Differential sensitivity to capture stress assessed by blood acid–base status in five carcharhinid sharks

Abstract

Stress from fishing capture can incite potentially lethal physiological changes in fishes. Blood acid-base status has routinely been utilized to gauge the magnitude of the stress response, which is dependent on the nature of the capture event and metabolic capacity of the species in question. The mortality induced by demersal longline capture has been shown to vary among taxonomically similar carcharhinid elasmobranchs. In this study, we aimed to: (1) quantify and compare blood acid-base disturbances associated with longline capture in five carcharhinid species; (2) examine the extent to which these disturbances correspond with reported at-vessel mortality rates; and (3) investigate how interspecific differences in the physiological stress response could relate to life history, ecology, and phylogeny. Results showed that blood acid-base disturbances from longline-capture varied between species, with relative degrees of disturbance by species proportional to previously reported at-vessel mortality rates. In addition, the degree in which metabolic and respiratory acidoses influenced relative depressions in blood pH also differed by species. The differences in blood acid-base status point to discrepancies in the aerobic and anaerobic capacities among these taxonomically similar species, and are important when considering the effects of, and possible means to mitigate deleterious consequences from, longline fishing capture.