Selectivity of Water Dams on Glass Eel : Transcriptomics Approach

Physical obstacles to upstream migration such as dams are a major impairment of natural colonisation

and dispersion of eels. Dams and obstacles also increase the energy demand of fish, even if there is a

fish friendly device to allow them to swim across the obstacle. Besides, local accumulation of eels

below dams may increase the mortality associated with predation. Obstacle to eel migration may

select on different trait of life history. While quantitative impact of dams is subjected to numerous

studies, little is known about their intra-specific selectivity. Even the fishway efficiency analyses are

scarcely hinting at their potential selective effect (Castro-Santos 2004; Noonan, Grant & Jackson 2012).

The main issue of this study is to pinpoint phenotypic traits that predisposed glass eels to dams successful

passage. The approach we adopted is individual-centred and without any a priori hypothesis on traits

involved by the putative dams selective pressure. We analyzed the expression of 15000 known eel genetic sequences

based on previous studies (Coppe et al. 2010; Pujolar et al. 2012). Transcriptome analysis of three main

tissues (brain, liver and muscle) from individuals sampled on three successive forebays separated by

dams indicate different gene expression profiles in brain between the two upstream forebays.

The functional role of the overall set of regulated genes strongly suggests cytosqueletal and neural changes

as well as synaptic plasticity. Their interpretation at higher phenotypic level and further research perspectives

are discussed.