A new satellite technology for tracking the movements of Atlantic bluefin tuna

Abstract

The movements of Atlantic bluefin tuna (Thunnus thynnus thynnus) have captured the interest of scientists and fishers since the time of Aristotle. This tuna is unique among bony fish for maintaining elevated body temperatures (21°C above ambient) and attaining large size (up to 750 kg). We describe here the use of a pop-off satellite tag, for investigating the Atlantic-wide movements and potential stock overlap of western and eastern Atlantic bluefin tuna. The tag also archives data on water temperatures. The objectives of this study were to evaluate the effectiveness of the technology, study the movements of Atlantic bluefin tuna, examine their thermal niche, and assess survivorship of tagged fish. The pop-off satellite technology provides data independent of commercial fisheries that, when deployed in sufficient quantity, should permit a critical test of the stock structure hypotheses for Atlantic bluefin tuna.Atlantic bluefin tuna are endothermic fish (1), seasonally distributed over the north Atlantic Ocean and Mediterranean Sea, where they are exploited intensively by commercial and recreational fisheries. Despite international management, exploitation has reached a peak in the past decade (2) and the sustainability of the fishery is in question. Bluefin tuna in the Atlantic and Mediterranean are managed as separate eastern and western stocks. Considerable debate centers on the appropriateness of this subdivision given the evidence for transoceanic mixing (3). To understand the life history of bluefin tuna and develop competent management strategies, temporal and spatial movement patterns must be identified (4). Data on bluefin tuna dispersal patterns have been difficult to obtain because of the limited resolution of analytical tools available for studying pelagic fish. To date, tag and recapture programs using conventional tags (fisheries-dependent indicators of movement) have been the method of choice for describing the distribution of Atlantic bluefin tuna, as in most tuna fisheries (5). Conventional tag and release data indicate that transAtlantic movements of all size classes of Atlantic bluefin tuna occur (3, 6-8). Recently, microprocessor-based, data storage tags (archival tags) have been developed for monitoring the geoposition (based on ambient light levels), thermal physiology, and diving behavior of large pelagic vertebrates (9-13). Although the data intensity of archival tags is high (2 megabytes), their major limitation is the need to recapture the animal to access the data. This requires deployment of large numbers of tags in species with high exploitation rates. In addition, the multinational nature of most oceanic fisheries complicates the coordination of archival tag recoveries. Archival tags have been deployed recently on Atlantic bluefin tuna (9), but significant numbers of returns take years to retrieve. Satellite tags (conventionally towed or attached) have been employed to study the large-scale movements and physiology of marine mammals, birds, and sea turtles (14-18). These ta...

Movements of Marine Fish and Decapod Crustaceans: Process, Theory and Application

“…However, the necessity for understanding the movements of fast swimming and deep diving (> 1000 m) pelagic fish that are being exploited by fisheries has resulted in the invention of 'pop-off' transmitter tags that are programmed to detach from the animal and float to the surface to transmit position and archived data (Priede and French, 1991;Gunn and Block, 2001). Together with implanted DSTs these have been used successfully for studies of bluefin tuna (Thunnus thynnus) (Block et al, 1998) and swordfish (Xiphias gladius) (Sedberry and Loefer, 2001). For example, data were retrieved from 95% (Block et al, 1998) and 90% ) of tags detached from bluefin tuna.…”

“…Together with implanted DSTs these have been used successfully for studies of bluefin tuna (Thunnus thynnus) (Block et al, 1998) and swordfish (Xiphias gladius) (Sedberry and Loefer, 2001). For example, data were retrieved from 95% (Block et al, 1998) and 90% ) of tags detached from bluefin tuna.…”

Ability of Archival Tags to Provide Estimates of Geographical Position Based on Light Intensity

“…At a slower rate of data acquisition, data can be recorded for up to eight to ten years, depending on battery life and amount of memory. Archival tags have been used to chronicle horizontal and vertical movement patterns, residence time in particular areas, and location of possible spawning areas for a variety of marine fishes (Gunn et al, 1994;Metcalfe and Arnold 1997;Block et al, 1998a;1998b;Lutcavage et al, 1999).…”

Convergent evolution in locomotory patterns of flying and swimming animals

“…In this study, we employed two basic animalattached recording systems: a multisensor datalogger 42 and a popup satellite archival tag 44 . The multisensor data loggers used are described in detail in Wilson et al 42 In brief, acceleration and depth are recorded at a fixed frequency, which was determined according to the species in question (Table 1).…”