Sex differentiation and sex determination in eels: consequences for management

Abstract

The aim of this review is to present an overview of the sex differentiation and sex determination processes in eels in relation to the urgent need to provide scientific knowledge to better protect and manage the Anguilla genus. Indeed, the global decline of the three main temperate eel stocks, Anguilla anguilla, Anguillidae (Fisheries Management and Ecology, 2003, 10, 365); Anguilla japonica, Anguillidae (Casselman, Eel Biology, Springer Japan, 2003, 293) and Anguilla rostrata, Anguillidae (Tatsukawa, Eel Biology, Springer, Japan, 2003, 255), raises concerns about the necessity to better understand all stages of the life cycle of eels (Righton and Walker, Journal of Fish Biology, 2013, 83, 754). Little is known about the mechanisms involved in the production of males and females in this species with environmental sex determination. Previous reviews identifying the density of individuals as the major factor influencing sex determination were undertaken (Krueger and Oliveira, Environmental Biology of Fishes, 1999, 55, 381; Reviews in Fish Biology and Fisheries, 2005, 15, 37). Here, we review the current advances on the subject, focusing on the roles of early growth rate and interindividual relationships, which are mechanisms underpinned by density, as well as the sex differentiation process, and we question how this knowledge might influence global conservation measures.

Short-term responses of glass eels transported from UK to small Belgian streams

“…However, once they become silver eel they will migrate over longer distances downstream to reach the sea, which may cause delays and mortality (Verbiest et al, 2012). Another point to consider further is the impact of such restocking practices in upper rivers on the future sexual differentiation of the restocked individuals (Geffroy and Bardonnet, 2015).…”

The Reversible Sex of Gonochoristic Fish: Insights and Consequences

“…Cortisol mediated by the hydroxysteroid dehydrogenase hsd11b2 gene was shown to promote 11KT synthesis [Fernandino et al, 2012]. A similar mechanism might be acting in the European eel Anguilla anguilla for which high density promotes male differentiation, since larvae have been shown to have both elevated cortisol and 11KT levels [Geffroy and Bardonnet, 2016].…”

Freshwater eels: A symbol of the effects of global change

“…More generally, the large diversity of tactics during the continental phase and presumably during the spawning migration may correspond to remarkable bet‐hedging well suited to address environmental variability (Daverat et al., ; Righton et al., ). The environmental sex determination may also be a compensatory mechanism: The higher production of females in a context of depleted population may mitigate the reduction in eggs production that would result from the decline in silver eel abundance (Geffroy & Bardonnet, ; Mateo, Lambert, Tétard, & Drouineau, ), especially since eels have a high fecundity.…”

“…Carbon dioxide from firn and ice core records (Law Dome, Antarctica) and Cape Grim, Australia (deseasonalized flask and instrumental records). Sources (Steffen et al, 2005), population (Goldewijk, Beusen, & Janssen, 2010), CO 2 (Etheridge et al, 1996;Langenfelds et al, 2011;MacFarling Meure, 2004;MacFarling Meure et al, 2006), water use (Alcamo et al, 2003;aus der Beek et al, 2010;Flörke et al, 2013), energy use (GEA Writing Team, 2012), and GDP (World Bank indicators) Year mitigate the reduction in eggs production that would result from the decline in silver eel abundance (Geffroy & Bardonnet, 2016;, especially since eels have a high fecundity.…”