Abstract
The effects of pelagic trawling on the health and welfare of Atlantic herring (Clupea harengus L.) were investigated on a refrigerated seawater vessel operating in the North Sea. A total of 495 Atlantic herring (Clupea harengus L.) were sampled during five hauls from two fishing trips in September 2021 and 2022. For assessments of consciousness and mortality, a Reflex Action Mortality Predictor test (i.e. RAMP-test) was used on herring collected following trawling and pumping. Inspections for external and internal damage or wounds were performed via morphological welfare indicators and analyses of photos and radiographs. In addition, blood samples were taken and analysed for haematological indicators of stress. Following trawling and pumping, only 5% of the investigated herring showed signs of external wounds associated with the morphological indicators of welfare, and no internal damage was observed in the radiographic inspections. However, 96% of the assessed herring scored 0 on all three reflexes included in the RAMP-test and were therefore judged dead. On average, herring lost 95% of their scales, while 95% of herring had a very high degree of ruptured red blood cells (i.e. haemolysis). Extensive scale loss results in a deterioration of the skin's protective barrier function, which in turn impairs the osmoregulatory capacity of the herring. This was evident by elevated levels of plasma osmolality and circulating chloride concentrations, which could also likely explain the high occurrence of haemolysis in captured herring. Extended trawling time and larger catch size proved to be two important factors to consider, as the former led to increased plasma levels of osmolality, whereas the latter was associated with elevated plasma levels of lactate and cortisol. In conclusion, the high mortality appears to be influenced by a combination of factors such as severe stress, loss of osmoregulatory ability, crowding density within the trawl, and extended trawling times. This study provides important information on the welfare of wild Atlantic herring caught using pelagic trawls and highlights areas where improvements can be made to safeguard the welfare of fish captured in pelagic fisheries in the future.
| Originalsprog | Engelsk |
|---|---|
| Artikelnummer | 17530 |
| Tidsskrift | Scientific Reports |
| Vol/bind | 14 |
| Antal sider | 12 |
| ISSN | 2045-2322 |
| DOI | |
| Status | Udgivet - 2024 |
Bibliografisk note
Funding Information:We sincerely thank the crew of HG62 Beinur for their hospitality and technical assistance during our fishing trips in the North Sea. We also appreciate the support of Animal Protection Denmark and the Danish Pelagic Producers Organisation (DPPO) for initiating the project and providing practical and administrative assistance. Special thanks to Lina de Nijs for her fieldwork assistance and valuable discussions, as well as to Dorte Schr\u00F8der-Petersen and Martin Pastoors for their insightful discussions. Additionally, we are grateful to Dr. Jeroen Brijs for his valuable input on the final manuscript and constructive feedback during the review process. This research was supported by Open Philanthropy.
Publisher Copyright:
© The Author(s) 2024.