Important questions to progress science and sustainable management of anguillid eels

David Righton ,Martin Castonguay ,Thomas C Pratt ,Naoko Fukuda ,Kristen Steele ,Niklas Sjöberg ,Håkan Westerberg ,Kieran Mccarthy ,John M Casselman ,Kim Aarestrup ,Kenzo Kaifu ,Kazuki Yokouchi ,Adam T Piper ,Hiromi Shiraishi ,Éric Feunteun ,Claude Belpaire ,Céline Hanzen ,Gaël Simon ,Reinhold Hanel ,Katsumi Tsukamoto ,Michael J Miller ,Estibaliz Díaz ,Elisabeth Faliex ,Pierre Sasal ,Elsa Amilhat ,D J Jellyman ,Robert Schabetsberger ,Alan Walker ,Hendrik Dörner ,Matthew Gollock

doi:10.1111/faf.12549

Abstract

AbstractAnguillid eels are found globally in fresh, transitional and saline waters and have played an important role in human life for centuries. The population status of several species is now of significant concern. The threats to populations include direct exploitation at different life stages, blockages to migratory routes by dams and other structures, changes in river basin management that impact habitat carrying capacity and suitability, pollution, climate change, diseases and parasites. While much has been done to understand eel biology and ecology, a major challenge is to identify the key research and management questions so that effective and targeted studies can be designed to inform conservation, management and policy. We gathered 30 experts in the field of eel biology and management to review the current state of knowledge for anguillid eel species and to identify the main topics for research. The identified research topics fell into three themes: (a) Lifecycle and Biology; (b) Impacts and (c) Management. Although tropical anguillid eels are by far the least well understood, significant knowledge gaps exist for all species. Considerable progress has been made in the last 20 years, but the status of many species remains of great concern, particularly for northern temperate species. Without improved engagement and coordination at the regional, national and international level, the situation is unlikely to improve. Further, adaptive management mechanisms to respond to developments in science, policy and our knowledge of potential threats are required to ensure the future of these important and enigmatic species.

Highlights

Anguillid eels are found across the globe except in the eastern Pacific and South Atlantic
Common features of many of these areas include westward flowing equatorial currents, the presence of oceanographic fronts and subsurface tongues of high salinity (Schabetsberger et al, 2016). For temperate species such as the European eel (A. anguilla) and the American eel (A. rostrata), spawning occurs far offshore, in an area extending more than 2,000 km of longitude, to the south of a strong temperature front in the Sargasso Sea (Hanel et al, 2014; Kleckner & McCleave, 1988; Miller et al, 2015, 2019; Munk et al, 2010; Schoth & Tesch, 1982), eggs and adult Anguilla have never been found in the Sargasso Sea
How can we develop effective management frameworks for eel stocks at local, national and international levels?

Summary

Introduction

Anguillid eels are found across the globe except in the eastern Pacific and South Atlantic. More research on the factors governing the survival and behaviour of leptocephali will contribute to a better understanding of the relationship between the dynamics of the larval stage and recruitment success, which is true for species that spawn sympatrically and/or in very distant areas (Miller & Tsukamoto, 2017).

Results

Conclusion