Research
Why are pelagic fishes attracted to FADs? How do the fish find the FADs? How long do they stay around the FADs? These are important questions that researchers at the University of Hawaii and other collaborating institutions have been trying to answer. The FAD system not only provides fishermen with better opportunities to catch fish, but also provides scientists with an opportunity to learn more about the biology and behavior of these hard to study pelagic fishes.
Why are pelagic fishes attracted to FADs?
Researchers at the University of Hawaii have begun to get answers to this question using several different techniques. In order to determine the short-term movement patterns of tunas, researcher attach acoustic transmitters to fish caught at FADs and follow them around for up to 48 hours to see where they go. Using this technique, they have found that subadult yellowfin tuna caught around FADs spend their days around the FADs but leave them at night and venture off as far as 5 miles. This information can be valuable in helping FAD managers determine how far apart FADs should be. Acoustic transmitters attached to the fish also relay information about their depth. Studies have shown that small bigeye tuna spend more time closer to the surface around FADs than when they are in free schools away from the FADs.
In another use of acoustic transmitters, data loggers attached to some FAD moorings are monitoring the longer term movement patterns of tunas returning to the FADs.
These studies have found that tunas tagged around seamounts behave very similarly to tunas tagged around FADs. It is thought that maybe the FAD serves the same function as a seamount, providing a point of reference for the tuna.
In the near future, standard tag-and-release research will be conducted to investigate the long term movement patterns of tunas around FADs and their influence on the movement patterns of tunas in Hawaiian waters in general.
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