Dataset: Lionfish and grouper density

To determine patterns of lionfish (Pterois volitans) and Nassau Grouper (Epinephalus striatus) abundance and body size over the first decade of the lionfish invasion, we examined fish survey data collected in the Exuma Cays, The Bahamas, from when lionfish first arrived in the study area in 2005 through 2015. We surveyed reef-resident fishes at three spatial scales: (1) small patch reefs; (2) medium-sized patch reefs; and (3) large reefs.  Small reefs included 32 coral patch reefs (ca. 6 m2) as well as 16 artificial reefs (ca. 1 m2) constructed of concrete blocks. Surveys were conducted annually on these reefs from June to August during 2005–2015, with the exception of 2006 and 2012–2014. A pair of trained observers recorded the abundance and visually estimated body size (to nearest cm total length, TL) of all resident fishes on each reef. Censuses consisted of divers slowly circling the reefs at distances of ~3, ~1, and 0 m and then using flashlights to thoroughly search all holes and crevices. Medium-sized reefs comprised six natural coral patches (ca. 6 to 23 m2). Fish populations on these reefs were censused in 2006–2012 and 2015 following the same protocol as for the small reefs. At the largest scale, ten reefs (ca. 1400 to 4000 m2) were surveyed as part of a long-term lionfish manipulation experiment. All resident fishes in 400 m2 survey areas (two 10 x 10 m plots and four 2 x 25 m transects) were censused on each reef. We examined fish surveys that were conducted in June 2009, before any lionfish manipulations, to surveys conducted in July/August 2015, 3 years after the experiment of Albins (2015) was completed. Lionfish were never manipulated on one of these large reefs, which was isolated from other reefs. We examined a complete time series of surveys on this particular reef, including censuses conducted in both winter (November–February) and summer (June–August) of 2009, 2010, 2011, and in summer of 2012 and 2015.

Additional methods for surveys of large reefs included in: Albins, MA. 2015.