Encorat project proposes the seasonal management of gillnets to protect crested cormorants

O proxecto Encorat propón a xestión temporal das pesquerías de enmalle para protexer os corvos mariños cristados

Led by the Animal Ecology Group (GEA) of CIM-UVigo, its conclusions were presented on Monday. The installation of LED lights on the nets has not been effective in reducing accidental bird mortality

The crested cormorant is an endangered seabird that has suffered a significant decline in recent years throughout Spain due to overfishing of its prey species, oil pollution and, according to several previous studies by the Animal Ecology Group of the Marine Research Center of the University of Vigo, accidental mortality in gillnets. To address the latter aspect, project Encorat – Actions to reduce the accidental mortality of the cormorant (Phalacrocorax aristotelis) in gillnets in the North Atlantic Marine Demarcation, was launched earlier this year.. With funding from the Biodiversity Foundation through the Pleamar program, the research group from the CIM-UVigo, with the collaboration of the Department of Biology of Organisms and Systems of the University of Oviedo  focused, on the one hand, on evaluating the effectiveness of a prototype LED light fixture installed in gillnets to prevent accidents and, on the other hand, to carry out a study on the feeding areas of individuals and their overlap with fishing areas.

The team, led by GEA researcher José Carlos Noguera, presented their conclusions on Monday after working for one year in Galician and Portuguese waters, in a virtual event through the UVigo Remote Campus. José Carlos Noguera was accompanied by researchers Álvaro Barros and Alberto Velando, from the University of Vigo and David Álvarez, from the University of Oviedo. Barros explained that over the past year, 46 juvenile birds were tagged with GPS devices in different breeding colonies on the Ons and Sagres islands, in the Atlantic Islands National Park, “which is where there are enough nests and accessible locations to work.” This action made it possible to obtain more than 18,000 locations. The spatial analysis of the data obtained indicates that “there are differences related to sex in the post-generative dispersive movements, with females being the most dispersed”. He also pointed out that the analyses indicate that the juvenile feeding area increases with age, standing within a maximum radius of 4km around the breeding colonies during the months of May and June and then locating at a maximum of 8km. Based on these data, the researchers recommend “carrying out a seasonal management of fisheries based on the use of gillnets in areas of greatest use by juvenile birds, for example, by limiting the number of fishing boats within 4km of the colonies between May and August”. In these areas of special protection, Barros points out, “we should start thinking about limiting uses and it should be a good start of the dialogue to limit certain fishing devices in specific periods of the year and in defined locations, if with these measures we achieve an important reduction in the mortality of endangered species”.

LED devices did not prove to be effective

The other line of research of the project aimed at reducing the accidental capture of crested cormorants by installing LED-type light devices in the gillnets. The idea was that the lights would allow the birds to detect the presence of the nets in the water and thus avoid them. After field experiments carried out in Galicia and Asturias, specifically on two coastal vessels in the ports of Tapia de Casariego and Laxe, they were able to show that the installation of these devices in the fishing gear had no effect on fishing activity,number of catches, or in the economic results  of fishing trips. Another important conclusion of the study is the confirmation of “suspicions of high mortality in this type of gillnet”, as in the course of the project they were able to ascertain the death of at least five individuals in the rigs of three ships, as explained by José Carlos Noguera. “It may seem that there are not many, but if we take into account that it was for 15 days of work and that in all of Galicia there are about 1000 boats with permission for this type of device and another 221 in Asturias, we can get an idea ofthe conflict  with this type of activity ”. However, he also emphasized that not all of the boats work in zones dangerous for crested cormorants. The results are also very relevant, as “this is the first study carried out in the North Atlantic demarcation that demonstrates the capture of crested cormorants crested in gillnets,” as Álvaro Barros pointed out.

The other part of the study, which aimed to evaluate the efficiency of LED installation in nets, did not get the expected results. Scientists could not observe a positive effect of these devices to reduce the accidental mortality of these birds. However, the results do confirm, the researcher point out, “an association of mortality with certain environmental conditions that could have affected the effectiveness of the devices.” Based on these data, the main researcher of the project José Carlos Noguera points to the need of conducting large-scale studies on the effectiveness of these deterrent devices, as well as try different designs.

In conclusion, the researchers consider it advisable to carry out a detailed in situ study of the use of gillnets and their relationship with mortality, as well as to implement mitigation measures in areas of special protection, such as Natura Network spaces, which are home to importantpopulations of this species, including in this group the National Park of the Atlantic Islands of Galicia.

Source: DUVI