Effects of oxygen depletion on the ecology, blood physiology and fishery of the Norway lobster Nephrops norvegicus

Abstract

Biomass, population structure, food selection and blood (haemolymph) physiology of the Norway lobster Nephrops norvegicus were investigated in SE Kattegat, an area where low oxygen concentrations (< 2 ml l super(-1), 30% O sub(2)-saturation) have occurred in the bottom water for 1 to 3 mo periods in most years in the 1980's. During the study period (October 1984 to September 1989) lobster biomass decreased in the area from 0.8 kg h super(-1) (catch per unit effort) to zero (estimated during the last 12 mo of the investigation). Males contributed on average 78% of the population density, except in September 1988 during severe hypoxia when a reversed sex ratio was found and females (even berried) dominated (75% of density). The food of N. norvegicus belonged to 4 major groups; crustaceans, echinoderms, molluscs and polychaetes. The dominant species eaten within these groups were also found to be dominants in the benthic infauna.