The introduced green crab (Carcinus maenas) as a novel food resource for the opportunistic kelp gull (Larus dominicanus) in Argentine Patagonia

KASINSKY, TATIANA; ALEJANDRO GATTO; KASINSKY, TATIANA; ALEJANDRO GATTO; PABLO MARTÍN YORIO; POLLICELLI, MIRIAM; PABLO MARTÍN YORIO; POLLICELLI, MIRIAM; SUÁREZ NICOLÁS; CYNTHIA IBARRA; SUÁREZ NICOLÁS; CYNTHIA IBARRA

Aquatic Invasions

Regional Euro-Asian Biological Invasions Centre

Lugar: Helsinki; Año: 2020 vol. 15 p. 140 - 159

1798-6540

Introduced species are one of the main threats to biological diversity, but they can alsofacilitate native species through mechanisms such as trophic subsidy. We quantifiedthe diet of breeding kelp gulls (Larus dominicanus) and their consumption of theintroduced green crab (Carcinus maenas) at five colonies located along over 600 kmof coastline in Patagonia, Argentina, and analyzed differences in consumption ratesamong breeding locations. Results based on pellet analysis (n = 961 pellets) showedthat kelp gulls consumed green crabs during most or part of the breeding cycle atall study locations (0?73.9%, depending on location, year and breeding stage).Green crab consumption differed among breeding locations, with lower consumptionfurther from the reported location of first Argentinean introduction (Golfo SanJorge, Chubut, Patagonia) in 1999?2000. Despite kelp gulls regularly consumedgreen crabs at most breeding locations, this invasive species was not an importantcomponent in their diet. Both stomach content and stable isotope analyses frombreeding kelp gulls indicated that the main prey were fish such as Argentine anchovyand Argentine hake (Engraulis anchoita and Merluccius hubbsi, respectively) andsquat lobster (Munida gregaria). At Isla Vernaci Este and Punta Tombo, green crabswere found in only one stomach of all kelp gull age classes sampled (incubatingadults (n = 42), young chicks (n = 75), and old chicks (n = 105)). Based on carbonand nitrogen isotopic values from blood samples from incubating adults (n = 54),Bayesian mixing model outputs showed that green crabs contributed 7.3?23.9% tothe overall diet. The study showed that the relatively recent introduction of greencrabs supplements the available prey base of a widely distributed and abundantpredator, the kelp gull, at least during its breeding season in a large coastal sector ofcentral Patagonia. The extent to which the kelp gull in coastal Patagonia may beshaping the establishment, abundance, and population dynamics of the introducedgreen crab is still unknown and will require further research.