Title
Importance of fishery discards in the diet of Kelp Gull (Larus dominicanus) at Golfo San Jorge, Patagonia (Importance of fishery discards in the diet of Kelp Gull (Larus dominicanus) at Golfo San Jorge, Patagonia)
Author(s)
Zevallos, D. G.;Marinao, C.;Yorio, P.
Published
2017
Publisher
Ornitología Neotropical
Abstract
The consumption of fish discards at sea is currently an important component in the feeding ecology of many gull species. Diet studies are key to assess the relative contribution of discards to their trophic ecology, as well as to begin to understand the potential effects of fishing activity on their reproductive parameters and population dynamics. The present study analyzes the dietary composition of breeding Kittiwakes (Larus dominicanus) breeding on the northern coast of Golfo San Jorge, Chubut, Argentina, during the 2007 breeding season at three breeding localities: Isla Vernacci Sudoeste (45°11'S, 66°31'W), Isla Felipe (45°04'S, 66°19'W) and Isla Laguna (45°02'S, 65°53'W). Three sampling periods were selected: incubation, small chicks and large chicks. Diet samples were obtained by stomach washing. The results obtained in the three colonies analyzed confirm that in the coasts of northern Patagonia the Kittiwake is a generalist and opportunistic species that during the breeding season feeds on a wide variety of prey, mainly fish and marine invertebrates. During the large chicks stage, the frequency of occurrence of fish increased while that of polychaetes decreased. Fish were the most frequent prey in Golfo San Jorge, represented mostly by common hake (Merluccius hubbsi), a species of demersal habits, and therefore generally inaccessible to a surface predator such as the Kittiwake. It is highly probable that the common hake come mostly from discarded fish. Future studies should assess the spatio-temporal patterns in the distribution of fishing vessels and their relationship with the proportion of fishery discards in the diet of Cook's Gulls. The consumption of fishery discards at sea is currently an important component in the feeding ecology of many gull species. Diet studies are key to assess the relative contribution of discards in their trophic ecology, and to start to understand the potential effects of fishing activities on their breeding parameters and population dynamics. The present study analyzes the dietary composition of Kelp Gulls (Larus dominicanus) breeding on the northern coast of Golfo San Jorge, Chubut, Argentina, during the 2007 breeding season in three sites: Isla Vernacci Sudoeste (45 degrees 11 ' S, 66 degrees 31 ' W), Isla Felipe (45 degrees 04 ' S, 66 degrees 19 ' W) and Isla Laguna (45 degrees 02 ' S, 65 degrees 53 ' W). Three sampling periods were selected: incubation, small chicks and large chicks. Diet samples were obtained through stomach flushing. The results obtained in the three colonies analyzed confirm that on the northern Patagonian coast the Kelp Gull is a generalist and opportunistic species that feeds during the breeding season on a wide variety of prey, mainly fish and marine invertebrates. During the large chick stage, frequency of occurrence of fish increased while that of polychaetes decreased. Fish were the most frequent prey in the Golfo San Jorge, represented mainly by the Argentine hake (Merluccius hubbsi), a demersal species that is in general inaccessible for surface predators like the Kelp Gull. It is highly likely that Argentine hake consumed by Kelp Gulls comes mainly from fishing discards. Future studies should evaluate spatio-temporal patterns in the distribution of fishing vessels and their relation with the proportion of fishery discards in Kelp Gull diet.
Keywords
Argentina;Diet;Feeding ecology;Fishery discards;Golfo San Jorge;Larus dominicanus;Merluccius hubbsi;northern patagonia;feeding ecology;calonectris-diomedea;commercial;fisheries;seabird communities;incidental captures;chafarinas islands;trawl fisheries;argentina;marine;Zoology

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PUB21273