Research Needs to Assess Oil-Related Impacts on Whale Sharks in the Northern Gulf of Mexico

The Problem

The Gulf of Mexico (GOM) provides essential habitat for many shark and ray species, including the whale shark, Rhincodon typus (Hoffmayer et al., 2006).  The oil spill resulting from the explosion of the BP/Deepwater Horizon platform on April 20, 2010 in the northern GOM is currently located in whale shark essential habitat (Hoffmayer et al, 2005) and is posing a critical threat to this species in the region. From 2002 to 2009, more than 300 GOM whale shark sightings were reported to the Gulf Coast Research Laboratory's (GCRL) Whale Shark Sightings Survey, and more than one-third of the sightings were within the oil coverage area (Figure 1). Given the amount of time whale sharks spend at/near the surface of the water (Figure 2), there is considerable potential for harm or death to these individuals resulting from direct exposure to and contamination from the spill (via oiling or clogging of their gills), as well as from depletion of prey, or consumption of oil-contaminated prey (Figure 3). In addition, the dispersants currently being used to ‘break up’ the oil will significantly increase the potential for exposure of sharks throughout the water column. What is unknown is if whale sharks are able to detect the oil and dispersants in the water and will avoid the areas affected or if they will directly encounter the oil without warning.

Whale Shark Observations near BP's MC252 oil spill
Figure 1. Map depicting historic (2002-2009) whale shark sighting locations shown within
the estimated boundaries of the Deepwater Horizon oil spill coverage as of July 2, 2010.

Figure 2. Whale sharks surface filter feeding in the northern Gulf of Mexico.

Figure 2. Whale sharks surface filter feeding in the northern
Gulf of Mexico. Photo credit: GCRL, June 26, 2006.

Figure 3. Oil at the surface near the accident site.

Figure 3. Oil at the surface near the Deepwater Horizon
accident site. Photo credit: Vernon Asper, May 7, 2010.

Unfortunately, this problem is going to be far-reaching and has the ability to impact whale shark populations outside of the northern Gulf of Mexico. Over the last few years, GCRL researchers and their colleagues have documented direct evidence of connectivity between whale shark populations in the northern Gulf of Mexico with those in the southern Gulf of Mexico and the Caribbean Sea.

This connectivity has been documented through the use of photo-identification (Ecocean: and passive-acoustic tracking (Marine Meganet: Additionally, recent genetic studies have shown that whale sharks may comprise a single global population, meaning any mortalites in the northern Gulf of Mexico may impact sub- populations in other parts of the world.

Due to the slow growth rate, late age of maturation, and low fecundity (number of offspring) of whale sharks, they are currently listed as a “vulnerable” species by the International Union for the Conservation of Nature and Natural Resources (IUCN) and are protected internationally by its inclusion in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). If our northern Gulf of Mexico whale shark population declines as a result of this oil spill, the recovery time would be extremely slow.

What Needs to be Done?

Researchers at GCRL are currently seeking funds to monitor oil impacts on whale sharks and other large pelagic animals in the northern Gulf of Mexico.  Two immediate needs have been identified in order to gain a better understanding of how these sharks are being impacted by the oil spill.

How Can You Help?

Although, the financial responsibility for oil spill monitoring, clean-up and damages, lies in the hands of BP Corporation, it may take years before financial support is available for research funding or reimbursement. It is paramount that monitoring projects be implemented immediately. To help support immediate monitoring and research of whale sharks and other large pelagic species in the northern Gulf of Mexico, please click on the link below:

give to whaleshark researchSupport Whale Shark Research

*Please be sure to designate your donation for Whale Shark Research.

You can also help support this research by spreading the word about the GCRL’s Whale Shark Sighting Survey. Participation and awareness of the survey will increase the likelihood of reported sightings and aid with documentation of whale shark distribution in the northern Gulf of Mexico.