Chase Encirclement Stress Studies on Dolphins Involved in Eastern Tropical Pacific Ocean Purse-Seine Operations During 2001

摘要

A suite of complementary stress studies was conducted August-October 2001 to investigate potential effects of repeated chase and encirclement on northeastern offshore spotted dolphins (Stenella attenuata attenuata) and eastern spinner dolphins (Stenella longirostris orientalis). The studies were conducted as part of a larger research program mandated under the 1997 International Dolphin Conservation Program Act (IDCPA) to investigate whether the eastern tropical Pacific tuna fishery is having a significant adverse impact on these dolphin stocks. Known collectively as the Chase Encirclement Stress Studies (CHESS), the investigations included analyses of blood constituents, immune function, thermal condition, behavioral ecology, reproductive parameters, set-associated behavior, and stress-response protein profiles in spotted dolphin skin. Several lines of investigation revealed the expected acute stress-response in chased and captured dolphins. Concurrent histopathological studies in other dolphins sampled in conjunction with the tuna fishery demonstrated focal heart lesions as evidence of prior tissue damage in 36% of the individuals. These lesions are the likely consequence of stress responses that may or may not have been fishery related, but nevertheless are consistent with changes in circulating adrenal hormones observed in the dolphins that were sampled during this study. Considered together and in combination with other IDCPA studies, the investigations that comprised CHESS have provided new and informative baseline data on stress processes in pelagic dolphins involved in tuna fishing operations; however, there is insufficient evidence to establish whether or not repeated chase and encirclement leads to serious injury, negative effects on reproduction, or cryptic post-release mortality.