Assessment of fish welfare in trawl caught atlantic herring

Sammanfattning

With the gain of scientific evidence concerning nociception in fish, the awareness about fish's welfare has been increasing not only for authorities but also for consumers. However, there is still a long way to go concerning how fish are being caught and slaughtered. In terms of welfare, fisheries are without any doubt a source of both stress and pain. Trawling has proved to be the most stressful fishing method; nevertheless, little has been done to try to minimise or better avoid such stress. This study's goal was to assess the welfare of pelagic fisheries using Atlantic herring (Clupea harengus) as a model. This study stands out from others because it follows the fish from the minute it is pumped until they are dead. Two research trips were made, one onboard a commercial trawler and the other on a vessel that uses a hook in line as its fishing gear. Each captured individual went through a series of tests. First, consciousness assessments and morphological injuries and then blood sampling to get the physiological indicators of stress and x-ray to check for internal damage. Overall, individuals captured by a commercial trawler present higher mortality and extreme stress levels when compared with the ones caught by hook in line. However, the morphological assessment showed that all the individuals caught during the first research trip appeared to be fine apart from the scale loss. Therefore, based on the results of this study, it is possible to see that the welfare of fish is highly compromised during pelagic fisheries. However, it is hard to pinpoint the exact cause of death. Most likely, the individuals died due to a combination of factors, where osmotic imbalance due to the impairment of the skin and the overcrowding at the cod end are believed to be the most significant ones.