title: Habitat use and diel vertical migration of bigeye thresher shark: Overlap with pelagic longline fishing gear.
abstract: Pelagic longliners targeting swordfish and tunas in oceanic waters regularly capture sharks as bycatch, including currently protected species as the bigeye thresher, Alopias superciliosus. Fifteen bigeye threshers were tagged with pop-up satellite archival tags (PSATs) in 2012-2014 in the tropical northeast Atlantic, with successful transmissions received from 12 tags for a total of 907 tracking days. Marked diel vertical movements were recorded on all specimens, with most of the daytime spent in deeper colder water (mean depth = 353 m, SD = 73; mean temperature = 10.7 °C, SD = 1.8) and nighttime spent in warmer water closer to the surface (mean depth = 72 m, SD = 54; mean temperature = 21.9 °C, SD = 3.7). The operating depth of the pelagic longline gear was measured with Minilog Temperature and Depth Recorders (TDRs), and the overlap with habitat utilization was calculated. Overlap is taking place mainly during the night and is higher for juveniles. The results presented herein can be used as inputs for Ecological Risk Assessments for bigeye threshers captured in oceanic tuna fisheries, and serve as a basis for efficient management and conservation of this vulnerable shark species.
authors.affiliation: Portuguese Institute for the Ocean and Atmosphere, I.P. (IPMA), Avenida 5 de Outubro s/n, 8700-305 Olhão, Portugal; Centre of Marine Sciences (CCMAR), University of Algarve, FCT, Ed. 7, Campus de Gambelas, 8005-139 Faro, Portugal. Electronic address: rpcoelho@ipma.pt.
authors.forename: Rui
authors.initials: R
authors.lastname: Coelho
authors.affiliation: Portuguese Institute for the Ocean and Atmosphere, I.P. (IPMA), Avenida 5 de Outubro s/n, 8700-305 Olhão, Portugal; Centre of Marine Sciences (CCMAR), University of Algarve, FCT, Ed. 7, Campus de Gambelas, 8005-139 Faro, Portugal.
authors.forename: Joana
authors.initials: J
authors.lastname: Fernandez-Carvalho
authors.affiliation: Portuguese Institute for the Ocean and Atmosphere, I.P. (IPMA), Avenida 5 de Outubro s/n, 8700-305 Olhão, Portugal.
authors.forename: Miguel N
authors.initials: MN
authors.lastname: Santos
mesh_terms: D025041:Animal Migration; D000818:Animals; D001267:Atlantic Ocean; D002940:Circadian Rhythm; D003247:Conservation of Natural Resources; D017753:Ecosystem; D005398:Fisheries; D012754:Sharks / Q000502:physiology*
keywords: Alopias superciliosus; Bycatch; Fisheries; Pop-up satellite archival tags (PSATs); Sharks; Susceptibility; Temperature and Depth Recorders (TDRs); Vertical habitat