Reproductive biology of the conger eel from the south coast of Brittany, France and comparison with the European eel

• Published in: Journal of fish biology Vol. 59; no. 2; pp. 302 - 318
• Main Authors: SBAIHI, M, FOUCHEREAU-PERON, M, MEUNIER, F, ELIE, P, MAYER, I, BURZAWA-GERARD, E, VIDAL, B, DUFOUR, S
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell 01.08.2001
• Subjects: Agnatha. Pisces; Anguilla anguilla; Animal and plant ecology; Animal, plant and microbial ecology; Animals; Autoecology; Biological and medical sciences; Brackish; Conger conger; Freshwater; Fundamental and applied biological sciences. Psychology; Marine; Vertebrata; Bretagne; North Atlantic; France; Europe; Atlantic Ocean; ANE, France, Brittany, Concarneau Bay; Anguilla anguilla; Growth; Interspecific comparison; Germinal cell; Marine environment; Sexual maturation; Ovary; Reproduction; Vertebrata; Vitellogenesis; Pisces; Body size; Female genital system; Sex steroid hormone; Gonadosomatic index; Age; Oocyte
• ISSN: 0022-1112; 1095-8649
• DOI: 10.1006/jfbi.2001.1642

The gonadosomatic indices (I sub(G)) of female conger eel Conger conger, aged between 2 and 11 years postmetamorphosis, ranged between 0.04 and 4.78 and were correlated with both age and body length. Microscopical examination of the gonads showed immature ovaries at two main stages of oocyte development, pre-vitellogenic oocytes for I sub(G)<1, and oocytes at an early vitellogenic stage (lipid vesicle stage) forI sub(G) >1. The immaturity of the conger eels sampled in Concarneau Bay indicates that this species probably spawns in deeper oceanic waters. Radioimmunoassays (RIA) of sex steroids gave low serum levels of oestradiol and of 11-ketotestosterone, but higher levels of testosterone correlated with increase in I sub(G). Immunoenzymatic assay (ELISA) indicated low serum levels of vitellogenin (VtG), which were significantly correlated withI sub(G) . The pre-vitellogenic and early vitellogenic stages observed in the coastal C. conger were similar to the oocyte stages found in the European eel Anguilla anguilla, at the yellow and silver phases of its life cycle respectively. However, other morpho-functional changes, associated with silvering in Anguilla species, such as the increase in ocular index, and regression of the digestive tract, did not occur at the early vitellogenic stage in conger eels. Copyright 2001 The Fisheries Society of the British Isles