What are some of the causes for the decline of the northern rockhopper?

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 (Arctophoca tropicalis).[6] Surveys show that the birds are at risk of infection by goose barnacles. House mice (Mus musculus) have been introduced into their environment by human sea expeditions. The mice have proven to be invasive, and consume northern rockhopper eggs, as well as hunt their young. In order to preserve the birds, a culling of the mice is being considered. The climate change conditions alter food availability since it reduces nutrients and productivity. This causes an effect on the body mass, causing a negative impact on their reproductivity success.

Some of the causes of the decline of the northern rockhopper include climate change, overfishing and introduction of invasive species such as mice.