Manta ray

Page - September 21, 2007

Estimated population:

Data from 2001/2002 suggests a local population of about 177,220 in the Gulf of California. Populations around Hawaii appear to be stable. Most other populations worldwide are declining.

Ways to identify this species:

The manta ray is the largest of the rays, with distinctive 'wings' or pectoral fins measuring over 25 feet in width, and unique 'horns' or cephalic fins on either side of their head. Manta rays have black, dark brown or blue backs and a white underside. This species is found in temperate and tropical waters around coral reefs, continents, seamounts and islands.

Biology

  • Manta rays are largely plankton-feeding, but also feed on fish larvae and small organisms. Manta rays have reduced, nonfunctional teeth, which do not enable them to consume larger species.
  • These creatures use their 'horns' to direct plankton and water into their mouth.
  • Manta rays are known to migrate all over the world in search of upwelling, plankton-rich waters.
  • During times of mating, mantas gather in large numbers and females are courted by several males. When courtship is successful, reproduction occurs belly-to-belly. Mantas reproduce via aplacental viviparity, meaning they hatch from eggs, but the eggs hatch and the babies develop inside the mother where there is no placenta for nourishment.
  • Gestation is around a few months and 1-2 manta "pups" are born rolled up. Baby mantas become active as soon as they 'unroll'.
  • To breathe, manta rays have five pairs of gills on their underside.
  • Unlike other rays, mantas lack a spine on the tail and their only defenses are their size and 'wings'. They are not threats unless attacked or threatened.
  • The Hawaiian Islands and Island of Yap populations have a closed population structure, meaning they rarely venture from their coastal waters or migrate away from the island groups.
  • Manta rays are known to live in over 20 years.

Threats

  • Natural predators include large sharks and occasionally killer whales.
  • Although there are few fisheries for manta rays, their fins, skin, liver, meat and branchial filaments are sometimes traded.
  • Manta rays do not make up extremely large by-catch in other fisheries, but some moralities do exist through the tuna purse seine fisheries as well as other fisheries.
  • Unfished populations are not thought to be threatened; however, inshore threats such as pollution, coastal development and eco-tourism pressure exist.

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