Feeding energetics of the Norway lobster, Nephrops norvegicus in the Firth of Clyde, Scotland

The diet of the Norway lobster Nephrops norvegicus in the Firth of Clyde consists of crustaceans, molluscs, and to a lesser extent polychaetes and echinoderms. The proportion of bivalves was higher in the diet of N. norvegicus from south of Little Cumbrae than in the diet of N. norvegicus from south of Ailsa Craig which contained larger proportions of echinoderms. This appears to reflect the faunal composition of the areas. There were marked interspecific differences in the energy contents and organic contents of prey organisms. Diel variation in food consumption was investigated in animals trawled at 4h intervals over a 24h period. The results suggested periodicity of foraging with gut contents being lowest during the afternoon. The reasons for this are discussed. The rates of weight-specific oxygen consumption (MO2) were determined for quiescent and for active male and female Nephrops norvegicus. The scope for activity was found to be approximately four times basal metabolism. The recent feeding history was observed to have a marked effect on metabolic rate. The MO2 significantly decreased following 8 and 12 weeks of starvation, and rapidly increased again after re-feeding. An energy budget was constructed for Clyde Sea Nephrops norvegicus. The scope for growth was significantly greater for animals in May than November. No significant differences in scope for growth were found between animals from the Little Cumbrae and Ailsa Craig sites.