Summer foraging areas for lactating New Zealand sea lions Phocarctos hookeri

Abstract

The overlap between marine mammal species and fisheries is a source of ongoing conflict and concern. This study used satellite telemetry to examine the foraging patterns of 26 lactating female New Zealand sea lions Phocarctos hookeri from the Sandy Bay colony, Enderby Island, Auckland Islands (50°50' S, 166°28' E), over 4 consecutive austral summers from 2001 to 2004. Animals were fitted with satellite-linked platform transmitting terminals (PTTs), which yielded 9200 filtered foraging locations at sea. Trips lasted a mean of 66.2 h (SE = 4.2, n = 183). Mean return travel distance per trip was 423 km (SE = 43.9, max. = 1087, n = 183). There was a high level of variation in individual foraging parameters, and evidence of individual preference and partitioning in foraging locations among individuals within the colony. New Zealand sea lions exhibited preferential use of the continental shelf and its edge and this pattern was consistent among years. Female foraging locations overlap temporally and spatially with the operation of the sub-Antarctic arrow squid trawl fishery. Here we identify the key foraging areas for female New Zealand sea lions from Sandy Bay, show how these overlap with the operational areas of the squid fishery and discuss the importance of these findings to the management of New Zealand sea lions and the sub-Antarctic squid fishery. KEY WORDS: Phocarctos hookeri · New Zealand sea lions · Foraging ecology · Fisheries interactionResale or republication not permitted without written consent of the publisher

Change in the foraging strategy of female South American sea lions (Carnivora: Pinnipedia) after parturition

“…Whatever the reasons for those contrasting results, the differences between the corrected isotopic signals of serum and blood cells clearly reveal a marked shift after parturition towards coastal, benthic prey to the detriment of off-shore, pelagic prey, as already reported for other pinnipeds (Chilvers et al, 2005). After parturition, lactating females need to satisfy the high energy requirements involved in pup rearing, particularly during the first weeks when they need to provide lipidrich milk to their pups, so they are expected to shift to highly nutritious prey.…”

Foraging behaviour indicates marginal marine habitat for New Zealand sea lions: remnant versus recolonising populations

“…We used data from Chilvers et al (2005) and Chilvers (2009) for comparison with our results. These studies reported the latest data available for the Auckland Islands at the 3 breeding colonies (Enderby, Dundas and Figure of Eight Islands).…”

“…Females at the Auckland Islands foraged within a wide continental shelf (narrower on the west of the group of islands, see maps in Chilvers et al [2005]), mostly at the edge of the shelf or above the continental slope.…”

“…The satellite tracking technique used similar instruments. However, the methods used to filter the Argos locations differed between the studies (a speed-only filter was applied to Argos locations for the Auckland Islands data; Chilvers et al 2005). The purpose of applying different filters was to obtain the best estimates of foraging ranges; the choice of filter depended on the configuration of the sites and the foraging characteristics of the animals.…”

“…Chilvers et al (2005) presented foraging areas and trip characteristics of female New Zealand sea lions around the Auckland Islands. They showed that these animals also foraged for long periods and in large areas compared to other otariid species.…”