Featured Species Friday: Spotted Eagle Ray (Aetobatus narinari)

I’m really excited about this week’s featured species: the Spotted Eagle Ray (Aetobatus narinari). If you’ve never had the pleasure of diving with these rays, put it on your bucket list! They are one of the most amazing rays to see in the wild, especially when they come together in large schools. With their duck-like beak, bright white spots contrasted on their blue-green skin, and a wing span of over 6 feet (1.8 m) the spotted eagle ray is an incredibly unique looking species and one that is easily recognized by divers (Tricas, Deacon, Last, McCosker, Walker, Taylor, 1997).

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Smith, M. (Photograher). (2007). Spotted eagle ray [Digital Image]. Retrieved from http://animalstime.com/spotted-eagle-ray-facts/

Like most rays, these rays have flat, bony plate-like teeth that are used to crush the hard shells of their prey like oysters, clams, and snails (Kyne, Ishihara, Dudley, & White, 2006). Their ducklike snouts are specially adapted for digging deep into the sand and rooting out crustaceans.

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Bester, C. (Photographer). (n.d.). Spotted eagle ray jaws [Digital Image]. Retrieved from https://www.floridamuseum.ufl.edu/

Watch spotted eagle rays feed in the Galapagos!

BBC Earth [BBC Earth]. (2012 June 27). Spotted Eagle Rays- Galapagos- BBC [Video Clip]. Retrieved from https://www.youtube.com/

The spotted eagle ray has been described as having a generally timid demeanor by divers (Tricas, et al., 1997). However, they are equipped with a small stinging bard at the base of their tails in case of predatory attack. These barbs have small serrations along the edge, just like the teeth of a shark. These barbs are designed to quickly penetrate the attacker in one smooth stroke, but the real damage is done when the barb is removed. The serrations tear away at the flesh as the barb is pulled out, leaving the victim with a nasty jagged wound (Bester, n.d.). So lesson of the day: if you ever accidentally step on a sting ray and are unlucky enough to end up with a barb: DO NOT REMOVE IT YOURSELF!! You will do more damage by removing it. Allow a surgeon to remove it at the hospital.

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Island Blues (Photographer). (2011 March 27). Spotted eagle ray barb [Digital Image]. Retrieved from http://blindman.fr.yuku.com/

The stinging barb is not the spotted eagle rays only line of defense against predators like the great hammerhead (Sphyrna mokarran) and tiger shark (Galeocerdo cuvier). These rays are also highly active. They are capable of astonishing acrobatics, twisting, turning, and pivoting at high speeds to evade capture by their pursuers. They have even been seen leaping high into the air to escape the sharks! Fishermen have even documented cases of these animals leaping into their boats. The ray in the photos below ultimately escaped the hammerhead’s pursuit.

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Carter News Agency (Photographer). (2017 March 8). Spotted Eagle Ray Escapes Hammerhead Shark [Digital Image]. Retrieved from http://nypost.com/
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Carter News Agency (Photographer). (2017 March 8). Spotted Eagle Ray Escapes Hammerhead Shark [Digital Image]. Retrieved from http://nypost.com/
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Carter News Agency (Photographer). (2017 March 8). Spotted Eagle Ray Escapes Hammerhead Shark [Digital Image]. Retrieved from http://nypost.com/
 

Currently the spotted eagle ray is considered Near Threatened by the IUCN (Kyne et al., 2006). They are a species that is considered to have low fecundity, which means they have a low ability to produce an abundance of offspring. Spotted eagle rays reach sexual maturity between 4 and 6 years of age, so they are relatively slow to reach sexual maturity compared to bony fishes. Females will spend 12 months gestating 1 to 4 pups per litter, and it is suspected that they are not able to reproduce each year. It is also not known how long they live for, or how long they are able to be reproductive for. Given all of these factors, the spotted eagle rays are considered to have a limited productive output (Last & Stevens, 2009).

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Two spotted eagle rays beginning the mating process [Digital Image] (n.d.). Retrieved from http://spottedeagleray.weebly.com/
Despite some data deficiency that might ultimately elevate their status to Threatened at the next evaluation, conservation efforts in some regions are already in place.

  • Under the Florida Administrative Code spotted eagle rays cannot be harvested, possessed, landed, purchased, sold, or exchanged in Florida (Kyne, et al., 2006)
  • Great Barrier Reef Marine Park gives protection to the spotted eagle ray along the eastern coast of Australia (Kyne, et al., 2006)
  • Use of the Turtle Exclusion Devices (TEDs) in prawn trawl fisheries decreases the likelihood of large individuals as bycatch (Stobutzki, Miller, Heales, & Brewer, 2002)
  • In the Maldives, recognition of the value of sharks and rays to tourism has given rise to the creation of protected areas around dive sites (Anderson & Waheed, 2001)
    • The Maldives also banned the export of rays in 1995 and the export of ray skins in 1996 (Anderson & Waheed, 2001)
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Sutherland, P. (Photographer). (n.d.). Spotted Eagle Rays in the Maldives [Digital Image]. Retrieved from http://ocean.nationalgeographic.com/ocean/photos/ocean-rays/#/rays01-spotted-eagle-ray_17857_600x450.jpg

While these are wonderful conservation efforts on behave of a few countries, to better provide conversation action on a large scale much more information about this species including fisheries, life history (age, growth, longevity, habitat use, migration/movement patterns, nursery areas, and reproduction studies) are needed (Kyne, et al., 2006). Thankfully, some dedicated Gills Club scientists, in conjunction with several institutions, are hard at work!

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Shields, C.A. (Author). (2017 August 3). Gills Club Facebook Post [Screen Capture]. Retrieved from https://www.facebook.com/

The spotted eagle ray has a special place in my heart. I was lucky enough to join the Shedd Aquarium in May of 2016 on the R/V Coral Reef II for 9 days in the Exuma Cays Land and Sea Park. On our first dive trip out in the park, a beautiful spotted eagle ray came through our group with a huge remora (Echeneidae) under one its pectoral fins. It stayed around for about 10 minutes before it slowly turned and went about its day. It was a truly beautiful experience. I encountered several more elasmobranchs on that trip. I’ll be sharing more of those species and experiences in up coming Features Species!

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Flannery, A. (Photographer). (2016 May 10). Spotted Eagle Ray (Aetobatus narinari) in Exuma Cay Land and Sea Park, Bahamas [Digital Image].

Ray Stats

Family: Myliobatidae

Wing Span:  As large as 11.5 feet (3.5 m), though typically closer to 6 feet (1.8 m)

Weight: 500 lbs (230 kg)

Habitat: Near continents, islands, atolls in tropical waters; coastal

Depth: Waters less than 200 feet (60 m)

Reproduction: Typically Aplacental viviparity, though cases of parthenogenesis have been documented

Gestation: 12 months

Litter Range: 1 to 4 pups per litter

Home Range: Worldwide distribution in tropical to temperate seas

Diet: Hard shelled invertebrates like clams, oysters and snails

IUCN Status: Near Threatened

(Harmon, Kamerman, Corwin, & Sellas, 2016; Last & Stevens, 2009; Kyne, et al., 2006; Tricas, et al. 1997)

Hope you enjoyed one of my favorite ray species this week. Please let me know what species you’d love to learn more about. I’ll be sure to feature them in up coming Featured Species Fridays! If you missed last week, be sure to check out the Blue Shark (Prionace glauca). Until next time finactics!

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Featured Image Source

Spotted Eagle Ray [Digital Image] (n.d.). Retrieved from http://staticflickr.com/

Literature Cited

Anderson, C. and Waheed, A. 2001. The economics of shark and ray watching in the Maldives. Shark News 13:1.

Bester, C. (n.d.). Aetobatus narinari. Retrieved August 03, 2017, from https://www.floridamuseum.ufl.edu/fish/discover/species-profiles/aetobatus-narinari/

Harmon, T. S., Kamerman, T. Y., Corwin, A. L., & Sellas, A. B. (2016). Consecutive parthenogenetic births in a spotted eagle ray Aetobatus narinari. Journal of Fish Biology, 88(2), 741–745. http://doi.org/10.1111/jfb.12819

Kyne, P.M., Ishihara, H, Dudley, S.F.J. & White, W.T. 2006. Aetobatus narinari. The IUCN Red List of Threatened Species 2006: e.T39415A10231645. http://dx.doi.org/10.2305/IUCN.UK.2006.RLTS.T39415A10231645.en

Last, P.R. and Stevens, J.D. 2009. Sharks and Rays of Australia. Second Edition. CSIRO Publishing, Collingwood.

Stobutzki, I.C., Miller, M.J., Heales, D.S. and Brewer, D.T. 2002. Sustainability of elasmobranches caught as bycatch in a tropical prawn (shrimp) trawl fishery. Fishery Bulletin 100: 800-821.

Tricas, T.C.; Deacon, K.; Last, P.; McCosker, J.E.; Walker, T.I.; Taylor, L. (1997). The Nature Company Guides: Sharks and Rays. (L. Taylor, Ed.). Hong Kong: The Nature Company, Time Life Books.

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