Bycatch mitigation measures to reduce the impact of fisheries-related mortality of cetaceans in north Spanish gillnet and purse seine fisheries

This is a poster presented at the 2023 ICES conference.

Mitigation measures and improvement of scientific knowledge to reduce accidental captures of cetaceans during fishing activities are the focus of regulations that respond to the need to adopt measures based on the EU request on "emergency measures to prevent the bycatch of cetaceans in the northeast Atlantic”. These emergency measures are aimed at eliminating, in particular, incidental catches of common dolphins (Delphinus delphis) in the Bay of Biscay. The most important and best documented threat to cetaceans in Spanish fishing grounds in the ICES area is that produced by entanglement in commercial fishing gear. The problem of accidental capture in different fishing grounds of the Iberian Peninsula has been known since ancient times and causes mortality rates that can be serious in some areas/species.
Acoustic deterrent devices test pilots have been carried out in NW Spain. Several different models of pingers have been used in the short distance gillnet fisheries in Galicia, to test their effectiveness in reducing catches of common dolphin and common porpoise (Phocoena phocoena). In the sardine purse seine fishery, the use of pingers has been tested to avoid the effect of predation and damage to the nets of bottlenose dolphins (Tursiops truncatus). The effectiveness of bycatch reduction devices such as pingers depends on the behavior of cetaceans in and around the fishing gear. Although there have been several previous studies, such behavior is likely to be species, gear, and catch reduction device specific and may vary regionally and over time, as responses may involve learned behavior. An approximation to the problem is carried out with the input of the fishing sector to study future directions. Lessons learned and potential measures are proposed based on the opinions of fishermen collected in surveys carried out on boats