Essential pelagic habitat of juvenile blue shark (Prionace glauca) inferred from telemetry data

Abstract

Knowledge on the distribution and habitat use of species is an important precondition for their appropriate management and conservation. This is particularly challenging for highly mobile marine predators such as blue shark that migrate between dynamic and transient oceanic habitats. In addition, blue shark populations have complex spatial structures due to age and sexual segregation, and accurately identifying oceanic nursery habitat is vital to ensure population growth via survival of juveniles. In this study, long-term satellite telemetry data (up to 950 d) was used to estimate the broad-scale habitat utilization of juvenile blue shark and predict their distribution in the North Atlantic. Habitat utilization models were fitted separately for three juvenile life stages that recruit to the pelagic longline fishery (small juvenile males and females, large juvenile and sub-adult females and large juvenile males), and subsequently validated using fisheries data. The models demonstrated that the patterns of spatiotemporal distribution and segregation are shaped to a large extent by differential habitat preferences, notably for distinct ranges of sea surface temperature. For the first time, this modeling approach provides a unifying framework to understand the essential pelagic habitat and dynamic spatial structuring of blue shark at the scale of an entire ocean basin. It represents an important contribution to our understanding of the spatial ecology of pelagic sharks by presenting novel clues to their behavioral strategies in exploiting the most productive oceanic habitats, and offers a promising tool for their management in the face of current intensive shark exploitation.