Abstract

In fish populations, reproductive dynamics is a process depending on the body size of the females, and has notable importance on intensity and duration of reproductive activity. In this study, we analyzed the duration and intensity of reproductive activity as a function of the body size in Merluccius gayi gayi females from samples obtained in 1998 off central-south Chile. The gonadosomatic index (GSI), the specific gonadal index (SGI) and the duration and intensity index (DII) of reproductive activity were computed. The DII represents the area under the GSI of length classes over a year. A linear relationship between the GSI and the SGI was found (r2 = 0.980), suggesting that the changes in the variables are due to changes in ovary weight and not in total weight. The major reproductive activity occurred from August to October, with secondary reproductive activity evident from February to April. The DII as a function of the female length was described by a log-normal model (r2 = 0.96, n = 17.418, p < 0.01). It is postulated that Merluccius gayi gayi females of medium sizes (40-55 cm TL) represent the more important population fraction in terms of major reproductive intensity and duration. Females of greater size (> 55 cm TL) present reproductive activity restricted only to the main reproductive season (August-October).