EPA's Vessel General Permit and Small Vessel General

Staghorn coral require relatively clear water and depend almost entirely upon symbiotic
photosynthesizers (zoozanthelle) for nourishment (Porter 1976, Lewis 1977, Jaap et al. 1989,
Mieog et al. 2009) and is much more susceptible to increases in water turbidity than are some
other corals. Different strains of symbiotic zoozanthelle (Symbiodinium spp.) can confer
different thermal and light tolerances to acroporiids (Abrego et al. 2009, Ainsworth and Hoegh-
Guldberg 2009, Abrego et al. 2010). The type of Symbiodinium spp. may change during
ontogeny or remain the same, depending upon acroporiid species, and may be the same as parent
colonies or not (Baird et al. 2007, Gómez-Cabrera et al. 2008, Abrego et al. 2009).
Status and trends
Staghorn coral was listed as threatened under the ESA on May 9, 2006 (71 FR 26852). Staghorn
coral underwent precipitous declines in the early 1980s throughout its range and this decline has
continued. Although quantitative data on historical distribution and abundance are scarce, best
available data indicate declines in abundance (coverage and colony numbers) by greater than
97%.
Staghorn corals still occupy their historic range, but localized range reductions and extirpations
have occurred with most populations experiencing losses from 80-98% of their 1970s baseline
(Bruckner 2002). Monitoring data from around the USVI indicates that staghorn corals have
virtually disappeared from the north side of Buck Island, St. Croix, and only a few localized
areas off the southern reef contain staghorn corals, representing 2-3% of the coral cover in these
areas (Rogers et al. 2002). Surveys of fragments of staghorn from nearshore areas of St. Thomas
and outlaying cays indicate that colonies of these corals were once much more abundant than the
numbers recorded in the 2003 survey (Rogers et al. 2008).
In Puerto Rico, well-developed and dense thickets of staghorn coral were present through the late
1970s at many reefs surrounding the main island, and also the offshore islands of Mona, Vieques
and Culebra (Almy and Carrión-Torres 1963, McKenzie and Benton 1972, Goenaga and Cintrón
1979, Boulon Jr. 1980). Later, in 1978-79 during an island-wide survey, staghorn coral was
found on only 20% of those reefs (Bruckner 2002). Prior to Hurricane David in 1979, 20
random 0.6 m 2 photoquadrats were selected from each of 10, 40-m-long transects parallel to the
depth contours across the reef (16.7 to 19.2 m depth). Based on analysis of point count data,
staghorn coral had a mean total cover of 31.1% (range of 9.9 to 56.9%); after the storm, total
cover of staghorn coral dropped to a mean of 0.90% (range of 0.02 to 2.7%)(NMFS 2008a). In
the summer of 2004, there was an epidemic outbreak of white pox disease at Los Corchos Reef
in Culebra, Puerto Rico. Prior to the outbreak, coral cover on the reef reached values of 80%.
However, three weeks after Tropical Storm Jeanne, 80 to 90% of the staghorn coral colonies at
permanent monitoring sites at Los Corchos were already dead or dying; likely as a result of
impacts from both disease and storm damage (NMFS 2008a). During the 2005 bleaching event,
near Culebra Island, almost 100% of staghorn colonies suffered partial to complete mortality due
to bleaching (García-Saís et al. 2008). Similar to the situation in USVI, the bleaching event was
followed by a white plague-like massive outbreak that caused mass mortality and resulted in a
net 20-60% decline in living coral cover at surveyed reefs of the east coast within a period of
approximately six months.
Following the 2005 bleaching event, monitoring data indicate that total coral cover is now less
191