International eel symposium, 2003 - Quebec August 11, 2003
Oral Presentation

Analysis of Morpho Anatomical Changes Occuring during Artificially-Induced Sexual Maturation for European Eel from Loire River in Experimental Conditions

Séchet, C.* CEMAGREF (Agricultural and Environmental Engineering Research), Freshwater Systems Management Department, 50 avenue de Verdun; 33612 Cestas cedex. France.
Elie, P. CEMAGREF (Agricultural and Environmental Engineering Research), Freshwater Systems Management Department, 50 avenue de Verdun; 33612 Cestas cedex. France.

Presenter email address: christine.sechet AT bordeaux.cemagref.fr

Abstract Text: The objective of this study is to evaluate the capacity of downstream migrating eels to sexually mature and to try and determine the main parameters that can characterize the state of evolution of eels during sexual maturation. Eels (Anguilla anguilla) from Loire river, were injected weekly with gonadotropin to induce sexual maturation. Throughout the experiment, anatomical parameters (gonado-somatic index GSI, hepato-somatic index HIS, digestive tract index DTI) were monitored during monthly sacrifices. Morphological parameters (body weight, total length, body girth, ocular index OI, length of the pectoral fin), which have already been analyzed during the silvering phase, were measured every two weeks. Treated eels reacted positively to injections by maturing and releasing genital products (92% of the eels ovulated). For these individuals, the parameters (GSI, OI), which started to develop during the growth and silvering phases, increase considerably during maturation (mean GSI was multiplied by 10 and mean OI by 2). Other parameters such as body length and HSI did not vary contrarily to what occurs during the first stages of silvering, or increase at the end of maturation, as body girth, weight. The four parameters (GSI, OI, body girth and weight) can be used to monitor non-invasively, the evolution of sexual maturation.