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Scientific Name:
Cetorhinus maximus.
Family:
Cetorhinidae
Description:
The Basking Shark is the second largest shark in the world,
exceeded only by the Whale Shark. The average size of an adult
specimen is 22-29 feet (700-900 cm). A 30 (920 cm) foot
specimen was reported to weigh 8,600 pounds (3,900 kg).
Bigelow and Schroeder report a specimen captured in Musquash
Harbor, New Brunswick that measured 40 feet long.
The basking shark is recognized by its large size, a conical
snout, a subterminal mouth and enormous gill slits. The teeth
are tiny and very numerous with about one hundred in each row.
In younger, smaller specimens, the snout is much longer,
projecting far beyond the mouth giving the shark a bizarre
'big-nosed" appearance. When the shark reaches a length of
between 12 and 16 feet, the snout begins to appear relatively
shorter and more in proportion with the rest of the body.
Habits:
The basking shark is not an aggressive or dangerous shark. They
are very large and powerful fish and like any large animal
should be treated with respect. Basking sharks spend much of
their time sunning themselves on the surface of the water,
often lying with their backs and large dorsal fins completely
above the water surface. These sharks feed on plankton, the
tiny plants and animals which drift in the water column. The
basking sharks feeds by swimming with it's enormous mouth wide
open. Water pours into the mouth of the shark and exits though
the gill openings. Each gill arch contains numerous bristle-like
rakers which act like giant filters and allow the water to pass
through but trap the plankton and funnel it toward the mouth. A
feeding basking shark, 20 feet long, with its mouth gaping wide
and it's gills flared out is certainly an imposing sight.
Basking sharks may be found singly or in small groups. Those
seen in the area of New England are usually travelling singly
but they are known to gather in loose schools of up to 100 in
areas where there is an abundance of plankton. It is usually in
the warmer months of the year that we find this fish in New
England waters but it is by no means a warm water fish. Rather
it is classified as a boreal (cold-water) and temperate fish.
It is believed that those individuals that spend the summer here
simply withdraw to deeper water in the fall where the
temperatures do not fall so low. Those seen this summer have
been spotted at varying distances from shore, from many miles to
very close to the shore.
History:
In Colonial times, Basking Sharks were so abundant that they were
collected off Provincetown on Cape Cod in such numbers as to provide
a source of oil for the lamps of the colonists. A single fish yields
between 80 and 400 gallons of oil. More recently, this species has
been used as source of fish meal and animal feed. Because it is such
a slow-growing and slow-to-reproduce fish, commercial fishing for
basking sharks has fallen away due to overfishing.
Historically, the Basking sharks have often been viewed as a menace
to fishing stocks. Along the coast of British Columbia salmon
fisherman regard them as a nuisance due to their sheer size and their
habit of swimming into valuable fishing gear and destroying it trying
to escape. The sharks are not after the salmon or cod; they are
competing with them in their search for food. In Canada, the
fishermen went to the government for help. The Department of
Fisheries went after the Basking sharks with harpoons first and when
that didn't work took to shooting at them with rifle. The final
solution was to develop a razor sharp blade of steel fitted to a
fast-moving ship.> The ship sped into schools of Basking Sharks
and cut them to pieces. As many as 18 were killed in a single day.
Basking shark carcasses wash up on beaches every so often. With their
long cartilaginous vertebrae and strange skull, the decomposing body
has often been taken for the remains on an unknown "sea
monster." Living specimens too, leaping from the sea to shake
off skin parasites, might also have contributed to some of the
reports of unusual and unidentified sea creatures which filter
through the media from time to time.
A young, female basking shark, Cetorhinus maximus (total length 2.6 m)
captured off the Pacific coast of Honshu, Japan, in early May 1977 was
examined and estimated to be less than 6 months old, judging by the
number of calcified rings in the vertebral center. The elongate,
hook-like snout with a ventral groove continuous with the palate is
considered a characteristic juvenile feature of Cetorhinus, found only
in very young specimens. It is thought that the snout structure is
related to juvenile feeding, probably both in the mother's womb, if
oophagy in fact occurs, and during the early, free-living stage, when
the snout shape may increase the efficiency of water flow into the
mouth. The likely rapid change from the juvenile snout condition to the
adult type is probably produced by allometric growth of the rostral
cartilage's. The size and estimated age of the specimen conform well to
a growth curve derived from Atlantic and Mediterranean basking sharks,
indicating that no significant differences exist in age / length
relationships of Cetorhinus populations world-wide.
Abstract:
Very little is known about the fundamental biology of the basking shark.
The population size can only be guessed at; its behavior is only partly
understood; and its reproduction is a mystery. Despite this, commercial
fishing pressure continues. English Nature (formerly the Nature
Conservancy Council) has recommended that the species be listed as an
endangered species; the UK Government has, to date, rejected this
advice.
Oil emulsion of Cetorhinus maximus is a brand-new anti-carcinoma
medicine made from marine organisms. Through transplanted physical tumor
tests on 3 kinds of mice--S180, HeLA, Lewis, the maximum inhibitory rate
was 58%, 55% and 49% respectively. The clinical observations were based
on 45 cases out of which 25 were gastric carcinoma, 7 esophagus
carcinoma and 13 carcinoma of the lungs. Most of these cases were in
middle or terminal stages. The curative effect of the oil emulsion on
gastric carcinoma and esophagus carcinoma was obvious. Marked
improvements of the patient's condition such as weight increase, partial
shrinkage of the swollen lump and life extension constitute the
distinctive features of oil emulsion of Cetorhinus maximus. Most solid
tumors start as a small mass of avascular tissues which must be
nourished by the host's vascular network in order to grow and later
metastasize. Thus an inhibition of neovascularization, or
anti-angiogenesis, is a possible therapeutic approach to controlling the
growth of tumors. Cartilage, a source of this inhibitor, is vascular and
rarely invaded by neoplastic tissues. An abundant source of cartilage or
anti-angiogenic factor was sought in sharks, because their skeletal
tissue is entirely cartilage. When basking shark (Cetorhinus maximus)
fin cartilage was extracted for 41 days in 1 M guanidine solution and
tested for anti-angiogenic activity against V2 carcinoma in the rabbit
cornea, the vascular growth of the treated animals was 25% that of the
control. In addition, shark cartilage contains inhibitors of many
proteases including trypsin, plasmin and chymotrypsin.
The biology of basking sharks (Cetorhinus maximus) is briefly reviewed
and fisheries for the species discussed. It is apparent that, contrary
to earlier interpretations, basking sharks probably do not form locally
discrete stocks and that the decline of earlier fisheries, notably that
at Achill Island, Eire, was unlikely to be due to over-fishing of local
stocks. The history of most basking shark fisheries is that of economic
failure due to marketing difficulties and uncertainty of catch. The
seasonal inshore movements of basking sharks can be highly erratic, and
harpoon fisheries for the species are restricted by a requirement for
calm, sunny conditions. The current European fisheries have recently
been severely restricted owing to a collapse in the market for the liver
oil.
Determination of squalene content of shark liver oil. The squalene
contents of four kinds of shark liver oil were examined from Cetorhinus
maximus, Rhincodon typus, Notorhynchus platycephalus and Carcharhinus
latistomus. The method used in the study was Perepletchik's method, and
contents obtained were 11.06%, 13.76%, 6.79%, and 6.07%, respectively.
From Oct. 1978 through Jan. 1982, the Cetacean and Turtle Assessment
Program (CETAP) conducted a series of surveys of the waters of the US
outer continental shelf (OCS) between Cape Hatteras, North Carolina and
Cape Sable, Nova Scotia. The study area included the OCS from the
shoreline to approximately 9 km beyond the 1,829 m isobath. The CETAP
data base, pooled from all years of the study, includes 1,677 sightings
identified as sharks. One or more shark sightings occurred in every month
of the year, and sharks were observed in all portions of the study area.
Aerial survey data predominate; approximately 4 out of 5 shark sightings
were made from airplanes. Only three types of sharks were readily
identifiable and recorded in significant numbers: basking sharks
(Cetorhinus maximus --360 sightings), blue sharks (Prionace glauca --361
sightings) and hammerhead sharks (Sphyrna spp.--329 sightings).
Aid in releasing entrapped whales (Cetacea) and sharks (Cetorhinus
maximus) and minimizing damage to fishing gear was given to inshore
fishermen. Gear damage caused by these animals was monitored during 1984
throughout Newfoundland and Labrador. Damage reports to fishing gear via
cards and on-site reporting indicates a total of 261 cases estimating a
total gear loss of $81,000. Codtraps (52%) are the most commonly damaged
gear; salmon nets, primarily in Labrador, and groundfish gillnets
account for most of the remaining damage.
Shark (Cetorhinus maximus) cartilage contains a substance that strongly
inhibits the growth of new blood vessels toward solid tumors, thereby
restricting tumor growth. The abundance of this factor in shark
cartilage, in contrast to cartilage from mammalian sources, may make
sharks an ideal source of the inhibitor and may help to explain the
rarity of neoplasm's in these animals. The distribution and the times of
the main catches of the basking shark, C. maximus (Gunnerus), in the
commercial fishery off the coast of Norway during the seasons of 1971,
1972 and 1973 are given and analyzed. No easily recognized regularities
have been identified from season to season so that it is evident that
there is no pattern of migration towards the Norwegian coast comparable
to that of the bluefin tuna, Thunnus thynnus L., which once provided a
substantial fishery in the same area.
A description, including measurements, is given of the brain and cranial
cavity of C. maximus-. The significance of the small brain and its
enclosure by a relatively large cranial cavity in a thick cartilaginous
skull is discussed.
Though Finland is commonly believed to be the boundary of the C. maximus-
range, occasional occurrence of the shark outside its range has been
reported by several authors. The capture of a 2m long basking shark in
the Kandalaksha Bay in July 1976 provides further support for the view
that the range of the basking shark may extend as far as the western
White Sea. The shark had copepods in its stomach, which suggests that
they may be using the food resources of the Kandalaksha Bay where the
zooplanlton biomass is as high as 0.3 g/mSUP-3 in July.
During 1978, some rare fishes were observed along the coasts of
Charente-Maritime, especially Pseudotriakis microdon, Lampris regius-
and Scymnorhinus licha-. Data on the distribution of Cetorhinus maximus-
along the coast and the catch in the sea of the freshwater fish
Gymnocephalus cernua- is given. Three albinos fishes were observed.
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