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constantly outdated shark taxonomy page, a monster list of shark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.
spotted spiny
dogfish, North Pacific spiny dogfish, spiny dogfish, mudshark.
Latin Name: Squalus
suckleyi (previously Squalus acanthias)
Family: Squalidae
Identification:
The spotted spiny dogfish has a conical snout with a
rounded tip. Dorsal fins are relatively low compared to A.acanthias.
First dorsal fin spine is opposite or slightly posterior to free rear tip of
pectoral fins. Pelvic fin origin closer to second fin than first dorsal fin.
Dorsal coloration grey to brown above with small white spots.
White spots may be randomly positioned or follow the lateral line. Occasionally
spots are absent. Eyes large. Mildly venomous spines on
first and second dorsal fins. Anal fin absent. Ventral coloration white.
Size: Maximum
length 1.6 meters. size at birth 22-33 cm. Maximum recorded age 66 years.
Habitat: Often
cruise over sand
and mud bottoms. Also frequently encountered over rocky reefs. From 0 to 900 meters.
Inhabits estuarine, coastal and offshore waters sometimes migrating over great distances -
30 tagged individuals traveled from British Columbia to Japan, 7000km!
Normal migration patterns are usually more localized; The British Columbian
population is split into two distinct subgroups. One subgroup appears to be
resident but the other migrates between Canada and the US probably in order to stay within a
more comfortable seasonal
temperate range.
Abundance and distribution:
Endemic to the North Pacific, from the Koreas and Japan, northward to Russia (Kamchatka,
Sea of Okhotsk and Sakhalin), the Bering Sea and the Aleutian Islands, and
eastwards in the Gulf of Alaska, British Columbia and Washington south to
southern Baja California. In North America, S. suckleyi is extremely common off
British Columbia and Washington, but decline in abundance off the Oregon and
California coasts. It occurs in a wide depth range from very shallow waters in
some areas down to depths of at least 1236 m (Ebert, 2003). Squalus suckleyi
appears to prefer water temperatures between 7 and 15°C, and often makes
longitudinal and depth migrations to follow this temperature preference (Ebert,
2003).
Behavior: Cruises
over soft bottoms either alone or in small groups. Occasionally schools (often
segregated by sex) in response to food supply such as squid or salmon runs. May also
form schools with other species such as leopard sharks and smoothhounds. Diet
consists mainly of bony fishes. Other foods include octopus, squid and
crustaceans.
Reproduction: Ovoviviparous.
Litter size from 1- 20. Spotted spiny dogfish have a slow maturity rate (around 12 years) which makes them very vulnerable to
over fishing. They also have the longest gestation period of any known vertibrate 18-24 months.
Observations:
Photographs:
Quadra Island, British Columbia, Canada.
Similar species:
Spiny Dogfish Squalus acanthias. The spiny dogfish or spurdog is a
virtually indistinguishable species occurring in the Atlantic. Geographic range
is the best identification method. According to a 2010 paper by Ebert et al,
S.acanthias does not occur in the North Pacific.
The spiny dogfish has a greater vertebral count
averaging 112. The North Pacific spiny dogfish has an average vertebral count of
99 (within a range of 97 to 106).
Reaction to divers: These
are curious and harmless sharks that will often closely approach divers and on
occasion accompany them on their dives. If divers are buzzed by a dogfish they can
often be recalled by tapping two stones together. The dogfish seem to find this irresistible
and will repeatedly return to satisfy their curiosity. If engaging in dogfish
feeds it is possible to play tug of war with these little sharks. Care should be
taken to avoid their mildly venomous spines.
Diving logistics:
On Vancouver Island dogfish are present during the summer months most often from
July to September. It is possible to see them occasionally whilst
shore diving in Saanich Inlet during this period. Reputedly they are relatively
common to the north around Campbell River. For an overview of the dive sites of
Saanich Inlet visit the Victoria Scuba Club Website listed on the elasmo-links
page.
On Quadra Island it is possible to go on a
freestyle dogfish feed. This is one of the most entertaining shark interactions
that you could have.
Resurrection and redescription of Squalus suckleyi (Girard,
1854) from the North Pacific, with comments on the Squalus acanthias subgroup
(Squaliformes: Squalidae) DAVID A. EBERT 1, 2, 3, 8, WILLIAM T. WHITE 4, KENNETH J. GOLDMAN5, LEONARD
J.V. COMPAGNO6, TOBY S. DALY–ENGEL7 & ROBERT D. WARD4
Migration Patterns of Spiny Dogfish (Squalus
acanthias) in the North Pacific ocean - G.A. McFarlane and J.R. King. -
Fisheries and Oceans Canada.
Maximum Ages of Ground Fishes in Waters off
Alaska and British Columbia and Considerations of Age Determination. -
Kristen M. Munk - Alaska Fisheries Research Bulletin Vol. 8 No.1 Summer 2001.
Reef Sharks and Rays of the World
- Scott W. Michael.
Coastal Fish Identification,
California to Alaska. - Paul Humann - New World Publications.
Sharks - Andrea and Antonella
Ferrari - Firefly
Marine life of the North Atlantic
- Andrew J Martinez - Down East Publications.
