Experimental removal of the invasive peacock hind (roi) Cephalopholis argus, in Puako¯, Hawai'i: Methods for assessing and managing marine invasive species

Invasive species are a growing concern for marine biodiversity, particularly in Hawai'i with its large proportion of endemic species. This research focused on the feasibility of removing the introduced predatory peacock grouper Cephalopholis argus, locally known as roi, as a management tool for Hawaiian coral reef ecosystem restoration. The objectives of this study were to investigate the dynamics of C. argus on 1.3 hectares (ha) of coral reef at Puako¯, Hawai'i, and to (1) compare population density estimate methods in order to accurately evaluate abundance, (2) estimate population mortality and catchability rates, and (3) quantify the re-colonization rates by mapping distribution and movements in response to a depletion experiment. The number of individuals removed during a fish-down experiment provided a direct measure of initial population abundance (20.2 roi ha^-1). A Leslie depletion model yielded the most accurate assessment of initial density (-15.8% error) compared to belt transects (+75.7% error) and tow-board census (-70.2% error). Estimates of total mortality were low (0.12 to 0.14), and fishing mortality ranged from negligible to 8.0% yr^-1in west Hawai'i. Roi movement was monitored through a mark and re-capture program. Tagged individuals traveled 50 to 150 m from the periphery toward the center of the removal area (1 roi every 1 to 2 mo). This study engaged the local Hawaiian fishing community in assessing and managing marine invasive fish species, quantified the feasibility of roi removal as an ecosystem management tool, and provides evidence for effective roi population control through spear-fishing methods at the local (1.3 ha) patch-reef scale.