Not just a
huge collection of
Elasmodiver.com contains images of sharks, skates, rays, and a few
chimaera's from around the world. Elasmodiver began as a simple web
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.
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
Names: Blotchy Swell Shark,
Japanese Swell Shark, Swellshark, Balloon Shark.
Name: Cephaloscyllium umbratile.
Body blotched with shades of grey and brown. Darker
blotches form 7 poorly defined saddles on body and tail. ventrum
lighter and mostly unspotted. First dorsal origin posterior to pelvic fin origin. Second dorsal fin
much smaller than first with origin slightly posterior to origin of anal fin. Eye large and golden. Spiracle small. Body
shape may appear much wider due to ingestion of water when threatened.
Found on rocky reefs of the continental slope from
18-220m. Mostly between 90-200m.
Abundance and Distribution:
Northwest Pacific Ocean from Honshu, Japan south to
Korea, Mainland China and Taiwan.
Records of blotchy swell sharks from Papua New Guinea
and New Zealand probably refer to Steven's swell shark C.stevensi
and the draftboard shark C.isabellum respectively. Abundant where is
Diet: Varied. Small fishes, crustaceans and cephalopods.
Known to prey on at least 10 other cartilaginous species including
the lantern sharks and the cloudy catshark and its eggs.
Listed as Data Deficient by the IUCN. Little is known of the biology
but this is a relatively small oviparous species and may therefore
be more productive than larger live-bearing sharks. Although no data
are available to assess population trends, the species is apparently
still abundant in areas that are heavily fished by trawlers. Small
scyliorhinid species have proven resilient to population decline,
even where they are heavily fished (for example the Smallspotted
Catshark (Scyliorhinus canicula) in the northeast Atlantic).
However, records of Japanese Swellshark apparently include C.
umbratile and a smaller undescribed sympatric species. The two
species may be confused and C. umbratile is a larger catshark, and
may be more vulnerable to depletion. Therefore this species is
assessed as Data Deficient until further information is available on
its life-history, catches in fisheries and population trends.
However, the blotchy swell shark is a retained
bycatch of commercial bottom trawl and longline fisheries off Japan
(Taniuchi 1988). It is captured incidentally by shrimp bottom
trawlers using nets with mesh ~2-4 cm in diameter, so both adults
and juveniles are retained by the trawl (S. Iglésias pers. obs.
2007). The species is sometimes observed on the Tachi and Nan Fang
Hao fish markets, Taiwan. It is apparently still abundant in areas
that are heavily fished by trawlers
The Japanese swell shark lays two flattened egg cases throughout the
year with no apparent seasonal preference. Captive female sharks
held without a mate have continued to deposit egg capsules for
multiple years implying that this species is able to store sperm.
Tateyama, Honshu, Japan.
The Blotchy Swell Shark shares much of its range with a smaller undescribed
species of swell shark (Compagno et al. 2005).
Reaction to divers:
Remains motionless. When harassed by divers the Japanese swell shark
may attempt to inflate but more commonly relocates.
logistics: The blotchy swell shark
generally inhabits sites too deep for observation by divers. It is
occasionally seen within recreational limits by divers in Chiba and
on the Izu Peninsula on the south side of Honshu Island, Japan.
Citations: Iglésias, S., Tanaka, S. & Nakaya,
K. 2009. Cephaloscyllium umbratile. The IUCN Red List of Threatened
Species. Version 2015.2. <www.iucnredlist.org>.