Effective size closely approximates the census size in the heavily exploited western Atlantic population of the sandbar shark, Carcharhinus plumbeus

Abstract 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’ 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°C or when dissolved oxygen concentration was reduced below 3.5 mg l−1 (51% oxygen saturation between 24–32°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.

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Population and Conservation Genetics of Marsupials

Australian Journal of Zoology ◽

10.1071/zo9890161 ◽

1989 ◽

Vol 37 (3) ◽

pp. 161 ◽

Cited By ~ 8

Author(s):

WB Sherwin ◽

ND Murray

Keyword(s):

Population Genetics ◽

Conservation Genetics ◽

Current Knowledge ◽

Effective Size ◽

Individual Species ◽

Census Size ◽

Electrophoretic Data ◽

Marsupial Species ◽

Small Effective Size ◽

Census Number

This article summarises current knowledge of marsupial population genetics, and discusses its relevance to the conservation of marsupial species. It has been suggested that there is much lower genetic variation within marsupial populations than in eutherian mammals. This trend is not evident in the electrophoretic data summarised here. However, genetic differentiation between populations, subspecies, and species of marsupials appears to be slightly lower than comparable values for eutherians. Genetic estimates of migration between populations are scarce at present, but show values that are comparable with eutherians. Some studies of marsupial population genetics have used non-electrophoretic characteristics, or have addressed the possibility of selection on the characters analysed. Although few, these studies indicate the suitability of marsupials for such investigations. Recent debate over the theories and applications of conservation genetics has made it clear that more research is required on individual species. Given the record of extinction of marsupials in the last 200 years, it is important to test the applicability of these theories to individual marsupial species. Several examples are discussed emphasising the need for ecological studies that estimate the effective number of reproducing individuals per generation. This figure, called the effective size, is the corner- stone of conservation genetics theory, being an important determinant of both the rate of loss of variation between individuals, and the rate of inbreeding. The effective size of the mainland population of the eastern barred bandicoot, Perameles gunnii, appears to be only about one-tenth of its census number. This result is comparable with estimates made in other vertebrates, and demonstrates that many marsupial species which appear to have an adequate census size on ecological grounds may face genetic problems resulting from small effective size.

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World phylogeography and male-mediated gene flow in the sandbar shark, Carcharhinus plumbeus

Molecular Ecology ◽

10.1111/j.1365-294x.2010.04626.x ◽

2010 ◽

Vol 19 (10) ◽

pp. 1994-2010 ◽

Cited By ~ 80

Author(s):

DAVID S. PORTNOY ◽

JAN R. MCDOWELL ◽

EDWARD J. HEIST ◽

JOHN A. MUSICK ◽

JOHN E. GRAVES

Keyword(s):

Gene Flow ◽

Sandbar Shark ◽

Carcharhinus Plumbeus

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Year-Round Aggregation of Sandbar Shark, Carcharhinus plumbeus (Nardo, 1827), in Boncuk Cove in the southern Aegean Sea, Turkey (Carcharhiniformes: Carcharhinidae)

Zoology in the Middle East ◽

10.1080/09397140.2018.1540148 ◽

2018 ◽

Vol 65 (1) ◽

pp. 35-39

Author(s):

Halit Filiz

Keyword(s):

Aegean Sea ◽

Sandbar Shark ◽

Carcharhinus Plumbeus

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Life in the Slow Lane: Ecology and Conservation of Long-Lived Marine Animals

Life in the Slow Lane: Ecology and Conservation of Long-Lived Marine Animals ◽

10.47886/9781888569155.ch9 ◽

1999 ◽

Keyword(s):

Simulation Model ◽

Maximum Size ◽

Population Projections ◽

Population Declines ◽

Sandbar Shark ◽

Carcharhinus Plumbeus ◽

Marine Animals ◽

Important Species ◽

Age Structured ◽

Stage Class

Abstract. —The sandbar shark Carcharhinus plumbeus is the most important species caught in the commercial shark fishery operating off the U.S. Atlantic and Gulf of Mexico coasts. Previous demographic studies of this and other species of sharks have utilized age-structured, deterministic life tables that provided point estimates of maximum rates of increase. To reduce some of the uncertainty in estimates of age at maturity and longevity—especially acute in the case of the sandbar shark—I constructed a stage-based model based on an Usher matrix that utilizes the more reliable estimates of size at maturity and maximum size for this species in the northwest Atlantic. Because demographic variability also can affect estimated rates of increase, I introduced stochasticity into the model by randomly selecting fecundity rates from an empirically determined distribution, and natural mortality rates from estimates obtained through four life history methods. The simulation model was applied to females only. Population projections 20 years forward in time without exploitation predicted slowly growing populations at approximately 1.3%/year. Application of a constant instantaneous mortality rate (F ) of 0.1 to each stage-class separately indicated that removal of large juveniles would produce the greatest population declines, whereas removal of age-0 individuals would be sustainable. The simulation model was then used to predict potential outcomes under three hypothetical harvesting scenarios using the current U.S. commercial quota indicating that all strategies produced pronounced population declines.

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Gastric evacuation in the sandbar shark, Carcharhinus plumbeus

Journal of Fish Biology ◽

10.1111/j.1095-8649.1985.tb04263.x ◽

1985 ◽

Vol 26 (3) ◽

pp. 239-253 ◽

Cited By ~ 32

Author(s):

R. J. Medved

Keyword(s):

Sandbar Shark ◽

Carcharhinus Plumbeus ◽

Gastric Evacuation

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Demography of the central california population of the Leopard Shark (Triakis semifasciata)

Marine and Freshwater Research ◽

10.1071/mf9920183 ◽

1992 ◽

Vol 43 (1) ◽

pp. 183 ◽

Cited By ~ 36

Author(s):

GM Cailliet

Keyword(s):

Population Growth ◽

Reproductive Rate ◽

Shark Species ◽

Sandbar Shark ◽

Lemon Shark ◽

Carcharhinus Plumbeus ◽

Net Reproductive Rate ◽

Leopard Shark ◽

Triakis Semifasciata ◽

Leopard Sharks

Demographic analyses can be quite useful for effectively managing elasmobranch fisheries. However, they require valid estimates of age-specific mortality and natality rates, in addition to information on the distribution, abundance, habits and reproduction of the population, to produce reliable estimates of population growth. Because such detailed ecological information is usually unavailable, complete demographic analyses have been completed for only four shark species: the spiny dogfish, Squalus acanthias; the soupfin shark, Galeorhinus australis; the lemon shark, Negaprion brevirostris; and most recently the sandbar shark, Carcharhinus plumbeus. In California, reliable estimates of age, growth, mortality, age at maturity, and fecundity are available only for the leopard shark, Triakis semifasciata. A demographic analysis of this species yielded a net reproductive rate (Ro) of 4.467, a generation time (G) of 22.35 years, and an estimate of the instantaneous population growth coefficient (r) of 0.067. If the mean fishing pressure over 10 years (F= 0.084) is included in the survivorship function, Ro and r are reduced considerably, especially if leopard sharks first enter the fishery at early ages. A size limit of 120 cm TL (estimated age 13 years), especially for female sharks, is tentatively proposed for the leopard shark fishery.

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