AEBR 370 Spatial risk assessment of threats to yellow-eyed penguin/hoiho (Megadyptes antipodes)

Roberts, J.; Webber, D.N. (2025). Spatial risk assessment of threats to yellow-eyed penguin/hoiho (Megadyptes antipodes). New Zealand Aquatic Environment and Biodiversity Report No. 370. 162 p.

This research assessed the threats facing the northern population of yellow-eyed penguins/hoiho. The northern population includes the New Zealand South Island/Te Waipounamu and Stewart Island/Rakiura. Population models were developed for regional sub-populations from 1991 to 2023, to track changes in population size over time. The study found that hoiho numbers have declined across all areas, driven mainly by poor survival of juveniles and adults.

• Key threats include commercial set-net entanglements, which caused an estimated 17 deaths in 2022–23, mostly around Otago Peninsula, where risks have risen sharply since 2018–19.
• Malnutrition affects chicks and juveniles the most, particularly females, diseases have the greatest effect on chicks and juveniles, and predation primarily affects juveniles and adults.
• Warming sea temperatures across their range correlate with lower survival rates across all ages, suggesting climate change impacts on their main prey species.
• Otago Peninsula faces the highest overlap with human-related threats including direct interactions with humans and their dogs, recreational netting, oil spill risk, and other threats.

Projections suggested that the population could stabilise if either juvenile or adult deaths are halved, but eliminating chick deaths alone would not suffice.

This research is provides information required for guiding conservation efforts to meet the goal of halting the decline.

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