Shark Ressearch
Movements of Sharks Associated With Cage Dive Ecotourism
Principal Investigators: Carl Meyer & Kim Holland
Project Overview
Concern exists that commercial shark cage diving conducted 3 miles offshore from Haleiwa Harbor increases the risk of shark attack on swimmers, surfers and divers along the North Shore of Oahu (Hawaii). Much of this concern is based on the belief that sharks associated with these commercial tours follow the tour boats back toward shore whenever the boats leave their offshore operation sites. We are using cutting edge technology to track the long-term movements of sharks captured at the cage diving sites and evaluate the public safety implications of these operations.
Research Questions
We are addressing the following specific questions:
(1) How often do sharks visit the cage diving sites and how long do they stay?
(2) Do sharks captured at the cage diving sites ever come into shallow inshore areas utilized by people?
(3) Do sharks follow the cage diving boats back toward harbor?
(4) How far do sharks that visit cage diving sites range?
Methods
We captured 30 sharks (Galapagos and sandbar sharks) at cage diving sites and surgically implanted them with small ultrasonic transmitters. We stationed underwater listening stations (acoustic receivers) at the cage diving sites, at the entrance to Haleiwa harbor channel and at surf breaks along the North Shore of Oahu. We are using this system to remotely track shark movements at multiple locations along the Hawaiian archipelago. The system consists of small, underwater receivers that listen continually for the presence of sharks implanted with coded pulse acoustic transmitters (within a detection range of up to 1000m). The receivers are periodically retrieved by divers and downloaded to find out which sharks have visited, when they came and how long they stayed at each location.
Preliminary Results
Galapagos and sandbar sharks are the most common species seen at cage diving sites (98% of all sharks observed). These species are rarely implicated in attacks on humans. Sharks remain at cage diving sites throughout the day and disperse at night. Sharks that visit cage diving sites also migrate seasonally to deep waters off the West side of Oahu. Inshore movements by sharks associated with cage diving operations are extremely rare. There is no evidence of sharks following boats back to the harbor. Current cage diving operations appear to pose no significant threat to public safety.
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Shark Research