The data presented in this file have been published in: Tsounis, G., Steele, M. A., & Edmunds, P. J. Elevated feeding rates of fishes within octocoral canopies on Caribbean reefs.Coral Reefs (2020) 39:1299-1311, doi: 10.1007/s00338-020-01963-1.

Surveys were conducted at octocoral communities in St John, US Virgin Islands, in February and March 2016. Building on our previous studies on the environmental impact of octocoral community structure (Tsounis and Edmunds 2017; Tsounis et al. 2018), the present study was conducted at East Cabritte, Europa Bay, and East Tektite, within the Virgin Islands National Park, along the south shore of St. John.

Hypothesis (1) was tested: Fish abundance and their feeding rates are higher within the canopy of dense octocoral communities than outside, as a result of octocorals providing visual cover.

Methods: Point census surveys in 1 x 2 m quadrats placed within canopies and outside of canopies were used to quantify the abundances of fishes by family, and in these quadrats the foraging rates of fishes were estimated from the rate at which they took bites from benthic surfaces. An L-shaped PVC frame (1 x 2 m, hereafter referred to as “quadrat”) was placed haphazardly on the reef at each site, and then the observer retreated 5-7 m away and let 2-3 minutes pass to allow fishes to acclimate to the presence of the PVC frame. Each quadrat was observed for 5 min, during which the total number of bites on benthic surfaces by fishes (pooled among taxa) was counted. Quadrats in which fish reacted to the presence of the observer, for example, by seeking refuge in response to the diver, were excluded from the data.

Locations within each of the three sites were defined as within canopy ("in") if at least two large octocoral colonies were present in the quadrat. Where this criterion was not met, the area was categorized as outside of canopy ("out"). "Large colonies" were defined by the estimated mean height of arborescent octocorals at each site, and thus differed among sites. Large colonies were > 20 cm tall at Europa Bay and East Tektite, and > 30 cm tall at East Cabritte.