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The general objective of the project is to establish a collaboration between the artisanal fishing sector and the conservation of the Mediterranean shag. A collaboration that will make this fishery more sustainable, especially in protected areas on the coast of Catalonia, the Balearic Islands, Murcia and the Valencian Community.

Specific objectives:

(1) Reduce by-catch of shag in the artisanal fixed-net fishery within and outside the Natura 2000 Network.
(2) To know the coastal fish community and its intra- and inter-annual fluctuation through the diet of the shag.
(3) Detect and describe the areas of interaction between the shag and the fishery that is the protagonist of the study.
(4) Determine the parasite load of the shag and evaluate which fish species participate in closing the life cycle of the parasites; fish with a higher prevalence of parasites that would reduce their quality for human consumption and that would be the vectors of transfer to the cormorant with effects on their physical condition.

– Action 2: Evaluation of coastal fish communities, through the use of prey ingested by the European shag as a bioindicator.
– Action 3: Monitoring and habitat use of the shag
– Action 4: Seabed mapping. From the tracks recorded by the GPS devices installed on the artisanal boats and the cormorants.
– Action 5: Parasites. Anisakid infection in the shag
– Action 6: Disclosure. Action focused on the dissemination of the results derived from the project.

For objective I, mitigation of bycatch, 21 artisanal fishing vessels have been monitored with GPS devices to better understand their way of working and determine areas of interaction with shags. More than 100 mitigation tests have also been carried out on eight vessels, using lights and scarecrow elements to prevent birds from becoming entangled in the nets. These measures have been accompanied by an analysis to determine effects on the catchability of commercial species and other bycatches. Likewise, the link and cooperation with the fishing sector has been strengthened. By means of autonomous hydrophones, faunal groups such as cetaceans have been identified interacting near the fishing nets, with the bottlenose dolphin (Tursiops truncatus) being the main cause of the interaction and breakage of the nets.

A historical evolution of the artisanal fixed-net fishery has been carried out using data extracted from the artisanal fleet census and 15 interviews with active or retired fishermen, with the intention of determining how fishing effort has varied and how it may have affected the population dynamics of the shag.

As for objective II, 1,000 pellets have been analysed and a diet of great richness has been discovered, which can be used as a bioindicator of the coastal fish community. 10 fortnightly samplings (May-November) and one punctual (summer) have been carried out in Catalonia, the Valencian Community (Castellón) and Murcia. In addition, 60 stable isotope analyses have been carried out on the captured shag for tagging.

It has been observed that the presence of Gymnammodytes sp., Ariosoma balearicum, Trachinidae and Sparidae is dominant each year. There are alternations between species, but it is closely related to the presence or absence of the sonso. There appears to be a predator-prey relationship between Gymnammodytes sp. and Ariosoma balearicum, but both the Trachinidae and the Sparidae replace the sonso when it decreases in presence. It is a varied diet that fits into the existing fish community. It can function as a regulator of these communities. It has a similar dynamic to the artisanal wool fishery, which provides information for its management.

For objective III, the breeding and resting areas of the species have been delimited to create these areas at risk of interaction with gillnets. A total of 14 chicks and 49 adults of different ages were tagged, most of which came from roosts and secondly from nests. The ages of the tagged specimens vary from chicks to adults over three years old. From the movements of the 25 specimens marked with GPS, movements are observed a short distance from the coast, related to fishing activity, and fidelity to nests or roosts.

The fishing areas of the breeding specimens are close to the nests with a high frequency and only make occasional routes further away. There is a very marked relationship throughout the year between the continent and the Balearic Islands. Fishing depths vary depending on the breadth of the continental shelf, and between continent and islands, mostly up to 20 meters, but reaching 60 m. Cormorants’ feeding is focused on the daytime period, with an average frequency of 20 dives per hour.

The existing cartography has been analysed and a new device has been designed to map the seabed in a simple way. Finally, 195 hectares of mapping not known to date are provided, creating maps that present the tracks together with the seabed cartography found/made. A non-mapped area has been prioritized and is very important as a foraging area for cormorants. This area is considered the most important fishing ground for sandeel (Gymnammodytes spp.) in Catalonia. A dam that modulates the presence of cormorants and is highly coveted by artisanal fishermen.

For objective IV, parasites, the presence of parasites has been quantified, confirming that shag cormorants have a high number of these parasites, which could affect populations and that it would be necessary to continue studying.

From the collection campaign of entangled birds, 13 specimens were obtained reported by the fishermen and collected by the members of the DESMARES II team. The digestive tracts of 16 cormorant specimens have been dissected to separate, count and identify the parasites present. It has always been a nematode that is quite certainly the species Contracaecum rudolphii, a parasite whose life cycle ends in the adult phase in the cormorant. The results show a very variable parasite load in the individuals studied, but extremely high in some of them.

The species of fish found in the stomachs are some of those already described as species present in their diet. Few species repeat in more than one stomach, which shows that it is an opportunistic or unselective species with its prey. The presence in the same stomach of several individuals of a given species such as sardines, castanets or three-tailed fish, fish that move in schools, shows that they also take advantage of the opportunity for large catches when possible.

Finally, with regard to the dissemination of the project, all the work carried out in this project has been shown to both the agents involved and the general public, with various articles for the informative press, press releases, information on radio and television with a large audience, as well as information panels, presentations at congresses, activities with talks, travelling exhibitions and the recording of three videos showing the main results. one of them in animation format.