Cut the line or remove the hook? An evaluation of sublethal and lethal endpoints for deeply hooked bluegill

摘要

Research on a wide range of fish species has revealed that deep hooking is perhaps the single most important determinant of injury and post-release mortality in recreational fisheries. However, there is little information on the best option for dealing with deeply hooked fish that are to be released; should the line be cut or should the hook be removed? Using bluegill sunfish (Lepomis macrochirus) as a model we investigated sublethal (e.g., swimming performance, physiological condition, injury levels) and lethal consequences associated with removal of deeply ingested hooks versus cutting the line and leaving the hook embedded in the esophagus, relative to shallowly hooked controls. Neither hook retention nor deep hook-removal altered the swimming performance of the fish in this study relative to controls. However, there was evidence of short-term physiological disturbance. For example, hematocrit was reduced for fish that had hooks removed, consistent with visual observations of bleeding. In addition, blood glucose levels tended to be higher and plasma Na super(+) levels tended to be lower in deeply hooked fish that had hooks removed indicating stress and ionic imbalance even 24h after capture. During holding experiments we noted the highest mortality levels in fish for which the hook was removed (33% after 48h and 44% after 10 days). Mortality rates were lowest for the controls (0% after 48h and 4% after 10 days) and intermediate for the line-cut treatment (8% after 48h and 12.5% after 10 days). After 48h, 45.5% of the fish from the line-cut treatment group were able to expel the hook originally embedded in their esophagus, and at the end of the 10 day study, 71.4% had expelled the hook. Even with the hook left in the esophagus, fish were able to feed although at lower rates than controls during the first 48h of holding. By 10 days post-capture, there were no differences in feeding rates as evidenced by growth patterns among the treatment groups, nor were there differences in the hepatosomatic index. Collectively, the findings from this study demonstrate that cutting the line is a more effective release method than removing the hook when fish are deeply hooked. As such, angler education efforts should focus on disseminating this message to anglers as well as encouraging the use of gear and techniques that minimize incidences of deep hooking (e.g., circle hooks, non-organic bait).