Samples Collected for Study of Age and Growth of Invasive Roi

Of the invasive fish species on Hawaiian reefs, one of the most problematic is the peacock grouper, Cephalopholis argus, known locally as roi. In an effort to better understand the biology and population dynamics of this species, PIFSC scientists from the Coral Reef Ecosystem Division (CRED) participated in biological sampling of roi caught at fishing tournaments on the Kona coast of Hawaii Island during August 13–14, 2011. The tournaments were sponsored by the Dive Hilo dive club and by visiting divers from Maui. Fishers in the tournament targeted roi and other invasive fish species.

Roi. Image courtesy of John Randall.
Roi. Image courtesy of John Randall.

Roi was introduced to waters of Hawaii Island and Oahu in the 1950s and has become well established throughout Hawaiian waters, spreading as far north as French Frigate Shoals in the Northwestern Hawaiian Islands. Tournaments l ike the Kona event are part of a grassroots effort to control invasive fish populations. Roi is ciguatoxic in Hawaii, and, thus, is harmful to humans if eaten. Because of this link to ciguatera poisoning, fishermen donate their catches of roi to scientists for research, including studies of ciguatera, food web modeling, and other aspects of fisheries science. CRED staff traveled to Kona to collect biological samples of roi, including otoliths for an age and growth study. The growth research employs standard otolith techniques with the goal of assessing demographic variability in roi at multiple spatial scales.