Time matters: post-surgical recovery of gastric evacuation rate in Atlantic cod

During the last decades, new technology has allowed collection of physiological and behavioral data from free-ranging specimen, minimizing stress and providing more reliable data than traditional methods. However, such biotelemetric methods demands surgical introduction of a foreign object into the fish, which may affect the animal, and studies dealing with the affect of surgery and implants are still scarce. A variable known to be sensitive to postsurgical and other stressors is the gastric evacuation rate (GER). GER is tightly linked to gut blood flow and in the present study we analysed how GER was affected after surgically introducing dummies of a blood-flow biotelemetry system into the abdominal cavity of Atlantic cod. Two days post surgery the cod with implants were, together with a control group, force-fed a standardized meal and the stomach contents recovered 24h later. This procedure was repeated for both groups of fish after one additional week of recovery. After two days GER was significantly lower in the group of fish with surgical implants compared to the control group, but the difference was not maintained after one additional week of recovery. We conclude that 10 days of postsurgical recovery will stabilize GER in cod. The results indicate that the presence of the implant per se did not affect GER but that the effects observed came from surgery and/or postsurgical stress. 10 days should consequently be a starting point for future studies even if longer recovery periods will probably be beneficial to the animal