Tagging and Tracking of Marine Animals with Electronic Devices

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2 Tagging and Tracking of Marine Animals with Electronic Devices

3 Reviews: Methods and Technologies in Fish Biology and Fisheries VOLUME 9 Series editor: Jennifer L. Nielsen U.S. Geological Survey, Alaska Science Center Anchorage, Alaska For further volumes:

4 Jennifer L. Nielsen Haritz Arrizabalaga Nuno Fragoso Alistair Hobday Molly Lutcavage John Sibert Editors Tagging and Tracking of Marine Animals with Electronic Devices 123

5 Editors Jennifer L. Nielsen US Geological Survey Alaska Science Center 4210 University Drive Anchorage AK USA Nuno Fragoso Large Pelagic Research Center University of New Hampshire Durham NH USA Molly Lutcavage Large Pelagic Research Center University of New Hampshire Durham NH USA Haritz Arrizabalaga Marine Research Division AZTI Tecnalia Herrera Kaia Portualdea, z/g Passaia Spain Alistair Hobday CSIRO Marine & Atmospheric Research Castray Esplanade Hobart TAS 7001 Australia John Sibert Pelagic Fisheries Research Program University of Hawaii 1000 Pope Road Honolulu HI USA Chapters 7, 15 c UK Crown Chapter 9 c Canadian Crown Chapter 19 was created within the capacity of an US governmental employment and therefore is in the public domain. ISSN ISBN e-isbn DOI / Springer Dordrecht Heidelberg London New York Library of Congress Control Number: c Springer Science+Business Media B.V No part of this work may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission from the Publisher, with the exception of any material supplied specifically for the purpose of being entered and executed on a computer system, for exclusive use by the purchaser of the work. Printed on acid-free paper Springer is part of Springer Science+Business Media (

6 Preface: Applications of Electronic Tagging to Understanding Marine Animals Overview The 2nd international tagging and tracking symposium was held in San Sebastian, Spain, in October 2007, seven years after the first symposium was held in Hawaii in 2000 (Sibert and Nielsen, 2001). In the intervening seven years, there have been major advances in both the capability and reliability of electronic tags and analytical approaches for geolocation. Advances such as increased data storage capacity, sensor development, and tag miniaturization have allowed researchers to track a much wider array of marine animals, not just large and charismatic species. Importantly, data returned by these tags are now being used in population analyses and movement simulations that can be directly utilized in stock assessments and other management applications. Since the first symposium, the increased use of electronic tags on fish in particular is also evident in the growth of peer reviewed literature on this subject (Fig. 1). The number of papers increased more rapidly after the first symposium, and we anticipate a similar positive effect following publication of these proceedings. Given the number of papers published each year, the relevance of these proceedings is also clear, as it is likely to contain a significant proportion of the expected peer reviewed literature produced in San Sebastian Fig. 1 Number of publications each year related to electronic tagging of fish identified from ASFA using the keyword combinations: (electronic or sonic or archival or pop-up or (pop up) or PSAT) and (tag and fish and PY = ) N Hawaii v

7 vi Preface: Applications of Electronic Tagging to Understanding Marine Animals The 2nd symposium attracted over 150 participants from 19 countries, including 29 students. A total of 70 oral presentations and 29 posters were presented over five days. 1 While studies related to commercially important tuna and billfish dominated, presentations spanned a wider range of taxa than in 2001, including the behavior of escaped cod, migrating salmon, and shark feeding to conservation and fisheries management. Twenty five of these contributions are included in this volume. These papers are divided into three sections, the first describing insights in behavior achieved using acoustic, archival, and novel tags, the second reporting on advances in methods of geolocation, while the final section includes contributions where tag data have been used in management of marine species. Behavioral Insights Based on Use of Electronic Tags Behavior Using Acoustic Tags Acoustic transmitters have a long history of use in the ocean, with individual fish followed for as long as the ocean conditions and vessel or researcher stamina allowed (e.g., Brill et al., 1999; Holland et al., 1999; Lutcavage et al., 2000; Arnold and Dewar, 2001). More recently, acoustic monitoring has been used to monitor the movements of fish using pre-deployed acoustic receivers (e.g. Klimley and Butler, 1988; Heupel et al., 2006). The advantage of both approaches is that there is no need to recapture animals, and data is gathered in real-time (tracking) or near real-time (monitoring). Since the first symposium, there has been an increase of what might be termed experimental studies, where comparisons between treatment groups are made. Enhancement programs are one approach to bolster population sizes following overexploitation, yet the behavioral differences between wild and cultured animals may result in complex interactions leading to failure of these programs, and potentially negative effects on wild stocks (Ruggerone et al., 2003; Kostow, 2008). Fairchild et al. (this volume) compared the movements and habitat use of cultured and wild juvenile winter flounder (Pseudopleuronectes americanus) with acoustic tags and three tracking systems in New Hampshire, USA. They found similar home range sizes between groups, but cultured fish initially dispersed more widely while wild fish maintained high release site fidelity. A second example is provided by Lino et al. (this volume) using wild and hatchery reared white seabream (Diplodus sargus) released on artificial reefs in Southern Portugal. Individuals had different behavior at release, habitat association and daily movements, showing that habitats used by wild bream may not be optimal release locations for hatchery-produced fish. Understanding movement patterns and habitat associations of cultured and wild fish is significant for developing techniques for enhancement programs and for defining 1

8 Preface: Applications of Electronic Tagging to Understanding Marine Animals vii essential fish habitats (Palumbi, 2004). As both these studies showed, electronic tags allow particular insight into these behaviors. Survival of Atlantic salmon (Salmo salar) followingthe first of several spawning years was investigated in Norway using acoustic tags and receivers by Halttunen et al. (this volume). Despite their weakened condition after spawning and overwintering in the river, survival of fish returning to the ocean was very high. Estimates of mortality will be useful for improved understanding of the relatively poorly defined contribution of iteroparity (more than one spawning event by individual fish) to the population dynamics of this species. While many of the electronic tagging studies have a single species focus, Goñi et al. (this volume) report on vertical behavior of juvenile albacore in the Bay of Biscay and simultaneously collected prey distribution data from echosounders. Although tuna depth distribution did not relate to prey distribution, the combination of these technologies is suitable for developing fine-scale understanding of tuna behavior. Ultimately, simultaneous monitoring of predators and their prey could be used to correct catchability estimates from surface trolling fleets fishing in the area. The last two contributions in this section call for the need for increased coordination between scientists and equipment manufacturers in design of acoustic tracking networks and development of data sharing protocols as part of an international tagging and monitoring program. Grothues (this volume) notes that a range of automated telemetry systems for tracking acoustically tagged marine fauna are deployed in coastal regions around the world. These systems use various coding, signal reception, data handling and storage, and deployment architecture. Problems arise because tags of one code scheme are not detected by listening devices from another scheme due to technical constraints and proprietary interests. Solutions for cross-equipment communication exist at both the transmitter and receiver ends of the technology, and Grothues outlines why scientists and manufacturers need to discuss and mitigate negative effects of diversification without the loss of its benefits. Similarly, as part of the development of the Ocean Tracking Network, O Dor and Stokesbury (this volume) report that researchers are pressing for standards and protocols to allow universal storage and sharing of a broad spectrum of biological and physical oceanographic information. Such data sharing will be crucial if this ambitious international network is to maximize contributions to ocean management. Behavior Using Internal or Pop-Up Archival Tags Despite advances since the first symposium, there is still much to be learned about the vertical behaviors of marine fishes. Quayle et al. (this volume) report on the behavioral modes of European sea bass (Dicentrarchus labrax) as they migrate between seasonal feeding and spawning grounds using miniature electronic data storage tags (DSTs). Schaefer et al. (this volume) describe the vertical movements and habitat utilization of skipjack (Katsuwonus pelamis), yellowfin (Thunnus albacares), and bigeye (Thunnus obesus) tunas in the equatorial eastern Pacific Ocean, ascertained through archival tag data. Significant portions of time for

9 viii Preface: Applications of Electronic Tagging to Understanding Marine Animals all species were spent above the thermocline at night, but much less at day. Differences in species-specific physiological abilities and tolerances to environmental characteristics of their vertical habitat seem to be responsible. Neilson et al. (this volume) investigated horizontal movements of Atlantic swordfish (Xiphias gladius) using pop-up satellite archival tags on fish in Canadian waters. Reported tag attachments of up to 411 days are among the longest periods of attachment reported for any fish species. They reported no movement from the western North Atlantic to the eastern North Atlantic from the tags recovered to date. Their results challenge the assumption of current stock assessments that swordfish move freely between these regions. Ultimately, results from these types of study on the comparative vertical and horizontal movements, behavior, and habitat utilization, should improve understanding of species-specific vulnerability to purse-seine and longline fisheries, estimates of stock mixing rates, and how to avoid unwanted bycatch. Industrialized purse-seine fishing on anchored fish attraction devices (FADs) has existed in the Papua New Guinea EEZ for more than a decade, yet little is known about the effect of the FADs on fish behavior and distribution. Leroy et al. (this volume) describe vertical behavior and FAD effects on three species of tropical tuna via archival and acoustic tagging carried out in this region. Distinct vertical behavior modes for bigeye and yellowfin tuna were identified that may influence potential vulnerability to industrial purse-seine capture. Unfortunately, the considerable vertical overlap in distribution limits the potential for targeting particular species or size classes of tuna through fishing depth selection. It is widely assumed that the impact of tagging on the subsequent behavior of the fish is negligible, however, this is rarely tested (see however Wilson and McMahon, 2006). Jolivet et al. (this volume) examined the effects of T-bar and DST tagging on survivalandgrowthof Europeanhake (Merluccius merluccius). While conventional tagging affects fish survival rates, electronic tagging is feasible on small individuals of this species with expected survival rate and recapture probability close to that of conventional tagging. Electronic tagging can also shed light on the physiology of marine species. Addis et al. (this volume) report on body temperature in the Atlantic bluefin tuna (Thunnus thynnus) in the Mediterranean Sea and temperature variability associated with the stress of capture. The investigation was carried out in traditional traps (tonnara) of the Mediterranean Sea. Fish body temperature increased by about 2 C during capture ( mattanza ). High body temperature and stress-related physiological disturbance can speed up the onset and progression of bacterial growth and biochemical deterioration, reducing the quality and marketability of harvested meat. Behavior Using Novel Tags While information on location, depth, and temperature are now routinely provided from both archival and acoustic tags, additional insight can be gained when additional sensors are employed. Gleiss et al. (this volume) deployed a multi-channel

10 Preface: Applications of Electronic Tagging to Understanding Marine Animals ix data logger on two lemon sharks (Negaprion brevirostris) as a first step determination of behavior and metabolic rate in free-swimming sharks. Individuals were equipped with archival tags measuring 13 parameters, and four behaviors were characterized. Tail-beat frequency was correlated with overall dynamic body acceleration, which can in turn be correlated with activity-specific metabolic rate, potentially allowing estimates of energy expenditure in sharks. Very high resolution data collection often requires short deployment periods, secure tag attachment and rapid release. Houghton et al. (this volume) describe a novel tag attachment method applied to ocean sunfish (Mola mola) for short-term deployments of high-resolution data loggers. They tested a low-impact harness system with an automated release mechanism that allowed retrieval of the detached devicesat sea. This study revealedinteresting high resolution movementdata, which suggested that molas employ a unique mode of swimming. Feeding is a key factor affecting the growth, survival and reproductive success of marine fish. Understanding feeding in relation to spatial movements and habitat use is therefore critical to realistic parameterization of models of fish populations and ecosystem dynamics. Nonetheless, obtaining information about feeding from fish in the wild over extended time scales is problematic. Metcalfe et al. (this volume) describe an archival tag for monitoring feeding and spawning based on a modification of the archival tag (Cefas G5, Lowestoft, UK) previously used to monitor penguin feeding via jaw movements. In typical usage, the new tag can store 96 h of data when logged at 30 Hz, or months of data collected if pre-programmed to log data for short, separate occasions. In laboratory studies with Atlantic cod different types of jaw movement could be discriminated. These authors also reported preliminary attempts to monitor movements of the cloacae of female cod as a possible means of identifying spawning activity. The next step is to translate these tagging approaches to wild fish, which is sure to yield novel insights and allow greater understanding of movement, distribution patterns and associated behavior. Geolocation Methods Archival tags (implanted and pop-up) provide ambient light records from which estimates of dawn and dusk can be used to calculate longitude (from local noon) and latitude (from local day length) (Gunn et al., 1994; Hill, 1994; Musyl et al., 2001). Unfiltered and uncorrected geolocation data are often noisy leading to errors in estimated location, the so-called geolocation problem (Welch and Eveson, 1999). Light-based estimates of latitude are especially difficult around the two equinox periodssince day lengthis approximatelyequal at all latitudes. A range of statistical approaches have recently been developed to improve light-based position estimation (Sibert et al., 2003), and in particular, light has been supplemented with additional information, such as sea surface temperature, or depth, to refine the position estimation (e.g., Teo et al., 2004; Lam et al., 2008). Estimates of uncertainty with location estimates were routinely provided by presenters at this symposium, which

11 x Preface: Applications of Electronic Tagging to Understanding Marine Animals is to be commended. This should become standard practice throughout the field, and while perfect location estimates may be unattainable, this field of study has matured and will continue to add increased value to electronic tagging studies. Thygesen and Nielsen (this volume) provide some simple and general expressions for the accuracy of geolocation, which may be obtained by optimal filtering of measurements from archival tags. Using an idealized geolocation problem where the animal performs a random walk, they derive simple closed-form expressions for the steady-state variance and for the characteristic time scale of the filter. This leads to temporal and spatial scales defining the limit of resolution and explains the difference between what can be obtained for fast-moving and slow-moving animals. These results are particularly useful to the planning of a tagging study, because estimates of accuracy can be computed ahead of time using only three parameters: the swimming speed of the animal, the sample interval, and the variance on the measurement error. Thygesen et al. (this volume) present a novel statistical analysis, based on Hidden Markov Models to reduce the effect of measurement errors that impact the accuracy of estimates of fish position based on data from archival tags. The method is illustrated using a simulated data set wheregeolocation relies on depth data exclusively. Nielsen et al. (this volume) have developed a state space model for light-based geolocation of electronically tagged marine animals for improving the precision of the reconstructed geographical tracks. Unlike earlier models reliant on previously calculated raw geolocation estimates from outside sources, their model uses light data to produce the most probable track. This paper illustrates the application of the model to mako sharks and blue marlin and compares the results to satellite-based tracks from the same animals. This new model was vastly superior to previous light-based methods in all cases. Sibert et al. (this volume) employ error propagation analysis to the fundamental equation relating latitude to solar elevation and time of day, and find that large latitude errors are caused by mathematical amplification of small errors in relating solar irradiance to solar elevation. Their analysis leads directly to a method of removing bias from latitude estimates in state-space track reconstruction models, and test this using archival tags deployed on moorings and on freely swimming tuna. Another geolocation alternative, particularly suited for pop-up archival satellite tags, proposed by Royer and Lutcavage (this volume) is for the tag sensor to detect a sunrise or sunset event and then transmit only this information. They show that this geolocation technique retains the essential information to correct for known problems such as errors at the equinoxes and conclude that sunrise/sunset-based geolocation is a viable technique to surmount tag design or engineering limitations when tracking pelagic fish. It is apparent that significant advances in geolocation are being made, and it is timely to consider if this issue is now close to optimal resolution. Evans and Arnold (this volume) report on a workshop on geolocation methods held prior to the 2nd electronic tagging symposium in San Sebastian. The geolocation workshop was convened by the Scientific Committee on Ocean Research Panel on New Technologies for Observing Marine Life. In addition to summarizing current research, technologies and the limitations of principal methods as discussed at the workshop,

12 Preface: Applications of Electronic Tagging to Understanding Marine Animals xi they present recommendations including a working group to promote and consider analytical techniques and software needs. They also advocated for increased dialogue between tag manufacturers and tag users regarding sensor performance, additional sensors, improved algorithms for light attenuation, and the compression and processing of data by tags prior to storage or transmission to satellite. If these recommendations are followed, consolidation of approaches may occur in the coming years, such that scientific effort currently devoted to geolocation can be redeployed to address the management and conservation challenges to which electronic tagging is claimed to address. Applications of Electronic Tagging to Fisheries Management Problems Electronic tags have been deployed on a wide range of species for over a decade. In the case of exploited species, research proposals often stated that the ultimate goal of the research was to contribute to the sustainable management of the species. Similarly, conservation goals are also claimed to be advanced by knowledge of migration paths derived from electronic tags. Despite these claims, the transfer to management has not happened often enough. This is due in part to the large volume of raw data from the tags which is non-trivial to manage, and often not well understood. For some tag types, issues with geolocation and the subsequent effort directed at determining positions may have slowed uptake. However, many questions can be answered with the current level of position accuracy. A first application has been correcting longline effort for habitat preferences (e.g., Bigelow et al., 2002), 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). One challenge is processing and handling of tag data, such that it can be easily visualized and analyzed by a range of users, including assessment scientists and conservation planners. Before data can be efficiently used, this step must be solved, and many of the larger tagging laboratories around the world have developed systems for data management.in this section, Hartog et al. (this volume) describe a data handling system developed at CSIRO, Australia. Data from a variety of tags from different manufacturers, including archival tags, satellite tags and acoustic tags, are downloaded, processed and stored, in some cases without human intervention. The relational database in turn interfaces with (i) software programs to allow data access from local servers or via the internet, and (ii) a suite of environmental data to aid initial analyses and development and refinement of scientific hypotheses. This database is used to manage tag data that can be used in real-time spatial management (Hobday and Hartmann, 2006). The contribution by Hobday et al. (this volume) describes one of the few examples where electronic tag data have been used in real-time fisheries management.

13 xii Preface: Applications of Electronic Tagging to Understanding Marine Animals Pop-up satellite archival tagging data are incorporated into a habitat prediction model to support spatial management in an Australian longline fishery, specifically through reduction of unwanted bycatch of a quota-managed species, southern bluefin tuna (Thunnus maccoyii). Spatial zoning in the fishery is updated every two weeks, in part based on results from this model. The authors describe the development of the management application, in use since 2003, and emphasize that cooperation between scientists, fishery managers and stakeholders has led to successful uptake. This work clearly demonstrates that real-time, fine-scale spatial management is possible. A second example of the potential use of electronic tagging data, in this case acoustic tag data, is provided by Hobday et al. (second paper in this volume). These authors derive correction factors for a juvenile southern bluefin tuna abundance index based on five years of acoustic tag data in southern Western Australia, and show that electronic tagging data can be used to improve understanding of abundance patterns necessary for sustainable management of an exploited species. In addition to fisheries management application, electronic tag data can be used to support conservation, such as in the design of marine protected areas. Afonso et al. (this volume) used a combination of active tracking with passive, multi-scale monitoring and standard tag-release approaches to determine the spatial behaviors used throughoutthe life history of red porgy (Pagrus pagrus). They clearly illustrate how the observed movements of this exploited species might influence the size and spacing of a marine protected area network in the Azores. The Future Around the time of the first symposium (late 1990s) the focus of many studies was on the behavior of the fish, particularly in the vertical dimension, in part due to problems with geolocation. Bluefin tuna tagging studies were among the first to utilize implanted data loggers and fishery independent pop-up tags. These early studies aimed to address ocean basin scale migrations and identification of spawning areas (Gunn et al., 1994; Lutcavage et al., 1999; Block et al., 2001), but lacked the ability to finely geolocate. It was apparent at the 2nd symposium that the improvement in geolocation methods has allowed a shift to the horizontal dimension, to utilization of specific habitats, and behaviors in these locations. Most studies were now considering uncertainty in position estimation, and this should become standard practice in future. In the near future we are likely to see an increased focus on the integrated ecology of fish movements: why are fish behaving in the way we observe, how do they interact with each other and other species, and what is the outcome for the population and ecosystem? There were some excellent examples showing that electronic tag data are being utilized in management and assessment, but it is apparent that we can do more with the data that have already been collected. One challenge for the tagging community is to encourage and facilitate data sharing to provide more comprehensive information and longer time-series.

14 Preface: Applications of Electronic Tagging to Understanding Marine Animals xiii In the next seven years, until a possible 3rd symposium, electronic tags are likely to become increasingly sophisticated with tags monitoring aspects ranging from physiology to behavior as well as environmental parameters (Ropert-Coudert and Wilson, 2005). We can expect continued development of technology in several areas. The concept of tags that download data at fixed nodes has evolved from the simple bottom mounted transceivers discussed in the first symposium to the ecosystembased Ocean Tracking Network, and we can look forward to further development of this concept to even larger systems that can be included in global-scale integrated ocean observing systems. We can expect interactive tags that will exchange data with tags deployed on other animals not necessarily of the same species. New data processing algorithms and software packages will become available that are seamlessly integrated with data structures that include both oceanographic variables and data from other fish. We can expect new developments in non-light based location methodologies such as geomagnetic compasses as first proposed in investigations by Hunter et al. (1986) and Carey and Scharold (1999). Physiological, ecological, and ecosystem studies will all be improved by clever use of electronic tags and development of new sensors. Reduction in tag sizes, and extended battery times for tags will allow more complete descriptions of species life cycles and movements. This will support development of energetic models that include the costs of migrations or vertical behaviors, and testing of alternative models. In addition to the improved primary understanding of physiology, ecology and behavior, increased uptake by fisheries management should be a focus. Electronic tagging studies could support improved management by providing information on how changes in fishing regulations, such as spatial or temporal closures might modify sustainability. Increased collaboration with stock assessment scientists will ensure that analysis produces the desired parameters for spatially-explicit population dynamics models. Management uptake of electronic tag science will be maximized by partnerships with management that are established at the start of the research (Hobday et al., this volume), and by the use of data repositories that share the data on species from multiple sources (e.g., open access portals and websites). A second management need is in marine conservation. Tagging data may provide input for reserve design, in particular, to allow estimates of appropriate reserve size. Developments in reserve theory continue to evolve (Palumbi, 2004; Hughes et al., 2005; Baskett et al., 2007). Partnership with scientists involved in theoretical design of marine reserves will ensure appropriate data are gathered that facilitate fisheries management goals (Sale et al., 2005) and conservation. Sentinel animals with realtime reporting tags may also be used in real-time management of other ocean uses, such as drilling, and seismic surveys. Finally, the impact of climate change on the ocean is now apparent. As large scale research programs such as CLIOTOP 2 aimed at addressing the question of how climate change affects the oceans, tagging studies will be crucial for monitoring impacts on marine species, informing the development of adaptation strategies, and 2

15 xiv Preface: Applications of Electronic Tagging to Understanding Marine Animals underpinning approaches to enhance the resilience of marine ecosystems. Data from electronic tracking and tagging already play an important role in shaping the models used for predicting the effects of climate change on the future of tuna populations and changes in fish distribution (Lehodey et al., 2008). Acknowledgements The symposium organizers thank the science committee, and the local hosts of this symposium for contributions to a successful event. Invaluable editorial efforts by the associate editors have made this a quality volume with strong scientific contributions. We especially thank individual reviewers for their significant contributions to the quality of papers in this volume. Mention of trade names does not imply governmental endorsement. Alistair Hobday, Haritz Arrizabalaga, Nuno Fragoso, John Sibert, Molly Lutcavage, Jennifer Nielsen, Tasmania, Australia Pasaia, Spain Durham, USA Hawaii, USA Durham, USA Anchorage, USA References Arnold, G. and Dewar, H. (2001) Electronic tags in marine fisheries research: A 30-year perspective. In: Sibert, J.R. and Nielsen, J.N. (eds.), Electronic Tagging and Tracking in Marine Fisheries, pp Kluwer Academic Publishers, Dordrecht, The Netherlands. Baskett, M.L., Micheli, F. and Levin, S.A. (2007). Designing marine reserves for interacting species: Insights from theory. Biol. Cons. 137: Bigelow, K.A., Hampton, J. and Miyabe, N. (2002) Application of a habitat-based model to estimate effective longline fishing effort and relative abundance of Pacific bigeye tuna (Thunnus obesus). Fish. Oceanogr. 11: Block, B.A., Dewar, H., Blackwell, S., Williams, T., Prince, E.D., Farwell, C.J., Boustany, A., Teo, S.L.H., Seitz, A., Walli, A. and Fudge, D. (2001). Migratory movements, depth preferences, and thermal biology of Atlantic bluefin tuna. Science 293: Block, B.A., Teo, S.H.L., Walli, A., Boustany, A., Stokesbury, M.J.W., Farwell, C.J., Weng, K.C., Dewar, H. and Williams, T.D. (2005) Electronic tagging and population structure of Atlantic bluefin tuna. Nature 434: Brill, R. W., Block, B.A., Boggs, C.H., Bigelow, K.A., Freund E.V. and Marcinek, D.J. (1999). Horizontal movements and depth distribution of large adult yellowfin tuna (Thunnus albacares) near the Hawaiian Islands, recorded using ultrasonic telemetry: implications for the physiological ecology of pelagic fishes. Mar. Biol. 133(3): Carey, F.G. and Scharold, J.V. (1990). Movements of blue sharks (Prionace glauca) in depth and course. Mar. Biol. 106: Graves, J.E., Luckhurst, B.E. and Prince, E.D. (2002). An evaluation of pop-up tags for estimating post release survival of blue marlin (Makaira nigricans) from a recreational fishery. Fish. Bull. 100: