LAUSR

The gap between spawning and settlement location of marine fishes, wherein the larvae occupy an oceanic phase, is a great mystery in both natural history and conservation. Recent genomic approaches offer some resolution, especially in linking parent to offspring with assays of nucleotide polymorphisms. Here, we apply this methodology to the endemic Hawaiian Convict Tang (Acanthurus triostegus sandvicensis), a surgeonfish with a long pelagic larval stage of ~54-77 days. We collected 606 adults and 607 juveniles from 23 locations around the island of O'ahu, Hawai'i. Based on 399 SNPs, we assigned 68 of these juveniles back to a parent (11.2% assignment rate). Each side of the island showed significant population differentiation with higher levels in the west and north. The west and north sides of the island also had little evidence of recruitment, which may be due to westerly currents in the region or an artifact of uneven sampling. In contrast, the majority of juveniles (94%) sampled along the eastern shore originated on that side of the island, primarily within semi-enclosed Kāne'ohe Bay. Nearly half of the juveniles assigned to parents were found in the southern part of Kāne'ohe Bay, with local settlement likely facilitated by extended water residence time. Several instances of self-recruitment, when a juvenile returns to their natal location, were observed along the eastern and southern shores. Cumulatively, these findings indicate that most dispersal is between adjacent regions on the eastern and southern shores. Regional management efforts for A. triostegus and possibly other reef fishes will be effective only with collaboration among adjacent coastal communities, consistent with the traditional moku system of native Hawaiian resource management.