Spatial and Ontogenetic Patterns in the Trophic Ecology of Juvenile Bull Sharks (Carcharhinus leucas) From the Northwest Gulf of Mexico

A combination of stomach content and stable isotope (δ13C, δ15N, and δ34S) analyses were used to characterize and examine spatiotemporal and ontogenetic trends in the feeding ecology of juvenile bull sharks (Carcharhinus leucas) captured in estuaries throughout the northwest Gulf of Mexico (GoM) between 2013 and 2016. Shark diets were dominated by fish prey taxa [>98% index of relative importance (%IRI)], and of those identified to the family level, two families comprised greater than 50% IRI, Mugilidae (mullets: ∼32%) and Sciaenidae (drums and croakers: 27%). Clupeidae (herrings: 14%) and Ariidae (sea catfishes: 15%) also contributed substantially to the diet of juvenile sharks, though consumption of Ariidae increased as consumption of Clupeidae decreased in juvenile sharks larger than 893 mm Fork Length (FL) (∼1 year old). Values of δ15N increased significantly with shark size, indicating a shift toward larger or higher trophic level prey with increasing shark size. Latitudinal and temporal trends in δ13C and δ34S suggest isotopic variation occurred in correspondence with shifts in primary producer assemblages and environmental drivers of sampled estuaries. These results highlight the importance of teleost prey resources along the freshwater-marine continuum in the diet of juvenile bull sharks, as well as the utility of natural tracers in tracking ontogenetic trends in feeding ecology.

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Environmental drivers of abundance and residency of a large migratory shark, Carcharhinus leucas, inshore of a dynamic western boundary current

Marine Ecology Progress Series ◽

10.3354/meps13052 ◽

2019 ◽

Vol 622 ◽

pp. 121-137 ◽

Cited By ~ 6

Author(s):

KA Lee ◽

AF Smoothey ◽

RG Harcourt ◽

M Roughan ◽

PA Butcher ◽

...

Keyword(s):

Western Boundary Current ◽

Environmental Drivers ◽

Western Boundary ◽

Boundary Current ◽

Carcharhinus Leucas

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Feeding patterns of two sympatric shark predators in coastal ecosystems of an oceanic island

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2016-0105 ◽

2017 ◽

Vol 74 (2) ◽

pp. 216-227 ◽

Cited By ~ 6

Author(s):

Clément Trystram ◽

Karyne M. Rogers ◽

Marc Soria ◽

Sébastien Jaquemet

Keyword(s):

Trophic Ecology ◽

Dietary Habits ◽

Stomach Contents ◽

Nitrogen Isotope ◽

Oceanic Island ◽

Apex Predators ◽

Coastal Habitat ◽

Galeocerdo Cuvier ◽

Carcharhinus Leucas ◽

Bull Shark

Stomach contents and stable carbon and nitrogen isotope analyses (δ13C and δ15N) were used to investigate the trophic ecology of two apex predators, tiger sharks (Galeocerdo cuvier) and bull sharks (Carcharhinus leucas), from Reunion Island to describe their dietary habits at both the population and individual levels. In this oceanic island, the tiger and bull sharks were more piscivorous and teutophagous than noted in previous research from other localities. The δ13C values suggested that bull sharks depended on more neritic organic matter sources than tiger sharks, confirming a coastal habitat preference for bull sharks. Moreover, the total length of the bull shark influenced δ13C values, with smaller individuals being more coastal than larger individuals. All indicators suggest that there is a higher degree of similarity between individual tiger sharks compared with the more heterogeneous bull shark population, which is composed of individuals who specialize on different prey. These results suggest that the two species have different functions in these coastal habitats, and thus, they must be considered independently in terms of conservation and management.

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A decreasing trend in global soil water storage from 1981 to 2017

10.5194/egusphere-egu21-5756 ◽

2021 ◽

Author(s):

XinRui Luo ◽

Shaoda Li ◽

Wunian Yang ◽

Liang Liu ◽

Xiaolu Tang

Keyword(s):

Soil Water ◽

Water Loss ◽

Root Zone ◽

Carbon Sink ◽

Temporal Trends ◽

Water Storage ◽

Terrestrial Ecosystems ◽

Environmental Drivers ◽

Soil Water Storage ◽

Soil Drought

Soil water storage serves as a vital resource of the terrestrial ecosystems, and it can significantly influence water cycle and carbon cycling with the frequent occurrence of soil drought induced by land-atmosphere feedbacks. However, there are high variations and uncertainties of root zone soil water storage. This study applied comparison map profile (CMP), Mann-Kendall test, Theil-Sen estimate and partial correlation analysis to (1) estimate the global root zone (0~1 m) soil water storage, (2) and investigate the spatial and temporal patterns from 1981 to 2017 at the global scale, (3) and their relationships with environmental drivers (precipitation, temperature, potential evaportranspiration) using three soil moisture (SM) products &#8211; ERA-5, GLDAS and MERRA-2. Globally, the average annual soil water storage from 1981 to 2017 varied significantly, ranging from 138.3 (100 Pg a-1, 1 Pg = 1015 g) in GLDAS to 342.6 (100 Pg a-1) in ERA-5. Soil water storage of the three SM products consistently showed a decreasing trend. However, the temporal trend of soil water storage among different climate zones was different, showing a decreasing trend in tropical, temperate and cold zones, but an increasing trend in polar regions. On the other hand, temporal trends in arid regions differed from ERA-5, GLDAS and MERRA-2. Spatially, the SM products differed greatly, particularly for boreal areas with D value higher for 2500 Mg ha-1 a-1 and CC value lower for -0.2 between GLDAS and MERRA-2. Over 1981 to 2017, water storage of more than 50% of the global land area suffered from a decreasing trend, especially in Africa and Northeastern of China. Precipitation was the main dominated driver for variation of soil water storage, and distribution varied in different SM products. In conclusion, a global decreasing trend in soil water storage indicate a water loss from soils, and how the water loss affecting carbon sink in terrestrial ecosystems under ongoing climate change needs further investigation.

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Red Snapper: Ecology and Fisheries in the U.S. Gulf of Mexico

Red Snapper: Ecology and Fisheries in the U.S. Gulf of Mexico ◽

10.47886/9781888569971.ch20 ◽

2007 ◽

Keyword(s):

Gulf Of Mexico ◽

Fork Length ◽

Red Snapper ◽

Minimum Size ◽

Minimum Length ◽

Commercial Fishing ◽

Lutjanus Campechanus ◽

Commercial Harvest ◽

Length Regulation ◽

The U.S

Abstract.—Red snapper Lutjanus campechanus were sampled from commercial landings from the Gulf of Mexico (GOM) off Louisiana from October 2001 to May 2004. Fork length (FL), eviscerated weight, otoliths (both sagittae), and sex determinations were taken from 2,900 specimens; FL was subsequently converted to total length (TL) with the equation TL = 1.073 (FL) + 3.56. Red snapper ages (N = 2,867) estimated from counts of opaque annuli in otoliths ranged from 1 to 14 years; however, the vast majority (97.7%) of these were ages 2 to 6 years and the modal age was 3 years. Total lengths among 2,897 specimens ranged from 278 to 940 mm, modal TL was 400 mm, and 98% of all specimens were less than 600 mm TL. We also investigated the fate of red snapper regulatory discards (individuals <381 mm [15 in] TL) during 16 trips on working commercial vessels; over two-thirds of 4,839 red snapper assigned among four discard fate categories (ranging from alive and vigorous to dead) were returned to the water either in moribund or dead condition. Among 399 potential discards retained for age and length analyses, 86% were between 12 and 15 in (305–381 mm) TL and 85% were 2 years of age. The minimum size regulation appears to do little to protect juvenile red snapper from commercial fishing mortality. Heavy red snapper mortality, which begins as bycatch mortality in shrimp trawls, continues as discard mortality at sub-legal lengths when they first recruit to the offshore fishing grounds, and persists as harvest mortality among the youngest legal year- and size-classes. If the minimum size limit is intended to provide a respite from such mortality, a reconsideration of the utility of the minimum length regulation in the commercial harvest of red snapper may be warranted.

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Contrasting effects of climate change on seasonal survival of a hibernating mammal

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1918584117 ◽

2020 ◽

Vol 117 (30) ◽

pp. 18119-18126 ◽

Cited By ~ 3

Author(s):

Line S. Cordes ◽

Daniel T. Blumstein ◽

Kenneth B. Armitage ◽

Paul J. CaraDonna ◽

Dylan Z. Childs ◽

...

Keyword(s):

Climate Change ◽

Population Dynamics ◽

Life History ◽

Environmental Conditions ◽

Temporal Trends ◽

Life History Strategies ◽

Environmental Drivers ◽

Age Classes ◽

History Of ◽

Colorado Rocky Mountains

Seasonal environmental conditions shape the behavior and life history of virtually all organisms. Climate change is modifying these seasonal environmental conditions, which threatens to disrupt population dynamics. It is conceivable that climatic changes may be beneficial in one season but result in detrimental conditions in another because life-history strategies vary between these time periods. We analyzed the temporal trends in seasonal survival of yellow-bellied marmots (Marmota flaviventer) and explored the environmental drivers using a 40-y dataset from the Colorado Rocky Mountains (USA). Trends in survival revealed divergent seasonal patterns, which were similar across age-classes. Marmot survival declined during winter but generally increased during summer. Interestingly, different environmental factors appeared to drive survival trends across age-classes. Winter survival was largely driven by conditions during the preceding summer and the effect of continued climate change was likely to be mainly negative, whereas the likely outcome of continued climate change on summer survival was generally positive. This study illustrates that seasonal demographic responses need disentangling to accurately forecast the impacts of climate change on animal population dynamics.

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