Paul E. Aspholm

ORGANOCHLORINE CONTAMINATION IN DEEP-SEA FISH FROM THE DAVIS STRAIT

Eight species of deep-sea fish caught at various depths off the west coast of Greenland exhibited low to moderate organochlorine (OC) contamination. Polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane metabolites (DDTs) were the dominating organochlorines. Hepatic levels of sum-PCB (19 individual PCB congeners) ranged from 110 ng g−1 lipid weight in jelly wolf-fish (Anarhichas denticulatus) to 1156 ng g−1 in blue hake (Antimora rostrata). Sum-DDT (p,p′-DDE, o,p′-DDD, p,p′-DDD, multiplied by a factor (1.11), and p,p′-DDT) ranged from 70 ng g−1 in jelly wolf-fish to 1446 ng/g in blue hake. Sum-chlordanes (oxychlordone and trans-nonachlor) ranged from 28 ng g−1 in jelly wolf-fish to 309 ng g−1 in roughhead grenadier (Macrourus berglax). HCB (hexachlorobenzene) ranged from 3.6 ng g−1 in smalleyed rabbit-fish (Hydrolagus affinis) to 73 ng g−1 in tusk (Brosme brosme). Sum-HCH (hexachlorocyclohexanes α-HCH, β-HCH and γ-HCH) was of minor importance with levels ranging from 9.3 ng g−1 in Greenland halibut (Reinhardtius hippoglossoides) to 22 ng g−1 in tusk. The levels are lower than most of the corresponding published data from deepsea fish and probably reflect a moderately contaminated area. No simple relationship was found between organochlorine contamination and depth range of the investigated species.

Mercury and selenium in arctic and coastal seals off the coast of Norway

Mercury and selenium concentrations (wet weight) have been determined in samples of liver, kidney and brain of grey seal (Halichoerus grypus), harbour seal (Phoca vitulina), harp seal (Phoca groenlandica) and ringed seal (Phoca hispida) caught along the Norwegian coast, 114 individuals in all. Significant differences have been found in mercury contamination between the 4 species caught in the same coastal area, Jarfjord, located at the north-east of the Norwegian coast close to the Russian border. Very low hepatic mercury levels were found in the arctic species, ringed and harp seals, ranging from 0.20 to 0.67 and 0.04 to 1.0 microg g(-1), respectively, while in the coastal seal species the concentrations were 10 to 40 times higher. The corresponding ranges were 0.7 to 48.3 microg g(-1) in grey seals and 0.2 to 19.0 microg g(-1) in harbour seals. The median values were 13.5 and 0.7 microg g(-1), respectively. The highest levels were found in grey seals, indicating that particularly the stock frequenting the waters of the north-east coast of Norway and north-west coast of Russia had received a substantial mercury exposure. Fifty-five percent of these grey seals from Jarfjord had hepatic mercury levels above 10 microg g(-1) and 21% had levels above 20 microg g(-1). By a one-way analysis of covariance, sex and age were found to explain 28 and 30%, respectively, of the total variability in the mercury concentration in grey seal from Jarfjord. Significant differences in mercury concentrations were also found between stocks of harbour seals caught at different sites along the Norwegian coast, and decreasing concentration from the south to the north-east coast of Norway was revealed. The renal mercury levels in the arctic seals ranged from 0.08 to 0.45 microg g(-1), and about five times higher levels were found in grey seals and harbour seals. The mercury levels in the brain ranged from the detection level (0.01 microg g(-1)) to about 0.1 microg g(-1). The hepatic selenium levels in the arctic seal species ranged from 0.8 to 3.7 microg g(-1). The corresponding ranges in grey seals and harbour seals were 1.0 to 23.3 microg g(-1). The renal selenium levels were lower, and the levels in the brain were below the detection level (0.01 microg g(-1)). The mercury/selenium ratio was close to unity for mercury concentrations greater than 15 microg g(-1), and a nonlinear, concave relationship was found between the ratio of the hepatic mol concentrations of mercury and selenium and the hepatic mol concentrations of mercury.

Sealworm (Pseudoterranova decipiens) infection in common seals (Phoca vitulina) and potential intermediate fish hosts from the outer Oslofjord

Infection with Pseudoterranova decipiens in 45 common seals (Phoca vitulina) from the outer Oslofjord was investigated. Seals were collected before and during the phocine distemper virus epizootic in 1988 when the seal population in the area was reduced from about 350 to 100. In 1989, cod (Gadus morhua) and other fish species were sampled for comparison with earlier investigations on prevalence and abundance of P. decipiens infection in fishes from the outer Oslofjord. Seventy-two per cent of cod were infected with P. decipiens larvae in shallow waters between the seal skerries; the corresponding abundance was 2.2. At other fishing sites at increasing distances from the seal colony, abundance dropped to 0.05-0.20. Otoliths recovered from stomachs and scats indicated that gadids (Micromesistius poutassu, Trisopterus esmarkii and G. morhua) made up more than 80% of the seal diet. Bullrout (Myxocephalus scorpius) was also heavily infected with P. decipiens (prevalence 93% and abundance 8.4), but was not found in the seal diet. However, uninfected cod that enter shallow water from the surrounding deep waters became infected when they feed on bullrout. Recruitment to mature stock of P. decipiens occurs when highly infected cod are eaten by seals. The number of reproducing P. decipiens is very low in common seals. Only 2 seals (i.e. less than 5% of the sample) were simultaneously infected with mature worms of both sexes. The dramatic reduction of the seal stock in the outer Oslofjord by the epizootic did not seem to affect the abundance of P. decipiens in its intermediate hosts.

Anisakis simplex Rudolphi, 1809, infection in fillets of Barents Sea cod Gadus morhua L.

Abstract The purpose of this study is to record the infections of the whaleworm ( Anisakis simplex ) in fillets of Norwegian Arctic cod from coastal and oceanic waters of the Barents Sea. The percentage of cod infected was 96%. The mean intensity of A. simplex in fillets of oceanic and coastal cod was 4.3 and 6.1 respectively. These values were significantly different. Comparison with previous work indicates that the A. simplex infection in Barents Sea cod is little influenced by the large fluctuations in the abundance and distribution of the main fish stocks (i.e. capelin, herring and cod) in this ecosystem. It is not clear which factors are responsible for the maintenance of the high prevalences of Anisakis in the Barents Sea.

Helminth Parasites in Ringed Seals (Pusa hispida) From Svalbard, Norway with Special Emphasis on Nematodes: Variation with Age, Sex, Diet, and Location of Host

Abstract Complete gastrointestinal tracts from 257 ringed seals (Pusa hispida) from Svalbard, Norway, were examined for helminth parasites. Three different helminth groups were recorded (acanthocephalans 61.1%; nematodes 38%; cestodes 0.9%). Acanthocephalans (Polymorphidae) and cestodes (Anophryocephalus and Diphyllobothrium sp(p)., as well as unidentified species, were confined to the intestines. The anisakid nematodes Phocascaris phocae, Pseudoterranova sp(p)., Anisakis sp(p)., and Phocascaris/Contracaecum sp(p). were recorded in both stomachs and the anterior part of the small intestines. The abundance of nematodes and acanthocephalans varied significantly with sampling location of the seal hosts. This is likely due to the relative prevalence of Arctic versus Atlantic water in the different fjord systems, which strongly influences the age class and species of fish available as prey for the seals. Adult male ringed seals had significantly higher abundances of nematodes than did adult females or juveniles. Adult males also had significantly higher abundances of acanthocephalans than did adult females, but were not significantly different from juveniles in this regard. Nematode abundance increased significantly with age of male hosts, but this trend was lacking in female seals. Infection parameters appeared to be related to differences in the age of polar cod (Boreogadus saida) exploited by male, female, and juvenile seals.