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a large library of reviewed shark books, a constantly outdated shark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 nudibranches. 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.
Common
Names:
Atlantic sharpnose shark, sand shark, mud shark.
Latin
Name: Rhizoprionodon terraenovae
Family:
Carcharhinidae
Identification:
Long pointed snout. Slender body is grey/brown above usually with scattered
white spots. First dorsal starts just behind trailing edge of pectoral
fin. Second dorsal very low with long free rear tip.
Pectoral fins have conspicuous thin white posterior margin. Trailing edge of
caudal fin and second dorsal sometimes slightly dusky.
Size:
At birth 29-37cm. Males mature at 65-80cm. Females mature at 85-90.
Habitat:
Intertidal to 280m. Mostly over sandy or muddy bottoms.
females migrate inshore during the summer months to give birth. Males in the
northern Gulf of Mexico enter extremely shallow turbid water over the summer. It
is unclear exactly why they choose this environment because the salinity
and available dissolved oxygen in these areas is very low leading to a sparse
food supply. Dr Eric Hoffmeyer has demonstrated that during this time the mail
Atlantic sharpnose sharks live off the oil reserves stored in their livers. By
the end of the summer the liver shrinks considerably.
Distribution:
Western Atlantic Ocean from New England to the Yucatan in Mexico and possibly
further south. As it is difficult to positively identify the Atlantic sharpnose
shark from the Caribbean sharpnose shark (R.porosus) which has a more
southerly range, the southern boundary of R.terraenovae is debatable.
Abundance: An abundant
species in US waters. No directed fishery. IUCN red list: least concern.
Atlantic sharpnose sharks may actually be profiting from the plight of other
larger shark species that are no longer there to prey on them.
Behavior:Little
known
Reproduction:
Viviparous
with yolk sac placenta. Litter size 1 to 7. Size of litter corresponds to
relative size of the mother. Gestation listed as 10-11 months.
Observations:I noticed that all of the released Atlantic sharpnose sharks that I saw
underwater swam away with their mouths agape. As this is not particularly
efficient in a hydrodynamic sense this may be a reaction to the stress of capture and a way to temporarily
increase oxygen intake - the equivalent of breathing hard.
Photographs:
Mississippi Barrier Islands.
These rare images of free swimming Atlantic sharpnose sharks could not have been
taken without the help of Dr Eric Hoffmeyer and the staff at the Gulf Coast
Research Laboratory in Ocean Springs, MS. Many thanks to Eric and everyone
that helped make this happen!
Similar species:The Caribbean sharpnose shark R.porosus is virtually
identical to R.terraenovae. Positive identification can only be made
through vertebral counts and DNA analysis. These two sharks may ultimately prove
to be the same species.
Reaction to divers:
Due to their small size, timidity and preference for turbid inshore water, it is
very unusual for scuba divers to encounter Atlantic sharpnose sharks in the
wild.
Diving
logistics:
See reaction to divers above. Elasmodiver would be very interested in hearing
about any natural encounters.
Other diving locations submitted by
readers:
Further
reading:
Sharks
and Rays - Elasmobranch Guide of the World. Ralf M. Hennemann. IKAN.
