Electronic tagging and population structure of Atlantic bluefin tuna

“This has revealed the intricacies and previously unanticipated complexity of migratory paths of bluefin tuna (Thunnus thynnus) (22), unsuspected transoceanic migrations of leatherback turtles (Dermochelys coriacea) (Fig.”

“Advances in technologies such as satellite and Global Positioning System (GPS) transmitters [13], harmonic radar tracking [14] and electronic data storage tags [ 15 ] have led to a vast influx of data on the movement of tagged individuals [13] from a diverse range of species in habitats where direct observation is oft…”

“RMUs provide explicit, ecologically based spatial and demographic information about geographic distributions of marine turtle populations that could be integrated with other georeferenced layers, including human activities subject to management (e.g. fisheries operations, hydrocarbon extraction, coastal development, s…”

“On a global scale, determination of area use by the commercially important giant bluefin tuna (using geolocating bio-loggers) has revealed that the Atlantic has two major stocks, one in the east and one in the west, but that these two groups tend to overlap and are not as distinct as was previously thought (Block et a…”

“This hypothesis is supported by the most extensive electronic study 7 Atlantic bluefin tuna: a review published to date (Block et al. 2005), which tends to support spawning site fidelity in both the Mediterranean Sea and Gulf of Mexico.”

“However, the launch of extensive tagging campaigns (e.g., Block et al. 2005) and advancements in tag-to-tag communication could circumvent the B.S. Graham (*) Department of Oceanography, University of Hawai’i, Honolulu, HI, 96822, USA P.L. Koch Dept. of Earth & Planetary Sciences, University of…”

“…rapidly growing body of work devoted to the detailed study of free-ranging animal movements in the wild, reflecting the increase in the technological ability to accumulate data (Ferguson et al. 1998; Heide-Jørgensen et al. 2003; Block et al. 2005; RopertCoudert & Wilson 2005; Andrews et al. 2008).”

“The elaboration of an ever increasing array of tracking technologies has transformed this field of study (Block 2005, Block et al. 2005), with satellite tracking using the Argos system (Argos 1996) having become particularly prevalent in recent decades (Gillespie 2001).”

“…could not be received in space when animals are below the surface, but a satellite system could work for surfacing animals or with the help of pop-up archival tags M. Wikelski and others THE JOURNAL OF EXPERIMENTAL BIOLOGY 185A global tracking system for small animals (Block et al., 2005).”

“However, although useful for small demersal fish such as plaice and cod (e.g. Metcalfe and Arnold 1997) and large pelagic fish such as bluefin tuna (e.g. Block et al. 2005), archival tags are of little or no use for species, such as eels, where recapture rates or low or non-existent.”

“…for assessing the behaviors underlying stock structure, such as migratory pathways, home ranges, and core habitat utilizations, and it is being used to help fill this knowledge gap in highly migratory species such as tunas (Block et al. 2005) and sharks (Bonfil et al. 2005, Skomal et al. 2009).”

“Electronic tracking of marine predators has revealed a wealth of information on patterns of distribution and habitat use (Block et al. 2005), migratory patterns (Block et al. 2001), and foraging ecology (Sale et al. 2006).”

“Although there are apparent examples among the transoceanic migrations of sharks and tuna [70,71], the spatial and temporal resolution of these tracks is too poor to elucidate the exact relationship between the fishes’ headings and flow directions.”

“…technologies to track pelagic animals has yielded numerous insights into the biology of species such as salmon sharks (Weng et al. 2005), bluefin tuna ( Thunnus thynnus ) (Block et al. 2005), elephant seals ( Mirounga angustirostris ) (DeLong et al. 1992) and marine birds (Weimerskirch et al. 2002).”

“New telemetry studies are revealing that a range of migratory megafauna spend considerable time in coastal waters during vulnerable life history stages [12,13,33].”

“Specifically, information on movements and distributions of large marine predators collected by electronic tracking devices can provide guidance to the development of national and multinational fisheries management strategies and bycatch mitigation efforts, as well as support related policy efforts [15].”

“…temperature for spawning), this definition can potentially lead to drastic changes in the movement of fish feeding in high latitudes at the time of spawning migration; a behavior that has been successfully observed for example for bluefin tuna tagged with electronic tags (Block et al., 2005).”

“For example, the western Atlantic population of bluefin tuna is thought to spawn in the Gulf of Mexico and the Straits of Florida from April to July, but adult-sized individuals have been reported to occur in the central Atlantic Ocean and elsewhere during this period (Lutcavage et al. 1999; Block et al. 2005).”

“breeding groups, with individuals migrating to spawn in the Mediterranean Sea and the Gulf of Mexico [breeding partial migration (Block et al., 2005)].”

“…shocks were also experienced by cod in the Baltic Sea and Skagerrak and, in extreme cases, led to some cod experiencing daily thermal ranges greater than 10°C and up to 13°C, which is similar to or greater than the temperature ranges reported for deep-diving oceanic predators (Block et al. 2005).”

“However, there is also evidence of extensive migration of bluefin that results in mixing of these populations within the North Atlantic Ocean (Mather et al., 1974, Mather, 1980; NRC, 1994; ICCAT, 2001, 2013; Block et al., 2005; Rooker et al., 2008, 2014).”

“The level of mixing estimated from the tracking studies was higher than previously assumed by the International Commission for the Conservation of Atlantic Tunas (ICCAT) stock assessment models, which were used in setting management quotas for the tuna that resulted in overfishing (Block et al., 2005).”

“Similar to their Pacific congener (T. orientalis) (Bayliff et al., 1991; Bayliff, 1994), T. thynnus display highly migratory behaviors and trans-oceanic movement is well documented (Mather et al., 1995; Turner and Powers, 1995; Block et al., 2005; Rooker et al., 2006a).”

“The bluefin tuna occupying the GOM during the spawning season are extremely large in body size, with the mean size of electronically tagged bluefin tuna entering the GOM being 241 ± 28 cm CFL (Block et al. 2005).”

“2002) and bluefin tuna Thunnus thynnus (Block et al. 2005; Wilson et al. 2005).”

“Challenges in modeling and managing fishery resources with complex spatial patterns will become increasingly important as migration behaviors are discovered that do not conform to patterns of allopatry in coastal populations (e.g., Block et al. 2005; Kraus and Secor 2005).”

“For animals that remain submerged, pop-up archival tags (PATs) are favored (Block et al. 1998, 2005; Boustany et al. 2010; Campana et al. 2011; Carlson et al. 2010).”

“In the last few years, this biologging approach has been widely used for various marine species, greatly enhancing our knowledge of physiology, habitat use and movements of long-distance migrants (McConnell et al. 1992; Bost et al. 1997; Lutcavage et al. 1999; Costa & Sinervo 2004; Block et al. 2005).”

“Although some large deployment efforts have characterised habitat preference and movement patterns at relevant scales for management (e.g. Block et al., 2005; Block et al., 2011; Hartog et al., 2011; Hazen et al., 2013; Hobday and Hartmann, 2006), most tagging studies are local with short…”

“Using satellite technology, scientists have characterized the migration patterns of aquatic species such as the white shark (Carcharodon carcharias, L.) and bluefin tuna (Thunnus thynnus, L.) that criss-cross major oceans annually (Block et al., 2005; Bonfil et al., 2005).”

“However, the MeHg concentrations found in commercially harvested fish are an integration of feeding in deep and shallow waters across inshore and offshore habitats (Block et al., 2005; Hammerschmidt and Fitzgerald, 2006a).”

“Differences in track duration may bias the geographic ranges covered (Block et al. 2005), so longer tracks on YOY sharks may show more overlap with the 3 yr old sharks.”

“Such tracking is often difficult to accomplish, especially in migratory marine species (Block et al. 2005).”

“Recent tagging studies in the North Atlantic confirmed that this species today is not typically migrating south of 20° N (19).”

“However, recent satellite tagging data suggest mixing between populations (100).”

“1 years of age) at the time of trans-Atlantic movement showed this behavior [10].”

“Direct observations can help us follow dispersal by some larger marine animals directly (e.g., sea turtles, Nichols et al. 2000; tuna, Block et al. 2005), but most tropical marine W sh (Sale 1980) and invertebrate (Thorson 1950) species disperse via tiny pelagic larvae.”

“Satellite telemetry has been a primary tool to track long-distance movements of vertebrates from around the world [1,6,7], but the high cost of tags, satellite tracking data acquisition, and analysis (up to US $5K per animal) coupled with large body size requirements for tracked animals have precluded its application…”

“This technology provides an opportunity to collect fine-scale spatio-temporal information about species that would otherwise be difficult to study (i.e. tuna, Block et al., 2005; shearwaters, Shaffer et al., 2006; leopards, Gavashelishvili & Lukarevskiy, 2008).”

“…tracked (e.g. satellite tracking data for 2285 animals across four taxa hosted online at http://www.wildlifetracking.org; teleost fish (e.g. Block et al., 2005; Holdsworth et al., 2009; Sims et al., 2009), cetaceans (e.g. Heide-Jørgensen et al., 2006, Mate et al., 2007; Andrews et al.,…”

“For example, bluefin tuna tracked using light-based geolocator tags may show several years of residence in the western Atlantic and then NE Atlantic before returning to their breeding grounds in the Mediterranean (Block et al. 2005).”

“Acoustic tracking and recent developments in archival tagging have provided new information on the horizontal and vertical distribution (as well as stock structure, movement and mixing) of bluefin tuna in the North Atlantic (Block et al. 2005).”

“The PSATs used in our study functioned essentially as fisheries-independent, short-term conventional tags (Block et al., 2005; Bolle et al., 2005).”

“These results substantiate the results of tagging studies which suggest that Atlantic bluefin tuna show spawning site fidelity and that the Mediterranean Sea and Gulf of Mexico populations do not overlap on spawning grounds (Block et al. 2005).”

“…the development of satellite and other tagging technologies has greatly increased our understanding of the distribution patterns of tunas and billfishes (Sedberry & Loefer 2001, Boustany et al. 2002, Graves et al. 2002, Block et al. 2005), there are still information gaps for particular species.”

“The absence of tagged fish moving between the Gulf of Mexico and Mediterranean Sea has also previously been used to support the hypothesis of complete reproductive isolation between the two stocks (5, 7).”

“Annual migration patterns vary greatly among individuals, ages, and populations in some species (11, 23), and the “average” migration pattern might not be informative.”

“Evidence of trans-Atlantic movement was demonstrated here for adolescent bluefin tuna, with the majority of individuals present in the USA Atlantic Ocean derived from the Mediterranean Sea (~60%).”

“Although the tags employed are becoming increasingly sophisticated (eg, Block et al. 2005 ), this approach can only yield information about movements subsequent to tag application after the fish reaches some minimum size ( Webster et al.”

“…Marine Station, Stanford University, 120 Oceanview Boulevard, Pacific Grove, CA 93950, USA e-mail: lteo@ucdavis.edu western Atlantic stock of Atlantic bluefin tuna is known to spawn primarily in the GOM from April to June (Magnuson et al. 1994; Mather et al. 1995; Schaefer 2001; Block et al. 2005).”

“…larvae nor adults found in association with ambient water temperatures of .298C. Adult BFT generally migrate to the GOM from northern Atlantic feeding grounds between December and June (Block et al., 2005), although this may not be an annual occurrence for all individuals (Lutcavage et al., 1999).”

“Electronic tagging also revealed transoceanic movements by organisms such as bluefin tuna (Block et al., 2005), which was not only remarkable from an ecological perspective, but also revolutionized their management (Kaplan et al., 2010).”

“For fisheries targeting pelagic, migratory stocks, typically some but not all of the fishery occurs in EEZs [8,17,18,31,32].”

“For Atlantic bluefin tuna, there is strong seasonal and ontogenetic dependence of movement rates, where fish of different ages use different habitats during the year for foraging or spawning [6,7,18].”

“…but after a decade, there are limited examples of application of electronic tagging data to stock assessment, fisheries management, and conservation (see however Block et al., 2001, 2005; Graves et al., 2002; Kerstetter et al., 2003; Luo et al., 2004; Sibert et al., 2006; Seitz et al., 2007).”

“, around the Balearic Islands and in the Southern Tyrrhenian (14)], and by recent fishery (16) and tagging (11) data.”

“Atlantic bluefin experience sea-surface temperatures as low as 2 C (Block et al. 2001; Kitagawa et al. 2002; Block et al. 2005), and small juvenile Pacific bluefin range into surface waters of 11 C or less off northern California.”

“…using electronic tagging systems, have high- lighted the likely impacts of threats in wide-ranging species of marine fishes (Lutcavage et al. 2000; Block et al. 2005), reptiles (Godley et al. 2008), birds (Åkesson & Alerstam 1998) and mammals (Mate, Nieukirk &Kraus 1997; Thompson,Moss& Lovell…”

“Large ocean areas have been probed in situ using as cost-effective sampler stations several species of pelagic predators such as giant blue fin tuna (Block et al., 2001, 2005), several species of penguins (e.g., Charrassin et al., 2002; Wilson et al., 2005; Sokolov et al., 2006), sea turtles (e.g.,…”

“Moreover, such information is valuable for management purposes, especially in species that are at risk from expanding fisheries [4,5].”

“Movement of bluefin tuna across the 45° W management boundary has been observed with electronic tags (Block et al. 2005), highlighting the potential for consequential population mixing in certain regions of the North Atlantic Ocean (NAO).”

“Numerous studies have examined movement patterns and migration routes of long-distance migrants (Hughes et al., 1998; Fox, Glahder & Walsh, 2003; Luschi, Hays & Papi, 2003; Thirgood et al., 2004; Block et al., 2005; Stutchbury et al., 2009; Horton et al., 2011; Alves et al., 2013; Trierweiler et al., 2014), but simila…”

“Based on their separate spawning areas, as well as somewhat different life history traits, the Western Atlantic and the Eastern Atlantic/Mediterranean Sea stocks are considered as different by the International Commission for the Conservation of Atlantic Tunas (ICCAT), the international body responsible for the manage…”

“Movement studies using electronic tagging have offered significant insights into the selected habitats of fish (Sims et al. 2003, Block et al. 2005), reptiles (James et al. 2005a, Eckert 2006) and birds (Croxall et al. 2005).”