Hawaii’s Invasive Problem

I’ve been in and around Oahu’s waters ever since I was a little boy.  Throughout my years, what I’ve noticed is the drastic decline in our ocean’s nearshore resources.  A good amount of this might be due to the drastic increase of three invasive species of fish in Hawaii’s waters.  These three fish are the Peacock grouper (Roi), the Blacktail snapper (To`au), and the Blueline snapper (Ta`ape).  Although fishermen may not know of this or even notice it, divers can see how the abundance of certain native species of fish have declined, while the populations of these invasive ones have increased.  These three were introduced by the state to boost the nearshore fisheries, but the demand for the two snappers was very low and the roi were notorious for being carriers of ciguatera toxin.

The to`au and ta`ape mainly feed on small crustaceans which could be the cause of the small lobster and crab populations.  In this regard, the ta`ape have a greater impact than the to`au.  Ta`ape travel in large schools and when they go out to feed, their effects on the area are noticeable.  However, they both pale in comparison to the roi.  For example, an average roi (1.5 pounds) can eat up to 146 juvenile reef fish in one year.  With roi being capable of attaining 10 pounds, their impact on a reef can be immense.  In areas like Kona on the Big Island, you can find an average of 2-3 roi every 50 feet.

One of the ways that we can try and fix this problem is to increase the education and awareness of the impacts that these invasive species are having on our native reefs.  By making more people aware of this problem, the community might try and make a difference.  This eradication movement began in Maui and has since spread to all of the other Hawaiian Islands.  At this time, all of Oahu’s major dive tournaments have either converted their format to only allow the taking of invasive species or, at least, have introduced an invasive species category.  As more and more people are becoming aware of this problem, there is hope for the future of Hawaii’s reefs.

You can follow this link to learn more about what is being done: http://www.oc16.tv/shows/32

-Troy Maeda


Additional information:

Dierking and Meyer 09-prey regurg in roi

Dierking et al 2009-roi diet


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