#Cat goes fishing tiger shark drivers#
Studies on processes such as intra-population loss of diversity, adaptive change caused by evolutionary drivers in the environment, as well as the movement, decline, or extirpation of populations through time and space can now be undertaken 5, 12. The use of DNA extracted from museum specimens, in combination with modern molecular analytical tools, has revolutionized the ability to assess genetic changes at contemporary time scales 10, 11. In addition, the difficulties associated with the use of high-resolution genetic methods when sample sizes are low or when tissue samples vary in age, composition and provenance 9 also hinder our ability to assess intra-specific diversity. Indeed, the lack of dedicated sampling programs and the many species requiring monitoring makes it logistically impossible to oversee intra-specific diversity in most instances. Intraspecific diversity protection is a specified objective of the Convention on Biological Diversity (CBD but is rarely an integral part of monitoring activities, in particular for species that are not critically endangered 7, 8. Thus, species with many discrete populations with different genetic adaptations, including life history strategies, are assumed better at withstanding exploitation and environmental variation, than a single panmictic population. High genetic diversity may also have positive ecosystem effects by promoting productivity, abundance, and stability of community structure 4, 5, 6. Intraspecific genetic diversity is essential for long-term population persistence to avoid the negative effects of inbreeding 1, to buffer against environmental variation in time and space 2, and to ensure adaptability to a changing environment 3. 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. The change was most likely due to a shift over time in the relative contribution of two well-differentiated, but hitherto cryptic populations. Using Single Nucleotide Polymorphism (SNP) loci, we documented a significant change in genetic composition of tiger sharks born between ~19.
Here we report on temporal genomic analyses of tiger shark ( Galeocerdo cuvier) DNA samples that were collected from eastern Australia over the past century. 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.
In addition, in some locations the use of shark control programs also has had an impact on shark numbers.
Over the last century, many shark populations have declined, primarily due to overexploitation in commercial, artisanal and recreational fisheries.
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