Spatial and temporal trends in condition of Atlantic cod Gadus morhua on the Icelandic shelf

Abstract

Interannual (1993 to 2006), spatial and bathymetric trends in the hepatosomatic index (H) and relative body condition index (Kr) of Atlantic cod Gadus morhua in Icelandic waters were investigated from data collected during annual spring (March) groundfish surveys. Individual stomach content data were analysed to assess the relationship between condition and consumption of capelin Mallotus villosus. Liver condition was found to vary with region and depth, tending to be highest in deeper water and in the northern and eastern regions; where temperatures were relatively cold and capelin consumption relatively high. A continuous decline in condition of cod in waters off the east coast was observed throughout the study period. Mature cod were found to be in significantly better condition than immature cod of the same age, and mature females were in better condition than mature males. Different patterns emerged from the 2 condition indices; little variation in Kr was observed whereas H was found to be a dynamic index of condition, suggesting that these metrics are not equivalent measures of cod bioenergetic condition. © Inter-Research 2008.