Fecundity and the survival conditions of the offspring of the Baltic Cod Gadus morhua callarias (Gadidae)

Аннотация

The interannual and ontogenetic dynamics of the fecundity of the Baltic cod Gadus morhua callarias and the dependence of the number of the offspring on the reproduction conditions were studied. The absolute individual fecundity and the relative individual fecundity had no pronounced interannual dynamics for the period of 1994−2013. The maximal population fecundity was observed in early 1980, the minimal, in 1990−2000. Nearly every year, the highest contribution to the population fecundity belongs to the 4−5-year old females. The ranking of the survival rates and the year-class strength for the females at the age of 2 years showed that the emergence of the generations of high and average productivity (1980−1986) referred to the unfavorable and moderate survival conditions during the early ontogenesis. During the period of small stock (after 1987), the conditions were mostly favorable and moderate. It is suggested that the significant role in the offspring dynamics belongs to the factors linked to the population density. After 2005, favorable survival conditions promoted the increase of the Baltic cod abundance; this increase was also supported by the decrease of the commercial fishing and by the sporadic large-scale advective processes.