Egg production of Baltic cod (Gadus morhua) in relation to variable sex ratio, maturity, and fecundity
G.
Kraus, J. Tomkiewicz, F. W. Köster-2002
Can. J. Fish. Aquat. Sci, 59(12): 1908-1920
Abstract:
Observed
fluctuations in relative fecundity of Eastern Baltic cod (Gadus morhua
L.) were related to food availability during the main feeding period and
were used to develop a predictive model that explained 72% of the
interannual variations in fecundity. Time series of sex ratios, maturity
ogives, and relative fecundity were combined with mean weights-at-age and
stock sizes from an analytical multispecies model to estimate the potential
egg production (PEP). Relationships between PEP and independent estimates of
realized daily and seasonal egg production from egg surveys were highly
significant. The difference between estimates of potential and realized
seasonal egg production was of a magnitude corresponding to the expected
loss of eggs as a result of atresia, fertilization failure, and early egg
mortality. The removal of interannual variability in sex ratio, maturity,
and fecundity on estimates of PEP deteriorated the relationships in all
three cases. PEP proved to be superior to spawning stock biomass as measure
of the reproductive potential in a stock-recruitment relationship of Eastern
Baltic cod. PEP in combination with the reproductive volume explained 61% of
the variation in year-class strength at age 2.
(address not available)