Accidental interaction between cetaceans and the surface longline by the Spanish fleet from Atlantic Ocean

POSTER

Surface longlining is one of the most common fishing gears to capture swordfish (Xiphias gladius) and blue shark (Prionace glauca) in the Atlantic Ocean. Many Atlantic coastal countries (e.g. Spain, Portugal, Brazil, United States, Uruguay), as well as others from distant regions (e.g. Japan, China, Taiwan, Korea), fish in the Atlantic using this technique. Although it is a selective gear that does not usually interact with cetaceans, sometimes they do. In this work, the information from the Spanish On-Board Observer Program is analyzed, versus the data from an Electronic Monitoring System (EMS). During the period 2018-2022, a total of 3,246 fishing sets were analyzed, corresponding to 3.6 million hooks. Incidental catches of marine mammals are very low with a frequency of approximately one individual every 300,000 hooks. Dolphins emerge as the most frequent group, with 8 interactions involving at least 5 different species, with bottlenose dolphin (Tursiops truncatus 3 interactions) and false killer whale (Pseudorca crassidens; 2 interactions) being the most frequent. Furthermore, there were documented four entanglements of humpback whales (Megaptera novaeangliae) specimens. The number of entanglements observed in the EMS was smaller than those observed by onboard observers, which could suggest that the EMS tends to underestimate the fishing interactions of cetaceans in the open sea. This finding highlights a discrepancy that requires further investigation and evaluation, shedding light on potential limitations or biases inherent to the electronic monitoring system.