Saturday, December 1, 2012

Studying the effects of the Gulf oil spill on whale sharks

This is a report on a project led by ECOCEAN and supported with a grant from the Aquarium’s Marine Conservation Action Fund (MCAF) in 2010. MCAF supports the Aquarium’s commitment to ocean conservation by funding small-scale, high-impact projects across the globe. Since its founding in 1999, MCAF has funded more than 100 conservation projects in 36 countries and has disbursed more than $600,000 to protect highly vulnerable species and habitats and to conserve marine biodiversity. 

Whale sharks are gentle, beautiful animals, and at lengths reaching well over 40 feet, are the largest fish in the ocean. They are also one of only three known species of sharks that filter feed, straining their food from the water. Unfortunately, these magnificent animals face many threats to their survival. Overharvesting and bycatch along with habitat degradation have caused the International Union for Conservation of Nature (IUCN) to list whale sharks as “vulnerable to extinction.” In 2010, the sharks faced an additional threat when the 2010 BP Deepwater Horizon oil spill contaminated a large area of whale shark habitat.  Given the great potential for this spill to affect the whale sharks, it was imperative to track any changes in their population.  With support from MCAF, the organization ECOCEAN teamed up with the whale shark tourism industry to help monitor this species in the wake of the oil spill.

A whale shark filter feeds in the waters off the coast of eastern Mexico. Photo: ECOCEAN

The team focused their efforts on the waters surrounding Isla Mujeres and Isla Holbox, in eastern Mexico. Large numbers of whale sharks visit these waters every year, drawing thousands of tourists eager to see the sharks up close. The ECOCEAN researchers worked with a local whale shark research organization, Proyecto Domino, to train tour boat operators how to photograph the sharks to capture the unique markings that identify each individual. The tour operators taught these methods to tourists who came to swim with the sharks. With the help of the tourists, more than 5,000 images were collected and over 400 sharks identified during the 2010 season. These sightings were entered into the ECOCEAN’s database, which is the largest online whale shark photo-ID library.

Individual whale sharks can be identified by the unique pattern of markings on their skin.
The photo taken by this diver was entered into ECOCEAN’s database, which contains more than 43,000 photos of whale sharks. Photo: ECOCEAN

As ECOCEAN researcher Darcy Bradley notes, these sightings helped to, “establish a baseline on the number of whale sharks visiting the area. This was necessary to better understand the extent of pressure that the oil spill in the Gulf of Mexico may exert on whale sharks in the region - before these sharks potentially venture north to an area contaminated with oil.”

Additionally, Ms. Bradley notes:
Thanks to the 2010 pilot program, the 2011 whale shark season in Mexico has been a tremendous success in terms of sighting reports sent in to the ECOCEAN Whale Shark Photo Identification Library for new and returning sharks. This is crucial both for our efforts to better understand this impressive annual aggregation of whale sharks and to provide critical input to our work to better protect this threatened species.

Facebook Comments


Post a Comment