Spatial and temporal habitat use by white sharks (Carcharodon carcharias) at an aggregation site in southern New Zealand

Abstract

Subadult and adult white sharks aggregate seasonally near pinniped colonies in several parts of the globe. The time spent there may represent the most vulnerable part of their otherwise migratory life cycle. White sharks have low productivity and may suffer population declines even when afforded legislative protection. White sharks were protected in New Zealand in 2007, but are subject to ongoing incidental fishing mortality. We deployed electronic tags on white sharks at north-eastern Stewart Island in southern New Zealand to identify their temporal and spatial patterns of occupancy, and to inform management measures that aim to separate sharks from fishing effort. White sharks were present almost continuously from late summer to early winter, peaking in autumn (March–June). The population comprised mainly subadult and adult males and subadult females, with males predominating by 2.5:1 during autumn. White shark abundance was greatest in the Titi Islands, and there was fine-scale spatial and temporal variability in abundance. These sharks travel well beyond their aggregation sites, but the behaviour and dynamics of white sharks in other parts of New Zealand remain poorly understood. Any attempts to reduce incidental mortality by protecting white shark habitat must consider a wider spatial context.