Skin lesions on North Atlantic right whales: categories, prevalence and change in occurrence in the 1990s.

North Atlantic right whales Eubalaena glacialis experienced decreased reproduction and body condition in the 1990s, causing concern about the overall health of this critically endangered population. Images from a detailed photo-identification catalog of right whales were analyzed for the presence of skin lesions. Lesions were categorized as white lesions or blister lesions and each of those categories were further divided based on lesion morphology and location. Of 439 whales photo-analyzed between 1980 and 2002, white lesions were detected on 227 ind. (51.7%) and blister lesions were found on 76 ind. (17.3%). The majority of white lesions (72.8%) were detected in the Bay of Fundy where their prevalence increased dramatically during the 1990s (peaking at 40 and 41% of all identified whales in 1997 and 1999, respectively). A correlation between whale density and white lesions in the Bay of Fundy suggested that this lesion type may have been the result of a contagious agent, though the data on mother/calf pairs did not indicate transmission from mother to calf. Blister lesions appeared at low levels throughout the population over the study period. Neither lesion category was more prevalent on males or females, nor were there any differences between adults and juveniles. One white lesion type appeared exclusively on whales that had been entangled, and whose subsequent survival was in most cases questionable. This is the first detailed analysis of skin lesions in this species. Only 1 tissue sample has been previously obtained from a lesion, and thus the histology and etiology of these lesions remain unknown. Further work is needed to explore the role of disease and environmental variables in lesion prevalence.