REPRODUCTIVE STRATEGY OF APHANIUS-FASCIATUS NARDO, 1827 (PISCES, CYPRINODONTIDAE) IN THE MESOLONGI AND ETOLIKON LAGOONS (W. GREECE)

The reproduction and fecundity of Aphanius fasciatus were studied in 2 034 fish originating from three locations in the Mesolongi and Etoliko n Lagoon system. The sampling stations differed in water temperature a nd salinity. The species exhibits early sexual maturation and is able to reproduce several months after birth. The reproductive effort (GSI) and histological studies of the ovaries indicate that reproduction is extended and lasts from April to July. Differences in the GSI values were observed between the sites. Fish originating from the sites with higher salinity has significantly lower GSI values and in addition, la y fewer eggs per unit of size (total length, body weight, age) than th ose from the other sampling sites. The maturation of oocytes stops whe n the environmental conditions are not satisfactory for the survival o f eggs and larvae, and oocytes are subsequently absorbed. (C) 1998 Els evier Science B.V. All rights reserved.