Not just a
huge collection of
Shark
Pictures:
Elasmodiver.com contains images of sharks, skates, rays, and a few
chimaera's from around the world. Elasmodiver began as a simple web
based
shark
field guide
to help divers find the best places to encounter the different
species of sharks and rays that live in shallow water but it has
slowly evolved into a much larger project containing information on
all aspects of shark diving and shark photography.
There are
now more than 10,000 shark pictures and sections on shark
evolution, biology, and conservation. There is a large library of
reviewed shark books, a constantly updated shark taxonomy page, a
monster list of shark links, and deeper in the site there are
numerous articles and stories about shark encounters. Elasmodiver is
now so difficult to check for updates, that new information and
pictures are listed on an Elasmodiver Updates Page that can be
accessed here:
Family:
Aetobatidae. Containing the single genus
Aetobatus. Recently elevated to full
family status. Previously considered part of the family myliobatidae.
Identification:
A large eagle ray with a greenish, greyish or redish brown dorsum
covered in white or bluish white spots. Occasionally,
the white spots are slightly larger with black centers - ocelli. Spots may be
absent completely or confined to rear of disc. Disc rhomboidal, wing-like.
Anterior disc margins convex. Posterior margins concave. Curvature of fins
increases towards free tips. Prominent square head extends forward of pectoral
fins level with the eye. Snout narrow and pointed. Caudal fins extend
posteriorly beyond pectoral margin. Very long,
whip like tail often broken off part way. Tail length 2.1-2.5 disc width when in
tact. 1 or 2 tail spines, rarely up to 5. Mouth located ventrally. Teeth
plate-like. Nasal curtain (upper lip) large, fringed and deeply notched
centrally.
Size:
Wing
span to 300cm. Nose to tail (when complete) max 880cm.
Habitat:
Cruises
reef faces, sand flats and bays where it feeds on buried invertibrates. Also open ocean.
0-60m
Distribution:
Indo-Pacific coastlines from South Africa to the
central Pacific Ocean.
Diet:
Feeds by
plowing its flattened snout through the
sand, scooping up buried invertebrates. Preys on a wide range of demersal
crustaceans and mollusks such as hermit crabs, whelks, oysters and clams.
Reproduction:
Ovoviviparous. May produce litters of up to 10 pups
but usually 4 or less.
Conservation Status:
the spotted eagle ray is listed as VULNERABLE by the IUCN.
The Ocellated
Eagle Ray (Aetobatus ocellatus) has recently been re-described as a separate
species from the White-spotted Eagle Ray (A. narinari). This is a large eagle
ray with a widespread distribution across the Indo-Pacific in tropical and
warm-temperate waters. Recorded over the continental shelf from the surface to
60 m depth in coastal and open ocean environments. It sometimes enters lagoons
and estuaries and is often associated with coral reef ecosystems.
The Ocellated Eagle Ray is recorded from landing sites across much of its range,
particularly within Southeast Asia and the Indian Ocean. It is susceptible to
capture from a variety of fishing gear and its range overlaps with areas of
intense and generally unregulated fisheries in coastal and offshore
environments. Estuarine habitats in which it occurs are affected by development
and pollution across parts of its range.
The Ocellated Eagle Ray has low population rebound potential with low fecundity
(1-4 pups per litter); long gestation period (12 months) and possibly 2-3 years
between pregnancies; late maturation (five years), and an approximate 12-year
generation period. Molecular studies demonstrate considerable population
structuring for this eagle ray within the Indo-Pacific region, suggesting
limited recruitment to exploited populations. Based on inferred population
declines of >30% across much of its range, with ongoing threats due to largely
unregulated fishing pressure and habitat degradation and destruction, the
Ocellated Eagle Ray has a global assessment of Vulnerable. In Australian and
Oceania waters (Pacific Island nations) where there is limited fishing pressure
and some conservation measures in place through the use of marine reserves, this
species is assessed as Least Concern.
Photographs:
Nuku Hiva, French Polynesia.
Similar species:
Recent genetic, morphological and parasitic study
has split the spotted eagle ray into three species that can be identified easily
by range. The spotted eagle ray Aetobatis ocellatus is present in the
Indo-West/Central Pacific region. The whitespotted eagle ray is confined to the
tropical Atlantic including the Gulf of Mexico and Caribbean Sea, and the
Pacific eagle ray inhabits the tropical Eastern Pacific coast and Galapagos
Islands.
Further studies may
eventually split the central and western populations of A.ocellatus into two
distinct species.
Reaction to divers:
Somewhat
shy and hard to approach. Easiest to approach when they are preoccupied with feeding.
Diving logistics:
A common sight on many coral reefs
throughout its range but appearances are often unpredictable. The dive site off
Nuku Hiva where these images were taken, is one of thousands of sites where
these rays gather. Elsewhere in French Polynesia, Rangiroa is also a hotspot. In
February, spotted eagle rays mate on some of the deeper reefs (40-50m). At that
time of year, you may see great hammerheads predating on them.
Citations:
Kyne, P.M.,
Dudgeon, C.L., Ishihara, H., Dudley, S.F.J. & White, W.T. 2016. Aetobatus
ocellatus. The IUCN Red List of Threatened Species 2016:
e.T42566169A42566212. http://dx.doi.org/10.2305/IUCN.UK.2016-1.RLTS.T42566169A42566212.en.
Rays of the
World - Last, White, de Carvalho, Seret, Stehmann, and Naylor. CSIRO.