stations, pumping stations, tidal flaps and sluices, can adversely affect their continental life stages during migration. Typical negative effects of barriers include the loss of upstream habitats due to restrictions in river continuity, delays in migration and, of course, direct mortality at pumping stations, water intakes and, especially for downstream migrating silver eels, hydropower turbines.
In light of these developments, several measures were taken to facilitate an internationally coordinated management and aid the recovery of the eel stock: In 2007, the European Union passed Council Regulation 1100/2007 “establishing measures for the recovery of the stock”. Accordingly, Member States were obliged to identify natural habitats of the European eel and develop Eel Management Plans (EMP) in order to achieve an escapement target of 40% of silver eels as compared to pristine conditions. In 2009, the European eel was listed under CITES Appendix II, requiring export permits for eels. In 2011 EU Member States published a zero export quota for the species. However, illegal, unreported and unregulated (IUU) fishing is still regarded a major threat for the European eel.
Many measures have been proposed and implemented to comply with the goals of Council Regulation 1100/2007. Possible instruments were already listed in the Regulation, but MS could also implement other measures to reach the target in a results-based-management-approach.
This study revealed not only large knowledge gaps and data deficiencies in European eel management from a biological perspective but also from an economic point of view. To better assess the implications of different protection measures for industries like fisheries, aquaculture, fish processing and energy production, deeper knowledge on the economic impact of management measures on stakeholders is required.
On the basis of the available economic data on cost structures of fishers that carry out commercial fisheries (marine and freshwater) only a vague analysis of impacts is yet possible. Accordingly, the loss of direct revenues at a total closure of fisheries in Europe (glass, yellow and silver eels) is estimated to EUR 50 million per year. The most severe economic impacts may be caused by a closure of the glass eel fishery, since, as a secondary effect, the loss of seed would also result in a cessation of European eel aquaculture, with losses of EUR 37 million in revenues, and, consequently, to a large extent also of fish processing companies specialised on eel.
The putative costs to mitigate hydropower mortalities exceed the loss of revenues for a total closure of fisheries in Europe by far. In France alone, the impact of a seasonal shut down of hydropower facilities for 10 weeks on the aggregated revenue would range from EUR 127 million to EUR 634 million at a total loss in power generation from 1.5 to 7.7 Terawatt-hour (TWh). The possible costs of constructing upstream and downstream migration facilities are estimated to range between EUR 1,051 million to 3,110 million. This is 1.7 to 4.9 times as costly as a 10-week seasonal closure of the affected hydropower facilities, which means that migration facilities would be more cost effective after a two to five-year period. For Spain, losses are in the same range as in France, while for Greece and Germany losses were lower.
As a consequence, there is an urgent need to evaluate the effectiveness of measures for the protection and recovery of the European eel for conformity with the Precautionary Approach. All regulatory measures adopted for its stock recovery should directly target at a significant and verifiable reduction of eel mortalities. These include river continuity restoration and habitat quality improvement as well as significant reductions in commercial and recreational fisheries related mortalities. Prior to a decision on possible management actions a robust scientific impact assessment should be issued to inform decision makers about the costs and benefits to reach a certain management target.
Overall, it would be highly recommended to move from the current 40% regional level escapement targets to a mortality-based target in a revised version of an EU Regulation.
Link to the full study: http://bit.ly/629-189
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