Impact of environmental temperature on Atlantic cod Gadus morhua energy allocation to growth, condition and reproduction

Abstract

The effect of temperature on the allocation of energy to growth, condition and reproduction was examined in juvenile and adult Atlantic cod Gadus morhua inhabiting the southern Grand Bank off Newfoundland, Canada. The study period included both the warmest and coldest environmental conditions in the area over the past 60 yr. Temperature did not influence growth in length or weight, perhaps because growth at higher temperatures was limited by prey availability. Temperature significantly influenced both gutted body condition and liver condition (observed weight divided by predicted weight at length), but the effect was not consistent between the 2 measures of condition. Gutted body condition was highest at warm temperatures, whereas liver condition was highest at low temperatures. Measures of reproductive investment showed clear temperature effects. Fish matured earlier at both low and high temperatures than at intermediate temperatures. Fecundity of southern Grand Bank cod was highest at low temperatures, while the gonadosomatic index (GSI) was highest at warm temperatures. The lack of correlation with fecundity indicates that GSI may not be a good metric of reproductive investment but may be an indicator of how close fish are to spawning. The lower maturity and fecundity at intermediate temperatures could indicate a decrease in reproductive potential under these environmental conditions. Temperature throughout the entire year influenced fish condition, but only temperature during October to May affected reproductive investment. Most of the metrics were highly correlated between males and females, suggesting that both sexes make similar decisions about energy allocation over the observed temperature range. © Inter-Research 2010.