Basking Sharks Essay Research Paper Basking shark

Basking Sharks Essay, Research Paper

Basking shark Cetorhinus maximus (Gunnerus) 1765

Bone Shark

Bigelow and Schroeder, 1948, p. 147.

In light of recent reports of basking sharks along the New England Coast we have assembled this

page to provide information concerning this second largest of all sharks. This species is not known to

be aggressive or dangerous but like any large animal should be treated with respect. The information

below is taken from Bigelow and Schroeder, Fishes of the Gulf of Maine.

The basking shark resembles the mackerel sharks in the lunate shape of its caudal fin, with lower

lobe nearly as long as upper; also in the presence of a noticeable lunate furrow above and one below

on the root of the tail, and in the wide lateral expansion of the latter, forming a pronounced “fore and

aft” keel on either side; also in the facts that the second dorsal fin and the anal fin are much smaller

than the first dorsal, that its fifth gill opening is situated in front of the origin of the pectoral fin; in the

position of the mouth on the under side of the head; and in the wide separation of the nostrils from

the mouth. But the teeth of the basking shark are minute and very numerous (large and few in

number in the mackerel sharks); its gill openings are so large that they extend right around the neck,

with those of the first pair almost meeting below on the throat; and the inner margin of each gill arch

bears a great number of horny, bristle-like rakers, directed inward-forward, that correspond to the

rakers of various bony fishes in their position and in their function (see p. 30). It was the fancied

resemblance of these rakers to the whalebone of the whalebone whales that suggested the

vernacular name “bone shark” to the whalemen of olden times.

Corresponding to its feeding habits, the mouth of the basking shark is very large and widely

distensible at the corners. The snout is short, conical, with rounded tip on large specimens. But it is

much longer, relatively, on small ones, projecting far beyond the mouth, obliquely truncate in front,

terminating above in a sharp point, and with the head strongly compressed sideways abreast of the

front of the mouth. This results in so bizarre an appearance that the young basking shark was thought

at first to represent a separate species. A gradual transition takes place from the juvenile shape of

head to the adult shape when a length of 12 to 16 feet has been reached. We need only note further

that the triangular first dorsal fin stands midway between pectorals and pelvics; though not so high in

proportion as that of the mackerel-shark tribe, it rises high in the air when a large basking shark lies

awash on the surface, as is their habit, a convenient field mark (see figure).

Figure 8 – Basking shark (Cetorhinus maximus), 26 -1/2 foot female, Marthas Vineyard. . From

Bigelow and Schroeder. Drawinge by E. N. Fischer.

Color. Upper surface grayish brown, slaty gray, or even almost black. The lower surface has been

described repeatedly as white. But the Menemsha specimen described by Allen 57 was of a

somewhat lighter shade below than above, without white markings, as was a Massachusetts Bay

specimen recently examined by us; while one 14 feet long captured at West Hampton, L. I., on June

29, 1915 58 had the belly as dark as the back, with a white patch underneath the snout in front of the

mouth.

Size: The basking shark rivals, though it does not equal, the whale shark of tropical seas in size.

Reports that an occasional basking shark may reach a length of 50 feet probably are not an

exaggeration, for the catch on the coast of Norway, for the period 1884 to 1905, included one of

about 45 feet and three of about 40 feet, with the six next longest ranging between 36 feet and 30

feet 3 inches. The three longest for which we find definite measurements for the western Atlantic

were of 32 feet 2 inches, 32 feet, and 30 feet 3 inches. But others up to 35 feet long have been

credibly reported as killed near Eastport, Maine, many years ago; and one captured at Musquash

Harbor, New Brunswick, near the mouth of the Bay of Fundy in 1851 was said to have been about

40 feet long. It is probable that they are at least 5 to 6 feet long when born, the three smallest so far

reported having been between 5 feet 5 inches and about 8 feet 6 inches long. Matthews 59

concluded from studies of basking sharks taken near the Isle Of Skye that fish up to 10 feet are in

their first year, those of 15 feet in their second year. Males mature sexually at about 18 to 20 feet as

indicated by the lengths of their claspers, females at about 20 to 23 feet; i. e., when 3 years old or

perhaps 4, according to Mathews’ estimate.

We find no exact weights for large basking sharks from the Atlantic. But 6,580 pounds for one of 28

feet, and 8,600 pounds for another of 30 feet, from Monterey, Calif., is doubtless a fair indication of

what a fairly large one may b

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