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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