Sharks The Animal Answer Guide

84

Do sharks migrate?

Although some sharks, such as Bull and Bonnetheads, are comparative

stay-at-homes (see “Are any sharks territorial?” in chapter 4), others travel

long distances on a regular basis. It isn’t surprising that many long-distance

movers (Whale Sharks, Basking Sharks) are large, but even some relatively

small sharks such as Spiny Dogfish will cross entire ocean basins. Migra-

tory behavior is in fact a prime reason that many sharks are overfished.

Migrations can be both horizontal and vertical. Horizontal movements

are generally much greater and can be along coastlines or across oceans.

Coastal species stay near continental shelves, over depths of generally less

than 200 m (650 ft), but can still travel great distances. Coastal sharks in-

clude threshers, Sandbar, Blacktip, and Dusky sharks. Bigeye Threshers

(Alopias superciliosus) have been tracked from waters off New York to the

eastern Gulf of Mexico, a distance of 2,767 km (1,719 miles). Sandbar

Sharks move between the northeastern United States and the Yucatan Pe-

ninsula of Mexico, a distance of about 5,600 km (3,480 miles). Great Ham-

merheads are found along coastlines and also far at sea over seamounts.

One “coastal” individual was followed for 62 days. It left South Florida and

traveled north to New Jersey, sometimes drifting with the Gulf Stream.

It traveled a minimum distance of 1,200 km (745 miles). Scalloped Ham-

merheads tagged at Malpelo Island, Colombia, have been followed to the

Cocos Islands off Costa Rica (627 km, or 389 miles); and one shark then

moved to the Galapagos Islands, another 710 km (440 miles), for a mini-

mum distance of 1,340 km. Because Malpelo, Cocos Island, and the Gala-

pagos are among the few places where Scalloped Hammerheads are known

Chapter 5

Shark Ecology

http://www.ebook3000.com