Life-history traits inform population trends when assessing the conservation status of a declining tiger shark population

Brown, Christopher J.; Roff, George

doi:10.1016/j.biocon.2019.108230

Cited by 13 publications

(10 citation statements)

References 35 publications

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“…We propose that the most parsimonious explanation for this absence is a shift in the relative population abundance likely associated with human fishing activities. Our results mirror the findings of Brown and Roff 46 that reported a major decline in abundance of tiger sharks over three generations off the Queensland coast, with greater declines detected at the southern sites. However, we recognise that a number of factors could have partially contributed to our observations and uncertainties around this apparent dramatic shift in abundance, which we discuss below.…”

Section: Discussionsupporting

confidence: 90%

Retrospective genomics highlights changes in genetic composition of tiger sharks (Galeocerdo cuvier) and potential loss of a south-eastern Australia population

Manuzzi

Jiménez‐Mena

Henriques

et al. 2022

Sci Rep

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Over the last century, many shark populations have declined, primarily due to overexploitation in commercial, artisanal and recreational fisheries. In addition, in some locations the use of shark control programs also has had an impact on shark numbers. Still, there is a general perception that populations of large ocean predators cover wide areas and therefore their diversity is less susceptible to local anthropogenic disturbance. Here we report on temporal genomic analyses of tiger shark (Galeocerdo cuvier) DNA samples that were collected from eastern Australia over the past century. Using Single Nucleotide Polymorphism (SNP) loci, we documented a significant change in genetic composition of tiger sharks born between ~1939 and 2015. The change was most likely due to a shift over time in the relative contribution of two well-differentiated, but hitherto cryptic populations. Our data strongly indicate a dramatic shift in the relative contribution of these two populations to the overall tiger shark abundance on the east coast of Australia, possibly associated with differences in direct or indirect exploitation rates.

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Section: Discussionsupporting

confidence: 90%

Retrospective genomics highlights changes in genetic composition of tiger sharks (Galeocerdo cuvier) and potential loss of a south-eastern Australia population

Manuzzi

Jiménez‐Mena

Henriques

et al. 2022

Sci Rep

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“…Importantly, our ndings suggest that the current abundance of the putative southerly population has declined compared to pre-1990s levels. The apparent local depletion of tiger sharks at the south eastern distribution of the species in Australia support previous studies showing a reduction in the abundance and mean size of tiger sharks caught 30,31,37 . Although the species is not commonly commercially targeted off eastern Australia, the species is caught as bycatch and in Queensland and New South Wales' shark control programs.…”

Section: Discussionsupporting

confidence: 88%

“…We propose that the most parsimonious explanation for this absence is either a shift in relative population abundance or population distribution of two previously cryptic populations of tiger sharks, or both. It is possible that the shift was associated with human activities mirroring the ndings from Brown and Roff 37 that reported a major decline in abundance of tiger sharks over three generations off the coast of Queensland with greater declines detected at the southern sites . However, we recognise a number of factors could have affected our observations and there may be other alternative causal explanations for this apparent shift in abundance, which we discuss below.…”

Section: Discussionmentioning

confidence: 89%

Retrospective Genomics Suggests the Disappearance of a Tiger Shark (Galeocerdo Cuvier) Population Off South-Eastern Australia

Manuzzi

Jiménez‐Mena

Henriques

et al. 2021

Preprint

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Over the last century, many populations of sharks have been reduced in numbers by overexploitation or attempts to mitigate human-shark interactions. Still, there is a general perception that populations of large ocean predators cover wide areas and therefore their diversity is less susceptible to local anthropogenic disturbance. Here we report retrospective genomic analyses of DNA using archived and contemporary samples of tiger shark (Galeocerdo cuvier) from eastern Australia. Using SNP loci, we documented a significant overall change in genetic composition of tiger sharks born over the last century. The change was most likely due to a shift over time in the relative contribution of two well differentiated, but hitherto cryptic populations. Our data strongly indicate a dramatic shift in relative contribution of the two populations to the overall tiger shark abundance of the east coast of Australia, possibly associated with differences in direct or indirect exploitation rates.

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“…The overfishing of sharks is problematic, and a number of recent reports have indicated a marked reduction in the stocks of many species, which has often resulted in a demographic collapse at a regional scale (Davidson, Krawchuk & Dulvy, 2016; Taylor et al, 2016; Brown & Roff, 2019; Bargnesi, Lucrezi & Ferretti, 2020). In 1999, the Food and Agriculture Organization (FAO) formally recognized the vulnerability of sharks and rays, and launched an international plan for their conservation and management (Vannuccini, 1999).…”

Section: Introductionmentioning

confidence: 99%

A shot in the dark for conservation: Evidence of illegal commerce in endemic and threatened species of elasmobranch at a public fish market in southern Brazil

Cruz

Adachi

Ribeiro

et al. 2021

Aquatic Conservation

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1. The illegal sale of endangered elasmobranchs has been recorded in a number of different Brazilian states, where sharks and rays are being marketed primarily as 'cação' or 'viola'. Brazil is ranked among the top 10 nations worldwide that harvest most sharks, causing an immeasurable impact on the local elasmobranch populations.2. The present study applied the DNA barcoding technique, based on the cytochrome C oxidase subunit I gene, for the molecular identification of the elasmobranch species sold as processed products under the generic names of 'cação', 'mangona', 'azul', 'cambeva', 'fiuso' and 'lombo preto', in the fish market of the city of Florianópolis, capital of the state of Santa Catarina, Brazil.3. Nine elasmobranch species were identified in the 56 samples analysed, including six sharks and three rays, representing six families, the Carcharhinidae, Sphyrnidae, Squatinidae, Arhynchobatidae, Myliobatidae and Gymnuridae.Prionace glauca, identified in more than half (56%) of the samples analysed, is listed as Near Threatened by the International Union for the Conservation of Nature. 4. Six species identified in the present study, Sphyrna zygaena, Sphyrna lewini, Squatina guggenheim, Carcharhinus signatus, Gymnura altavela and Rioraja agassizii, are under some level of risk of extinction, while two others (Rhizoprionodon lalandii and Myliobatis goodei) are listed as Data Deficient.5. Our results indicate that the commercial exploitation of endemic sharks and rays at risk of extinction is commonplace in southern Brazil. This reinforces the need for more systematic monitoring of the trade in fishery products and more effective application of the environmental legislation and conservation programmes.

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Life-history traits inform population trends when assessing the conservation status of a declining tiger shark population

Cited by 13 publications

References 35 publications

Retrospective genomics highlights changes in genetic composition of tiger sharks (Galeocerdo cuvier) and potential loss of a south-eastern Australia population

Retrospective genomics highlights changes in genetic composition of tiger sharks (Galeocerdo cuvier) and potential loss of a south-eastern Australia population

Retrospective Genomics Suggests the Disappearance of a Tiger Shark (Galeocerdo Cuvier) Population Off South-Eastern Australia

A shot in the dark for conservation: Evidence of illegal commerce in endemic and threatened species of elasmobranch at a public fish market in southern Brazil

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