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constantly outdated shark taxonomy page, a monster list of shark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.
Spiny
dogfish, Common spiny dogfish, Piked dogfish, Mud shark.
Latin Name: Squalus acanthias
Family: Squalidae
Identification: Long,
flattened, pointed snout. Grey to brown above usually with small white spots.
White spots may follow lateral line. Eyes large. Mildly venomous spines on
first and second dorsal fins. Anal fin absent. Belly 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!
Newfoundland tagged individuals have been captured years later in Iceland.
Normal migration patterns are usually more localized; both Atlantic and Pacific
groups migrate between Canada and the US in order to stay within a seasonal
temperate range.
Abundance and distribution: Worldwide
in temperate seas. Known on the Atlantic coast from Labrador to the Gulf of
Mexico and on the Pacific Coast from the Aleutians to Central Baja. Once thought
to be the most abundant shark in the world the Spiny dogfish is now facing
commercial extinction and a grass roots movement around the world is attempting
to lobby for a reduction in quotas. In the UK and Europe Spiny dogfish are the
principal fish utilized in "fish and chips". It is also ground up to
be used in fertilizers.
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. 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: Saanich
inlet, Vancouver Island.
Similar species: Smooth
Dogfish mustelus canis which has a sympatric range from the Bay of Fundy
to the Gulf of Florida and from Southern Brazil to Argentina.
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.
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.
