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Of the six extant species of sea lions around the globe, three are endangered, including the New Zealand sea lion. Once intensely hunted for its pelt, the New Zealand sea lion now mainly breeds at remote sub-Antarctic islands. A main threat to this population is bycatch mortality in trawl fisheries near its breeding grounds. The GEMM Lab collaborated with scientists from the University of Tasmania and the National Institute of Water and Atmospheric research (NIWA) in New Zealand to assess the distribution and foraging ecology of New Zealand sea lions breeding at Campbell Island, with a primary goal to describe their overlap with fishing events in the region. In 2013, 21 male sea lions were incidentally killed in the southern blue whiting fishery near Campbell Island, and 25 individuals total were caught in the preceding 11 years. We tagged 25 sea lions at Campbell Island over three years and used habitat models to compare their distribution patterns to those of fishing activities. We analyzed the data this year and found that adult female and juvenile sea lions showed limited overlap with any fishery, yet sub-adult male sea lions foraged in deeper waters farther from Campbell Island and incurred a distinct area of overlap with the southern blue whiting fishery. This area coincides with the location of the majority of bycatch events in 2013. The dive capacity and breeding ecology of sub-adult males enables this population segment to access a unique foraging niche but puts them at risk of interaction with fishing activities. Our work highlights how spatial ecology can fill knowledge gaps about animal ecology and provide insights related to conservation management options. This work was funded by NIWA and New Zealand’s Ministry of Business, Innovation, and Employment.
Photo credit: New Zealand sea lions at Campbell Island, New Zealand. Photo by Mary-Anne Lea.