Nutritional limitation in populations of the Norway lobster, Nephrops norvegicus (L.) in the Firth of Clyde, Scotland
No aInitially, the thesis investigated the ecological energetics of N. norvegicus in order to construct an energy budget which could be used to estimate scope for growth. The diet of the Norway lobster Nephrops norvegicus in the Firth of Clyde was found to consist 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 crustaceans and echinoderms. This appears to reflect the faunal composition of the areas. Despite a number of measures taken to preserve stomach contents, a large proportion of the diet was found to be macerated beyond recognition, particularly in the stomachs of animals from the south of Ailsa Craig stocklet. There were marked interspecific differences in the energy contents and organic contents of prey organisms. The calorific values of the prey items were found to vary according to the proportion of organic matter in the tissue. Organisms with low organic contents such as brittle stars had lower calorific values than organisms with a large organic proportion such as soft-bodied polychaetes. Amounts of food consumption were calculated in 4h intervals over a 24h period. Results suggested that foraging is highest during the night at 2200-0200. A smaller increase in food consumption was also noticed during the morning at 0600-1000 and 1000-1400. The lowest amount of food was consumed between 1400-1800. Two different models were used to estimate the daily amounts of food consumption. The values obtained ranged from 476.5mg day-1 (wet weight) at Ailsa Craig in November to 1206.2 mg day-1 (wet weight) at Little Cumbrae in May.