Capture-induced stress in deep-water Arctic fish species

Abstract

There are significant conservation benefits to studying the stress response of commercially important fish species. Particularly in the Arctic ecosystem, where reducing ice extent has resulted in heightened interest in developing commercial fisheries, there is a need to better understand how fish respond to capture stressors. To that end, blood lactate and glucose of Greenland halibut Reinhardtius hippoglossoides and Greenland shark Somniosus microcephalus were assessed after capture from fishing gear to evaluate factors that might influence physiological disturbance. Greenland halibut lactate values had a mean of 1.0 ± 0.7 mmol/L and showed a positive relationship with time since capture. Blood glucose concentrations for Greenland halibut had a mean of 1.8 ± 0.6 mmol/L and were positively related to both time since capture and fork length. Greenland shark lactate values varied depending on depth, with individuals captured at 300–600 m displaying significantly lower concentrations (1.6 ± 0.5 mmol/L) than those caught at depths between 600 and 700 m (6.4 ± 2.4 mmol/L) and 700–900 m (3.7 ± 1.2 mmol/L). Glucose values for the Greenland shark had a mean of 4.9 ± 1.5 mmol/L and were positively correlated with body length. Relative to temperate fish species, the metabolite concentrations are low but the inherent challenges with deep-water fish makes it difficult to obtain baseline (pre-stress) values to quantify the magnitude of stress response. This is the first study to document stress metabolites in these two Arctic species and suggests that there is a body size and depth-related physiological response to capture.