Description | Distribution and Movements | Biology and Life History | Feeding Ecology | Natural Predators | Associated Fishes | Conservation
Whale Shark Feeding Ecology
Whale sharks are opportunistic filter feeders that often forage on spatio-temporally patchy food sources (Taylor et al. 1983, Colman 1997). Research has shown that whale sharks occur in areas of enhanced productivity (Iwasaki 1970, Arnbom and Papastavrou 1998, Duffy 2002) and may time their movements and migrations to coincide with localized productivity events to enhance feeding opportunities (Wilson et al. 2001). Aggregations have been reported to coincide with spawning events of lantern fish (Diaphus spp.) in the Coral Sea (Gunn et al. 1992), coral at Ningaloo Reef in Western Australia (Taylor 1994), red crab (Gecarcoidae natalis) off Christmas Island in the Indian Ocean (Colman 1997), copepods (Acartia clausi) in the Sea of Cortés (Clark and Nelson 1997), cubera snapper (Lutjanus cyanopterus) and dog snapper (Lutjanus joci) off Belize (Heyman et al. 2001). Seasonal distribution of whale sharks in the northcentral Gulf of Mexico may also be influenced by hydrologic and oceanographic features (e.g., Loop Current, Mississippi River plume, convergent zones, upwelling, and temperature discontinuities). Seasonal aggregations of whale sharks in the northwestern Gulf of Mexico have been associated with mass spawning of corals at the Flower Garden Banks National Marine Sanctuary off Texas, USA (Burks et al., 2006).
Whale sharks use three feeding methods:
- Passive--swimming slowly with mouth open, straining plankton from the water;
- Vertical--floating vertically, with little to no forward movement, using a suction method to draw prey into their mouths; and
- Active--suction filter-feeding while swimming steadily, enabling the whale sharks to draw water into their mouths at higher velocities. This type of feeding is also called “ram-filter feeding”.
Whale sharks might change their feeding behavior according to prey abundance and composition to maximize the relationship between energy expended with caloric intake. Passive feeding is a low-cost energetic mechanism that allows the shark to graze while in search of higher density food. Vertical feeding is a means to consume smaller patches of food with lower energetic costs than active feeding. Active feeding is typically only encountered in areas of high prey density because of the high energy expended by the shark to break the surface of the water and swim at a relatively quick pace. (Nelson and Eckert, 2007). In 2006, Gulf Coast Research Laboratory biologists encountered an aggregation of 16 whale sharks ram-filter feeding on a massive spawn of little tunny (Euthynnus alleteratus) eggs. The sharks were horizontal with the top part of their mouths out of the water, straining the eggs from the upper meter of the water column (Hoffmayer et al. 2007). (See Research)
Arnbom, T. and V. Papastavrou. 1988. Fish in association with whale sharks Rhincodon typus near the Galápagos Islands. Noticias de Galápagos 46:13-15.
Burks, C.M., W. B. Driggers III, and K.D. Mullin. 2006. Observations of whale sharks, Rhincodon typus, in the northern Gulf of Mexico. Fishery Bulletin 104: 579-584.
Clark, E. and D.R. Nelson. 1997. Young whale sharks, Rhincodon typus, feeding on a copepod bloom near La Paz, Mexico. Environmental Biology of Fishes 50:63-73.
Colman, J.G. 1997. A review of the biology and ecology of the whale shark. Journal of Fish Biology 51:1219-1234.
Duffy, C.A.J. 2002. Distribution, seasonality, lengths, and feeding behaviour of whale sharks (Rhincodon typus) observed in New Zealand waters. New Zealand Journal of Marine and Freshwater Research 36:565-570.
Gunn, J.S., A.W. Whitelaw, T.L.O. Davis, K. Bailey, and D.G. Itano. 1992. Tuna tagging in the Coral Sea. Australian Fisheries 51:22-24.
Heyman, W., R. Graham, B. Kjerfve, and R.E. Johannes. 2001. Whale sharks Rhincodon typus aggregate to feed on fish spawn in Belize. Marine Ecology Progress Series 251:275-282.
Hoffmayer, E.R., J.S. Franks, W. B. Driggers, K.J. Oswald, and J.M. Quattro. 2007. Observations of a feeding aggregation of whale sharks, Rhincodon typus, in the north central Gulf of Mexico. Gulf and Caribbean Research (In Press).
Nelson, J.D. and S.A. Eckert. 2007. Foraging ecology of whale sharks (Rhincodon typus) within Bahía de Los Angeles, Baja California Norte, México. Fisheries Research 84:47-64.
Iwasaki, Y. 1970. On the distribution and environment of the whale shark, Rhincodon typus, in skipjack fishing grounds in the western Pacific Ocean. Journal of The College of Marine Science and Technology 4:37-51.
Taylor, J.G., L.J.V. Compagno, and P.J. Struhsaker. 1983. Megamouth, a new species, genus and family of laminid shark (Megachasma pelagios, family Magachasmidae) from the Hawaiian Islands. Proceedings of the California Academy of Sciences 43:87-110.
Taylor, G. 1994. Whale Sharks, the Giants of Ningaloo Reef. Angus and Robertson, Sydney, 174 pp.
Wilson, S.G., J.G. Taylor, and A.F. Pearce. 2001. The seasonal aggregation of whale sharks at Ningaloo Reef, Western Australia: currents, migrations, and the El Nino/Southern Oscillation. Environmental Biology of Fishes 61:1-11.