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:
Common Names: Blue
stingray, bluespotted stingray.
Accepted Binomial:
Dasyatis chrysonota.
Family:
Dasyatidae.
Identification:
The blue stingray has a rhomboid disc with
a slightly produced snout, straight anterior margins,
rounded free tips and convex posterior margins. The
dorsal surface of the body disc is grey/tan to brown with irregular
greyish-blue marbling. Ventral surface pale/white. Tail relatively
short (less than 2x body length) with a long low ventral finfold and
a short low dorsal finfold. Tail terminates in a short tail filament
beyond the single large tail barb.
Size:
Total length up to
150cm. Disc width 75cm.
Habitat:
Found in shallow bays on the sand. From the surf line
down to at least 109m. Moves into deeper water during winter.
Distribution:
Eastern Atlantic and Indian Ocean. From
at least Angola to Natal, South Africa and possibly up to
Mozambique. Dasyatis chrysonota may be synonymous with
Dasyatis marmorata; a species that is wide ranging in the
Eastern Atlantic, Mediterranean and Indian Ocean.
Diet:
The blue stingray eats mostly crustaceans: swimming
crabs, mole crabs, mysids, shrimp, mantis shrimp and amphipods.
Reproduction:
Ovoviviparous. Litter size 1-7. In the
Eastern Cape of South Africa mating is most active in spring. nine
month gestation.
Conservation Status:
Listed as Least Concern by the IUCN.
Occasionally caught by shore anglers, but generally they are
released alive (Bianchi et al 1999, Cowley 1990, Cowley and Compagno
1993). In the recreational fishery rays are released alive after
measuring and/or weighing. Although no post-releases survival
experiments have been undertaken, there is no evidence (i.e., direct
observation) of high levels of post-release mortality from the sport
fishery. The blue stingray is not targeted (other than the sport
catch and release fishery), but is taken as a bycatch of trawlers
(Cowley et al. 1991) including those targeting hakes and soles, but
discarded (probably dead). However, there are extensive areas of the
Agulhas Bank that are untrawlable, and several inshore bays are
closed to trawling along the South African coast, offering it
refuge.
Photographs:
South Africa. Upper - Port Saint John
(Deep Cam image), lower - Cape Town.
Similar species:
The blue stingray Dasyatis chrysonota is
very similar to the Marbled stingray Dasyatis marmorata. These two
species may in fact be synonymous. There are two other blue spotted
stingrays in South Africa -
Bluespotted Ribbontail Stingray
Taeniura lymma and the
bluespotted maskray Neotrygon kuhlii.
Both have smaller more uniformly round spots.
Reaction to divers:
Somewhat skittish. May allow a slow non-threatening approach.
Diving Logistics:
Present all along the South African coastline. Seen by divers in Sodwana
Bay. Using a remote camera I photographed numerous blue stingrays at
80-100m off of Port Saint John during the winter Sardine Run (June). For more information
on the Sardine Run, please contact Bigfishexpeditions.com
References and Citations:
Smale, M.J. 2009. Dasyatis chrysonota. The IUCN
Red List of Threatened Species 2009: e.T161643A5471417. http://dx.doi.org/10.2305/IUCN.UK.2009-2.RLTS.T161643A5471417.en
. Downloaded on 31 October 2015.
Reproduction and embryonic development of the
blue stingray Dasyatis chrysonota in southern African waters.
Ebert and Cowley.
Sharks and Rays of Southern Africa. Compagno,
Ebert and Smale.
