276 research outputs found
Global tracking of shark movements, behaviour and ecology: A review of the renaissance years of satellite tagging studies, 2010–2020
No full textSatellite telemetry as a tool in marine ecological research continues to adapt and grow and has become increasingly popular in recent years to study shark species on a global scale. A review of satellite tag application to shark research was published in 2010, provided insight to the advancements in satellite shark tagging, as well as highlighting areas for improvement. In the years since, satellite technology has continued to advance, creating smaller, longer lasting, and more innovative tags, capable of expanding the field. Here we review satellite shark tagging studies to identify early successes and areas for rethinking moving forward. Triple the amount of shark satellite tagging studies have been conducted during the decade from 2010 to 2020 than ever before, tracking double the number of species previously tagged. Satellite telemetry has offered increased capacity to unravel ecological questions including predator and prey interactions, migration patterns, habitat use, in addition to monitoring species for global assessments. However, <17% of the total reviewed studies directly produced results with management or conservation outcomes. Telemetry studies with defined goals and objectives produced the most relevant findings for shark conservation, most often in tandem with secondary metrics such as fishing overlap or management regimes. To leverage the power of telemetry for the benefit of shark species, it remains imperative to continue improvements to tag function and maximize the outputs of tagging efforts including increasing data sharing capacity and standardization across the field, as well as spatial and species coverage. Ultimately, this review offers a status report of shark satellite tagging and the ways in which the field can continue to progress
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Data for: An ecological assessment of large coastal shark communities in South Florida
No full textThis dataset is associated to the article “An ecological assessment of large coastal shark communities in South Florida” by Tinari and Hammerschlag (2021), published in Ocean and Coastal Management, https://doi.org/10.1016/j.ocecoaman.2021.105772. Specifically, these are the data used to create figures 1, 2, 3, and 4 and tables 1, 2, 3, 4, and 5. These data are the results of standardized drumline surveys from Miami through the middle Florida Keys to examine spatial, seasonal, and environmental patterns in shark occurrence, catch per unit effort, composition, and demographic structure. Between 2009 and 2021, a total of 21,755 drumlines were deployed, capturing 3,398 sharks, comprising fifteen species. Ginglymostoma cirratum, (n=1335), Carcharhinus limbatus, (n=650), Negaprion brevirostris, (n=314), C. leucas, (n=253), and Sphyrna mokarran, (n=238) were the most common species encountered. At the assemblage level, relative abundance among regions and seasons were generally similar; however clear species-specific patterns of abundance, size structure, and sex-composition were detected by season, region, habitat, and management zones. These data serve as a baseline for future monitoring of shark populations in South Florida and assessing their response to environmental change. Mark recapture sharks were also analyzed to provide insights into the distances traveled and time at liberty
The Caribbean needs big marine protected areas
No full textThe attached document is the author(’s’) final accepted/submitted version of the journal article. You are advised to consult the publisher’s version if you wish to cite from it.NHM Repositor
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Survey of Fishes within a Restored Mangrove Habitat in Bill Baggs Cape Florida State Park, Key Biscayne, Florida
No full textRestoration and monitoring are important conservation tools to ensure the recovery and maintenance of human impacted habitats. Bill Baggs Cape Florida State Park, located in Key Biscayne, Florida, has been impacted by urban development and hurricanes, leading to the historical removal of much of the park’s native habitat, including mangrove forest. After Hurricane Andrew in 1992, restoration efforts led to the replanting of a 30-hectare mangrove forest within the park. Part of the forest’s design involved incorporating a series of 28 mangrove pools within the forest to act as nursery habitat. While there have been several studies examining fish using the mangrove pools early on in the forest’s recovery, no work regarding fish abundance and richness in this recovering habitat has been done in over ten years. This study examines the current relative abundance, richness, and trophic levels of fish within the restored mangrove pools and compare the current fish assemblage with historical data, and evaluates the potential impact of environmental factors on fish abundance and richness in the restored pools. To address these research goals, seven mangrove pools were sampled using BRUVS (baited remote underwater video stations) to establish the current abundance and richness of fish utilizing the pools. A subsample of BRUVS and seine was conducted to determine potential differences in fish families and feeding guilds observed between the techniques. This comparison was then assessed to examine the validity of statistically comparing historical data from previous studies (seine net sampling) to the current study (BRUVS sampling). Environmental data was also collected during each sampling for comparison against patterns of fish presence and abundance. 464 individual fish were observed over the course of BRUVS sampling. 20 taxa were observed, consisting of five families, two genera, and 13 species. Four of these species were not observed in any of the previous studies: nurse shark (Ginglymostoma cirratum), mangrove gambusia (Gambusia rhizophorae), sailfin molly (Poecilia latipinna), and schoolmaster snapper (Lutjanus apodus). The fish observed via BRUVS were categorized into three feeding guild: zoobenthivores, piscivores, and planktivores. There was a significant difference in the presence and abundance of fish families observed between BRUVS and seine but not between feeding guilds. While the current BRUVS sampling cannot be statistically compared to previous work seine sampling conducted in the park, the higher CPUE of hardhead silversides and goldspotted killifish from seine sampling in the current study indicates an increase in abundance of these ecologically important forage fish. No single environmental factor affected the presence and abundance of all fish families and feeding guilds. However, individual pools and turbidity emerged as significant factors in several instances. The presence of nursery species, occurrence of predatory species and increased abundance of small forage fish in the present study indicates that the mangrove fringed pools is acting as habitat for variety of economically and ecologically important species. Low species richness in comparison to natural forests in adjacent Biscayne Bay suggest that the young forest is still recovering as essential fish habitat and function not yet fully restored.</p
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Integrating Physiological and Reflex Biomarkers of Fishing Capture Stress in Coastal Shark Species
No full textIn both commercial and recreational fisheries, many sharks are captured and released alive due to harvest regulations, the capture of non-target species, or conservation ethics. Nevertheless, released individuals may suffer post-release fitness loss or even mortality due to capture stress. Additionally, some of these species that would otherwise be intended for release are found dead upon capture. Understanding physiological and behavioral responses of sharks to capture stress is important for determining best fishing practices and for establishing effective management strategies. In this study, I investigated sub-lethal effects of capture through monitoring blood glucose, lactate, hematocrit and reflex impairment on four species of coastal sharks: blacktip (Carcharhinus limbatus), great hammerhead (Sphyrna mokarran), nurse (Ginglymostoma cirratum) and sandbar (Carcharhinus plumbeus). A probability of impairment score was given to each individual based off reflexes developed for this study. I further evaluated inter- and intra- specific relationships between these parameters and fight time, season, and shark size. Of the physiological parameters accessed, lactate emerged as the most significant with increases associated with fight time, shark species, and reflex impairments. Reflex indices showed significant impairment with increasing fight time with the “Jaw” reflex being most significant in all evaluations. Species-specific differences were detected in all parameters with nurse sharks consistently having the lowest values and impairments while great hammerheads had the highest. These relative differences in species-specific stress responses is consistent with relative difference in fighting behavior exhibited for these species on a fishing line as well as reported at-vessel and post-release mortality rates for these species. Collectively, these results indicate that lactate can be used as a measure of shark capture stress, jaw reflex impairments can be utilized as significant indicators of shark capture stress on a species specific basis, and that species’ ecology likely contributes to these responses both physiologically and in terms of reflex impairment. This work connects species-specific reported at-vessel and post-release mortality rates with their responses to capture by revealing trends in physiological changes and reflex impairments. The drumline capture method used likely represents a more benign fishing method compared to typical recreational and commercial fishing gears and therefore these responses are likely subdued when compared to other fishing techniques. Therefore, continued investigation is warranted to better understand the varied responses among species and different capture techniques.</p
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Sea Turtle Protection in the Eastern Equatorial Pacific: A Strategy to Reduce Incidental Take and Promote Conservation
No full textFive species of sea turtle inhabit the Eastern Tropical Pacific Seascape. Based on the International Union for the Conservation of Nature, all five of these populations are threatened with extinction. Bycatch, the incidental take of non-target species in fisheries, is the leading cause of sea turtle decline within the region. To address this issue in the region, methods were used to analyze policy and management in attempts to better determine those gaps, which hinder sea turtle protection. Geographic Information Systems, specifically, ArcGIS, was used to determine areas of primary importance to sea turtles. The Inter American Tropical Tuna Commission (IATTC) provided data of purse seine interactions within sea turtles in the Eastern Equatorial Pacific Ocean. Interaction is defined as live sea turtles sighted by observers from purse seine vessels, whether or not they were involved in a set. Through hot spot cluster analysis and Inverse Distance Interpolation (IDW) the whereabouts of sea turtles was examined in relation to the marine protected areas and Exclusive Economic Zones of the Eastern Pacific countries. Second, an extensive literature review was conducted to identify gaps in current national, regional, and international management plans. With this information, one was able to gain a better understanding of the requirements for proper sea turtle protection and offer recommendations to improve current protection.</p
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Morphological characterization of peripheral blood leukocytes in blacktip sharks (Carcharhinus limbatus)
No full textThe function and morphology of leukocytes is not well studied in elasmobranchs, with most studies examining epibenthic species such as nurse sharks (Ginglymostoma cirratum). Examination of blacktip sharks (Carcharhinus limbatus), a neritic and migratory species, furthers understanding of the role of leukocytes in a greater variety of elasmobranchs. This study is also used to further research in comparative immunology, facilitating comparisons to other vertebrates with similar immune system function. This study focuses on the morphological characteristics of blacktip shark leukocytes using light, scanning (SEM), and transmission (TEM) microscopy. Morphological features were characterized for each leukocyte type, and the number and distribution of leukocytes in peripheral blood was determined. Lymphocytes and thrombocytes were visualized using SEM, but other leukocyte types proved too similar in morphology to erythrocytes to be characterized using this technique. Light and TEM microscopy allowed for conclusive characterization of the different leukocyte types. Lymphocytes, eosinophils, neutrophils, thrombocytes, and monocytes were all identified, and their ultrastructural features evaluated using TEM. Blacktips were found to have four distinct types of granulocytic cells in peripheral blood. A neutrophil was identified along with three morphologically distinct eosinophilic granulocytes referred to in this study as: (1) fine eosinophilic granulocyte (FEG), (2) coarse eosinophilic granulocyte (CEG) type 1, and (3) coarse eosinophilic granulocyte (CEG) type 2. Differential leukocyte counts and measurements were conducted on 22 shark samples. The counts were used to create a baseline for blacktip blood. Average blood cell type percentages per 100 cells include lymphocytes (68.08%), thrombocytes (17.31%), CEG type 2 (14.99%), CEG type 1 (14.66%), immature leukocytes (13.97%), neutrophils (1.69%) , FEG (0.55%), and monocytes (0.25%). Understanding the makeup of blacktip shark’s blood facilitates comparisons to other organisms and determination of conserved traits between species. This information can also be used to further understanding in husbandry, aid in the care of captive species, and in clinical assessments of wild sharks
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Evaluating the Efficacy of a Marine Reserve for Threatened and Endemic Sharks Off South Africa
No full textThe coastal waters of South Africa are habitat to a diverse composition of sharks, many of which are endemic to the region and/or classified by the International Union for Conservation of Nature Red List as threatened or data deficient. As fishing pressure in the nation’s waters persists, this region has become a research and conservation priority for elasmobranch fishes. Within the Western Cape, the De Hoop Marine Protected Area occupies approximately 288 km2 of coastal water and is considered one of South Africa’s flagship marine protected areas (MPAs). With its no-take status, the MPA provides protection for sharks within its confines; however, they are susceptible to capture by demersal shark longline vessels that target its boundaries. Baited remote underwater video surveys (BRUVS) were used to evaluate relative abundance of sharks at the community assemblage level and passive acoustic telemetry explored habitat-use patterns for six key species. When combined, these approaches revealed insights into the De Hoop MPA’s efficacy for the protection of local endemic and threatened species. Focal species included the endemic puffadder shyshark (Haploblepharus edwardsii), dark shyshark (Haploblepharus pictus), leopard catshark (Poroderma pantherinum), spotted gully shark (Triakis megalopterus), and pyjama catshark (Poroderma africanum) and juveniles of the threatened species, smooth hammerhead (Sphryna zygaena). Results revealed that relative abundance of sharks on a community assemblage level was significantly greater inside the MPA, supporting the hypothesis that sharks would be more abundant inside the MPA than outside of its boundaries. Additionally, relative abundance inside the MPA significantly increased on BRUVS samples that were deployed farther from the reserve’s exposed boundaries. Residency analysis of key species found elevated residency outside De Hoop’s borders and on the shark longline fishery-targeted Eastern Boundary of the MPA. Taken together, these results show that while the MPA is effective at containing increased shark abundance, the Eastern Boundary and adjacent unprotected waters are important for shark habitat utilization. These complementary findings demonstrate the utility of MPAs for protecting conservation priority shark species and reveal an opportunity to alter management for more sufficient protection.</div
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Determining trophic position of plasma and muscle tissue of sharks using compound specific stable isotope analysis
No full textThe intra-tissue comparison between plasma and muscle can be important in determining short and long timescale impacts of shark diet, with implications for the management and conservation of elasmobranch species. Amino acid compound specific stable isotope analysis (AA-CSIA) is used in this study as a powerful tool to infer conclusions about feeding ecology relationships and energy and nutrient transfer in elasmobranchs from South Florida waters. This method uses the δ15N values of specific amino acids to estimate trophic positions (TP) in various tissue types. Trophic ecology interprets the difference between two unique classifications of amino acids (AAs): “trophic amino acids” (TAAs), which are AAs that fractionate significantly with transfer through the food web, and “source amino acids” (SAAs), which are AAs that do not change significantly from the δ15N value at the base of the food web. In this study, five species of sharks were tagged and sampled during the months of September and November 2019 in South Florida: Carcharhinus limbatus (blacktip shark, n=3), Carcharhinus leucas (bull shark, n=3), Negaprion brevirostris (lemon shark, n=2), Rhizoprionodon terraenovae (Atlantic sharpnose shark, n=1), and Ginglymostoma cirratum (nurse shark, n=1). Blood plasma and muscle tissue were collected from the sharks and analyzed using AA-CSIA methodology. The findings demonstrate a significant difference in the TP calculated for muscle tissue (3.8 ± 0.2; mean ± SD) and plasma tissue (3.3 ± 0.4). A depletion in 15N in the urea synthesis intermediate glutamic acid (Glu) compared to other TAA δ15N values (e.g. leucine) in plasma reveals that urea synthesis, a crucial process for elasmobranchs, is a complicating factor in determining TP. This finding suggests the need for a new formulation of TP specifically for elasmobranch plasma. In addition, the average SAA δ15N values for both plasma and muscle samples were significantly different among species, indicating an inter-species variation of baseline N sources and highlighting the importance of using the AA-CSIA method that can distinguish between trophic and baseline differences. This multi-tissue and multi-species approach illuminates the importance of AA-CSIA as a crucial geochemical tool to understand overall trophic ecology in hopes of promoting effective management and conservation strategies for the future
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