Abstract
Several anguillid eel species have experienced severe population declines over the past decades, particularly the European eel (Anguilla anguilla), which is listed as critically endangered by the International Union for Conservation of Nature. To reduce fishing mortality, many European countries have introduced strict recreational eel fishing regulations increasing regulatory catch-and-release (C&R) practice. Despite high release rates, only limited information exists on the potential consequences of C&R on eels. A field experiment was conducted with pre-tagged eels in a semi-natural environment to investigate lethal and sublethal impacts of C&R. The experiment was combined with a citizen science study evaluating the effects of different hooks on catch rates, fish size, and hooking location to develop best practice guidelines. Short-term mortality (≤72 h) ranged from 0.0–18.2%, and adjusted long-term mortality (>72 h) from 0.0–46.2% depending on treatments, resulting in adjusted total mortality rates between 8.4% and 64.4% at the end of the study period (≥43 d). The only significant predictor of mortality was the occurrence of bleeding from hooking injuries. Deep hooking was common, and only few deep-hooked eels for which the fishing line was cut and the hook left in place shed the hook after release. However, no significant effect of C&R on eel condition was found. The citizen science study showed that anglers can significantly decrease the catch of small eels, and thus release rates, by using large J-hooks. Furthermore, large J-hooks or circle hooks reduced the likelihood of deep hooking compared to small J-hooks. Post-release mortality of eels caught in recreational fisheries needs to be considered in future stock assessments and management plans to ensure conservation of the European eel. This study also highlights the strength of combining citizen science with experimental studies to develop best practice guidelines promoting fish conservation.
Highlights
Several catadromous, anguillid eel populations including the American (Anguilla rostrate), Japanese (Anguilla japonica) and European eel (Anguilla anguilla) have experienced severe declines to less than 10% of their population levels compared to the 1970s, in recent decades
Several anguillid eel species have experienced severe population declines over the past decades, the European eel (Anguilla anguilla), which is listed as critically endangered by the International Union for Conservation of Nature
This is true for the European eel, a socio-economically important target species for both commercial and recreational fishers (e.g., Dekker, 2003; Dekker and Beaulaton, 2016; Dorow et al, 2010; Moriarty and Dekker, 1997; Ringuet et al, 2002), which has been listed as critically endangered by the International Union for Conservation of Nature (Jacoby and Gollock, 2014) and in Annex II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora to control its trade (CITES, 2014)
Summary
Several catadromous, anguillid eel populations including the American (Anguilla rostrate), Japanese (Anguilla japonica) and European eel (Anguilla anguilla) have experienced severe declines to less than 10% of their population levels compared to the 1970s, in recent decades (reviewed in Jacoby et al, 2015; Tzeng, 2016). Union (EU) came into force in 2007 obliging all EU member states to provide national eel conservation management plans by 2009 These management plans aim to ensure escapement of at least 40% of the adult eels from river and coastal catchments into the sea, where they can spawn, relative to the estimated escapement without anthropogenic impacts (EC, 2007). Various management measures such as restocking, habitat improvements, and commercial and recreational fishing regulations have been introduced by EU member states to meet the 40% escapement target. Some countries (e.g., United Kingdom, the Netherlands, and Sweden) have prohibited all recreational harvest of eel to reduce recreational fishing mortality (Ferter et al, 2013; ICES, 2013, 2016a,b) while others introduced seasonal closures, bag limits or higher minimum landing sizes in the recreational fishery (ICES, 2013, 2016a,b)
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