Diverse resource-use strategies in a large-bodied marine predator guild: evidence from differential use of resource subsidies and intraspecific isotopic variation

Shipley, Oliver N.; Gallagher, Austin J.; Shiffman, David S.; Kaufman, Leslie S.; Hammerschlag, Neil

doi:10.3354/meps12982

Cited by 24 publications

(21 citation statements)

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“…However, for higher order predators of historically low commercial value, such as sharks, assessments are much sparser. Sharks are medium to large-bodied predators that occupy meso-to-apex trophic positions throughout marine food-webs 21 – 23 and as a result are intrinsic to healthy ecosystem function and resilience 24 , 25 . Despite the historically low commercial value of shark meat, relative demand as a human protein source appears to be a growing global trend 26 .…”

Section: Introductionmentioning

confidence: 99%

Metal concentrations in coastal sharks from The Bahamas with a focus on the Caribbean Reef shark

Shipley

Lee

Fisher

et al. 2021

Sci Rep

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Over the last century anthropogenic activities have rapidly increased the influx of metals and metalloids entering the marine environment, which can bioaccumulate and biomagnify in marine top consumers. This may elicit sublethal effects on target organisms, having broad implications for human seafood consumers. We provide the first assessment of metal (Cd, Pb, Cr, Mn, Co, Cu, Zn, As, Ag, and THg) and metalloid (As) concentrations in the muscle tissue of coastal sharks from The Bahamas. A total of 36 individual sharks from six species were evaluated, spanning two regions/study areas, with a focus on the Caribbean reef shark (Carcharhinus perezi), and to a lesser extent the tiger shark (Galeocerdo cuvier). This is due their high relative abundance and ecological significance throughout coastal Bahamian and regional ecosystems. Caribbean reef sharks exhibited some of the highest metal concentrations compared to five other species, and peaks in the concentrations of Pb, Cr, Cu were observed as individuals reached sexual maturity. Observations were attributed to foraging on larger, more piscivorous prey, high longevity, as well a potential slowing rate of growth. We observed correlations between some metals, which are challenging to interpret but may be attributed to trophic level and ambient metal conditions. Our results provide the first account of metal concentrations in Bahamian sharks, suggesting individuals exhibit high concentrations which may potentially cause sublethal effects. Finally, these findings underscore the potential toxicity of shark meat and have significant implications for human consumers.

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Section: Introductionmentioning

confidence: 99%

Metal concentrations in coastal sharks from The Bahamas with a focus on the Caribbean Reef shark

Shipley

Lee

Fisher

et al. 2021

Sci Rep

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“…Understanding the resource‐use dynamics of higher predators can provide important insight into their functional role and broader processes that ultimately dictate the distribution of species in space and time (Dehling and Stouffer, ; Soberón ). This is because resource‐use characteristics are capable of structuring ecological communities through mechanisms such as the regulation of prey populations ( i.e ., direct foraging and risk effects, Heithaus et al ., ; Roff et al ., ), promoting ecosystem/food‐web connectivity (Doughty et al ., ; McCauley et al ., ; Shipley et al ., ) and engineering habitats (Hammerschlag, ; O'Shea et al ., ). Sharks are a group of predatory fish that predominantly occupy upper‐trophic positions (mesopredator to apex predator) throughout marine food webs (Cortes, ; Hussey et al ., ; Shipley et al ., ).…”

Section: Introductionmentioning

confidence: 99%

“…Sharks are a group of predatory fish that predominantly occupy upper-trophic positions (mesopredator to apex predator) throughout marine food webs (Cortes, 1999;Hussey et al, 2014;Shipley et al, 2019). Although the ecological roles of sharks are generally understood Roff et al, 2016), their functional roles can be diverse, warranting the need for context-(e.g., time of year, sex, size class, species) and location-specific assessments.…”

Section: Introductionmentioning

confidence: 99%

“…A further utility of stable isotope ratios is the rate at which they are incorporated into different bodily tissues (i.e., isotopic turnover rate), which allows for comparison of resource-use dynamics across varying temporal resolutions (Matich et al, 2011;Shipley et al, 2019). Examining the isotopic composition of fast-(e.g., blood plasma,~40 days, Zeichner et al, 2016) vs.…”

Section: Introductionmentioning

confidence: 99%

“…SEA provides a bivariate estimate of isotopic variability and represents the relative size of resource space utilized by individuals within a sampling population and incorporates about 40% of the available data(Jackson et al, 2011). Due to low sample sizes for some species and tissue types, small sample-size-corrected SEA (SEA C ) andBayesian-derived SEA (SEA B ) were also calculated for all four species.Because estimates of resource-use breadth can be biased by the proportion of data included in derivations of standardized ellipses (i.e., as a result of intra-specific variability in resource use), estimates of resource-use overlap between the three beach species were calculated based on an ellipse encompassing approximately 95% of the data(Shipley et al, 2018(Shipley et al, , 2019. Resource-use overlap of the three T A B L E 1 Summary information for elasmobranchs sampled on the First Coast by tissue type…”

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Resource‐use dynamics of co‐occurring chondrichthyans from the First Coast, North Florida, USA

Morgan

Shipley

Gelsleichter

2020

Journal of Fish Biology

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Recent studies on shark assemblages on the northeast Florida and southeast Georgia coast (hereafter referred to collectively as the “First Coast”) have demonstrated differences in species and age‐class composition of catch from previously characterized estuaries and newly surveyed area beaches, demonstrating that these regions may provide a critical habitat to different segments (i.e., life stages) of local shark populations. In this study, carbon and nitrogen stable isotopes (δ13C and δ15N) from muscle tissue and blood plasma were used to examine trophic dynamics (and temporal variability thereof) of the three dominant co‐occurring species found along First Coast beaches (the Atlantic Sharpnose shark Rhizoprionodon terraenovae, Blacknose shark Carcharhinus acronotus and Blacktip shark Carcharhinus limbatus) to determine if they exhibit overlap in resource use along with spatial and temporal habitat use. Although considered spatially segregated from the beach species, a dominant, age‐class species found in First Coast estuaries (juvenile Sandbar sharks Carcharhinus plumbeus) was also included in this analysis for comparison. Temporal variability of resource‐use characteristics was detected at the species level. Resource‐use overlap among species varied by tissue type and was generally higher for blood plasma, suggesting greater resource sharing over more recent time periods. Over longer time periods Atlantic Sharpnose and Blacktip sharks exhibited resource‐use expansion, whereas Blacknose sharks exhibited a narrowing in resource use, suggesting a more specialized foraging strategy compared to the other species. The resource‐use breadth of Sandbar sharks also expanded between blood plasma and muscle tissue. Significant size relationships were detected in Blacktip and Sandbar sharks, indicating ontogenetic resource shifts for both species. A diversity of highly productive resource pools likely support shark populations along the First Coast such that resource‐use differentiation is not required to facilitate species co‐occurrence. This work may shed light on understanding patterns of species co‐occurrence as well as aid in future conservation efforts.

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Evolution of realized Eltonian niches acrossRajidaespecies

et al. 2021

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The notion that closely related species resemble each other in ecological niche space (i.e., phylogenetic dependence) has been a long‐standing, contentious paradigm in evolutionary biology, the incidence of which is important for predicting the ecosystem‐level effects of species loss. Despite being examined across a multitude of terrestrial taxa, many aspects of niche conservatism have yet to be explored in marine species, especially for characteristics related to resource use and trophic behavior (Eltonian niche characteristics, ENCs). We combined ENCs derived from stable isotope ratios at assemblage‐ and species‐levels with phylogenetic comparative methods, to test the hypotheses that benthic marine fishes (1) exhibit similar assemblage‐wide ENCs regardless of geographic location and (2) display phylogenetically dependent ENCs at the species level. We used a 12‐species sub‐set of the monophyletic group Rajidae sampled from three independent assemblages (Central California, Gulf of Alaska, and Northwest Atlantic), which span two ocean basins. Assemblage‐level ENCs implied low trophic diversity and high evenness, suggesting that Rajidae assemblages may exhibit a well‐defined trophic role, a trend consistent regardless of geographic location. At the species level, we found evidence for phylogenetic dependence of ENCs relating to trophic diversity (i.e., isotopic niche width; SEAc). Whether individuals can be considered functional equivalents across assemblages is hard to ascertain because we did not detect a significant phylogenetic signal for ENCs relating to trophic function (e.g., trophic position). Thus, additional, complimentary approaches are required to further examine the phylogenetic dependence of species functionality. Our approach illustrates the potential of stable isotope‐derived niche characteristics to provide insight on macroecological processes occurring across evolutionary time, which could help predict how assemblages may respond to the effects of species loss.

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Diverse resource-use strategies in a large-bodied marine predator guild: evidence from differential use of resource subsidies and intraspecific isotopic variation

Cited by 24 publications

References 86 publications

Metal concentrations in coastal sharks from The Bahamas with a focus on the Caribbean Reef shark

Metal concentrations in coastal sharks from The Bahamas with a focus on the Caribbean Reef shark

Resource‐use dynamics of co‐occurring chondrichthyans from the First Coast, North Florida, USA

Evolution of realized Eltonian niches acrossRajidaespecies

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