Not just Shark
Pictures: Elasmodiver contains photos of sharks, skates, rays, and
chimaera's from around the world. It began as a simple web based
field guide to help divers find the best places to encounter
different species of sharks and rays but it has slowly evolved into
a much larger project containing information on all aspects of shark
diving and photography. There are now more than a thousand shark
pictures and sections on shark evolution, biology, and
conservation. There is a large library of reviewed shark books, a
constantly outdated shark taxonomy page, a monster list of shark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:
If you're looking for a
broader range of marine life pictures the following links represent
a new area that contains pictures on other marine organisms and on
marine habitats. This expansion of Elasmodiver is in its first
stages but will eventually include pages on everything from sea
stars to nudibranchs. Creating this portal will take time and for
now it consists of a token offering of fish pictures. Please return
regularly to enjoy the progress.
Identification:
Disc width roughly twice length. Dorsum covered in
an intricate pattern of tiny lines and swirls that form light and dark brown
spots and larger irregular circles fringed with white. Ventrum white,
cream or with a pinkish hue. Short tail has one or two tail stings (unborn
embryos already have fully formed tail stings). Dorsal fin absent. Very low
dorsal and ventral finfolds on tail.
Size: Wing
span to 400cm.
Habitat:
Sandy or muddy bays and brackish estuaries,
sometimes near
rocky
reef faces, and over sand flats. 2 to 100m depth.
Abundance and distribution:
Occurs in the eastern Atlantic Ocean from Portugal to Angola including the
Canary Islands, Madeira, and the Mediterranean and Black Seas. Also occurs in
the western Atlantic Ocean from Massachusetts to Argentina.
Behavior:
Lays motionless for much of the time under a thin covering of sand. Butterfly
ray footprints or beds (indentations left in the sand) can often be seen days
after the animal has moved on.
Feeds on fishes, crustaceans, mollusks and plankton.
Reproduction: Ovoviviparous.
4-7 embryos. Gestation lasts for about 6 months. Once the unborn spiny butterfly
rays have completely used up the reserves in the yolk sac, the mother secretes
uterine milk. Long villi (filaments) grow from the uterus walls into the
embryo's spiracles. Milk can then be directed more efficiently into the embryo's
mouth and throat.
Photographs: Los Gigantes, Tenerife,
Canary Islands, Eastern Atlantic Ocean.
Similar species:
Another species that shares the western range of the spiny butterfly ray is the
Smooth Butterfly Ray Gymnura micrura.
Reaction to divers:
If buried in the sand, the spiny butterfly ray will often remain motionless
while divers pass. Even after most of the sand has
been fanned away (as in the above picture) these rays are likely to remain
stationary as long as the observer uses slow, non threatening movements.
Diving logistics:
Spiny butterfly rays
are fairly abundant around the Canary Islands. Reportedly, there is one that has
taken up residence in the harbor on El Hiero. I have seen many beds in the El
Cabron Marine Park but no actual animals.
Occasionally spiny butterfly rays attend the organized ray feeds at
Los Gigantes on Tenerife (where the featured specimen was seen). Los Gigantes Diving offers freestyle feeds
once or twice per week. The divemaster takes a huge barrel of fish scraps to
60ft and offers them to the eagerly gathering ray species. After a while the
human participants usually help themselves to some fish and wander off to
interact with the rays on their own. The feed can be rather chaotic but the ray
action is almost guaranteed. Attending species include common eagle rays, common stingrays, roughtail rays, round stingrays and
occasionally angel sharks, butterfly rays, and marbled torpedo rays.
Very occasionally a large Bull Ray swims by. Contact Los Gigantes Dive Centre for further information.
Further reading:
Sharks
and Rays - Elasmobranch Guide of the World. Ralf M. Hennemann. IKAN.
