TRACE-METAL CONCENTRATIONS IN DEEP-SEA FISH FROM THE NORTH-ATLANTIC

Specimens of six species of continental slope fish (17 orange roughy H oplostethus atlanticus, 84 roundnose grenadier Coryphenoides rupestris , 37 rough-head grenadier Macrourus berglax, 27 Mediterranean grenadie r Coryphenoides [Chalinura] mediterranea, 25 spear-snouted grenadier C oelorhyncus labiatus and five armed grenadier Coryphenoides [Nematonur us] armatus), were collected between 1987 and 1995, and their muscle t issue subsequently analysed for mercury, lead, cadmium, copper and zin c. The early samples were collected in the Rockall Trough area by the research vessel Challenger. The 1995 samples were obtained from commer cial landings at Lochinver fishing port by fishing vessels which had b een operating on the Hebridean Continental Slope, in ICES areas 43E0, 44E0, 45E0, 46E1, 47E3 and 48E3. Sub-samples of the muscle tissue of i ndividual fish whose ages ranged from 3 to > 70 y, were analysed for t he above trace metals using atomic absorption spectrophotometry, follo wing nitric acid digestion. The mean mercury concentrations in all spe cies were below 0.5 mg/kg, ranging from a mean value of 0.06 mg/kg in roundnose grenadier to 0.42 mg/kg in orange roughy. However, individua ls from three of the six species were found to have concentrations gre ater than 0.5 mg/kg but less than 1.0 mg/kg (orange roughy up to 0.86 mg/kg, roughhead grenadier 0.89 mg/kg and armed grenadier 0.65 mg/kg). In all species, concentrations of mercury were found to increase with both age and length. Mean concentrations in shallow water commercial fish species are normally less than 0.1 mg/kg, although some long-live d fish predators can contain I mg/kg or more. The ranges of mean conce ntrations of zinc (2.2-6.7 mg/kg), copper (0.01-0.47 mg/kg) and cadmiu m (0.002-0.02 mg/kg) for all species were similar to those observed in commercially exploited shallow water marine fish landed at Scottish p orts, although some of the lead concentrations (means 0.004-0.72 mg/kg ) were rather higher. In Mediterranean grenadier, the concentrations o f copper, zinc, cadmium and lead decreased with increasing length/age of fish. Although this was also observed in orange roughy, the relatio nships were not as significant as those in the Mediterranean grenadier . Crown copyright (C) 1998 Published by Elsevier Science Ltd All right s reserved.