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Trans-Atlantic Pelagic Sharks Research Initiative

POPULATION GENETICS



POPULATION GENETICS
Phylogeography of pelagic sharks in the Atlantic Ocean using molecular markers


The correct identification and separation of the genetically differentiated populations within any species is extremely important for fisheries managements and conservation. Different stocks may be subject to different fishing pressures, and respond differently to such pressures, and should therefore be managed independently. Nonetheless, very little is currently known about how most of the commercially exploited pelagic sharks are genetically distributed and separated in the Atlantic Ocean.


OBJECTIVES

The aim of this project is to study the population genetics of oceanic sharks along the Atlantic Ocean, trying to separate the different populations for the most important species and providing management advice.


Specific objectives include:

1) To identify the geographical distribution of the reproductive stocks and the current genetic diversity levels of the Atlantic populations of blue shark (Prionace glauca), mako (Isurus oxyrhynchus), bigeye thresher (Alopias superciliosus), smooth hammerhead (Sphyrna zygaena), oceanic whitetip (Carcharhinus longimanus) and crocodile shark (Pseudocarcharias kamoharai),

2) To propose phylogeography hypothesis and establish relationships between the different populations,

3) To evaluate the occurrence of population structuring patterns on these migratory species,

4) To resolve any possible taxonomic uncertainties within these groups,

5) To provide advice for fisheries management and contribute for a more sustainable utilization of these resources in the Atlantic Ocean.


PRELIMINARY RESULTS

Crocodile shark: Population genetics studies within the TAPS initiative started in March 2010 with some 150 crocodile shark samples collected by Portuguese fishing vessels fishing in different areas of the NE, SE and SW Atlantic Ocean. The population genetics of this species is being analyzed by mitochondrial DNA techniques and the results will be available soon.

Blue shark: For the blue shark, we have been using mitochondrial DNA sequences and microsatellites for analyzing shark samples collected mainly along the SW Atlantic. Preliminary analysis already revealed some very interesting information about the genetic flux of this species in that SW Atlantic region. Ongoing studies are now focused on the remaining Atlantic Ocean regions in order to determine if different fishing stocks exist in the Atlantic and the possible locations of these stocks boundaries.

Bigeye thresher: Bigeye thresher shark samples have started being analyzed using mitochondrial DNA sequences. For this species we are currently developing microsatellite markers that can, in the future, be used for determining the presence of hybrid lineages, multiple paternity on pregnant females and philopatry within the populations.

Smooth hammerhead, mako and oceanic whitetip: Molecular analysis on these species has started recently and preliminary results will be available soon.


FUNDING

This project is coordinated by Drs. Fausto Foresti and Fernando Fernandes Mendonça from the Fish Genetics Laboratory at the State University of São Paulo, and is funded by FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo), with project Reference N° 2010/51903-2.
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