Long-term variation in the breeding diets of macaroni and eastern rockhopper penguins at Marion Island (1994–2018)

Populations of the macaroni penguin Eudyptes chrysolophus and eastern rockhopper E. filholi breeding at Marion Island (Prince Edward Islands) in sub-Antarctic Indian Ocean decreased from 1994 to 2018. We examined their diets when rearing chicks during this period. There was substantial overlap two species, with crustaceans, dominated by euphausiids Thysanoessa vicina Euphausia vallentini, making up >80% number >60% mass over study The lanternfishes Krefftichthys anderssoni Protomyctophum tenisoni were most-commonly consumed fish diet penguins three 25 years (1994, 1998 2014); they also most commonly penguins. Macaroni more amphipod crustacean Themisto gaudichaudii lanternfish Electrona carlsbergi as well a greater diversity larger-sized than did horsefish Zanclorhynchus spinifer found amounts 1996 1997. Despite annual variations relative prey contributions diets, there no significant long-term changes either species period or compared an earlier assessment 1982. conclude that proportions these are unlikely account for recent declines populations.