Shark Migration Linked to Bites: Attacks in Hawaii Increase in Fall, Says Study

Shark migration has been linked to bites in Hawaii, according to researchers from the University of Hawaii and the Florida Museum of Natural History. From September to November, the tiger shark migration results in a number of bites, their latest study found.

The shark migration was linked to bites by tagging over 100 tiger sharks over a 7-year period, with most of the shallow-swimming animals being female. The acoustic tags, which transmit to 143 "listening stations" surrounding Hawaii, let researchers know that approximately 25 percent of the female sharks migrate from the Northwestern Hawaiian Islands to the main, populated Hawaiian Islands in summer and fall.

"Both the timing of this migration and tiger shark pupping season coincide with Hawaiian oral traditions suggesting that late summer and fall, when the wiliwili tree blooms, are a period of increased risk of shark bites," study co-author Carl Meyer, a researcher at the University of Hawaii, said in a statement.

However, both Meyer and lead author Yannis Papastamatiou of the Florida Museum of Natural History caution that migration does not necessarily correlate with the shark bites near the islands. Shark bites are extremely rare, with only two to four per year in Hawaii, and they claim an average of 15 lives per year total, according to The International Shark Attack File.

Also, shark migration patterns are much more complicated than previously thought. Not all female tiger sharks migrate at the same time, or even choose to migrate, according to the study, which will be published in the journal Ecology in November.

"You see that in all groups - birds, fish, whales, turtles and now we're seeing in sharks as well," Papastamatiou told LiveScience.

Data revealed that pregnant females could be migrating up to 2,500 kilometers for better food availability and thermal environments. One tiger shark that was tagged was found as far away as the Mexican coast.

The tiger shark is dangerous because of its natural habits. In addition to swimming in shallow waters- this is the easiest way to encounter swimmers, surfers and beachgoers- the tiger shark also has the broadest diet, which could contribute to it biting humans.