Dataset Information

Weak population structure of the Spot-tail shark Carcharhinus sorrah and the Blacktip shark C. limbatus along the coasts of the Arabian Peninsula, Pakistan, and South Africa.

ABSTRACT: The increase in demand for shark meat and fins has placed shark populations worldwide under high fishing pressure. In the Arabian region, the spot-tail shark Carcharhinus sorrah and the Blacktip shark Carcharhinus limbatus are among the most exploited species. In this study, we investigated the population genetic structure of C. sorrah (n = 327) along the coasts of the Arabian Peninsula and of C. limbatus (n = 525) along the Arabian coasts, Pakistan, and KwaZulu-Natal, South Africa, using microsatellite markers (15 and 11 loci, respectively). Our findings support weak population structure in both species. Carcharhinus sorrah exhibited a fine structure, subdividing the area into three groups. The first group comprises all samples from Bahrain, the second from the UAE and Yemen, and the third from Oman. Similarly, C. limbatus exhibited population subdivision into three groups. The first group, comprising samples from Bahrain and Kuwait, was highly differentiated from the second and third groups, comprising samples from Oman, Pakistan, the UAE, and Yemen; and South Africa and the Saudi Arabian Red Sea, respectively. Population divisions were supported by pairwise F ST values and discriminant analysis of principal components (DAPC), but not by STRUCTURE. We suggest that the mostly low but significant pairwise F ST values in our study are suggestive of fine population structure, which is possibly attributable to behavioral traits such as residency in C. sorrah and site fidelity and philopatry in C. limbatus. However, for all samples obtained from the northern parts of the Gulf (Bahrain and/or Kuwait) in both species, the higher but significant pairwise F ST values could possibly be a result of founder effects during the Tethys Sea closure. Based on DAPC and F ST results, we suggest each population to be treated as independent management unit, as conservation concerns emerge.

SUBMITTER: Almojil D

PROVIDER: S-EPMC6194305 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

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Weak population structure of the Spot-tail shark Carcharhinus sorrah and the Blacktip shark C. limbatus along the coasts of the Arabian Peninsula, Pakistan, and South Africa.

Almojil Dareen D Cliff Geremy G Spaet Julia L Y JLY

Ecology and evolution 20180829 18

The increase in demand for shark meat and fins has placed shark populations worldwide under high fishing pressure. In the Arabian region, the spot-tail shark Carcharhinus sorrah and the Blacktip shark Carcharhinus limbatus are among the most exploited species. In this study, we investigated the population genetic structure of C. sorrah (n = 327) along the coasts of the Arabian Peninsula and of C. limbatus (n = 525) along the Arabian coasts, Pakistan, and ...[more]

PMID: 30377521

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Project description:Southeast Florida witnesses an enormous seasonal influx of upper trophic level marine predators each year as massive aggregations of migrating blacktip sharks (Carcharhinus limbatus) overwinter in nearshore waters. The narrow shelf and close proximity of the Gulf Stream current to the Palm Beach County shoreline drive tens of thousands of sharks to the shallow, coastal environment. This natural bottleneck provides a unique opportunity to estimate relative abundance. Over a four year period from 2011-2014, an aerial survey was flown approximately biweekly along the length of Palm Beach County. A high definition video camera and digital still camera mounted out of the airplane window provided a continuous record of the belt transect which extended 200 m seaward from the shoreline between Boca Raton Inlet and Jupiter Inlet. The number of sharks within the survey transect was directly counted from the video. Shark abundance peaked in the winter (January-March) with a maximum in 2011 of 12,128 individuals counted within the 75.6 km(-2) belt transect. This resulted in a maximum density of 803.2 sharks km(-2). By the late spring (April-May), shark abundance had sharply declined to 1.1% of its peak, where it remained until spiking again in January of the following year. Shark abundance was inversely correlated with water temperature and large numbers of sharks were found only when water temperatures were less than 25 °C. Shark abundance was also correlated with day of the year but not with barometric pressure. Although shark abundance was not correlated with photoperiod, the departure of the sharks from southeast Florida occurred around the vernal equinox. The shark migration along the United States eastern seaboard corresponds spatially and temporally with the spawning aggregations of various baitfish species. These baseline abundance data can be compared to future studies to determine if shark population size is changing and if sharks are restricting their southward migration as global water temperatures increase.

Dataset Information

Weak population structure of the Spot-tail shark Carcharhinus sorrah and the Blacktip shark C. limbatus along the coasts of the Arabian Peninsula, Pakistan, and South Africa.

Publications

Weak population structure of the Spot-tail shark <i>Carcharhinus sorrah</i> and the Blacktip shark <i>C. limbatus</i> along the coasts of the Arabian Peninsula, Pakistan, and South Africa.

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