Life history and distribution of the edible crab (Cancer pagurus) in Norway - Effect of temperature and other environmental parameters at high latitudes

Abstract

The overall aim of this study has been to provide information on how environmental conditions in Norway might affect the life history and distribution of the edible crab (<i>Cancer pagurus</i>). The results show that the size at which female crabs reach physiological maturity vary little, and just randomly, across northern Europe, and among latitudinally separated areas within Norway. Analysis of geographical differences in the frequency of molting show that female crabs at more northern latitudes have a slower growth, and consequently have a higher age at maturity. The results also show that peak periods of molting occur later at higher latitudes, indicating that the reproductive cycle of crabs in the north is delayed compared to further south. It is believed that these spatial differences in frequency and timing for onset of molting are due to geographical differences in temperature. Evidence that crabs in the north live under sub optimal thermal conditions is found in laboratory experiments, showing that individuals from northern and southern latitudes have the same lower thermal tolerance, and a common and rather warm thermal preference (~13 °C). Video transects conducted in Sognesjøen, on the west coast of Norway, revealed a high abundance of crabs at depths of ~400 meters, and show that the topography of Norway, with its deep fjords, force some crabs in some areas to move to depths greater than depth limitations given for this species in popular fact sheets.