(c) Cory Fults
Whale Sharks (Rhincodon typus) are known to be the largest fish in the world with some individuals measuring 20m (60 feet) long and weighing around 40 tons. Despite their tremendous size, they are gentle giants, using their nearly 1.5m-wide (5-foot) mouths to filter plankton out of large volumes of water as they swim. They have over 300 rows of tiny teeth and 20 filter pads that look like individual steel wool scrubbers. They open their mouths to let in the plankton-filled, ocean water utilizing a cross-flow filtration method, which keeps the plankton moving towards the back of the mouth. This concentrates the food near the throat without clogging the filtration system, allowing the shark to continuously feed. It is estimated that a 6.2m (20.4 ft.) whale shark may be able to ingest 2.7 kg (6 pounds) of plankton per hour at feeding sites (Motta et al. 2010).
Whale Sharks are believed to be highly migratory (often on the move) and are found in all of the worlds’ oceans in tropical and warm temperate waters (generally between 30°N and 35°S). Individuals are generally solitary but are known to gather in large groups for feeding in coastal waters in places such as the Yucatan Peninsula in Mexico, the Philippines and Western Australia.
Whale Sharks have a blue-grey body and numerous
white/light-grey spots. Individuals have distinctive patterning
of these spots, which allow researchers to record and track
individuals throughout their lifetimes.
Threats & Conservation
As of 2016, Whale Sharks are listed as Endangered according to the IUCN Red List of Threatened Species, with a decline of more than 50% over the last 75 years. The largest threats to the species are directed fisheries, fisheries bycatch and vessel strike. There are potential indirect threats of irresponsible tourism including greater potential for vessel strikes, provisioning and crowding/disturbance.
There have been numerous conservation efforts globally to limit or end directed fishing of Whale Sharks. Advancements in technology and increased awareness continue to decrease the incidental take of Whale Sharks as by-catch. Additional research is imperative to better estimate current populations and abundances of this species, their migratory patterns, and critical habitat for reproduction and feeding. Results from this research will allow for targeted management implementation.
- Pierce, S.J. & Norman, B. 2016. Rhincodon typus. The IUCN Red List of Threatened Species 2016: e.T19488A2365291. http://dx.doi.org/10.2305/IUCN.UK.2016-1.RLTS.T19488A2365291.en. Downloaded on 13 September 2017.
Motta, P., Maslanka, M., Hueter, R., Davis, R., de la Parra, R., Mulvany, S., Habegger, M., Strother, J., Mara, K., & Gardiner, J. (2010). Feeding anatomy, filter-feeding rate, and diet of whale sharks Rhincodon typus during surface ram filter feeding off the Yucatan Peninsula, Mexico Zoology DOI: 10.1016/j.zool.2009.12.001