The deep-sea environment is a sink for a wide variety of contaminants including heavy metals and
organic compounds of anthropogenic origin. Life history traits of many deep-water fish species including
longevity and high trophic position may predispose them to contaminant exposure and subsequent
induction of pathological changes, including tumour formation. The lack of evidence for this hypothesis
prompted this investigation in order to provide data on the presence of pathological changes in the liver
and gonads of several deep-water fish species. Fish were obtained from the north east region of the Bay
of Biscay (north east Atlantic Ocean) by trawling at depths between 700 and 1400 m. Liver and gonad
samples were collected on board ship and fixed for histological processing and subsequent examination
by light microscopy. Hepatocellular and nuclear pleomorphism and individual cases of ovotestis and foci
of cellular alteration (FCA) were detected in black scabbardfish (Aphanopus carbo). Six cases of FCA were
observed in orange roughy (Hoplostethus atlanticus) (n ¼ 50) together with a single case of hepatocellular
adenoma. A wide variety of inflammatory and degenerative lesions were found in all species examined.
Deep-water fish display a range of pathologies similar to those seen in shelf-sea species used for international
monitoring programmes including biological effects of contaminants. This study has
confirmed the utility of health screening in deep-water fish for detecting evidence of prior exposure to
contaminants and has also gained evidence of pathology potentially associated with exposure to algal
toxins.