Health Assessment In The Bowhead Whale

Abstract

Tissue samples and morphometric data were collected from 64 bowhead whales landed during the 1998-2002 subsistence hunts in Barrow and Kaktovik, Alaska. Our primary goal was to assess the health status of the Bering-Chukchi-Beaufort Seas stock of bowhead whales. Ages of whales were determined via aspartic acid racemization of the eye lens nucleus, baleen stable carbon isotope analysis and morphometric and histologic indices. We investigated the gross and microscopic anatomy of organs and blubber, thyroid hormone concentrations, serum haptoglobin, vitamin A and E concentrations in liver, blubber and serum and essential element concentrations in liver and kidney. Thyroid hormone and vitamin A were also evaluated as potential biomarkers of organochlorine (OC) concentrations in blubber, liver and serum. Neither of these substances was found to correlate with the relatively low OC concentrations found in these mysticetes. Histological changes of interest included renal interstitial fibrosis, hepatic periportal fibrosis/pigmentation/lipidosis, splenic extramedullary hematopoiesis and pulmonary fibromuscular hyperplasia. Changes in the kidney and lung were related to both age and renal and hepatic Cd concentrations. Most of the histological differences observed did not appear to adversely affect organ function or health of the individual. Thyroid hormone concentrations were stable over age/sex/seasonal groups, however, pregnant females had significantly lower total and free thyroxine than non-pregnant adult females and other age-sex classes. Serum haptoglobin was measured as an indirect determinant of acute inflammation, with three reactors found among 51 whales examined. Liver contained the highest mean concentrations of vitamins A and E (followed by epidermis, blubber, and serum and serum, epidermis, and blubber, in order). Finally, blubber percent collagen was measured at 30 locations on each whale and was found to be stable by site and most depths, with the most internal region of the reticular dermis being the only exception. Overall, the bowhead whales were healthy. However, climate change, offshore development and increases in arctic pollution emphasize the importance of baseline data collection. An ongoing surveillance effort is recommended to ensure that the species will be viable for generations to come and to assure subsistence users of the robust and healthy status of this stock of whales.