Blood chemistry, hematology, and morphology of wild harbor seal pups in Alaska

Recent declines in harbor seal (Phoca vitulina) populations in Alaska have emphasized the need to obtain health index biomarkers for comparative purposes. This study was designed to compare blood chemistry and morphology reference range values between 2 harbor seal pup populations in Alaska, 1 population in continued decline within Prince William Sound, and another population in recent increase on Tugidak Island. Significant site-specific differences occurred in 5 of the 8 mean hematology values as well as in 11 plasma chemistry values. We also determined significant year-to-year variability in 8 (36%) mean plasma chemistries. These results form the largest available field-based blood reference database for harbor seal pups. They demonstrate that blood values can vary on the population scale and that health assessment or ecophysiological studies involving blood chemistry must utilize an appropriate set of reference values for valid comparisons.