51 research outputs found

    Habitat use and behavior of the east Pacific green turtle, Chelonia mydas in an urbanized system

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    Green sea turtles, Chelonia mydas, are known to inhabit populated and often urbanized areas. To understand turtle habitat use and behavior within these unique habitats, seven juvenile green turtles were fitted with acoustic transmitters (September 2012 – August 2014), of which two transmitters included an accelerometer (AP transmitter). One individual fitted with an AP transmitter was tracked using a passive acoustic array in an urbanized river, the San Gabriel River, Long Beach, CA (33°45’ N, 118°05’ W). Three additional turtles in this river and three turtles (one with AP transmitter) in a restored estuary (33°44’ N, 118°03’ W) in southern California were actively tracked for two non-consecutive 24-h periods. Those fitted with AP transmitters indicated that turtles were less active at night (0.58 ± 0.56 m/s2 and 0.50 ± 0.63 m/s2) than during the day (0.86 ± 0.63 m/s2 and 0.78 ± 0.60 m/s2) at both sites. Activity data and corresponding movements of the actively tracked turtle fitted with the AP transmitter were used to infer resting periods for other tracked individuals. Turtles rested near bridge pilings and runoff outflows in the river to potentially shelter from tidal flow. Turtles used significantly larger daily areas in the urbanized river (0.046 ± 0.023 km2) where resources may be patchier and less abundant, compared to turtles in the estuary (0.024 ± 0.012 km2) where large, dense eelgrass beds are present. Based on the habitat use and behaviors of green sea turtles, it appears that some green sea turtles are able to make use of both highly developed and restored habitats and likely benefit from certain aspects of development

    The impacts of warming and hypoxia on the performance of an obligate ram ventilator

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    Climate change is causing the warming and deoxygenation of coastal habitats like Chesapeake Bay that serve as important nursery habitats for many marine fish species. As conditions continue to change, it is important to understand how these changes impact individual species\u27 behavioral and metabolic performance. The sandbar shark (Carcharhinus plumbeus) is an obligate ram-ventilating apex predator whose juveniles use Chesapeake Bay as a nursery ground up to 10 years of age. The objective of this study was to measure juvenile sandbar shark metabolic and behavioral performance as a proxy for overall performance (i.e. fitness or success) when exposed to warm and hypoxic water. Juvenile sandbar sharks (79.5-113.5 cm total length) were collected from an estuary along the eastern shore of Virginia and returned to lab where they were fitted with an accelerometer, placed in a respirometer and exposed to varying temperatures and oxygen levels. Juvenile sandbar shark overall performance declined substantially at 32 degrees C or when dissolved oxygen concentration was reduced below 3.5 mg l(-1) (51% oxygen saturation between 24-32 degrees C). As the extent of warm hypoxic water increases in Chesapeake Bay, we expect that the available sandbar shark nursery habitat will be reduced, which may negatively impact the population of sandbar sharks in the western Atlantic as well as the overall health of the ecosystem within Chesapeake Bay

    Combined Effects of Acute Temperature Change and Elevated pCO2 on the Metabolic Rates and Hypoxia Tolerances of Clearnose Skate (Rostaraja eglanteria), Summer Flounder (Paralichthys dentatus), and Thorny Skate (Amblyraja radiata)

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    Understanding how rising temperatures, ocean acidification, and hypoxia affect the performance of coastal fishes is essential to predicting species-specific responses to climate change. Although a population’s habitat influences physiological performance, little work has explicitly examined the multi-stressor responses of species from habitats differing in natural variability. Here, clearnose skate (Rostaraja eglanteria) and summer flounder (Paralichthys dentatus) from mid-Atlantic estuaries, and thorny skate (Amblyraja radiata) from the Gulf of Maine, were acutely exposed to current and projected temperatures (20, 24, or 28 °C; 22 or 30 °C; and 9, 13, or 15 °C, respectively) and acidification conditions (pH 7.8 or 7.4). We tested metabolic rates and hypoxia tolerance using intermittent-flow respirometry. All three species exhibited increases in standard metabolic rate under an 8 °C temperature increase (Q10 of 1.71, 1.07, and 2.56, respectively), although this was most pronounced in the thorny skate. At the lowest test temperature and under the low pH treatment, all three species exhibited significant increases in standard metabolic rate (44–105%; p \u3c 0.05) and decreases in hypoxia tolerance (60–84% increases in critical oxygen pressure; p \u3c 0.05). This study demonstrates the interactive effects of increasing temperature and changing ocean carbonate chemistry are species-specific, the implications of which should be considered within the context of habitat. Associated dataset: Gail D. Schweiterman, Daniel P. Crear et al. 2019. Metabolic Rates and Hypoxia Tolerences of clearnose skate (Rostaraja eglanteria), summer flounder (Paralichthys dentatus), and thorny skate (Amblyraja radiata) https://doi.org/10.25773/qmew-c18

    Extent and Causes of Chesapeake Bay Warming

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    Coastal environments such as the Chesapeake Bay have long been impacted by eutrophication stressors resulting from human activities, and these impacts are now being compounded by global warming trends. However, there are few studies documenting long-term estuarine temperature change and the relative contributions of rivers, the atmosphere, and the ocean. In this study, Chesapeake Bay warming, since 1985, is quantified using a combination of cruise observations and model outputs, and the relative contributions to that warming are estimated via numerical sensitivity experiments with a watershed–estuarine modeling system. Throughout the Bay’s main stem, similar warming rates are found at the surface and bottom between the late 1980s and late 2010s (0.02 +/- 0.02C/year, mean +/- 1 standard error), with elevated summer rates (0.04 +/- 0.01C/year) and lower rates of winter warming (0.01 +/- 0.01C/year). Most (~85%) of this estuarine warming is driven by atmospheric effects. The secondary influence of ocean warming increases with proximity to the Bay mouth, where it accounts for more than half of summer warming in bottom waters. Sea level rise has slightly reduced summer warming, and the influence of riverine warming has been limited to the heads of tidal tributaries. Future rates of warming in Chesapeake Bay will depend not only on global atmospheric trends, but also on regional circulation patterns in mid-Atlantic waters, which are currently warming faster than the atmosphere. Supporting model data available at: https://doi.org/10.25773/c774-a36

    The Distribution of Total and Organic Mercury in Seven Tissues of the Pacific Blue Marlin, Makaira nigricans

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    Tissue samples from Pacific blue marlin (Makaira nigricans) were collected at a fishing tournament in Kona, Hawaii, in August 1973. Analyses of total and organic (methyl) mercury indicated that the marlin may be biotransforming methyl mercury to inorganic mercury such that about 90 percent of the body burden of mercury is in the inorganic form. Specific analysis of a subsample of the tissues showed that the difference between the total and organic mercury concentrations was equal to inorganic mercury by weight

    Developing a cost-effective puerulus collector for the southern rock lobster (Jasus edwardsii) aquaculture industry

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    Due to the extended duration of larval development, commercial rock lobster aquaculture is proceeding through the harvest of wild pueruli. Puerulus collectors appropriate for commercial use were developed by: (i) obtaining information on appropriate collection materials from industry and past research; (ii) directly comparing catch rates from these materials; and (iii) designing and comparing collectors appropriate for large-scale commercial deployment built with selected materials. Jasus edwardsii pueruli settled on a variety of materials often bearing little resemblance to their natural habitat. 'Bottlebrush' collectors constructed from shade cloth and PVC conduit proved robust, easy to service and were relatively cost effective. 'Sandwich' collectors with filamentous material caught most pueruli, and required a shorter conditioning time than other collectors, but were heavy and relatively expensive to build. Loss of pueruli from collectors being hauled to the sea surface was minimal. Whilst providing details for the construction of cost-effective collectors, we also advocate a 'hands on' approach to designing collectors based on materials readily available to prospective farmers. © 2004 Elsevier B.V. All rights reserved
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