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Browsing by Author "Gallagher, Austin J."

Now showing 1 - 5 of 5
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    Detecting Mediterranean White Sharks with Environmental DNA
    Jenrette, Jeremy F.; Jenrette, Jennifer L.; Truelove, N. Kobun; Moro, Stefano; Dunn, Nick I.; Chapple, Taylor K.; Gallagher, Austin J.; Gambardella, Chiara; Schallert, Robert; Shea, Brendan D.; Curnick, David J.; Block, Barbara A.; Ferretti, Francesco (The Oceanography Society, 2023-01)
    The white shark (Carcharodon carcharias) is a globally distributed, ecologically important top predator whose biology and population dynamics are challenging to study. Basic biological parameters remain virtually unknown in the Mediterranean Sea due to its historically low population density, dwindling population size, and lack of substantial sightings. White sharks are considered Critically Endangered in the Mediterranean Sea, and recent analyses suggest that the population has declined by 52% to 96% from historical levels in different Mediterranean sectors (Moro et al., 2020). Thus, white shark sightings dating back to 1860 are being used to estimate population trajectories throughout the entire region. Though the population size is unknown, remaining individuals are thought to be primarily restricted to a handful of hotspots deemed important for their reproduction and foraging. One of these hypothesized hotspots is the Sicilian Channel, which accounts for 19% of total historical sightings.
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    Emergent research and priorities for shark and ray conservation
    Jorgensen, Salvador J.; Micheli, Fiorenza; White, Timothy D.; Van Houtan, Kyle S.; Alfaro-Shigueto, Joanna; Andrzejaczek, Samantha; Arnoldi, Natalie S.; Baum, Julia K.; Block, Barbara; Britten, Gregory L.; Butner, Cheryl; Caballero, Susana; Cardeñosa, Diego; Chapple, Taylor K.; Clarke, Shelley; Cortés, Enric; Dulvy, Nicholas K.; Fowler, Sarah; Gallagher, Austin J.; Gilman, Eric; Godley, Brendan J.; Graham, Rachel T.; Hammerschlag, Neil; Harry, Alastair V.; Heithaus, Michael R.; Hutchinson, Melanie; Huveneers, Charlie; Lowe, Chris G.; Lucifora, Luis O.; MacKeracher, Tracy; Mangel, Jeffrey C.; Barbosa Martins, Ana Paula; McCauley, Douglas J.; McClenachan, Loren; Mull, Christopher; Natanson, Lisa J.; Pauly, Daniel; Pazmiño, Diana A.; Pistevos, Jennifer C.A.; Queiroz, Nuno; Roff, George; Shea, Brendan D.; Simpfendorfer, Colin A.; Sims, David W.; Ward-Paige, Christine; Worm, Boris; Ferretti, Francesco (Inter-Research, 2022-02-28)
    Over the past 4 decades there has been a growing concern for the conservation status of elasmobranchs (sharks and rays). In 2002, the first elasmobranch species were added to Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Less than 20 yr later, there were 39 species on Appendix II and 5 on Appendix I. Despite growing concern, effective conservation and management remain challenged by a lack of data on population status for many species, human−wildlife interactions, threats to population viability, and the efficacy of conservation approaches. We surveyed 100 of the most frequently published and cited experts on elasmobranchs and, based on ranked responses, prioritized 20 research questions on elasmobranch conservation. To address these questions, we then convened a group of 47 experts from 35 institutions and 12 countries. The 20 questions were organized into the following broad categories: (1) status and threats, (2) population and ecology, and (3) conservation and management. For each section, we sought to synthesize existing knowledge, describe consensus or diverging views, identify gaps, and suggest promising future directions and research priorities. The resulting synthesis aggregates an array of perspectives on emergent research and priority directions for elasmobranch conservation.
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    First Application of 360-Degree Camera Technology to Marine Predator Bio-Logging
    Gallagher, Austin J.; Alsudairy, Nourah A.; Shea, Brendan D.; Payne, Nicholas L.; Duarte, Carlos M. (2021-07-26)
    Animal-borne video camera systems have long-been used to capture the fine-scale behaviors and unknown aspects of the biology of marine animals. However, their utility to serve as robust scientific tools in the greater bio-logging research community has not been fully realized. Here we provide, for the first time, an application of 360-degree camera technology to a marine organism, using a large tiger shark as a proof-ofconcept case study. Leveraging the three-dimensional nature of the imaging technology, we derived 224 seafloor habitat assessments over the course of the nearly 1-h track, whereby the shark was able to survey similar to 23,000 square meters of seafloor; over threetimes greater than the capacity of non 360-degree cameras. The resulting data provided detailed information on habitat use, diving behavior, and swimming speed, as well seafloor mapping. Our results suggest that 360-degree cameras provide complimentary benefits-and in some cases superior efficiency-than unidirectional video packages, with an enhanced capacity to map seafloor.
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    Humpback Whale Instigates Object Play with a Lion’s Mane Jellyfish
    Shea, Brendan D.; Gallagher, Austin J. (MDPI, 2021-05-24)
    Cetaceans are well-known for their intelligence, charismatic nature, and curiosity. Many species, particularly odontocetes, are known to investigate and manipulate novel objects they encounter. Yet, disentangling the drivers of these behaviors and distinguishing between those that are simply playful and those which serve a specific function remains challenging due to a lack of direct observations and detailed descriptions of behaviors. This is particularly true for mysticetes such as humpback whales (Megaptera novaeangliae), as records of object use are far less common than in odontocetes. Here, we present evidence of novel object use from a first of its kind encounter between an individual humpback whale and a large lion’s mane jellyfish (Cyanea capillata) in the coastal waters off New England. We detail the interaction and discuss possible drivers for the behavior, with a focus on cetacean innovation, ectoparasite removal, and wound healing.
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    Quantifying longline bycatch mortality for pelagic sharks in western Pacific shark sanctuaries
    Shea, Brendan D.; Gallagher, Austin J.; Bomgardner, Lindsay K.; Ferretti, Francesco (American Association for the Advancement of Science, 2023-08)
    Marine protected areas are increasingly touted for their role in conserving large marine predators such as sharks, but their efficacy is debated. Seventeen “shark sanctuaries” have been established globally, but longline fishing continues within many such jurisdictions, leading to unknown levels of bycatch mortality levels. Using public data from Global Fishing Watch and Regional Fisheries Management Organizations, we quantified longline fishing within eight shark sanctuaries and estimated pelagic shark catch and mortality for seven pelagic shark species. Sanctuary mortality ranged from 600 individuals (Samoa) to 36,256 individuals (Federated States of Micronesia), equivalent to ~5% of hypothesized sustainable levels for blue sharks to ~40% for silky sharks, with high mortality levels in the Federated States of Micronesia, Palau, and the Marshall Islands. Unsustainable mortality rates were exceeded for silky sharks in two sanctuaries, highlighting a need for additional stock assessments and implementation of bycatch reduction measures. Big data integration workflows represent a transformative tool in fisheries management, particularly for data-poor species.