Seasonal changes in maturity in the conger eel Conger myriaster at the Pacific coast of Atsumi peninsula, central Japan

Abstract

Seasonal changes in gonadal development were investigated in the conger eel Conger myriaster, collected at a fixed station in the Pacific coast of Atsumi peninsula, central Japan, from November 1996 to September 1998. Out of 188 individuals collected, 182 were female and there were six individuals, the sex of which were unknown. Female individuals caught from March to August were immature (gonadosomatic index (GSI) <1) with the oocytes at the chromatin nucleolus or the perinucleolus stages. From September to January, some relatively matured individuals (GSI: 2-4) appeared at the station, with the oocytes at the oil droplet or the primary yolk globule stages however, they were not caught after February. These results suggest that female C. myriaster on this coast gradually grow up from summer to winter, then the relatively matured larger individuals migrate to elsewhere in early spring.