Evaluating dolphin damage in trammel net fisheries in the Valencia region: Insights to improve management

Abstract

[EN] Interactions between dolphins and trammel net fisheries have been described in the Mediterranean Sea as having negative consequences for both cetaceans and fishers. There is a need for studies that evaluate the economic costs caused by dolphins feeding from entangled fishes in trammel nets since most cetacean species involved in these interactions are endangered. This study aims to evaluate the economic impact of the interaction between dolphins and trammel nets fisheries in the coastal waters of the Valencian region in the western Mediterranean Sea. We conducted at-port visual inspections of nets from April 2018 to March 2019, which included 1,849 fishing operations with trammel nets, and we recorded damages to the net and catch and the value of the fishery. Thirty-two interactions were detected during the year of the study. The only observed species interacting was the common bottlenose dolphin. No bycatch of dolphins was reported. The interactions have been impacted seasonally and most of them took place in February and March. There were no significant differences in catch when comparing sets with and without depredation or damage in nets due to depredation by dolphins. Also on average, no differences were found in the value of the catch when comparing sets with or without damage caused by dolphins. The main cost to the fisher was the cost of repairing the nets. The estimated financial loss per vessel and year was €556 (95%CI: €303¿€809). This represents less than 1% of the total yearly income of each vessel in our area. We suggest implementing tools to economically compensate artisanal vessels for any damage caused by dolphins in order to avoid increasing the hostile feeling of fishers towards dolphins and to apply conservation measures to protect this cetacean species.