Tracking Coral Reef Health
RHI symbol
Coral Cover
Herbivorous
Fish
Fleshy
Macroalgae
Com mercial
Fish
The Reef Health Index( RHI) integrates four indicators to measure coral reef health( coral cover, fleshy macroalgae, herbivorous fish and commercial fish). The RHI“ pie” symbol on the map is displayed at the site, subregional and national levels.*( For more information visit www. caribnode. org)
No Data
Very Good
St. Vincent and the Grenadines( SVG)
The Reef Health Index for SVG includes comparable data from different surveys: 1 survey in 2005 by The Nature Conservancy( TNC), 8 surveys in 2008 by TNC; 15 in 2011 by Steve Newman and Stacey Williams of FORCE 1, 15 in 2014 by Robert Steneck of University of Maine and 3 in 2014 by Grenadines Network of Marine Protected Areas( GNMPA)( 1 long term monitoring site( LTM) in South Coast Marine Conservation Area( MCA), 1 in Mustique MCA, 1 in Tobago Cays MP). SVG is divided into subregions based on similar biogeographic features to facilitate data reporting. Data were not available for 8 subregions. Subregions for the 6 ECMMAN countries are numbered 1 to 41 from Grenada north to St. Kitts and Nevis.
Subregion Subregion Description # Sites Score
8- 9 10- 11 12
13- 14 15- 16 17
18- 19 20- 21 22- 23
24- 25
W. Union: narrow fore reef, complex structure, good coral cover, abundant fish. North: abundant finger coral, octocorals. Limited data. East: shallow, windward-sheltered fringing reefs, low coral. Palm Island: hardground with octocorals, sponges, small head corals. Tobago cays: Largest coral reef-seagrass extent in SVG. Many reef types. Horseshoe Reef: unique narrow, semicircular-shaped reef, deep( 8-15 m), mostly star coral( Orbicella), numerous fish. Patch reefs: shallow relict elkhorn with crustose coralline algae( CCA), some live elkhorn. Hardbottom: shallow, mixed coral, octocoral and seagrass. Mayreau East: high structure, many corals, octocorals, fish, high current. Data gap: around Mayreau, outside of park boundaries. W. Canouan: fringing fore reef, good coral cover, limited data. Shallow reefs no data. Upland construction impacts. E. Canouan: low relief, moderate coral cover, high CCA, limited data.
W. Mustique: shallow nearshore boulders covered with small corals, some elkhorn, abundant Diadema. Pillories- sloping fore reef mixed algae, corals octocorals, some elkhorn and staghorn coral. Lagoon- complex fore reef. Plantain- low relief reef, small corals. Petit Mustique- low relief fore reef, abundant sponge, octocorals. Data gaps: 13, 14, 17, Mustique east.
Bequia West: narrow fringing reef, steep slope, numerous octocorals, corals and fish. East: fringing reefs to north, data gaps east & Isle A Quatre. Baliceaux West: hardbottom with octocorals, sponges, some small corals. Data gaps: subregions 19, 20, 21, 23.
Subregion 24: West coast: leeward, narrow shelf, steep slope. Shallow: nearshore boulders from land covered with small corals, some elkhorn, high Diadema. Slope: fringing reef, high coral cover, complex structure, high diversity of corals, sponges, octocorals and fish in 10-30 m. S. coast: Variety of reefs found in 3-10 m along Indian, Villa, Calliaqua, Canash Bays & Young Island, some high coral cover; Blue Lagoon-large living elkhorn reef. High sedimentation in some areas. E. coast: data gap, patch reefs in NE Owia / Sandy Bay; east coast
Indicator Description of St. Vincent and the Grenadines’ Reef Health Threatened Healthy
15
7
7
13
Corals |
Corals build the reef’ s 3D structure, provide habitat, and protect coastlines
• Coral cover high( range 3-55 %), but lower than historic
• Complex reef structure had high coral cover(> 30 %); W. coast > E. coast
• Several new healthy elkhorn corals found; largest stand at Blue Lagoon
• Corals at risk from high sedimentation, storms & bleaching events
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Steve Nimrod
Steve Nimrod
Fleshy macroalgae, when too abundant, outcompete corals
• Most reefs( 25 of 42 sites) had more live coral than algae( range 3-60 %)
• East coast reefs and South Coast mainland reefs had more macroalgae
Fleshy • Less macroalgae on reefs with abundant Diadema( shallow boulder reefs) macroalgae • Lack of crustose coralline algae on many reefs; less open space for corals
Ken Marks Ken Marks
Herbivorous Fish |
Herbivorous fish clean algae off reefs
• Biomass was fair( 331-6219 g / 100 m 2); Tobago Cays, W. coast highest
• Parrotfish common on all reefs; most small in size( 0-5 cm size class)
• Few large parrotfish; less grazing allows algae to overgrow corals
• Many juveniles suggests populations could increase if protected
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Ken Marks |
Ken Marks |
Commercial Fish |
Groupers & snappers are key predators that keep food chain in balance
• Commercial fish biomass was low( range 15-1300 g / 100m 2)
• Few groupers & snappers; most small in size( most 6-10 cm size class)
• Reefs with more complex structure had more fish( West coast reefs)
• More fish & larger-sized fish in no-take protected area( Tobago Cays)
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Emma Doyle |
Ken Marks |
Diadema |
Diadema urchins clean algae off reefs and open space for coral recruits
• West coast of St. Vincent and shallow boulder reefs had more Diadema
• Reefs with more urchins had less macroalgae
• Diadema urchins are important since few large herbivorous fish
• Reducing sediments and nutrients will improve sea urchin habitat
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Clare Morrall |
Ken Marks |
Coral Recruits |
Coral recruits are“ baby” corals. Recruits prefer algal free areas
• Recruits abundant, varied by reef type, most were smaller-sized species
• Several elkhorn coral recruits seen suggests hope for recovery
• High silt covering many reefs prevented coral growth or settlement
• Reducing sediments and increasing herbivory will improve substrate
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Steve Nimrod |
Ken Marks |
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