| Sharks, tunas, and billfishes are fished extensively throughout the world and large numbers are released annually due to domestic and international management measures. The extent to which capture stress affects post-release survivorship is unknown for many of these species. Most fishing techniques cause high anaerobic activity, muscular fatigue, and time out of water, resulting in physiological homeostatic disruptions that may compromise survivorship. In this study, blood biochemistry coupled with tagging and acoustic tracking were used to quantify physiological disruptions associated with capture stress in large pelagic fishes and to test hypotheses on post-release survivorship given this perturbation. Blood was sampled from 356 fish comprising 15 species of tunas (n=237), sharks (n=91), and marlin (n=6) after exposure to rod and reel capture. For each species or species group, physical and environmental factors related to the angling event were correlated to blood chemistry parameters using multifactor analyses of variance. For those species with statistically meaningful sample sizes (bluefin tuna [Thunnus thynnus], yellowfin tuna [T. albacares], skipjack tuna [Katsuwonus pelamis], Atlantic bonito [Sarda sarda ], and blue sharks [Prionace glauca]) significant (p<0.01) linear relationships were found between angling time and blood cortisol, pH and gases, lactate, glucose, and electrolytes, indicating significant homeostatic perturbations as consequences of capture. Conventional tagging, pop-up satellite tagging, and acoustic tracking were used to assess post-release behavior and survivorship of fish with known blood chemistry. Of the 202 fish tagged after blood sampling, four bluefin tuna, two yellowfin tuna, and seven blue sharks were subsequently recaptured 44-1,580 days after release. Seven bluefin tuna, four yellowfin tuna, two white marlin, and four blue sharks were acoustically tracked for 1-24 hours after prolonged angling bouts; blood chemistry data were indicative of greater than average levels of stress. With the exception of one bluefin tuna, tracked fish survived and exhibited distinct post-release recovery periods of about two hours characterized by limited vertical activity. It is hypothesized that physiological disturbances were corrected during this period. The results of this study support the hypothesis that pelagic sharks, tunas, and marlin are capable of recovery from physiological stress when not subjected to extensive physical trauma. |
