International Fund for Animal Welfare (IFAW) scientists are concerned that the protected whale shark, the world's largest fish, may be a quiet victim of the recent oil spill in the Gulf of Mexico. IFAW is responding to an urgent appeal for assistance from the University of Southern Mississippi's Gulf Coast Research Laboratory (USM-GCRL) to conduct research on whale shark biology, behavior and movement patterns in the Gulf before it's too late.The newly discovered essential whale shark feeding area may already be contaminated. It's been three weeks with very few sightings of whale sharks in what are usually normal congregate areas of the northern Gulf of Mexico, leading scientists to worry they may be the unseen victims of the Gulf oil spill.
Not only are whale sharks the biggest fish in the sea but they may also be one of the most vulnerable to the effects of the Deepwater Horizon oil spill. Despite their large size, whale sharks feed on the tiniest of creatures — plankton, fish larvae and small crustaceans. However, whale sharks in the northern Gulf may be adding oil and toxic oil dispersant chemicals to their diet as they have been found in areas within and surrounding oiled waters.
"These whale sharks are facing a lethal one-two punch," said IFAW biologist Jacob Levenson. "First is the impact on the animal's ability to breathe as a result of the oil physically coating its gills and secondly is the long term impacts of passively accumulating toxins from oil and liberal dispersant use."
Unlike birds, fish, mammals and other animals, because sharks are negatively buoyant and lack a gas-filled swim bladder, they quietly sink into the depths when they die, never to be seen again. Other than a few accounts of their occurrence, in aggregations, information is scant for whale sharks in the northern Gulf of Mexico.
Levenson is joining scientist, Dr. Eric Hoffmayer of the USM-GCRL to conduct research that is crucial to understand how the toxic oil is impacting whale sharks and deciding what can be done to save them before time runs out. The information gathered by the team is also critical to ensure that government and oil companies have accurate information to best protect this species. Currently, there are no provisions in place in BP's spill response plan to protect these beautiful and rare animals.
Levenson and Hoffmayer will make several day trips offshore in boats with aircraft support to gather data and tag animals for future satellite tracking.
"Figuring out what happens to these goliath fish is not just good science, it's important to understand how this toxic cocktail moves through the food chain. Whatever happens to whale sharks is likely to be experienced by manta rays and other animals not normally tested as part of NOAA's Seafood Monitoring Program," added Levenson.
So far, Dr. Hoffmayer has been able to deploy a few satellite tags when he encountered an aggregation of over 100 whale sharks this past June. He is currently tracking one shark with a surface satellite tag in the offshore waters of the Gulf. So far the shark has stayed away from the area impacted by the oil spill. He is hoping to tag several others to determine their daily movements.
Source: International Fund for Animal Welfare
