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constantly outdated shark taxonomy page, a monster list of shark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 of elasmodiver.com that contains pictures of
other marine organisms and of marine habitats. This expansion of
Elasmodiver is in its first stages but will eventually include pages
on all types of marine mammals, bony fishes and marine invertebrates
as well as coastal habitats, reefscapes and other imagess relating
to the ocean. Please return regularly to enjoy the progress.
Latin Name:
Malacoraja senta Synonyms: Raja senta.
Family: Rajidae
Other Names:Gladde rog Netherlands Dutch, Raie lisse Can
Quebec French, Raie lissée France French, Vatos neted Romania Rumanian.
Identification:
Disc heart shaped. Disc width
and length roughly equal. snout pointed. Rostral cartilage very thin. Tail about
half total length. Dorsum mostly smooth. A single distinct row of thorns extends
along centre line of back and tail. Tail thorns diminish in adults and are
virtually invisible in older male specimens. Thorns also on centre-line of
snout, around eyes, and a small cluster on each side of mid line behind head and
on the anterior margin of the disc close to the rostral cartilage. Dorsum light brown to grey with
irregular scattered dark blotches. Dark ringed white blotch midway along centre
line of back. One or two dark edged white bands along tail. White blotches and
bands fade in adulthood. Ventrum pale with a few indistinct pale spots.
Size: Maximum
length 61cm.
Habitat:
The smooth skate can be found on soft mud and clay bottoms as well as sandy,
broken shell and gravel substrates. From 25 to 1436 meters but
usually found between 70 and 480 meters. Tolerates moderately low salinity
environments in the Gulf of St Lawrence.
Smaller specimens
tend to be found at deeper depths.
Abundance and distribution:
Smooth
skates inhabit a relatively small area in the western North Atlantic Ocean from
Newfoundland to New Jersey. They are found in the inshore waters of the St
Lawrence river estuary to deep offshore banks but they do not occur evenly
throughout that range and are probably confined to a handful of deep troughs
separated by shallower banks.
The Laurentian
Channel in the Gulf of St. Lawrence, southwest Grand Bank, Flemish Cap,
northeast Newfoundland Shelf and the Labrador Shelf have all been identified as
containing sub populations of smooth skates.
Diet:
Smooth skates have an extremely rigid diet of mostly small crustaceans.
Large adults occasionally consume small benthic fishes. The diet of smooth
skates may be a contributing factor in their narrow range.
Reproduction:
Oviparous. Smooth skate egg capsules are deposited on sand and mud bottoms.
Egg cases range in size from 5 to 5.9 cm in length. They are rectangular in shape with
hardened pointed corners. Studies of mature collected specimens indicate that
smooth skates may be sexually active throughout the year.
Females mature at
41–54 cm total length (TL) and between 8–9.5 years of age, and males mature at
49–57 cm TL and between 8 and 10 years of age.
Vulnerability:
The smooth
skate is assessed 'endangered' in Canadian waters and 'near threatened' in US
waters by the IUCN. Although this species is not the
focus of a directed fishery it is caught in trawling/dredging operations
targeting other benthic fishes and invertebrates. Surveys indicate that the
abundance of the smooth skate has declined by 73% to 91% (depending on the
region) over a 29 year period.
Despite a
reduction in ground fishing efforts and although smooth skates are a 'no take'
species, biomass of the two main sub-populations in Canadian waters have not
recovered at all in the last two decades.
The US
sub-populations are also very close to being classed as over fished.
Photographs:
Kings Beach, Rhode Island. Specimen released from
bycatch collected while trawling for squid. Images were made possible through
the cooperation of Brian Raymond.
Similar species:
There are a number of other skates inhabiting this region. The barndoor skate
has a vaguely similar shape but a much more acutely pointed snout. Winter and
little skates have blunter snouts and smaller spots.
Reaction to divers:
Swims away and resettles when closely approached.
Diving logistics:
The smooth skate generally inhabits depths
exceeding normal diving limits.
