MANAGEMENT, CONCLUSIONS, REFERENCES

 

MANAGEMENT

Comparing the European eel population dynamics to a tree, its roots are in the Sargasso Sea, the rising and descending sap in the trunk and the main branches is represented by the North Atlantic circulation, which spread the leptocephali and glass eel to North Africa and European coast. The leaves represent the different catchments where elver, yellow and finally silver eel are produced and contribute to feed the spawning stock in the roots of the eel tree (Figure 13).

This helps to understand that to have a real impact on the future eel population, it is necessary to manage the stock not only at the scale of the catchments, i.e. the management unit corresponding to one leave, but also to a larger scale corresponding to the canopy that represents the different areas of colonization. This scale and complexity of management is difficult to organize and requires coordination among all EU states exploiting the resource.

In order to manage and restore the eel population, which is considered as endangered and included in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), the Council of the European Union made a proposal for a Council Regulation establishing measures for recovery of the stock of European eel (13139/05 Peche 203 – COM(2005) 472 final). This regulation would establish a framework for the protection and sustainable use of the stock of European eel of the species Anguilla anguilla in EC maritime waters and in the estuaries and rivers of Member States that flow into the seas in ICES areas III, IV, VI, VII, VIII and IX or into the Mediterranean and Black seas.
The plan proposes seasonal closures in order to reduce catch by 50 percent with an exemption allowed only if a long term management plan is established. This objective is defined as an escape to the sea of at least 40 percent of the biomass of adult eel relative to the best estimate of natural escape defined according to: historical data or by habitat-based assessment of potential eel production, in the absence of anthropogenic influences or with reference to the ecology and hydrography of similar river systems. The management plans may contain different measures, such as fishery regulations, restocking, improvement of river habitats, temporary switching off of hydroelectric power turbines, etc.

FIGURE 13
Functional scheme of the eel population: “The Eel Tree”

The eighth article is of particular interest: “if a Member State operates a fishery on glass eels, it has to guarantee that 60 percent of all glass eels caught during the whole year are utilized as part of a restocking program in European inland waters having access to the sea, for the purpose of increasing the escapement levels of adult silver eels. In order to ensure that 60 percent of glass eels caught are used in a restocking programme, Members States must establish an appropriate reporting system.”
That implies together with the reduction of the catch, a major decrease of the production of wild seed available for export to Asian countries. The evaluation of the efficiency of the management plans has to be assessed and for this reason a project called “Abundance and colonization indicators of European eel in the central part of its colonization area (INDICANG)” is being undertaken.
The diversity of the situations is such that each production unit should be considered separately. This approach was largely recommended by the scientific community, as it makes possible a systemic analysis. Fishing activity is not the only factor affecting eel populations. Other causes impact aquatic productivity, e.g. exploitation of the water for energy needs, exploitation of wetlands for urban and agricultural needs. Local scale efforts are insufficient because a restoration of the habitats and eel resource in only one catchment area cannot lead to a restoration of the resource on a European scale taking into account the diverse structure of the population. The implementation of a network of pilot catchment areas projects will allow a broader approach on a European scale, e.g. on a set of rivers between the Cornwall and the north of Portugal, as proposed in the INDICANG project (Prouzet, 2004).

CONCLUSIONS

The biological cycle of the European eel is not yet replicated under artificial conditions, meaning that the removal of seed from the natural environment is still necessary to supply the aquaculture sector. This species is presently considered endangered and in order to manage and restore eel stocks, the EC is defining a regulation to establish measures for the recovery of its stocks (Figure 14).
Recent research indicates that the successful reproduction of the European eel will require a further decade for it to be carried out on a large scale, which means that eel farming will have to rely on wild-caught juveniles until then. Collection of glass eels will increasingly become uncertain, particularly if the eel population continues to decline at the present rate. In this case, the priority will be to ensure the natural colonization of glass eels migrating through the estuary of a given catchment area. If some catchments receive a surplus of natural recruitment a portion of the glass eels arrivals will be assigned to the stocking of rivers or lakes in Europe with insufficient recruitment. This stocking will be made either by the direct introduction of glass eels in rivers or by the release of elvers pre-grown in hatcheries. In both cases, strict sanitary controls would have to be enforced.
To implement this plan, the EU will have to fund the purchase of wild seed from fishers and elvers from eel farms. Government funding would ensure implementation of the plan and ultimately integrate eel production with natural recruitments to increase spawning stock in open waters. Fishing restrictions would protect these stocks. This also implies a transparency of the marketing networks. The European regulation proposes a decrease in glass eel harvest, and restrictions on the export outside the natural area of eel colonization. A restriction of 60 percent of the catch has been made (35 percent in 2009, to reach 60 percent in 2013). If this becomes law, it is highly probable that supplying glass eels from Europe to the Asian market will be greatly disrupted.

FIGURE 14
Eel regulation and restocking versus CBA

 

 

REFERENCES

R elease
aquaculture
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