Southern rockhopper penguin eye. The rockhopper penguin complex is confusing. Many taxonomists consider all three rockhopper penguin forms subspecies. Some split the northern subspecies ("moseleyi") from the southern forms ("chrysocome" and "filholi"). Still others consider all three distinct. The subspecies recognized for the southern rockhopper penguin complex are: The northern rockhopper penguin lives in a different water mass than the western and eastern rockhopper penguin, separated by the Subtropical Front, and they are genetically different. Therefore, northern birds are sometimes separated as "E. moseleyi". The rockhopper penguins are closely related to the macaroni penguin ("E. chrysolophus") and the royal penguin ("E. schlegeli"), which
Northern rockhopper penguin drop in the population at Gough Island has been described as equivalent to the loss of 100 birds every day since the 1950s. A study published in 2009 showed that the world population of the northern rockhopper had declined by 90% since the 1950s, possibly because of climate change, changes in marine ecosystems and overfishing for squid and octopus by humans. Other possible factors in the decline include disturbance and pollution from ecotourism and fishing, egg-harvesting, and predation and competition from subantarctic fur seals ("Arctocephalus tropicalis"). Surveys show that the birds are at risk of infection by goose barnacles. House