An investigation into the diet of Elephant fish (Callorhinchus milii) in Aotearoa/New Zealand

Chondrichthyans (sharks, skates, rays, and chimaeras) are increasingly understood to be an important part of ocean ecosystems, but this ecological role is still unclear. The Elephant fish (Callorhinchus milii) is a chimaera species endemic to New Zealand and southern Australia, found at depths up to 200 m. Despite being commercially and recreationally targeted across much of its New Zealand range, little is known about the Elephant fish, including its feeding ecology. This study used stomach content analysis of Elephant fish samples to generate a more comprehensive understanding of the diet of Elephant fish, and to identify biological and/or environmental predictors that may explain any variation in diet. Crustaceans, in particular pagurids and brachyurans, such as Lophopagurus spp. and Leucosiidae spp., were the most important prey type for the Elephant fish examined, with a relative importance of 56%, followed by molluscs, with a relative importance of 30%. The single most important prey item was Leucosiidae spp., which occurred in nearly half of all stomachs and had a relative importance of 26%. Depth was found to be the greatest predictor of variation in Elephant fish diet, with samples taken from greater depths containing more bivalve molluscs and polychaetes, and those from shallower depths containing more gastropod molluscs and brachyuran crabs. Location and sex were also found to influence Elephant fish diet variation. These findings were consistent with studies of other shallow-water callorhinchids and deep-sea chimaera species around the world. The implication of these findings for the management and conservation of Elephant fish are discussed. In addition, possible avenues for further research are discussed, including the use of fatty acid profiles and stable isotope analysis in future dietary analysis, and the need to expand the spatial and temporal range of this research.