Impacts of ghost fishing on European lobster (Homarus gammarus) and brown crab (Cancer pagurus) in Raet national park, Norway
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Lost fishing gear pose a threat to marine life in large parts of the world. Fishing gear have the potential to continue to fish for a long time after it has been lost, referred to as “ghost fishing”, an issue which has achieved increased attention the past years. The impacts of ghost fishing on different species vary, for example depending on gear type and location. This study investigated effects ghost gear had on lobster (Homarus gammarus) and brown crab (Cancer pagurus) in Raet national park, situated on the Norwegian Skagerrak coast. Gear used in these analyses (n = 1502) were retrieved by using remotely operated vehicle (ROV) from June 2019 – March 2022. A total of 68 lobsters and 944 brown crabs were retrieved throughout the study period. Total loss of lobster and brown crab to ghost fishing were estimated and compared to commercial and recreational landings. Three scenarios are presented, depending on the assumed survival of lobster and brown crab caught in lost gear of three, six and 12 months. A considerable share of study species could potentially be fished by ghost gear compared to local landings. Between 466 (12 months survival) and 1864 (3 months survival) lobsters were estimated to be lost to ghost fishing each year, while 726 were reported in the commercial fishery and 7932 were caught in the recreational fishery. For brown crab, between 6468 (12 months survival) and 25872 (3 months survival) could be lost due to ghost fishing each year. Commercial catches of brown crab were 3228 individuals. By comparing the ghost gear catches to the estimated lobster population, 12% could be lost due to ghost fishing in Raet national park each year. There were significant size differences between individuals caught in ghost gear and measurements from standardized trap fishing experiments. Ghost gear appeared to accumulate larger brown crabs, whereas the median of lobsters caught in ghost gear were close to the minimum legal size (25 cm). There were seasonal variations in number of lobster and brown crab in ghost gear, peaking towards the last months of the year for both species. Wrasse traps had the highest catch per unit for both study species. The overall findings suggest ghost fishing potentially having a considerable impact on the study species in the national park. Recommendations on reducing impacts of ghost gear in the future are to target newly lost gear with high catch per unit of animals, in addition to increased awareness on how to properly prepare and set the gear in order to reduce human-induced losses.