Shark Ecology 87tropics, they descend to open ocean depths as great as 1,000 m (3,300 ft),
where they remain active for months, probably feeding.
These findings solve one of shark biology’s great mysteries, namely
where Basking Sharks go in the winter. Because they “disappeared,” it was
guessed that they hibernated on the bottom somewhere. The new informa-
tion is based on “pop-up” tags that periodically record depth, temperature,
and location: these tags break free from the shark, float to the surface, and
transmit their stored data via satellite to a laboratory (see “How do scien-
tists study the movements of large sharks?” in chapter 12). We don’t know
what the sharks do after their tags are shed. It is assumed that they return
to northern areas the following spring because that is when they start to
reappear in surface waters off New England. Learning that Basking Sharks
probably feed in deep, cool waters for months at a time also calls into ques-
tion their name. They are called “Basking” Sharks because it was assumed
that their slow movement at the surface was for sunbathing (Irish fisher-
men used to also call them “sunfish”). It now seems more likely that they
are at the surface because that’s where their food is located at high lati-
tudes. We are open to suggestions for a new name for this plankton-eating,
migrating giant.
We know less about ray migrations, especially among smaller species.
Atlantic Stingrays migrate seasonally, apparently avoiding cold water. Dur-
ing summer and fall they occur in areas such as the Chesapeake Bay, but
when surface waters cool, they move south or offshore to warmer water.The migration track of Nicole, a 4 -m female White Shark who swam from South Africa to western Australia and back
over a nine-month period. Redrawn from R. Bonfil et al., “Transoceanic migration, spatial dynamics, and population linkages of white sharks,”
Science 310 ( 2005 ): 100 – 103 ; used with permission of Wiley-Blackwell