Background/Question/Methods A variety of hypotheses regarding the coexistence of coral-reef fishes involve interspecific competition. Coral reefs on exposed coastlines in Hawai‘i are dominated by cauliflower coral (Pocillopora spp.), whose highly complex branches provide habitat for a variety of fishes and invertebrates. Common inhabitants are the Galactic Scorpionfish (Sebastapistes galactacma) and the Speckled Scorpionfish (S. coniorta). These species have overlapping depth ranges: Galactic Scorpionfish deeper and Speckled Scorpionfish shallower. In the zone of overlap (reefs 4-9 m deep), these fishes inhabit coral colonies near one another, and occasionally co-occupy the same colony. Because these species are ecologically similar, interspecific competition could be limiting their abundances. To test this hypothesis, I conducted reciprocal removal experiments at two spatial scales. Between May and October of 2019, I maintained reciprocal press removals within clusters of coral colonies and followed the abundances of each species in the presence and absence of its putative competitor. In the summer of 2020, I began a second reciprocal removal among individual colonies occupied by both species. If competition is limiting one or both species’ abundances at either spatial scale, then removal of the competitor should lead to an increase in the abundance and/or a distributional shift of the remaining species. Results/Conclusions At the cluster scale, abundances of both species were nearly unchanged following the removal of the congener. At the scale of a single colony, both species showed a slight increase in abundance immediately following the removal of the other species, though abundance returned to pre-removal levels after a couple of months. These outcomes indicate that competition is not presently an important interaction between these species despite their ecological similarity. One potential explanation for these patterns could be a partitioning of food resources between the two species, which is currently being investigated. Alternatively, severe recruitment limitation in Hawai‘i may lessen competition between these species to levels that allow coexistence.
