Data from: Biogeophysical and physiological processes drive movement patterns in a marine predator

Background: Blue sharks (Prionace glauca) are among the most abundant and
widely distributed of oceanic elasmobranchs. Millions are taken annually
in pelagic longline fisheries and comprise the highest component of
auctioned fin weight in the international shark fin trade. Though studies
of blue sharks outnumber those of other large pelagic sharks, the species’
complicated and sexually segregated life history still confound current
understanding of Atlantic movement patterns. Lack of detailed information
regarding movement and vertical behavior continues to limit management
efforts that require such data for stock assessment and sustainable catch
modeling. Therefore, this study aims to describe behavioral and ecological
patterns distinct to aggregating and migrating blue sharks, and compare
the findings to existing Atlantic movement models. Results: Data collected
from 23 blue sharks instrumented with pop-up satellite archival tags were
used in statistical predictive regression models to investigate habitat
use during a localized aggregation in the northwest Atlantic, while
undergoing seasonal migrations, and with respect to environmental
variables. Deployment durations ranged from 4 to 273 days, with sharks
inhabiting both productive coastal waters and the open ocean, and
exhibiting long-distance seasonal movements exceeding 3700 km. While
aggregating on the continental shelf of the northwest Atlantic, blue
sharks displayed consistent depth use independent of sex and life stage,
and exhibited varied response to environmental (temperature and
chlorophyll a) factors. As sharks dispersed from the aggregation site,
depth use was influenced by bathymetry, latitude, demography, and presence
in the Gulf Stream. Mature females were not observed at the New England
tagging site, however, two mature females with recent mating wounds were
captured and tagged opportunistically in The Bahamas, one of which
migrated to the Mid-Atlantic Ridge. Conclusions: Vertical behaviors
displayed by blue sharks varied greatly among locales; depth use off the
continental shelf was significantly greater, and individuals exhibited a
greater frequency of deep-diving behavior, compared to periods of
aggregation on the continental shelf. Sexual segregation was evident,
suggesting mature and immature males, and immature females may be
subjected to high levels of anthropogenic exploitation in this region
during periods of aggregation. Analysis of the spatio-temporal tracks
revealed that nine individuals traveled beyond the United States EEZ,
including a mature female captured in The Bahamas that migrated to the
Mid-Atlantic Ridge. These results reflect and augment existing Atlantic
migration models, and highlight the complex, synergistic nature of factors
affecting blue shark ecology and the need for a cooperative management
approach in the North Atlantic.