DOI: 10.5061/dryad.2qp66
title: Data from: Biogeophysical and physiological processes drive movement patterns in a marine predator

description: 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.
description: bluesharkDailyMaxDepthHowey2017Daily instrument-recorded maximum depths for blue sharks.BlueSharkUKFSSTHowey2017UKFSST-filtered geolocations for blue sharks.BlueSharkCombined.txtbluesharkMinMaxDailyTemperatureHowey2017Minimum and maximum instrument-recorded temperatures for blue sharks.bluesharkMinMaxDailyTemperatureHowey.txt