Abstract
Between 2005 and 2009, we deployed 58 miniature pop-up satellite archival tags (PSAT) and 132 implanted archival tags on juvenile Atlantic bluefin tuna (age 2–5) in the northwest Atlantic Ocean. Data returned from these efforts (n = 26 PSATs, 1 archival tag) revealed their dispersal routes, horizontal and vertical movements and habitat utilization. All of the tagged bluefin tuna remained in the northwest Atlantic for the duration observed, and in summer months exhibited core-use of coastal seas extending from Maryland to Cape Cod, MA, (USA) out to the shelf break. Their winter distributions were more spatially disaggregated, ranging south to the South Atlantic Bight, northern Bahamas and Gulf Stream. Vertical habitat patterns showed that juvenile bluefin tuna mainly occupied shallow depths (mean = 5–12 m, sd = 15–23.7 m) and relatively warm water masses in summer (mean = 17.9–20.9°C, sd = 4.2–2.6°C) and had deeper and more variable depth patterns in winter (mean = 41–58 m, sd = 48.9–62.2 m). Our tagging results reveal annual dispersal patterns, behavior and oceanographic associations of juvenile Atlantic bluefin tuna that were only surmised in earlier studies. Fishery independent profiling from electronic tagging also provide spatially and temporally explicit information for evaluating dispersals rates, population structure and fisheries catch patterns.
Highlights
Management of Atlantic bluefin tuna (Thunnus thynnus) is shared by the International Commission for the Conservation of Atlantic Tunas (ICCAT) and national fisheries management agencies
Our combined archival and pop-up satellite archival tags (PSAT) tagging efforts track the growth of the 2003 year class and represent a consistent tagging effort through four years of this cohort
This study provides the first fishery-independent information on year-round spatial and vertical distribution of juvenile bluefin tuna in the northwest Atlantic and provides extensive data describing their year-long dispersal patterns and habitat utilization
Summary
Management of Atlantic bluefin tuna (Thunnus thynnus) is shared by the International Commission for the Conservation of Atlantic Tunas (ICCAT) and national fisheries management agencies. New information on migration patterns for adult western Atlantic bluefin tuna (ABFT) has revealed even stronger habitat connectivity among distant oceanic regions [1,2,3] than indicated by fisheries patterns and conventional tagging [4,5,6]. While adult bluefin tuna are exploited in the commercial fishery in the western Atlantic, juveniles are highly sought by recreational anglers, and constitute a multi-million dollar sport fishery. Conventional tagging and fisheries catch patterns have revealed dispersal patterns of juvenile ABFT in West Atlantic coastal areas during summer and fall [6,9,10] but their winter and springtime movements and behavior have only been surmised. Fisheries expeditions in the 1950’s and ‘60s found that some juvenile ABFT occupied the Gulf Stream over winter [6,11], but no exploratory cruises have taken place since
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