| Summary: | In this paper the proportion of females with postovulatory follicles in their ovaries in July 1995 is used to determine the length- and age-at-maturity of cod (Gadus morhua) in the year 1995. The proportion of females in the cortical alveoli stage is then used to estimate the same parameters for 1996. This histological method allows to accurately detect the proportion of both adult and primiparous females in the population at the very beginning of the gonad development, as it happens in the summer, and few months after spawning, when it is very difficult to make a visual diagnosis of the sexual maturity stage. Length and age at 50% maturity obtained from the curves plotting the proportion of cortical alveoli were 39.07 cm and 3.1 years, respectively. The same parameters obtained from postovulatory follicle frequencies were 42.65 cm and 3.9 years, respectively. During the period from 1990 to 1995, a decrease in both length- and age-at-maturity was observed for cod on Flemish Cap. It seems likely that in those recent years the age-at-maturity of female cod was fixed around age 3. The possibility that these features could be a density-dependent response is discussed.
|
|---|