Site fidelity and movements of sharks associated with ocean-farming cages in Hawaii

" Site fidelity and movements of sharks associated with ocean-farming cages in Hawaii "

Abstract:

Sharks are found in association with main Hawaiian Island ocean fish farms more frequently and at higher densities than is typical for coastal Hawaiian waters. Sharks attracted to fish farms could potentially threaten human water users, interact negatively with other fisheries, and seasonal migrations could be disrupted if individuals become entrained around farms throughout the year. We hypothesised that smaller coastal species would reside near farms, whereas more wide-ranging species would associate with farms only for short periods. We utilised passive acoustic telemetry to monitor the movements and behaviour of sandbar (Carcharhinus plumbeus) and tiger (Galeocerdo cuvier) sharks adjacent to two open ocean fish farms in Hawaii. Approximately half the tagged sandbar sharks showed site fidelity to the farms, with some individuals being detected repeatedly for 2.5 years. Sandbar sharks moved seasonally to the west coast of Oahu, suggesting that fish farms are not disrupting natural seasonal cycles in this species. Tiger sharks tagged near the cages were more transient, and showed much shorter residence times although some individuals returned sporadically to the cages over the 3-year period. Ocean fish cages appear to aggregate sandbar sharks, but are only ‘visited’ by tiger sharks. Although threats to public safety are probably minimal, the ecological effects of aggregating top-predators are still unknown.

Published: 13 December 2010

Yannis P. Papastamatiou, David G. Itano, Jonathan J. Dale, Carl G. Meyer and Kim N. Holland.

Marine and Freshwater Research 61(12) 1366-1375 doi:10.1071/MF10056

Hawaii - Politicians ignoring research data?

In the ongoing battle to preserve two shark diving operators from a small minded, fear based lynch mob who have run roughshod over Maui's politicians, the golden rule of the political set rears it's ugly head - "Ignore research data at your own peril."

Maui city council members glossed over and dismissed a recent study by Carl Meyer and Kim Holland proving sharks were not following commercial shark diving operators back to shore, a key anti-shark diving complaint.

But it gets worse. Not just happy to ignore research data some politicians, no doubt guided by anti-shark diving fear monger talking points, have denounced the data, attacking the two researchers in question and by proxy the University of Hawaii!

The Romans had a saying for this kind of behaviour "don't kill the messenger" and today blow back for "killing the messenger" in the form of an Op Ed reminded politicians in Oahu (hopefully more enlightened than Maui) of the golden rule of the political set:

Shark Tours - Study shows no increased risk

I am obliged to respond to Greg Knudsen's inaccurate characterization of our research paper concerning North Shore shark tours.

Three points:

1) The paper was not based solely on data from tour operators.

2) The operators' information was provided prior to the recent turmoil; there was no incentive for false reporting.

3) The paper was only published after review by independent experts. Soon-to-be-published results of shark tracking research show that sharks found at the tour sites don't come close to shore.

Several elected officials such as Mr. Knudsen took public positions on this topic before they had sufficient objective information or after listening to "instant experts." Apparently, ego now prevents them from changing their minds even though the scientific facts do not support their opinions. Objective data indicate that the tours do not cause increased risk to humans and do not significantly impact the biology of sharks. The tours do provide local employment and they probably increase the general public's appreciation of marine life and how worthy these resources are of our respect and protection.

Kim Holland, Ph.D.
Researcher, Hawai'i Institute of Marine Biology