Mystic Aquarium

Mystic Aquarium scientists participated in a series of studies investigating the potential effects of repeated chase and encirclement on northeastern offshore spotted dolphins (Stenella attenuata attenuata) and eastern spinner dolphins (Stenella longirostris orentalis ). The studies were mandated by Congress to investigate whether the eastern tropical Pacific tuna fishery is having a significant adverse impact on these dolphin stocks.

These studies known as the Chase Encirclement Stress Studies (CHESS), included analyses of blood constituents, immune function, thermal condition, behavioral ecology, reproductive parameters, set-associated behavior after chase and encirclement with a tuna purse seiner. Scientists at Mystic Aquarium led the blood constituent and immune function analyses. The expected acute stress response was measured through several lines of investigation. Samples from those animals that were repeat captured 2 and 3 days later revealed a decrease in immune function; however low sample size prevented definitive conclusions from being drawn. CHESS have provided new and informative data on stress processes in pelagic dolphins involved in the tuna fishing operations; however, there is insufficient evidence to establish whether or not repeated chase and encirclement leads to a serious injury, adverse effects on reproduction, increase in disease susceptibility and/or post-release mortality without further investigation.