|Fabián Andrés Sánchez Dorado|
|Use of Microsatellites to Estimate the Genetic Variability of Two Endangered Shark Species in Costa Rica, Silky (Carcharhinus falciformis) and Scalloped Hammerhead (Sphyrna lewinii)|
|Location: Costa Rican Pacific Ocean (Economic Exclusive Zone)|
|Species: Sharks: Carcharinhus falciformis (silky) and Sphyrna sp. (hammerhead)|
|Abstract: The unsustainable shark fishing practice locally called "finning" is dramatically decreasing several shark populations worldwide. Unfortunately, laws in Costa Rica do not offer a quick and effective solution for this threat. Using Microsatellite and PCR reaction, the genetic variability of two populations of sharks will be estimated within the Costa Rican Fishing Economic Exclusive Zone. To achieve our goals, six different microsatellite markers will be tested on 200 shark tissue samples taken from pelagic and nursery areas on long line fishing boats. The data will let us know if the finning practice is affecting one or several shark populations which could generate inbreeding behavior. Also, based on findings, the Costa Rican government will be able to create new laws and improve the existing ones on behalf of these ancestral fishes.|
Project Update: June 2006According to the project's timeline, the sampling period is almost completed. DNA extraction and amplification will begin in two weeks. To date, 90% of the samples have been collected (100 samples per species) and the standardized DNA extraction method has been tested, showing excellent results.
The methodology proposed to collect samples, did not work as intended. The original thought was that samples would be obtained directly from sharks caught on long line boats; however, after six months, the number of samples from silky (25 samples) and hammerhead (4 samples) sharks did not correspond with the project expectations. The sample acquisition method was modified. Project investigators are now visiting unloading docks in Puntarenas, a coastal city where domestic and international boats bring their catches. Fishermen have agreed to open the docks to field assistants during the sampling phase, making it possible to expand the study (funding permitting) to cover more shark species and a larger geographic area.
Results will fill an important gap of knowledge regarding the two endangered shark species. The most important achievement will be the establishment of the level of genetic variability between and within populations, which can be determinant because groups carrying the highest genetic variation are better able to flourish in the face of specific threats. The outcome will illustrate the current situation for a specific geographic area, which is currently subject to severe exploitation.
The scientific information generated will be useful for government agencies when creating new laws, improving existing laws and to encourage law enforcement. Knowledge about the shark population demonstrated by the transference of genes between and within groups will indicate how long these specific shark species can survive at the current level of exploitation. The next step is to expand this study, increasing the study area and number of shark species involved to include the black tip, blue and thresher sharks. Significant presence of these specific shark species has been noted at the ship docks.