Evaluation of the Behavioral and Physiological Effects of Internal Tagging on Atlantic Croaker

Benthic species such as Atlantic croaker found in the Chesapeake Bay during the summer months have been subject to an increase in the intensity and duration of hypoxia which may result in physiological stress and altered behavior. This study is part of a larger project which seeks to evaluate the behavioral responses of croaker under such conditions through acoustic telemetry. In order to eliminate confounding factors due to surgical implantation of acoustic tags, a laboratory study was conducted with croaker under similar environmental conditions as those found in the Bay. In this study, the behavioral and physiological responses of croaker (n = 24) surgically implanted with dummy transmitters (n = 12) and those without transmitters (n = 12) were compared under hypoxic (2 mg/L DO) and normoxic (6 mg/L DO) laboratory conditions. Fish were sacrificed after a 2-week acclimation period. Blood samples were collected for hematology, plasma chemistry and phagocytosis assays, and tissue samples were collected for histopathology. In addition, internal and external health assessments were performed on hypoxic and normoxic fish to assess their overall health. The results from this study were used to validate the survival and behavior of fish tagged surgically in the field study.