Shark Behavior 69
nighttime dispersal, although groups of Whitetips have been filmed feed-
ing at night.
Aggregation in sharks doesn’t necessarily mean lying on the bottom in the
manner of Port Jackson, Nurse, and Whitetip Reef sharks. Actively swim-
ming sharks form daytime resting aggregations too. Aggregations of Black-
tip Reef Sharks are frequently observed milling around in water so shallow
that their dorsal fins stick out; what they’re doing is not really known, but
their behavior does not appear to involve active feeding. Young Blacktip
Sharks (Carcharhinus limbatus) also aggregate by day and disperse at night,
again returning to the same daytime locales over a period of three years.
The world’s largest aggregation of
Whale Sharks, the biggest fish in the
sea. On August 12 , 2009 , 420 Whale
Sharks were spotted off the Yucatan
Peninsula of Mexico in an area about
3 km × 6 km ( 1. 9 × 3. 8 miles). The
sharks were feeding on recently
spawned eggs of Little Tuna. The
upper photo (A) shows 220 Whale
Sharks and four tour boats; the lower
photo (B), from a lower altitude,
shows 68 Whale Sharks, one boat,
and two pairs of snorkeling tourists.
From Rafael de la Parra Venegas et al., “An
unprecedented aggregation of Whale Sharks,
Rhincodon typus, in Mexican coastal waters of
the Caribbean Sea,” PLoS ONE 6 , no. 4 ( 2011 ):
e 18994 ; photo used by permission of Alistair
Dove / Georgia Aquarium