How Does Diet Affect Snapper (Chrysophrys auratus) Movement?

Abstract

Predators adjust their movement patterns in response to the distribution and diversity of prey items, a process which needs to be considered in species management. In this study, the diet and movement dynamics of snapper (Chrysophrys auratus [Sparidae]) were examined to determine how the distribution of food resources influences movement. The aim of this study was to evaluate the relationship between snapper movement and the spatial distribution of prey items across diel and seasonal time periods. Stomach contents of 186 adult snapper within the outer Hauraki Gulf were analysed to determine important prey items of snapper across different habitats, daily time periods, seasons and size. Crustaceans were identified as the most important prey item to snapper followed by teleostei and molluscs. The habitat that snapper foraged over had a significant effect on the types of prey that were selected, as did time of day and seasons. These changes in prey selection are likely due to changes in prey availability between habitats, seasons and diel time periods. The dominance of Paguridae sp. within the diet corresponds to the diel activity patterns of that prey item. Fifteen snapper were also acoustically tagged in the Cape Rodney-Okakari Point Marine Reserve to determine the individual movement dynamics over diel and seasonal time periods and the influence infaunal prey items may have on the habitat selection. Evidence of snapper changing the area they occupy to include different infaunal prey items was observed over diel and seasonal time periods. Snapper home ranges were largest during the day, while dawn and dusk were similar in size. Spring saw an increase in the area of home ranges and associated infaunal prey items. As home ranges expanded in spring, cross-reserve boundary movements became more frequent, most likely related to spawning activity. Snapper show high intraspecific variation in both diet and movement dynamics with clear preferences towards prey items and areas occupied within a temperate marine reserve over seasonal and diel time periods. Applying the resource use of snapper to the spatial management will allow for greater protection and contributes to a broader understanding on snapper diet and movement ecology.