Population trends, breeding success and diet composition of gentoo Pygoscelis papua, magellanic Spheniscus magellanicus and rockhopper Eudyptes chrysocome penguins in the Falkland Islands

Data on population size, breeding success and diet composition of gentoo (P ygoscelis papua), magellanic (Spheniscus magellanicus) and rockhopper (Eudy ptes chrysocome) penguins, collected as part of the Falkland Island Seabird Monitoring Programme from 1986/1987 to 1998/1999, were analysed with regar d to spatial and temporal variation, as well as potential interaction with local commercial fisheries. No significant population trends were detectabl e, mainly because of the short time-series and large spatial and inter-annu al variation in the number of breeding pairs in the colonies monitored. How ever, the breeding success of all three penguin species has improved slight ly over the last few years, indicating a potential for increasing populatio ns in the near future. During the breeding season, all three penguin specie s preyed opportunistically on a mixture of fish, squid and crustaceans. Die t composition too showed a high degree of spatial and temporal variation. H owever, in all three penguin species studied, squid gradually disappeared f rom the diet over successive years, to be replaced by fish. Coincidentally, the commercial catches of the squid species Loligo gahi in Falkland Island s waters decreased and the by-catch of nototheniid fish increased. All thre e penguin species compete directly with the commercial fishing fleet for L. gahi; however, there may also be competition for Patagonian toothfish (Dis sostichus eleginoides), hake (Merluccius sp.) and southern blue whiting (Mi cromesistius australis), because juveniles of these species were found regu larly in penguin diets.