Fish assemblages and benthic habitats of Buck Island Reef National 

Monument (St. Croix, U.S. Virgin Islands) and the surrounding seascape: 

A characterization of spatial and temporal patterns

A cooperative investigation between NOAA and the National Park Service

May 2008

NOAA Technical Memorandum NOS NCCOS 71

Simon J Pittman 

Sarah D Hile

 Christopher FG Jeffrey

Chris Caldow

Matt S Kendall

Mark E Monaco

 Zandy Hillis-Starr
Mention of trade names or commercial products does not constitute endorsement or recommendation for their use by the 

United States government.

Citation for this Report:

Pittman, S.J., S.D. Hile, C.F.G. Jeffrey, C. Caldow, M.S. Kendall, M.E. Monaco, and Z. Hillis-Starr. 2008. Fish assemblages 

and benthic habitats of Buck Island Reef National Monument (St. Croix, U.S. Virgin Islands) and the surrounding seascape: 

A characterization of spatial and temporal patterns. NOAA Technical Memorandum NOS NCCOS 71. Silver Spring, MD. 96 

pp.
Fish assemblages and benthic habitats of Buck Island Reef National 

Monument (St. Croix, U.S. Virgin Islands) and the surrounding seascape: 

A characterization of spatial and temporal patterns

Simon J Pittman1,2, Sarah D Hile1, Chris FG Jeffrey1, Chris Caldow1, Matt S Kendall1, 

Mark E Monaco1

 and Zandy Hillis-Starr3

1 NOAA/National Ocean Service/National Centers for Coastal Ocean Science/Center for Coastal Monitoring and 

Assessment/Biogeography Branch

2 Marine Science Center, University of the Virgin Islands, St. Thomas, U.S. Virgin Islands

3

National Park Service, St. Croix, U.S. Virgin Islands

Biogeography Branch

Center for Coastal Monitoring and Assessment (CCMA) 

NOAA/NOS/National Centers for Coastal Ocean Science

1305 East West Highway (SSMC-IV, N/SCI-1)

Silver Spring, MD 20910

NOAA Technical Memorandum NOS NCCOS 71

May 2008

United States Department of 

Commerce

National Oceanic and 

Atmospheric Administration

National Ocean Service

Carlos M Gutierrez

Secretary

Conrad C Lautenbacher, Jr.

Administrator

Jack Dunnigan

Assistant Administrator

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

About this Document

The report provides a spatial and temporal characterization of the fish and benthic communities of Buck Island Reef 

National Monument and the surrounding seascapes of northeastern St. Croix, United States Virgin Islands. The project is 

a component of NOAA’s Caribbean Coral Reef Ecosystem Monitoring (CREM) project of NOAA’s Coral Reef Conservation 

Program (CRCP) and the National Park Service (NPS). The project integrates field data on coral condition, living marine 

resources and benthic habitats through an ongoing multi-agency collaboration between NOAA’s Center for Coastal 

Monitoring and Assessment Biogeography Branch (CCMA-BB), NPS, U.S. Geological Survey and the Virgin Islands 

Department of Planning and Natural Resources (VI-DPNR).

This Technical Memorandum is part one of a series of reports that focus on providing a quantitative spatial and temporal 

characterization of living marine resources and benthic communities associated with marine protected areas in the U.S. 

Caribbean. This project complements the National Coral Reef Ecosystem Monitoring Program’s (NCREMP) Coral Reef 

Ecosystem Monitoring grants awarded to the VI-DPNR by CRCP. The integration of the NOAA/NPS lead efforts with data 

generated by VI-DPNR provides robust spatial and temporal data to characterize St. Croix coral reef ecosystems. This 

project was funded by NOAA’s CRCP and National Centers for Coastal Ocean Science’s CCMA and CSCOR, NPS’s 

Natural Resource Preservation Program (NRPP) at Buck Island Reef National Monument and NPS’s South Florida/

Caribbean Inventory and Monitoring Program.

Related projects include:

Caribbean Coral Reef Ecosystem Monitoring

http://ccmaserver.nos.noaa.gov/ecosystems/coralreef/reef_fish.html

Development of Reef Fish Monitoring Protocols to Support the National Park Service Inventory and Monitoring Program

http://ccmaserver.nos.noaa.gov/ecosystems/coralreef/fish_protocol.html

Coral bleaching and recovery observed at Buck Island, St. Croix, U.S. Virgin Islands, October and December, 2005

http://ccmaserver.nos.noaa.gov/ecosystems/coralreef/reef_fish.html

National Coral Reef Ecosystem Montoring Program

http://ccma.nos.noaa.gov/ecosystems/coralreef/coral_grant.html

Benthic Habitat Mapping of Puerto Rico and the U.S. Virgin Islands

http://ccma.nos.noaa.gov/ecosystems/coralreef/usvi_pr_mapping.html

Seafloor Characterization of the U.S. Caribbean - R/V Nancy Foster 

Missions

http://ccma.nos.noaa.gov/products/biogeography/usvi_nps/

overview.html

All photographs provided in this document were taken by NOAA/NOS/

NCCOS/Center for Coastal Monitoring Assessment Biogeography Branch 

in St. Croix, USVI unless otherwise indicated.
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. vi

Project Team

Richard Berey

Laurie Bauer (NCCOS CCMA)

Craig Bonn (NCCOS CCFHR Beaufort Lab)

Chris Caldow (NCCOS CCMA)

Don Catanzaro (NPS)

John Christensen (NCCOS CCMA)

Randy Clark (NCCOS CCMA)

Michael Coyne (NCCOS CCMA)

Kimberly Foley (NCCOS CCMA)

Alan Friedlander (NCCOS-CCMA)

Ricky Grober-Dunsmore (USGS)

Sarah Hile (NCCOS CCMA)

Zandy Hillis-Starr (NPS)

Chris Jeffrey (NCCOS CCMA)

Thomas Kelley (NPS)

Matt Kendall (NCCOS CCMA)

Ian Lundgren (NPS)

Philippe Mayor (NPS)

Tom McGrath (NCCOS CCMA)

Charles Menza (NCCOS CCMA)

Jeff Miller (NPS)

Wendy Morrison (NCCOS CCMA)

Mark Monaco (NCCOS CCMA)

Shelby Moneysmith (NPS)

Brenda-Lee Phillips (NPS)

Simon Pittman (NCCOS CCMA)

Caroline Rogers (USGS)

Paige Rothenberger (VI DPNR)

Carrie Stengel (NPS)

Henry E. Tonnemacher

Joel Tutein (NPS)

Rob Waara (NPS)

Jenny Waddell (NCCOS CCMA)

Kimberly Woody (NCCOS CCMA)
p. vii

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Executive Summary

Since 1999, NOAA’s Biogeography Branch of the Center for Coastal Monitoring and Assessment (CCMA-BB) has been 

working with federal and territorial partners to characterize, monitor, and assess the status of the marine environment 

around northeastern St. Croix, U.S. Virgin Islands. This effort is part of the broader NOAA Coral Reef Conservation 

Program’s (CRCP) National Coral Reef Ecosystem Monitoring Program (NCREMP). With support from CRCP’s 

NCREMP, CCMA conducts the “Caribbean Coral Reef Ecosystem Monitoring project” (CREM) with goals to: (1) spatially 

characterize and monitor the distribution, abundance, and size of marine fauna associated with shallow water coral reef 

seascapes (mosaics of coral reefs, seagrasses, sand and mangroves); (2) relate this information to in situ fine-scale 

habitat data and the spatial distribution and diversity of habitat types using benthic habitat maps; (3) use this information 

to establish the knowledge base necessary for enacting management decisions in a spatial setting; (4) establish the 

efficacy of those management decisions; and (5) develop data collection and data management protocols. The monitoring 

effort in northeastern St. Croix was conducted through partnerships with the National Park Service (NPS) and the Virgin 

Islands Department of Planning and Natural Resources (VI-DPNR). The geographical focal point of the research is Buck 

Island Reef National Monument (BIRNM), a protected area originally established in 1961 and greatly expanded in 2001; 

however, the work also encompassed a large portion of the recently created St. Croix East End Marine Park (EEMP). 

Project funding is primarily provided by NOAA CRCP, CCMA and NPS. 

In recent decades, scientific and non-scientific observations have indicated that the structure and function of the coral 

reef ecosystem around northeastern St. Croix have been adversely impacted by a wide range of environmental stressors. 

The major stressors have included the mass Diadema die off in the early 1980s, a series of hurricanes beginning with 

Hurricane Hugo in 1989, overfishing, mass mortality of Acropora corals due to disease and several coral bleaching events, 

with the most severe mass bleaching episode in 2005. The area is also an important recreational resource supporting 

boating, snorkeling, diving and other water based activities. With so many potential threats to the marine ecosystem and 

a dramatic change in management strategy in 2003 when the park’s Interim Regulations (Presidential Proclamation No. 

7392) established BIRNM as one of the first fully protected marine areas in NPS system, it became critical to identify 

existing marine fauna and their spatial distributions and temporal dynamics. This provides ecologically meaningful data to 

assess ecosystem condition, support decision making in spatial planning (including the evaluation of efficacy of current 

management strategies) and determine future information needs. The ultimate goal of the work is to better understand the 

coral reef ecosystems and to provide information toward protecting and enhancing coral reef ecosystems for the benefit of 

the system itself and to sustain the many goods and services that it offers society. This Technical Memorandum contains 

analysis of the first six years of fish survey data (2001-2006) and associated characterization of the benthos (1999-2006). 

The primary objectives were to quantify changes in fish species and assemblage diversity, abundance, biomass and 

size structure and to provide spatially explicit information on the distribution of key species or groups of species and to 

compare community structure inside (protected) versus outside (fished) areas of BIRNM.

Methods:

For each biannual survey mission, selection of sample sites occurred via a stratified random design (2001-2006) 

using hard and soft bottom habitat types delineated in NOAA’s benthic habitat map (Menza et al., 2006). In 2003, after 

implementation of the park’s Interim Regulations, sampling was also stratified by whether or not the site was located 

inside or outside BIRNM to evaluate effect of the fishing closure (only 2003 to 2006). Fish were surveyed during daylight 

hours along 25 m long by 4 m wide belt-transects for a fixed duration of 15 minutes. All species observed were identified 

to the lowest possible taxonomic level and their abundance was counted and grouped by size class. To quantify benthic 

habitat, five 1 m2

 quadrats were randomly placed on the transect and used to examine the relatively fine-scale biotic and 

abiotic components of the seascape (e.g., coral cover, macroalgal cover, etc.). In addition, Geographical Information 

System (GIS) tools were used to quantify the seascape surrounding each transect using habitat distributions represented 

in NOAA’s benthic habitat maps (e.g., amount of seagrass, number of habitat types, etc.).

Comparative analyses of biotic components inside versus outside BIRNM were conducted using a wide range of fish 

variables representing community, trophic, family and individual species level data incorporating measures of abundance, 

biomass and diversity. A total of 884 transects collected between 2003 and 2006 inclusively were used to examine 

differences in fish metrics inside versus outside BIRNM. Benthic comparisons used 716 benthic surveys on hardbottom 

habitat types conducted between 2001 and 2006. Abundance maps were used to examine species distributions for both 

juveniles and adults and interpolations of point data were used to examine broad-scale spatial patterns of fish and benthic 

habitat variables.

Major findings: 

Diversity hotspots

• Despite heavy impacts from disease, bleaching and hurricanes, the area around the eastern tip of Buck Island remains 

ecologically distinctive having some of the highest live coral cover and rugosity in the mapped region, also with high 

calcareous coralline algal cover, high fish species richness, biomass of herbivorous fish and high abundance for many 

common fish species.

Executive Summary
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. viiiExecutive Summary

• The linear reef (i.e., barrier reefs) and adjacent colonized pavement that extends east-west from Teague Bay to 

Coakley Bay and now falls within the EEMP “no-take zone” and “recreation zone” was found to support high coral 

species richness and fish species richness.

• Extensive areas with high coral species richness, high live coral cover for Montastraea cavernosa and M. annularis, 

high fish species richness and high abundance for several fish species including coney (Cephalopholis fulva), rock 

beauty (Holacanthus tricolor) and queen triggerfish (Balistes vetula) occurred along the northernmost edge of the 

benthic habitat map. This indicates that important deeper water habitat is likely to exist beyond the scope of this report, 

requiring further benthic habitat mapping effort combined with visual census (diver/remotely operated vehicle [ROV]) 

to capture data on fish communities (see Foster Mission web site: http://ccma.nos.noaa.gov/products/biogeography/

usvi_nps/overview.htm).

• Many of the coral reefs with highest fish species richness were within 200 m of seagrass beds. Several other studies 

have demonstrated links between fish distribution on coral reefs and proximity to seagrass beds suggesting that many 

species may benefit from complementary resources provided by seagrasses in close proximity to coral reefs. This 

highlights the importance of considering mosaics of habitat types in resource management decision making.

Benthic habitat

• The benthic environment inside BIRNM was significantly different to the outside for 75% of fine-scale variables quantified 

within 1 m2 quadrates and 78% of seascape variables quantified within 100 m2 radius seascape units surrounding each 

transect.

• Seventy-eight percent of the mapped area inside BIRNM was hardbottom habitat dominated by colonized pavement and 

22% was softbottom (sand and seagrasses); outside BIRNM, 46% was hardbottom and 54% softbottom. Seascapes 

inside BIRNM also had significantly higher mean habitat richness.

• Coral cover for all major scleractinian (hard coral) families was significantly higher inside BIRNM and coral reefs had 

a significantly higher ratio of live coral cover to macroalgal cover than outside BIRNM.

• Overall, hardbottom habitats of the study area were dominated by turf algae (37%) and macroalgae (11.4%), with 

mean scleractinian coral cover of only 5.6% ranging from 12.1% on patch reefs to 2% on the less rugose reef rubble.

• Across years (2003-2006), macroalgal cover showed some indication of decline both inside and outside BIRNM.

• Filamentous cyanobacteria/macroalgal blooms were detected in the fall sampling period with mean cover as high as 

18% in October 2005; a year with anomalously high summer water temperatures that also resulted in a mass coral 

bleaching event.

• Peaks in mean algal turf cover (50-60%) were detected in the spring (2006) season following the mass coral bleaching 

event and mean live coral cover approximately one year after the event was the lowest since this study commenced.

Fish

• A total of 201 fish species/species groups were identified from 56 families. Nine of the 10 most frequently encountered 

species belonged to the families Labridae (wrasse), Acanthuridae (surgeonfish) and Scaridae (parrotfish).

• The majority of the most abundant fish across the study region were found in highest densities over hardbottom habitat 

types, yet most also utilized multiple habitat types including seagrasses and sand.

• Fish metrics significantly higher on hardbottom habitat inside BIRNM included fish biomass (all fish combined), herbivore 

biomass, parrotfish biomass, shark and ray biomass, coney (C. fulva) density and biomass, blue tang (Acanthurus 

coeruleus) density and biomass, and striped parrotfish (Scarus iseri) biomass.

• Fish metrics significantly higher outside BIRNM included ecologically important predator groups such as piscivore 

biomass (including sharks and rays), snapper (Lutjanidae) density, and grunt (Haemulidae) density and biomass. 

• Red hind (Epinephelus guttatus) and coney (C. fulva) exhibited distinct patterns in spatial distributions, with high coney 

density mostly over the contiguous colonized hardbottom areas (much of which is inside BIRNM) and high densities of 

red hind found mostly to the south of Buck Island (many outside BIRNM).

• Very few of the largest (>35 cm) and very few of the smallest (<5 cm) size classes were observed for groupers 

(Serranidae) and snappers. Groupers and snappers in the largest size class (>35 cm) were recorded at <1% and 3%, 

of survey sites, respectively. 

• Body lengths of the largest individuals of several common groupers, snappers and grunts were less than the maximum 

size recorded for the species. The largest yellowtail snapper (Ocyurus chrysurus) was approximately 70% of the 

maximum known adult size, schoolmaster snapper (Lutjanus apodus) 66%, bluestriped grunt (Haemulon sciurus) 65-

76%, white grunt (H. plumierii) 56-66% and red hind (E. guttatus) 60% of known maximum size.

• Highest densities of threespot damselfish (Stegastes planifrons), a potential indicator of healthy reefs with high live 

coral cover, were found around the eastern tip of Buck Island within BIRNM and the fringing reef extending east-west 

along the northeast coast of St. Croix.
p. ix

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Historic and recent changes in fish populations

• Synoptic overview of inter-annual differences inside and outside BIRNM showed no consistent decline for any of the 

39 fish metrics inside BIRNM, but instead showed increases every year between 2003 and 2006 for mean fish density 

(all species combined). Densities in 2005 and 2006 were significantly higher than 2003. It is not yet clear if this has 

resulted from initiation of NPS Interim Regulations and enforcement patrols.

• No such increases were recorded outside BIRNM, instead considerable and consecutive inter-annual decline was 

apparent for grunt biomass, especially bluestriped grunt (H. sciurus), and density and biomass of stripped parrotfish 

(S. iseri). Densities in 2005 and 2006 were significantly lower than 2003.

• Only three Nassau grouper (Epinephelus striatus), three yellowfin grouper (Mycteroperca venenosa) and one tiger 

grouper (M. tigris) were observed in the study region over the course of six years of monitoring using 1,275 samples. 

Notably, these three species were completely absent from the Buck Island nearshore areas in 2001-2006, but were 

present in low abundance in 1979. These grouper species are highly vulnerable to fishing due to their large body 

size and relatively slow maturity and this historical difference in abundance indicates that the grouper have been 

overfished.

• In contrast, coney (C. fulva) and red hind (E. guttatus) were more abundant around Buck Island between 2001 and 

2006 than in 1979.

• Threespot damselfish (S. planifrons), a potential indicator of healthy reefs with high live coral cover, was more abundant 

around Buck Island in 1979 than in the 2001-2006 sampling period.

Macroinvertebrates

• Long-spined urchin densities (Diadema antillarum) around Buck Island have not recovered since the mass mortality in 

1983. However, this study and the scientific literature indicate that some minor recovery may be occurring in lagoonal 

and back reef areas along the sheltered coastline of northeastern St. Croix. Long-spined urchins were once important 

ecosystem engineers controlling the abundance of algae in the region and little is known about the factors (e.g, 

limitations to recruitment) that are controlling population recovery.

• Coral reef ecosystems of the study region, particularly the large expanse of seagrasses between Buck Island and St. 

Croix support regionally important populations of adult and juvenile queen conch (Strombus gigas). This is important 

since queen conch is an important food resource in the Virgin Islands and according to NOAA’s Office of Protected 

Species, queen conch is declining throughout the species’ range.

Recommendations:

Additional mapping, inventory and monitoring efforts are required to explore the deeper water ecosystems within the BIRNM 

that exist outside NOAA’s current benthic habitat map. In addition, acoustic tracking studies may reveal the mechanisms 

underlying some of the observed temporal changes in fish communities and will determine connectivity between lagoons 

and coral reefs offshore. Tracking will also provide important information on the time that individual fish spend inside and 

outside the boundaries of protected areas. Very little is known about the timing of movements during the daily home range, 

ontogenetic shifts and spawning migrations and spatial pathways for such movements for most species. Some targeted 

surveying for specific substrate types may be required to identify the extent of suitable settlement habitat for juvenile 

grouper in the study region or whether groupers are instead immigrating into the region from settlement habitat outside. 

Long-term monitoring is necessary to determine the magnitude of the apparent declines and to track the trajectory of 

recovery for species that exhibited an increase in density after several years of decline. Long-term monitoring effort may 

also reveal direction in the change for the many species that were too highly variable from year to year to provide such 

information over the four years of data used. Within the BIRNM-EEMP Marine Protected Area (MPA) complex, resource 

managers and stakeholders should examine the option of closing the gap between the southern boundary of BIRNM and 

the no-take zone of EEMP along the northeastern coast of St. Croix. An adjoining of the boundaries would incorporate 

an extensive area of seagrass habitat thus ensuring full protection of important complementary resources that provide 

food and habitat for many fish (both resident and transient species). These seagrass beds are also regionally important 

habitat for queen conch and may provide important resources for Caribbean spiny lobster. Further targeted surveys are 

required to assess and monitor the status of queen conch populations and to determine whether long-spined urchins are 

recovering. Such information will help to determine if management intervention is needed to assist recovery of sea urchin 

populations and to evaluate the conch fishery. Additional work to map the distribution of juvenile and adult Caribbean 

spiny lobster populations using existing survey data and to determine the factors that explain spatial distributions would 

be very valuable in supporting ecosystem-based management of marine resources in the region. Benthic habitat maps 

should be periodically updated due to the dynamic nature of coral reef ecosystems. This is particularly important when 

linking fish seascape structure and when assessing seascape change such as quantifying gain or loss of major habitat 

types.

Executive Summary
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. x
p. xi

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Contents

i Executive Summary

ii Table of Contents

iii List of Tables and Figures

1 Introduction of Study Area ................................................................................................................................1

1.1 Background ..........................................................................................................................................1

1.2 Environmental monitoring and ecosystem changes around Buck Island .............................................3

1.3 Benthic habitat mapping in the region ..................................................................................................4

2 Methods ..............................................................................................................................................................5

2.1 Field survey methods ............................................................................................................................5

 2.1.1 Benthic habitat surveys....................................................................................................5

 2.1.2 Fish surveys.....................................................................................................................6

 2.1.3 Macroinvertebrates count ................................................................................................7

 2.1.3 Observer training .............................................................................................................7

 2.1.4 Data management ...........................................................................................................7

2.2 Analyses ...............................................................................................................................................7

 2.2.1 Characterizing patterns in benthic habitat cover..............................................................7

 2.2.2 Characterizing patterns in fish species communities .......................................................9

 2.2.3 Comparison of fish densities and species presence between 1979 and 2001-2006 .......10

 2.2.4 Characterizing patterns in macroinvertebrate abundance ...............................................10

3 Results ................................................................................................................................................................11

3.1 Benthic habitat cover.............................................................................................................................11

 3.1.1 Characterization of colonized hardbottom areas..............................................................11

 3.1.2 Benthic cover inside and outside BIRNM .........................................................................13

 3.1.3 Spatial patterns in benthic cover ......................................................................................14

3.1.4 Seasonal and inter-annual patterns in benthic cover .......................................................19

 3.1.5 Mapping threatened Acropora spp. inside and outside BIRNM .......................................21

3.2 Fish communities, groups and species .................................................................................................23

 3.2.1 Fish community metrics....................................................................................................23

 3.2.2 Fish community composition ............................................................................................23

 3.2.3 Fish groups.......................................................................................................................23

 3.2.4 Individual species .............................................................................................................28

 3.2.5 Spatial distribution patterns and species-habitat associations .........................................31

 3.2.6 Fish size frequency distributions ......................................................................................41

 3.2.7 Comparison of fish densities and species presence between 1979 and 2001-2006 .......45

 3.2.8 Synoptic overview of inter-annual trends in mean fish metrics (2003-2006)....................45

 3.2.9 Seasonal and inter-annual patterns in fish community metrics ........................................49

 3.2.10 Seasonal and inter-annual patterns in fish groups and species.......................................51

3.3 Macroinvertebrate spatial distribution patterns and species-habitat associations ................................57

 3.3.1 queen conch (Stombus gigas)..........................................................................................57

 3.3.2 Long-spined urchin (Diadema antillarum) ........................................................................59

 3.3.3 Historical comparison of Diadema abundance.................................................................60

 3.3.4 Caribbean spiny lobster (Panulirus argus) .......................................................................60

4 Discussion .........................................................................................................................................................61

References ...................................................................................................................................................................67

Appendix A ..................................................................................................................................................................69

Appendix B ...................................................................................................................................................................70

Appendix C ..................................................................................................................................................................71

Appendix D ...................................................................................................................................................................76

Appendix E ...................................................................................................................................................................79

Acknowledgements......................................................................................................................................................80
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. xii

List of Tables

Table 1. Abiotic and biological variables measured to characterize benthic assemblages along fish transects

in St. Croix. ....................................................................................................................................................6

Table 2.. The number of hardbottom benthic habitat sites surveyed by mapped habitat type for the St. Croix 

study region as a whole and inside and outside of BIRNM. ..........................................................................7

Table 3 Number of hardbottom benthic habitat sites surveyed by mission and mapped habitat type. ......................8

Table 4. Length at first maturity estimates used to determine approximate size classes for juvenile/subadult

and adult fish. ................................................................................................................................................10

Table 5.. Mean estimates of percent cover of selected benthic groups inside and outside BIRNM. ............................13

Table 6 Comparison of coral species richness and ratio of coral to macroalgae in major habitats inside and 

outside BIRNM. .............................................................................................................................................13

Table 7.. Differences in seascape composition (amount and richness of habitat types) surrounding transects 

inside and outside BIRNM. ............................................................................................................................14

Table 8.. Results of ANOSIM test for significant difference in fish community composition using species 

biomass between samples grouped by habitat type. .....................................................................................25

Table 9.. Results of ANOSIM test for significant difference in fish community composition using species 

biomass between samples grouped by habitat type and management domain. ...........................................25

Table 10.. Twenty most frequently observed species in the CREM Buck Island survey area ........................................27

Table 11.. Summary information on selected species from five key fish families showing maximum size observed

in the study region (northeastern St. Croix) compared with maximum known size for the species and 

the proportion of juveniles found inside and outside BIRNM. ........................................................................41

Table 12.. Comparison of mean density for a range of key fish species from 1979 and 2001-2006 monitoring 

periods within 500 m surrounding Buck Island.. ............................................................................................45

Table 13.. Summary statistics (mean + SE) for a range of fish variables grouped by year (2003-2006) for the

 study region (northeastern St. Croix). ...........................................................................................................46

Table 14.. Summary statistics (mean + SE) for a range of fish variables grouped by year (2003-2006) inside 

BIRNM, northeastern St. Croix. .....................................................................................................................47

Table 15. Summary statistics (mean + SE) for a range of fish variables grouped by year (2003-2006) outside 

BIRNM, northeastern St. Croix. .....................................................................................................................48

Table 16. Spring and fall total abundance and mean (+ SE) density for the 20 most abundant fish species 

across northeastern St. Croix. .......................................................................................................................49

Table 17. Estimates of total queen conch abundance (number of individuals) by life stage for three islands in 

the U.S. Caribbean (2004-2006). ..................................................................................................................58

Table 18. Abundance of spiny lobster (Panulirus argus) in hard and soft habitats of the study region and inside 

and outside BIRNM (northeastern St. Croix) between 2003 and 2006. ........................................................60

Table 19. Life history characteristics and vulnerability to fishing for three large-bodied species and two smallerbodied species of grouper. ............................................................................................................................65

Table B1..USVI finfish landings as a proportion of the total finfish landings reported for the U.S. Caribbean in

1980. Listed are the most commonly landed species and species groups. ...................................................70

Table C1..Fish species list and summary data on occurrence, abundance and biomass (2001-2006) for the 

study region (northeastern St. Croix) .............................................................................................................71

List of Figures

Figure 1.. The island of St. Croix, USVI showing the distribution of surrounding nearshore habitat types using 

NOAA’s benthic habitat map and the administrative boundary of BIRNM. .................................................1

Figure 2.. Boundaries of the original BIRNM (1961) and the expanded boundary (2001). .........................................2

Figure 3.. Image of bleached coral at BIRNM (October 2005). A 1 m2 quadrat is shown for a scaling reference; 

and chronology of major broad-scale stressors to coral reef ecosystem structure and function in 

the Buck Island region, St. Croix since 1980. .............................................................................................2
p. xiii

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Figure 4.. Benthic habitat maps constructed for the Buck Island region since the 1960s; subset of Gladfelter 

et al. (1977); Anderson et al. (1986); and subset of CCMA-BB’s digital map using a 100 m2 MMU 

based on methods described by Kendall et al. (2002).................................................................................4

Figure 5.. Ship survey tracks and bathymetric data from NOAA’s acoustic multibeam seafloor mapping 

activities within and surrounding BIRNM. ...................................................................................................4

Figure 6.. NOAA benthic habitat map showing hard and softbottom habitat types inside and outside BIRNM. .........5

Figure 7. Images of NOAA trained observers recording fish species and benthic habitat composition. ....................5

Figure 8. A selection of habitat types designated in the hierarchical classification scheme of NOAA’s benthic

habitat map for the U.S. Caribbean . ...........................................................................................................6

Figure 9. Image of queen conch. ................................................................................................................................7

Figure 10. Seascape sample units of 100 m radius surrounding each fish transect used in a GIS to quantify 

variability in seascape composition. ............................................................................................................8

Figure 11. Percentage cover for key benthic components across hardbottom sites in the study region 

(northeastern St. Croix) from 2001-2006.....................................................................................................11

Figure 12. Percentage cover for key components of the benthic community across hardbottom habitat types

in the study region (northeastern St. Croix) between 2001 and 2006. .......................................................11

Figure 13.. Abundance of coral genera found across hardbottom sites in the study region (northeastern 

St. Croix) between 2001 and 2006. ............................................................................................................12

Figure 14.. Abundance of coral genera by hardbottom habitat type in the study region (northeastern St. Croix) 

between 2001 and 2006. ............................................................................................................................12

Figure 15.. Spatial distributions of benthic components at all transects in the study region (northeastern St. Croix) 

between 2001 and 2006 for percentage of live coral cover (hard coral including fire coral), number 

of coral species/groups and rugosity. .........................................................................................................15

Figure 16.. Spatial distributions of benthic components at all transects in the study region (northeastern St. Croix) 

between 2001 and 2006 for macroalgal cover, algal turf cover and coralline algal cover. ..........................16

Figure 17.. Spatial distributions of coral cover for individual coral species at all transects in the study region

(northeastern St. Croix): Diploria strigosa, Montastraea annularis and Montastraea cavernosa. ..............17

Figure 18.. Spatial distributions of coral cover for individual coral species at all transects in the study region

(northeastern St. Croix): Siderastrea siderea and Porites astreoides. ........................................................18

Figure 19. Seasonal and inter-annual patterns of live coral cover inside and outside BIRNM over a four year 

sampling period. ..........................................................................................................................................19

Figure 20. Seasonal and inter-annual patterns of marine plant cover inside and outside BIRNM over a four 

year sampling period. ..................................................................................................................................20

Figure 21. Images of the two types of Acropora species recorded in the study region (northeastern St. Croix)..........21

Figure 22. Spatial distribution of Acropora palmata and A. cervicornis in St. Croix, U.S. Virgin Islands. . ...................22

Figure 23. Comparison of mean (+ SE) values inside versus outside BIRNM for biomass of all species, biomass 

of all herbivores and biomass of all piscivores (including sharks and rays). ..............................................24

Figure 24. Comparison of mean (+ SE) values inside versus outside BIRNM for number of fish species, 

Shannon-Weiner diversity using abundance data and taxonomic diversity using 

presence-absence data. ..............................................................................................................................24

Figure 25.. Non-metric multidimensional ordination based on between site similarity in fish community 

composition using species biomass data for community similarities by habitat structure, dominant 

softbottom habitat type inside versus outside BIRNM and by dominant hardbottom habitat types 

inside versus outside BIRNM.......................................................................................................................25

Figure 26.. Comparison of mean (± SE) density and biomass inside versus outside BIRNM for grouper, grunt, 

snapper and parrotfish. ...............................................................................................................................26

Figure 27.. Comparison of mean (± SE) density and biomass inside versus outside BIRNM for sharks and rays........27

Figure 28.. Comparison of mean (± SE) density and biomass inside versus outside BIRNM for two grouper 

species: coney (C. fulva) and red hind (E. guttatus). ..................................................................................28

Figure 29.. Comparison of mean (± SE) density and biomass inside versus outside BIRNM for three snapper 

species: yellowtail snapper (O. chrysurus), schoolmaster (L. apodus) and gray snapper (L. griseus). ......29
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. xiv

Figure 30. Comparison of mean (± SE) density and biomass inside versus outside BIRNM for two grunt 

(Haemulidae) species: French grunt (H. flavolineatum) and bluestriped grunt (H. sciurus). .......................30

Figure 31. Comparison of mean (± SE) density and biomass inside versus outside BIRNM for three numerically

dominant herbivore species: blue tang (A. coeruleus), striped parrotfish (S. iseri), redband parrotfish

(S. aurofrenatum).........................................................................................................................................31

Figure 32. Interpolated spatial surfaces representing number of fish species, herbivorous fish biomass and 

piscivorous fish biomass. ...........................................................................................................................32

Figure 33. Spatial distributions of juvenile and adult coney (C. fulva) and red hind (E. guttatus) in northeastern 

St. Croix. .....................................................................................................................................................33

Figure 34.. Mean (+ SE) density for juvenile/subadult and adult by observer habitat type for coney (C. fulva)

 and red hind (E. guttatus). .........................................................................................................................34

Figure 35.. Spatial distribution of juvenile and adult for yellowtail snapper (O. chrysurus), schoolmaster 

(L. apodus) and gray snapper (L. griseus) in northeastern St. Croix. .........................................................35

Figure 36.. Mean (+ SE) density for juvenile/subadult and adult by observer habitat type for yellowtail snapper 

(O. chrysurus), schoolmaster (L. apodus) and gray snapper (L. griseus). ..................................................36

Figure 37.. Spatial distributions of juvenile and adult for French grunt (H. flavolineatum), bluestriped grunt 

(H. sciurus) and white grunt (H. plumierii) in northeastern St. Croix. ..........................................................37

Figure 38.. Mean (+ SE) density for juvenile/subadult and adult by observer habitat type for French grunt 

(H. flavolineatum), bluestriped grunt (H. sciurus) and white grunt (H. plumierii). .......................................38

Figure 39.. Spatial distributions of juvenile and adult for blue tang (A. coeruleus), ocean surgeonfish (A. bahianus), 

redband parrotfish (S. aurofrenatum) and striped parrotfish (S. iseri) in northeastern St. Croix. ...............39

Figure 40. Mean (± SE) density for juvenile/subadult and adult by observer habitat type for blue tang 

(A. coeruleus), ocean surgeonfish (A. bahianus), redband parrotfish (S. aurofrenatum) and striped 

parrotfish (S. iseri). ......................................................................................................................................40

Figure 41. Length frequency histogram for key fish families over hardbottom sites inside and outside BIRNM for 

grouper, snapper, grunts, parrotfish and surgeonfish. .................................................................................42

Figure 42.. Size class frequency histogram for selected fish species over hardbottom sites inside and outside 

BIRNM for coney (C. fulva), red hind (E. guttatus), yellowtail snapper (O. chrysurus), schoolmaster 

(L. apodus), French grunt (H. flavolineatum) and bluestriped grunt (H. sciurus). .......................................43

Figure 43.. Size class frequency histogram for selected fish species over hardbottom sites inside and outside 

BIRNM for blue tang (A. coeruleus), ocean surgeonfish (A. bahianus), redband parrotfish 

(S, aurofrenatum) and striped parrotfish (S. iseri). ......................................................................................44

Figure 44. Mean (+ SE) density for all species combined by sampling season for both inside and 

outside BIRNM.............................................................................................................................................49

Figure 45. Seasonal and inter-annual (2003-2006) change in mean (+ SE) fish biomass inside and 

outside BIRNM for all fish biomass, herbivorous fish biomass and piscivorous fish biomass. ...................50

Figure 46.. Seasonal and inter-annual (2003-2006) change in mean (+ SE) fish diversity inside and 

outside BIRNM. ...........................................................................................................................................51

Figure 47.. Seasonal and inter-annual (2003-2006) change in mean (+ SE) fish biomass inside and 

outside BIRNM for groupers, snappers, grunts and parrotfish. ..................................................................52

Figure 48.. Seasonal and inter-annual (2003-2006) change in mean (+ SE) fish biomass inside and 

outside BIRNM for coney (C. fulva) and red hind (E. guttatus)....................................................................53

Figure 49.. Seasonal and inter-annual (2003-2006) change in mean (+ SE) fish biomass inside and 

outside BIRNM for yellowtail snapper (O. chrysurus), (b) schoolmaster (L. apodus) and 

gray snapper (L. griseus). ...........................................................................................................................54

Figure 50.. Seasonal and inter-annual (2003-2006) change in mean (+ SE) fish biomass inside and 

outside BIRNM for French grunt (H. flavolineatum) and bluestriped grunt (H. sciurus). .............................55

Figure 51.. Seasonal and inter-annual (2003-2006) change in mean (+ SE) fish biomass inside and 

outside BIRNM for blue tang (A. coeruleus), redband parrotfish (S. aurofrenatum) and 

striped parrotfish (S. iseri). ..........................................................................................................................56

Figure 52.. Mean (± SE) density for juvenile and adult queen conch (S. gigas) by habitat type, and all queen 

conch inside and outside BIRNM by dominant habitat types in the study region (northeastern 

St. Croix) between 2004 and 2006. ............................................................................................................57
p. xv

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Figure 53.. Spatial distributions of juvenile (immature) and adult (mature) queen conch (S. gigas) density 

in the study region (northeastern St. Croix) between 2004 and 2006. .......................................................58

Figure 54. Sighting frequency of sexually immature, mature, and all queen conch from three study sites in the 

U.S. Caribbean: Southwest Puerto Rico; northeastern St. Croix and St. John. ..........................................58

Figure 55.. Spatial distribution of long-spined sea urchins (Diadema antillarum) in the study region 

(northeastern St. Croix) between 2005 and 2006. ......................................................................................59

Figure 56.. Mean (± SE) density for long-spined urchin (Diadema antillarum) by habitat type and inside 

and outside BIRNM (northeastern St. Croix) between 2005 and 2006. ......................................................59

Figure 57.. The changing abundance of Diadema antillarum in (a) the lagoon and on bank barrier coral reefs 

within 500 m of Buck Island and (b) Teague Bay and adjacent nearshore lagoonal environments 

showing little to no recovery in over two decades since mass mortality event............................................60

Figure A1. Map of the East End Marine Park and park zoning. ...................................................................................68

Figure D1. Spatial distributions of juvenile and adult for bluehead wrasse (T. bifasciatum), queen triggerfish

(B. vetula), rock beauty (H. tricolor) and slippery dick (H. bivittatus) in northeastern St. Croix ...................76

Figure D2. Spatial distributions of juvenile and adult princess parrotfish (S. taeniopterus) and stoplight 

parrotfish (S. viride) in northeastern St. Croix. ............................................................................................77

Figure D3. Spatial distributions of juvenile and adult threespot damselfish (Stegastes planifrons), foureye 

butterflyfish (Chaetodon capistratus), spotfin butterflyfish (Chaetodon ocellatus), banded butterflyfish 

(Chaetodon striatus) and great barracuda (Sphyraena barracuda) in northeastern St. Croix. ...................78

Figure E1. Raw census data grouped by year of survey for fish metrics that exhibited an increase or decline

 every year over the study period (2003-2006). ..........................................................................................79
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. xvi
1 - Introduction and Study Area

p. 1

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

1. Introduction and Study Area

1.1 Background

Buck Island Reef National Monument (BIRNM) is located on the northeastern shelf of St. Croix, in the U.S. Virgin Islands 

(USVI; Figure 1) and encompasses an uninhabited island of approximately 712,000 m2 and the surrounding mosaic of 

coral reefs, seagrasses and sand patches. The Monument is under the jurisdiction of the U.S. National Park Service 

(NPS) and was originally designated by the U.S. Department of Interior in 1961 according to Presidential Proclamation 

3443, in order to preserve the island and the surrounding submerged lands which at that time included “one of the finest 

marine gardens in the Caribbean Sea”. The original monument encompassed 880 acres (approximately 3.56 km2) and 

marine areas were zoned to form a protected “Marine Garden” (259 acres or approximately 1.04 km2), which included 

extensive stands of the now federally protected elkhorn coral (Acropora palmata) and an area with restricted fishing (445 

acres or approximately 1.8 km2; Figure 2a). The “Marine Garden” was one of the first “no-take” marine reserves in U.S. 

waters and in the Caribbean region. The boundaries were slightly modified in 1975 (Presidential Proclamation 4346), but 

it was not until 2001 that the monument was greatly expanded to 19,015 acres (approximately 77 km2) under Presidential 

Proclamation 7392 (Figure 2b). At that time, new regulations were enacted making the entire monument a no-take and 

“restricted anchoring” zone. The BIRNM expansion was the first substantial no-take area established for the island of St. 

Croix and it now protects about 7.4 percent of the St. Croix shelf area. The expansion resulted in a 10-fold increase in 

protection of shallow water (<30 m) hardbottom and sand habitat types and a seven-fold increase for seagrasses when 

compared with the 1961 Monument (Kendall et al., 2004a). In January 2003, BIRNM became contiguous with the East 

End Marine Park (EEMP) through the adjoining of the southern boundary of BIRNM and northern boundary of EEMP. 

However, over 80% of EEMP is open to fishing including an area that extends between the southern boundary of BIRNM 

and the EEMP no-take coastal lagoon zone (see zoning map in Appendix A). In April 2003, NPS implemented the Interim 

Regulations (36 CFR Part 7.73; Federal Register Volume 68, No. 65) and begun work on the General Management Plans 

for BIRNM.

Figure 1. The island of St. Croix, USVI showing the distribution of surrounding nearshore habitat types using NOAA’s benthic habitat 

map (Kendall et al., 2002) and the administrative boundary of BIRNM.

Study region

In recent decades, the ecological structure and function of coral reef ecosystems of the northeastern St. Croix study region 

have deteriorated dramatically due to a combination of stressors including fishing, anchor drops, excessive nutrient inputs, 

Diadema die-off, mass coral bleaching related to anomalous sea water temperatures, the emergence of widespread coral 

diseases and extensive hurricane damage (Bythell et al., 1993; Rogers and Beets, 2001). The enlarged monument now 

incorporates components of the marine ecosystem, which have been impacted by fishing of finfish, conch and lobster. 

Currently the expanded area is being illegally fished using hand and rod fishing, spear fishing, fish traps, gill or trammel 

nets, and long-lines in the deeper portions of the Monument. Law enforcement patrols have been active since 2003 and 

compliance is increasing. These deleterious environmental changes together with significant changes in management 

strategies, such as boundary expansion, require that the ecological patterns and processes characterizing the region be 

adequately inventoried, spatially characterized and continuously monitored to support the resource-management decisionmaking process. Knowledge of the current status of fish communities coupled with a spatially explicit understanding of the 

key resources and followed by a program of long term monitoring of fish and benthic communities will enable evaluation 

of management efficacy that is required to guide future management actions. In addition, comparison between managed 

versus unmanaged areas (e.g., inside and outside the protected area) allows managers to assess the impact, if any, of a 
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 2

Figure 2. (a) The boundaries of the original Buck Island Reef National Monument established in 1961 and (b) the expanded 

boundary established in 2001. Source: National Park Service, St. Croix.

change in regulation and evaluate the resources that are included or excluded from protection. This report represents an 

evaluation and characterization of fish and their habitat both inside and outside BIRNM and summarizes the first six years 

of long-term monitoring data collected using consistent survey methods and a stratified-random sampling design.

Providing park managers with scientifically validated evidence of reserve effectiveness or ineffectiveness is not only 

essential to informing resource management, it is critical to building public support for management plans. In response, 

NPS in partnership with NOAA’s Center for Coastal Monitoring and Assessment Biogeography Branch (CCMA-BB) 

initiated their Caribbean Coral Reef Ecosystem Monitoring (CREM) project at BIRNM in February 2001. In 2003, the U.S. 

Virgin Islands Department of Planning and Natural Resources joined this collaborative effort to monitor the broader region 

including the East End Marine Park (EEMP). This effort supports objectives of the NPS Inventory and Monitoring Program 

with an objective to “improve park management through greater reliance on scientific knowledge”, BIRNM is one of seven 

National Parks forming the NPS’s South Florida/Caribbean Network (NPS-SFCN) with special requirements for producing 

natural resource inventories and conducting ecosystem monitoring. This project provides data and data interpretation to 

meet NPS BIRNM Government Performance Results Act Goals pertinent to Threatened and Endangered Species Ia2A, 

Natural Resource Data Sets IB01 and Visitor Understanding IIb1 by providing new information on the condition of the 

monuments marine resources.

Figure 3. (a) Bleached coral at BIRNM (October 2005). A 1 m2 quadrat is shown for a scaling reference. (b) Chronology of major broadscale stressors to coral reef ecosystem structure and function in the Buck Island region, St. Croix since 1980.

a) b)

2005

2000

1995

1990

1985

1980

Hurricane Hugo

Fall 1989

} Diadema die-off, early 1980s

Mass Acroporid death

Coral diseases, early 1980s

Mass coral bleaching, Fall 1998

Hurricane Lenny, Fall 1999

Hurricane Marilyn, Fall 1995

Mass coral bleaching, Fall 2005

1 - Introduction and Study Area
p. 3

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

1.2 Environmental monitoring and ecosystem changes around Buck Island

Many marine ecological studies have been carried out in the region with long-term monitoring studies first conducted 

by scientists at the West Indies Laboratory (WIL) in the 1970s and a series of permanently marked sites for long-term 

monitoring of coral reef community structure and function initiated by the NPS in the 1980s. Results of early monitoring 

efforts have revealed some major changes, primarily in live coral cover and structure that have occurred across the region. 

Gladfelter et al. (1977) reported greater than 50% Acropora palmata on the reef crest of the north and south bank-barrier 

reefs and the northern forereef around Buck Island, but by 1984 large areas of dead A. palmata colonies encrusted with 

algae and gorgonians and other dead Acropora species (including A. cervicornis) were reported and were thought to have 

resulted from a mass mortality event caused by coral diseases such as white-band disease (Anderson et al., 1986). At the 

same time, the widespread die-off of Diadema antillarum sea urchins in the early 1980s, a key algal grazer and ecosystem 

engineer, altered the ecosystem dynamics on many shallow-water coral reefs in the region (Lessons et al., 1984). In 1989, 

Hurricane Hugo passed directly over the region with reported wind speeds of 260 kph. Bythell et al. (1993) and Rogers et 

al. (1982) resurveyed permanent transects and reported extensive localized damage with the southeast reef front razed 

to substrate level between the surface and 7 m depth and the reef crest behind it smothered in a 1 m deep layer of broken 

coral rubble. Although some coral had recovered by 1991, the community composition remained altered. In the 1990s the 

region was again impacted by hurricanes with Hurricane Marilyn in 1995 and Hurricane Lenny in 1999.

Extensive bleaching was observed at BIRNM in the fall of 1998 when water temperature reached a maximum of 29.9oC 

(Rogers and Beets, 2001). More recently, in 2005, CCMA-BB, NPS-SFCN and U.S. Geological Survey (USGS) scientists 

observed widespread coral bleaching around BIRNM, which was part of a mass bleaching event that occurred throughout 

the tropical western Atlantic (Clark et al., in press). During October 2005, over 90% of the coral was bleached at almost 

all NPS/USGS permanent monitoring sites (J. Miller, pers. comm.). Furthermore, bleaching was observed in 91 of 94 

randomly selected survey sites, with an estimated 53% of the coral cover bleached (Clark et al., in press; Figure 3). 

In addition, changes in the amount and spatial arrangement of seagrasses and sand habitat types has occurred in the 

BIRNM region, and have been reported in neighboring islands, yet are largely unquantified (but see Rogers and Beets, 

2001; Kendall et al., 2005). The chronology of major events resulting in deterioration of coral reef ecosystem structure and 

function in the St. Croix study region is depicted in Figure 4.

Various species of bleached coral. All photographs were taken during the October 2005 St. Croix mission.

Fish and fish communities respond to changes in their environment including habitat loss and extractive activities, such 

as fishing, but few historical monitoring surveys have focused on fish communities. Illegal commercial fishing has also 

been observed within BIRNM (NPS records). The Caribbean Fisheries Management Council (CFMC) reports that USVI 

fisheries target approximately 180 species of fish (64 species commonly caught), queen conch (Strombus gigas) and 

spiny lobster (Panulirus argus; CFMC, 1985; Appendix B).

1.3 Benthic habitat mapping in the region

In 1976, the first benthic habitat map was drawn by scientists at the WIL to depict the spatial distribution of marine habitat 

types around Buck Island using both quantitative and qualitative ground-truthing of aerial photographs (Gladfelter et al., 

1977; Figure 4a). Almost a decade later, Anderson et al. (1986) updated the original benthic habitat map using 1984 

ground-truthed aerial photographs (Figure 4b). In 1999, NOAA’s National Ocean Service acquired aerial photographs in 

order to create benthic habitat maps in response to a need to identify Essential Fish Habitat (EFH) in the U.S. Caribbean. 

CCMA-BB digitized benthic habitat for a 490 km2

 area of nearshore coral reef ecosystems in the USVI using a 1 acre 

1 - Introduction and Study Area
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 4

c)

a) b)

Figure 4. Benthic habitat maps constructed for Buck Island region since the 1960s. (a) Subset of Gladfelter et al. (1977); (b) Anderson 

et al. (1986); and (c) subset of CCMA-BB’ s digital map using a 100 m2 MMU based on methods described by Kendall et al. (2002).

(approximately 4,047 m2) minimum mapping 

unit (MMU). Thematic accuracy around the 

test area of BIRNM was assessed using 120 

stratified-random benthic surveys resulting in 

an overall map accuracy of 93.6%, with 100% 

users accuracy for submerged vegetation, 97.2% 

for hardbottom habitat types and 86.1% for 

sand (Kendall et al., 2002). Data and methods 

are available online: http://ccma.nos.noaa.gov/

products/biogeography/benthic/htm/data.htm

In addition, with an objective to study fishseascape relationships at a finer spatial scale, an 

area of approximately 50 km2 around Buck Island 

was also digitized to a spatial resolution of 100 m2

(Figure 4c).

In 2004, 2005 and 2006 CCMA-BB and NOAA’s 

Office of Coast Survey, in collaboration with NPS, 

USVI Territory and private sector partners, used 

multibeam sonar and underwater video to map 

bottom features (>20 m depth) and characterize 

nearshore benthic structure around BIRNM 

(Figure 5). These data are a component of the 

Seafloor Characterization of the Caribbean project 

supported by NOAA’s Coral Reef Conservation 

Program (CRCP) and are available online at http://

ccma.nos.noaa.gov/products/biogeography/

usvi_nps/overview.html. Data includes 5 m point 

data files, digital terrain models and mosaics of 

the acoustic backscatter. Figure 5. (a) Ship survey tracks and (b) bathymetric data from NOAA’s acoustic 

multibeam seafloor mapping activities within and surrounding BIRNM.

a)

b)

1 - Introduction and Study Area
2 - Methods

2. Methods

To assist in monitoring coral reef ecosystem 

resources and to achieve a better understanding 

of fish-habitat relationships in the U.S. Caribbean, 

CCMA-BB developed a fish and macroinvertebrate monitoring protocol to provide 

precise, fishery-independent and size-structured 

survey data, needed to comprehensively assess 

faunal populations and communities (Menza et 

al., 2006). In addition, a complementary benthic 

composition survey was also developed to support 

studies of fish-habitat relationships. These data 

collection activities and analytical products are 

core components of NOAA’s CRCP implemented 

through CCMA-BB’s CREM project. CREM 

protocols were created primarily to quantify longterm changes in fish species and assemblage 

diversity, abundance, biomass and size structure 

and to compare these metrics between areas 

inside and outside of Marine Protected Areas 

(MPAs). A stratified random sampling design was 

used to optimize the allocation of samples and 

allow rigorous inferences to the entire study area, 

as well as, the selected management domains 

(e.g., inside and outside BIRNM). Two strata were 

selected based upon: 1) the study objectives; 

2) parsimony in the approach; and 3) results 

from statistical analyses of variance (Menza 

et al., 2006). The “hard” stratum comprised 

bedrock, pavement, rubble and coral reefs. The 

“soft” stratum comprised sand, seagrasses and 

macroalgal beds. In 2003, NPS management 

domains were incorporated as a second level of spatial stratification and were designated as “inside” and “outside” 

BIRNM (Figure 6).

2.1 Field survey methods

This report uses underwater census data 

collected in March/April and October/

November each year from 2003 to 

2006. This data set is part of a broader 

ongoing monitoring study that began 

in year 2001, with over 1,300 transects 

surveyed thus far around BIRNM. There 

are two complementary components to the 

biological field methods: (1) benthic habitat 

composition surveys and (2) fish surveys.

2.1.1 Benthic habitat composition surveys

To conduct benthic habitat surveys, a second 

observer places a 1 m2

 quadrat divided into 

100 (10 x 10 cm) smaller squares (1 square 

= 1% cover) at five randomly pre-selected locations along the transect, such that a quadrat is placed once somewhere 

within every 5 m interval along the transect (Figure 7). Percent cover is estimated within the quadrat in a two-dimensional 

plane perpendicular to the observer’s line of vision.

Information recorded include:

1) Habitat structure (e.g., colonized hardbottom, spur and groove, patch reef, pavement) - based on the habitat types 

used in the benthic habitat maps (Kendall et al., 2002; Figure 8), until 2004, after which habitat structure was classified 

only to hard, soft and mangrove.

2) Abiotic footprint - defined as the percent cover (to the nearest 1%) of sand, rubble, hardbottom, fine sediments and 

other non-living bottom types within a 1 m2 quadrat. 

3) Biotic footprint - defined as the percent cover to the nearest 1% of algae, seagrass, upright sponges, gorgonians and 

other biota and to the nearest 0.1% for live, bleached and recently dead/diseased coral within a 1 m2 quadrat.

Figure 7. NOAA trained observers recording fish species abundance and body 

length along a 25 x 4 m timed 15 minute belt transect (left); and benthic habitat 

composition recorded within five randomly placed 1 m2

 quadrats along the belt 

transect (right).

p. 5

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Figure 6. NOAA’s benthic habitat map showing hard and softbottom habitat 

types both inside and outside BIRNM. Spatial information was used to identify 

strata within which to allocate random samples for CREM fish and benthic 

habitat composition surveys (figure adapted from Menza et al., 2006).
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 6

Figure 8. A selection of habitat types designated in the hierarchical classification scheme of NOAA’s benthic habitat map (Kendall et 

al., 2002) for the U.S. Caribbean (clockwise from left to right): colonized pavement, patch reef, scattered coral and/or rock, linear reef, 

seagrass and sand. 

4) Transect depth profile - the depth at each quadrat position. Depth is measured with a digital depth gauge and rounded 

up or down to the nearest foot.

5) Maximum canopy height - for each biota type, height of soft structure (e.g., gorgonians, upright sponges, seagrass, 

algae) structure is recorded to the nearest 1 cm.

6) Hardbottom rugosity - measured by placing a 6-m chain at two randomly selected start positions ensuring no overlap 

along the 25-m belt transect. The chain is placed such that it follows the relief along the centerline of the belt transect. 

Two divers measure the straight-line horizontal distance covered by the chain.

7) Proximity of structure - on seagrass and sand sites, the habitat diver records the absence or presence of reef or hard 

structure within 4 m of the belt transect. 

Table 1 provides a list of measured variables. 

The habitat observer also counts queen conch 

(Strombus gigas), long-spined sea urchins 

(Diadema antillarum) and Caribbean spiny lobster 

(Panulirus argus) Further information about 

macroinvertebrate data collection is described 

in section 2.1.3. Conch were counted separately 

as mature and immature animals based on lip 

thickness and shell size.

2.1.2 Fish surveys

Fish surveys were conducted along a 25 m long 

by 4 m wide belt (100 m2

) using a fixed survey 

duration of 15 minutes (Figure 7). The fixed 

duration of 15 minutes standardizes the samples 

collected to facilitate between site comparisons. 

The number of individuals per species is recorded 

in 5 cm size class increments up to 35 cm using 

the visual estimation of fork length. Individuals 

greater than 35 cm are recorded as an estimate of 

the actual fork length to the nearest centimeter.

Table 1. Abiotic and biological variables measured to characterize benthic 

assemblages along fish transects in St. Croix.

Benthic Biota

Measurements

% Cover Height (cm) Abund. (#)

Abiotic

Hardbottom X X

Sand X

Rubble X

Fine sediment X

Rugosity

Water depth

Biotic

Corals (by species) X

Macroalgae X X

Seagrass (by species) X X

Gorgonians

Sea rods, whips and plumes X X X

Sea fans X X X

Encrusting form X

Sponges

Barrel, tubes, vase morphology X X X

Encrusting morphology X

Other benthic macrofauna

Anemonies and hydroids X X

Tunicates and zoanthids X

Macro-invertebrates

queen conch (by sexual maturity) X

Spiny lobster X

Long-spined urchin X

2 - Methods
p. 7

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

2.1.3 Macroinvertebrates counts

Queen conch

The abundance of immature and mature queen conch (Strombus gigas) was assessed and quantified within the 25 x 4 

m belt transects used for fish surveys. The maturity of each conch was determined by the presence (mature) or absence 

(immature) of a flared lip (Figure 9). Conch was included in the survey protocol from 2004 onward.

Figure 9. Image of queen conch and 

location of flared lip.

Caribbean spiny lobster

Abundance of Caribbean spiny lobsters (Panulirus argus) are reported for the period 2003 to 

2006. Lobster sightings were recorded during fish and benthic composition surveys (i.e., within the 

100 m2

 survey unit area). Lobsters were recorded if seen, but without active searches of holes or 

crevices. 

Long-spined sea urchins

Long-spined sea urchins (Diadema antillarum) were also counted within the 25 x 4 m belt transect 

between 2004 and 2006. No measurements of size or estimates of maturity were collected.

2.1.4 Observer training

Observers were trained and tested in the identification of species/groups for both fish and habitat surveys by pairing 

inexperienced and experienced observers in the water and comparing data. Fish size estimation training was carried out 

in situ by estimating lengths of model fish of various shapes and sizes.

2.1.5 Data management

All fish and benthic habitat survey data were quality assessed before storage on an online relational database. All 

survey data were stored with a unique identification number and a geographical coordinate to facilitate spatial analyses. 

The database including metadata that provide detailed field methods are available at: http://ccmaserver.nos.noaa.gov/

ecosystems/coralreef/reef_fish/protocols.html.

2.2 Analyses

2.2.1 Characterizing patterns of benthic 

habitat cover

The benthic habitat section of the report 

provides summary data from 716 benthic 

in situ surveys (approximately 3,580 

quadrats) on hardbottom habitat types 

(e.g., linear reef, colonized pavement, 

patch reefs) around BIRNM and the 

northeastern shore of St. Croix between 

2001 and 2006 (Tables 2 and 3). The 

number of surveys conducted during any 

single mission was relatively low for the 

least abundant hardbottom habitat types 

(i.e., reef rubble and bedrock), but high for 

Table 2. The number of hardbottom benthic habitat sites surveyed by mapped habitat type for the St. Croix study region as a whole and inside and outside of BIRNM. 

Mapped habitat categories are from Kendall et al. (2002).

Mapped habitat types

Number of sites surveyed

Area (km2

) % Area Inside Outside Total

Bedrock 0.58 2% 13 14 27

Linear reef 1.56 5% 22 33 55

Patch reef 4.10 13% 98 4 102

Pavement 22.19 70% 274 199 473

Reef rubble / macroalgae 0.23 1% 2 4 6

Scattered coral and/or rock 3.22 10% 36 17 53

Total 31.88 100% 445 271 716

Flared lip 

of shell

2 - Methods
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 8

colonized pavement and patch reefs (Table 3). Although many benthic variables have been measured during the surveys, 

this report focuses primarily on the areal abundance (% cover) of the sessile biotic components (Table 1). In addition, we 

also compared habitat composition at a broader scale by quantifying the amount of each habitat type and the number 

of habitat types in the seascape surrounding each fish and benthic habitat survey site. These seascape variables were 

quantified within a 100 m radius buffer using a custom-built Geographical Information Systems (GIS) tool developed 

specifically for this project (Diversity Calculator for ArcGIS 9.2 is freely available at http://arcscripts.esri.com). Essentially, 

the buffer is analogous to a quadrat, but instead of quantifying percentage cover of fine-scale components such as coral 

cover we quantify the amount of habitat type from the benthic habitat map. The selection of a 100 m radial seascape 

sample unit was determined from a review of several studies that have identified the first 100 m surroundings as most 

influential in determining fish species distributions (Kendall et al., 2003; Pittman et al., 2007; Figure 10).

Differences in the abundance of individual components of the benthos inside versus outside BIRNM were tested using 

the parametric Tukey’s HSD (Honestly Significant Difference) pairwise comparison for normally distributed data and the 

nonparametric Wilcoxon test for non-normally distributed data. Broad spatial patterns in the benthic variables were determined 

from visual interpretation of mapped values and simple deterministic interpolations. Interpolations were performed using 

the Inverse Distance Weighting (IDW) interpolator 

with a relatively small neighborhood of samples 

(n=5 points) to create spatial surfaces within a 

GIS. This technique makes few assumptions of 

the data and estimates cell values by averaging 

sample points within a neighborhood. The values 

are distance weighted such that points closer to 

the center of a cell are assigned more weight in the 

averaging process. All data were used to construct 

surfaces including samples where the measured 

variable was recorded as zero. For marine algae, 

the entire surface is shown (e.g., both hard and 

softbottom areas) since spatial variability of algae 

across seagrasses may also be informative. For 

other biotic components, such as corals, softbottom 

areas were masked out of the interpolated surface 

since few corals exist in sand and seagrass beds. 

The intent was not to create detailed and accurate 

spatial predictions, but instead to show a spatially 

continuous representation of fine-scale point data 

to aid in interpretation of broad-scale distribution 

patterns. The spatial extent of all analyses in this 

report is limited to the mapped portions of the study 

area.

Figure 10. Seascape sample units of 100 m radius surrounding each fish 

transect were used in a GIS to quantify variability in seascape composition. 

In this example, it is clear that each seascape unit is characterized by very 

different patch type composition and patch richness.

Table 3. Number of hardbottom benthic habitat sites surveyed by mission and mapped habitat type. Mapped habitat categories are 

from Kendall et al. (2002).

Sample period Location Bedrock Linear reef Patch reef Pavement

Reef rubble/ 

Macroalgae

Scattered 

coral / rock Total

2001 Spring Inside 3 3 16 24 2 48

2001 Fall Inside 1 10 13 2 26

2002 Spring Inside 5 5 18 2 5 35

2002 Fall Inside 2 16 12 3 33

2003 Spring Inside 3 10 27 1 41

Outside 1 5 29 2 37

2003 Fall Inside 1 5 3 25 2 36

Outside 1 9 24 1 35

2004 Spring Inside 1 12 2 15

Outside 1 2 1 6 2 12

2004 Fall Inside 6 26 3 35

Outside 3 5 19 1 2 30

2005 Spring Inside 2 4 6 18 3 33

Outside 4 5 1 20 1 31

2005 Fall Inside 8 37 3 48

Outside 3 36 1 6 46

2006 Spring Inside 10 31 5 46

Outside 1 2 1 30 2 2 38

2006 Fall Inside 4 2 7 31 5 49

Outside 3 2 1 35 1 42

Total 27 55 102 473 6 53 716

2 - Methods
p. 9

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

2.2.2 Characterizing patterns in fish species and communities

Assessing differences in univariate metrics inside versus outside BIRNM

Differences in univariate community metrics as well as individual species/group metrics inside versus outside BIRNM 

were tested using parametric and nonparametric tests as appropriate. Only data for years 2003 to 2006 were examined 

because allocation of samples prior to 2003 occurred using different strata (n=431 inside BIRNM; 291 hardbottom and 

140 softbottom; n=453 outside BIRNM; 303 hardbottom and 150 softbottom). Designations of habitat type (colonized 

hardbottom, seagrasses and unvegetated sediments) were collected by benthic habitat observers.

Diversity was measured using the Shannon Index (H’; Equation 1). In this way, the diversity measure incorporates richness, 

commonness and rarity. Although, the Shannon Index has been shown to be an effective discriminator of community 

structure it is not independent of sample size (Magurran, 1988). Taxonomic indices, on the other hand are considered to 

be significantly less influenced by sample size than the conventional species richness, evenness and diversity indices 

(Warwick and Clarke, 1995) and, therefore, more appropriate for any comparative studies with unbalanced sampling effort 

(Clarke and Warwick, 1998).

Taxonomic indices

Samples may differ in the way assemblages are composed at the genus, family, order, class and phylum levels of the 

standard Linnean taxonomic hierarchy. For example, species diversity may be similar between two samples, yet one 

may support several species belonging to the same family, while the other may support several species, all belonging 

to different families and even different classes orders, etc. Quantitative taxonomic diversity indices therefore provide an 

additional dimension of information that is likely to be more closely linked to functional diversity (Clarke and Warwick, 

1999). The importance of this measure of diversity is that families, orders, etc. as opposed to species, represent a greater 

variety of fundamentally different body plans and life histories.

As such Taxonomic diversity (∆) (Warwick and Clarke, 1995; Equation 2) was measured for all samples. Fish were 

distinguished at four taxonomic levels: species, genus, family and class.

Samples were grouped by habitat type as determined by benthic habitat observers and by management domain as 

determined by the mapped strata (e.g., inside and outside BIRNM).

Assessing differences in community composition inside versus outside BIRNM

Differences and similarities in the species composition of communities between samples (often referred to as assemblage 

or community structure) were examined using a species biomass by site data matrix. Samples with zero fish were removed 

from the data matrix. Infrequently observed species, with extreme outlying biomass were removed, including smallbodied pelagic schooling fish (e.g., Clupeidae, Antherinidae, etc.) and large-bodied broad ranging species (e.g., sharks, 

rays, barracuda). Infrequently observed fish that were not identified to species level were also removed. The matrix was 

square-root transformed to ensure that intermediate biomass species, in addition to the high biomass species, played a 

significant role in determining patterns in community composition. The data was then used to construct a matrix of the 

percentage similarity in community composition between all pairs of sites using the Bray-Curtis Coefficient (Equation 3). 

H’ = - Si pi

 ( loge pi ) (Equation 1)

Where H’ is a weighted combination of: total number of species (richness) and the extent to which the total 

abundance is spread equally amongst the observed species (evenness). pi is the proportion of the total 

count arising from the ith species.

(Equation 2)

Letting xi denote the presence or absence of the ith species and the Wij the “distinctness weight” given to 

the path length linking species i and j in the hierarchical classification, then taxonomic diversity (D) is 

defined simply as the average (weighted) path length between every pair of individuals. The null second term 

in the numerator has been included to emphasize that the weight for the path linking individuals of the same 

species is taken to be zero.

D =

SSi<j Wij Xi Xj + Si 0. xi (xi -1) / 2

SSi<j xi xj + Si xi (xi -1) / 2

2 - Methods

(Equation 3)

Where xij is the abundance of the ith species in the jth sample and where there are n species overall.

S’jk = 1 - 

Sn Xij i=1 - Xik

Sn Xij + Xik i=1
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 10

This algorithm is considered a robust estimator of ecological distance and has had widespread usage in ecology particularly 

for comparison of biological data on community structure (Faith et al., 1987). Its robustness is in part due to its exclusion 

of double zeros, that is, if two samples are missing the same species, they will not be regarded as similar based on the 

same absentees (Legendre and Legendre, 1998). This similarity coefficient reduces the comparison between all pairs of 

samples to single numerical values that are arranged in a secondary matrix from which pattern is examined. Sample sites 

were assigned a factor representing a dominant habitat type (e.g., either colonized hardbottom, seagrasses or sand) and 

a management domain (e.g., inside or outside BIRNM). Factors were used to identify pairs of treatments in order to test 

for significant differences using Analysis of Similarities (ANOSIM), a multivariate version of Analysis of Variance (ANOVA; 

Primer v5; Clarke and Warwick, 1994), and for visual examination of patterns of between site similarity using a nonmetric dimensional scaling plot (nMDS). In addition, 

Similarity percentages (SIMPER) were calculated and 

used to identify the species which contributed most to 

the differences between treatments (Primer v5; Clarke 

and Warwick, 1994).

Where species groups were used, herbivores included 

all species that were important consumers of marine 

algae; piscivores included all fish that were important 

predators of fish; snapper included all Lutjanidae 

spp.; groupers included all commercially harvested 

Serranidae spp.; grunts included all Haemulidae. 

Juveniles/subadults were identified based on length at 

maturity information provided by García-Cagide et al. 

(1994) and FishBase (http://www.fishbase.org, version 

11/2007), whereby, juveniles/subadults were fish with 

lengths less than the mean length at maturity and the 

remainder were considered as adults (Table 4). If the 

mean length at maturity was 14 cm then size classes <5 

and 5-10 cm were considered juvenile/subadult. Where 

length at maturity was unknown, 1/3 of maximum adult 

size was used to segregate juveniles/subadults from 

adults. For mapping of juvenile and adult distribution 

all samples were used from 2001 to 2006.

2.2.3 Comparison of fish densities and species presence between 1979 and 2001-2006

Data on mean fish densities from visual surveys conducted between January and September 1979 (Gladfelter, 1980) 

were used for comparison with 2001-2006 data. The 1979 surveys were conducted during the day at five hardbottom 

sites (each one of 40 x 40 m2

) within 500 m of Buck Island. Each of the five sites received replicate surveys (North lagoon 

n= 30, SW lagoon n=30, NW leeward n=30, S forereef n=32, E forereef n=25) resulting in a total sample size of 147. 

These sites were not randomly located, but were selected to represent a variety of coral reef environments across a 

complexity gradient. Census involved swimming back and forth across the study site counting all fish observed. A mean 

density for each species of interest was calculated from pooled data on mean densities for each of the five plots and was 

standardized to 100 m2 for comparative purposes. To provide a comparison with similar environments using CCMA-BB 

survey data from 2001-2006, only fish transects conducted over hardbottom habitat types within 500 m of Buck Island 

were used. This resulted in a sample size of 184 spatially random samples. Differences in technique were clearly evident 

resulting in limitations when attempting to undertake direct comparison, yet data can be usefully compared for presence 

and absence of species and any large differences in density between the two time periods. 

2.2.4 Characterizing patterns in macroinvertebrate abundance

For Diadema antillarum (long-spined sea urchins) and Strombus gigas (queen conch) mean (±SE) density and summary 

statistics were calculated by habitat type using NOAA’s benthic habitat map. To examine spatial distribution patterns, 

density data was overlayed on the benthic habitat map. In addition, for queen conch only, mean (±SE) abundance of 

juvenile and adults were determined for three Caribbean islands based on the area weighted abundance for each benthic 

habitat type in which queen conch surveys were conducted. Data collected between 2004 and 2006 were pooled to allow 

an adequate sample size (n≥2) with which to calculate means within each habitat type. The following equation was used 

to calculate total abundance estimates for each queen conch life stage:

Table 4. Length at first maturity estimates used to determine approximate 

size classes for juvenile/subadult and adult fish. Estimates are derived 

from data held by FishBase (http://www.fishbase.org, version 11/2007).

Species

Mean length at first 

maturity, Lm (cm)

Juvenile/subadult 

size class (cm)

Acanthurus bahianus 15.5 <15

Acanthurus coeruleus unknown <10

Balistes vetula 25 <20

Cephalopholis fulva 16 <15

Epinephelus guttatus 25 <20

Halichoeres bivittatus unknown <10

Haemulon flavolineatum 16 <15

Haemulon plumierii 19 <15

Haemulon sciurus 18.5 <15

Holacanthus tricolor 17.4 <15

Lutjanus apodus 25 <20

Lutjanus griseus 31 <20

Ocyurus chrysurus 24.5 <20

Scarus iseri unknown <10

Sparisoma aurofrenatum unknown <10

Sparisoma viride 16.3 <15

Thalassoma bifasciatum unknown 0-5

A Xh

h

l

h

=

∑

1

2 - Methods

where A is the total area of each mapped habitat,  is the mean density (# of queen conch/m2

) in each habitat, and l is 

the total number of mapped habitats in each island. A sampling unit was a 25 x 4 m wide belt transect or a 100 m2 area. 
3 - Results

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Mean densities were derived from multiple surveys that occurred within each habitat type. A range of the total abundance 

was calculated with the equation:

A X S E h ( )

h

l

h

=

∑ ±

1

.

where SE is the standard error of the mean queen conch density in each mapped habitat in each island.

p. 11

3. Results

3.1 Benthic habitat cover

Colonized pavement was the 

most spatially extensive habitat 

type (70% of the study area) and 

was therefore most intensively 

surveyed, followed by patch reefs 

(13%) and linear reef (5%; Table 3). 

Hardbottom habitat types combined 

formed a larger proportion (78%) of 

BIRNM than did softbottom areas 

(22%). In contrast, outside BIRNM, 

softbottom habitat types formed a 

larger proportion (54%) of the total 

mapped area than hardbottom.

Estimates of percent cover (mean 

± standard error [SE]) of selected 

benthic organisms are reported 

for: (1) the entire study area for all 

habitat types; and (2) inside and 

outside BIRNM using only three of 

the most abundant habitat types 

(colonized hardbottom, seagrasses, 

sand sites). These comparisons 

at broader thematic resolution are 

intended to highlight any major 

differences between inside and 

outside the protected area.

3.1.1 Characterization of colonized 

hardbottom types

Generally, colonized hardbottom 

habitat types were dominated by 

algae (36.7% ± 1.1% turf algae, 

11.4% ± 0.5% macroalgae, and 

1.8% ± 0.2% crustose coralline algae 

[CCA]; Figure 11). Dictyota spp., 

Halimeda spp. and Sargassum spp. 

were most abundant. Cyanobacteria 

and filamentous algae were grouped 

as a single component and had a 

mean cover of 4.3% ± 0.5%. Mean 

live scleractinian coral cover was 

5.6% (± 0.5%) across the region. 

The mean percent cover of live 

scleractinian coral was highest on 

patch reefs (12.1% ± 1.3%; p<0.05) 

and lowest on reef rubble (2.0% ± 

0.8%) and scattered coral and rock 

sites (3.4% ± 0.7%; Figure 12). 

Figure 11. Percentage cover for key benthic components across hardbottom sites (n=716) in 

the study region (northeastern St. Croix) between 2001 and 2006. CCA= crustose coralline 

algae; CB and FA= cyanobacteria and filamentous algae.

Figure 12. Percentage cover for key components of the benthic community across hardbottom 

habitat types (n=716) in the study region (northeastern St. Croix) between 2001 and 2006. 
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Figure 13. Abundance of coral genera found across hardbottom sites in the study region 

(northeastern St. Croix) between 2001 and 2006.

p. 12

Figure 14. Abundance of coral genera by hardbottom habitat type in the study region 

(northeastern St. Croix) between 2001 and 2006.

3 - Results

Gorgonians were highest on colonized pavement and lowest on reef rubble sites. The percent cover of sponges and fire 

corals were similar among the habitat types surveyed (Figure 12).

Live scleractinian coral cover included at least 23 coral genera, but only nine with a mean cover greater than 0.01% (Figure 

13). The three most abundant coral genus were Diploria spp. (1.2% ± 0.29%), Montastraea spp. (1.0% ± 0.09%) and 

Porites spp. (0.9% ± 0.06%). Diploria spp. cover was highest on colonized bedrock, linear reef and colonized pavement; 

Montastraea spp., Porites spp. and Acropora spp. was highest on patch reef and linear reef habitat types (Figure 14). 
p. 13

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

3.1.2 Benthic cover inside and outside BIRNM

Benthic composition of the major habitat types (hardbottom, 

seagrass and unvegetated sediments) occurring inside 

BIRNM was significantly different from those found outside. 

Colonized hardbottom inside BIRNM had significantly higher 

percent cover of live coral than colonized hardbottom sites 

outside and slightly lower macroalgal cover (Table 5). The 

cover of living Acropora was an order of magnitude greater 

inside compared with outside and percent cover of living 

Montastraea and Diploria was more than twice as high 

inside than outside (Table 5). Gorgonians and sponges also 

had higher mean percent cover inside BIRNM compared 

with outside.

Fewer significant differences were observed in seagrass 

and sand habitats. Percent cover of CCA and gorgonians in 

seagrass habitats were higher inside BIRNM compared with 

outside, whereas percent cover of sponges and seagrass in 

seagrass habitats were higher outside BIRNM than inside. In 

areas mapped as sand, only sponges and seagrass showed 

significant inside versus outside differences. Both had higher 

percent cover outside BIRNM than inside (Table 5).

Mean coral species richness inside BIRNM was slightly 

higher than outside, but not significantly different (Table 

6). Colonized hardbottom habitat inside BIRNM had a 

significantly higher coral:macroalgal ratio compared with 

outside. This difference reflects the higher percent cover of 

coral and lower cover of macroalgae inside BIRNM relative 

to outside and suggests BIRNM may contain coral reefs in 

better condition than surrounding areas.

Furthermore, at a broader spatial scale of 100 m radius, 

benthic habitat composition surrounding survey transects 

were significantly different inside versus outside BIRNM 

for seven of 10 seascape variables (Table 7). The mean 

area of seagrass surrounding transects outside BIRNM 

was significantly higher than inside, while seascapes inside 

BIRNM had significantly higher habitat diversity, area of 

patch reefs, colonized pavement and area of sand.

3.1.3 Spatial patterns in benthic cover

Visual examination of an interpolated surface of live coral 

cover indicated that areas with higher live coral cover were 

more extensive inside BIRNM than outside. For instance, live 

coral cover between 15-50% existed outside BIRNM in only 

one relatively small area (southeast of Buck Island along 

the north shore of St. Croix), whereas several areas inside 

BIRNM had live coral ranging from 15-50% (Figure 15a). The 

eastern tip and northwest end of Buck Island had the largest 

areas with live coral cover exceeding 15%. These two areas 

were also the most topographically rugose (Figure 15c) in 

the region forming a mosaic of branching coral dominated 

patch reefs interspersed among a matrix of massive coral 

dominated colonized pavement. Furthermore, two small 

areas inside the BIRNM had live coral cover exceeding 50% 

(Figure 15a). The number of hard coral species groups were 

relatively evenly distributed inside and outside BIRNM, with 

several areas in both domains having 9-14 coral species 

(Figure 15b). Overall, the existing boundary of BIRNM 

encompassed the majority of the most topographically 

complex hardbottom habitat types, with intermediate to high 

coral cover relative to that of the study region.

Table 5. Mean estimates of percent cover of selected benthic 

groups inside and outside BIRNM. Asterisks (*) indicate significant 

differences (p<0.05). 

Mean percent cover (+ SE)

Habitat Benthic Taxa Inside Outside

Colonized n = 310 n = 292

hardbottom Live coral* 4.9 (0.3) 2.4 (0.2)

Acropora* 0.3 (0.1) 0.03 (0.02)

Montastraea* 1.0 (0.2) 0.5 (0.1)

Diploria* 1.8 (0.2) 0.6 (0.1)

Agaricia 0.2 (0.02) 0.2 (0.03)

Algae 51.9 (1.6) 53.6 (1.8)

Macroalgae* 14.5 (0.9) 15.7 (0.8)

Turf algae 35.7 (1.6) 36.8 (1.7)

Crustose algae 1.8 (0.3) 1.6 (0.2)

Gorgonians* 2.1 (0.2) 0.7 (0.08)

Sponge* 1.4 (0.2) 1.7 (0.1)

Seagrass* 0.3 (0.2) 1.4 (0.5)

Seagrass n = 55 n = 115

Live coral 0.5 (0.21) 0.19 (0.08)

Acropora 0 0

Montastraea 0.04 (0.03) 0.01 (0.01)

Diploria 0.32 (0.1) 0.06 (0.03)

Agaricia 0.01 (<0.01) 0.03 (0.02)

Algae 14.89 (3.4) 9.46 (1.6)

Macroalgae 6.92 (1.1) 5.73 (0.6)

Turf algae 7.52 (2.9) 3.3 (1.4)

Crustose algae* 0.45 (0.3) 0.44 (0.3)

Gorgonians* 0.14 (0.06) 0.04 (0.03)

Sponge* 0.07 (0.04) 0.26 (0.07)

Seagrass* 19.84 (2.9) 40.32 (2.7)

Unvegetated n = 67 n = 41

sediments

(sand)

Live coral 0.2 (0.1) 0.01 (<0.01)

Acropora 0 0

Montastraea 0.02 (0.02) 0

Diploria 0.12 (0.1) 0

Agaricia 0.04 (0.04) 0

Algae 4.1 (1.5) 2.1 (0.3)

Macroalgae 2.7 (0.7) 2.0 (0.3)

Turf algae 1.0 (0.5) 0.1 (0.1)

Crustose algae 0.44 (0.4) 0

Gorgonians 0.05 (0.05) 0

Sponge* 0.001 0.1 (0.05)

Seagrass 0.7 (0.16) 2.3 (1.7)

3 - Results

Table 6. Comparison of coral species richness and ratio of coral 

to macroalgae in major habitats inside and outside BIRNM. 

Asterisks (*) indicate significant differences (p<0.05).

Mean % cover (+ SE)

Variable Habitat type Inside Outside

n = 310 n = 292

Number of 

coral species

Colonized hardbottom 5.3 (0.2) 5.2 (0.2)

Seagrass 0.47 (0.16) 0.56 (0.13)

Unvegetated sediments 0.3 (0.1) 0.1 (0.06)

Coral : Macroalgae ratio

Colonized hardbottom* 2.4 (0.5) 0.6 (0.1)

Seagrass 0.04 (0.02) 0.04 (0.02)

Unvegetated sediments 0.04 (0.03) 0.01 (0.01)
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 14

Intermediate to high levels of macroalgal cover (>20-

95%) and algal turf was evident over a broad expanse of 

hardbottom area, both within and outside BIRNM (Figure 

16a,b). Particularly high macroalgal cover was evident 

at deeper water sites along the northern boundary of the 

mapped/unmapped area and a large region along the 

eastern boundary of the study region (Figure 16a). Most of 

the hardbottom habitat inside BIRNM supported a high cover 

of algal turf (>30-96%; Figure 16b). In contrast, fewer areas 

had crustose coralline algae exceeding 30% cover (Figure 

16c). These areas of high CCA cover were relatively localized 

and occurred mostly over colonized pavement within BIRNM 

north and east of Buck Island (Figure 16b). Given that CCA 

is known to facilitate settlement of coral larvae, the observed 

spatial distribution of CCA suggests that hardbottom areas 

inside BIRNM may have greater potential for coral settlement 

and recruitment than hardbottom areas outside BIRNM.

Although the study region had relatively low mean coral 

cover (approximately 5%; Table 2), interpolations of live cover for the five most abundant coral species show that several 

areas inside BIRNM had higher coral cover for some species in comparison with areas outside (Figures 17 and 18). Live 

cover of Diploria strigosa exceeded 5% in several areas inside BIRNM including two areas north of Buck Island which 

ranged between 10 and 26% (Figure 17a). Outside BIRNM, maximum live cover of Diploria strigosa was 10% in only one 

area along the eastern tip of St. Croix. The spatial distribution of Montastraea annularis was similar to that of D. strigosa. 

Three areas north and two areas east-southeast of Buck Island had live cover of M. annularis ranging from 15-33%, 

whereas live cover of M. annularis exceeded 15% in only one area outside BIRNM directly south of Buck Island (Figure 

17b). Live cover of Montastraea cavernosa exceeded 5% in two areas inside BIRNM: (1) east of Buck Island and (2) 

north-northeast of Buck Island toward the edge of the study area; and one area outside BIRNM, southeast of Buck Island 

toward Point Udal on the island of St. Croix (Figure 17c). The highest cover of Siderastrea siderea ranged from 5.1-9.7% 

in two areas: (1) inside BIRNM north east of Buck Island and (2) outside BIRNM directly south of Buck Island close to St. 

Croix (Figure 18a). The highest cover of Porites astreoides ranged from 5-7% in two areas inside BIRNM (east of Buck 

Island) and one area outside BIRNM southeast of Buck Island (Figure 18b).

Table 7. Differences in seascape composition (amount and 

richness of habitat types) surrounding transects inside and 

outside BIRNM. Seascape composition was quantified within 100 

m radius seascape units surrounding each fish transect using 

the NOAA benthic habitat map. Asterisks (*) indicate significant 

differences (p<0.05).

Habitat type

 Mean area m2 (+ SE)

Inside Outside

Colonized hardbottom* 17232 (419) 15351 (576)

Colonized pavement* 11495 (394) 9910 (574)

Patch reef* 1341 (108) 395 (64)

Linear reef 1802 (147) 1650 (208)

Reef rubble 296 (70) 382 (82)

Scattered coral and/or rock* 1776 (136) 3015 (259)

Seagrass* 5812 (329) 10674 (556)

Sand* 6532 (284) 4061 (373)

Number of habitat types* 3.5 (0.06) 2.6 (0.06)

3 - Results

Diploria strigosa colony
p. 15

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Figure 15. Spatial distributions of benthic components at all transects in the study region (northeastern St. Croix) between 2001 and 

2006. (a) Percentage live coral cover (hard coral including fire coral); (b) number of coral species/groups; and (c) rugosity. White areas 

inside the mapped region denote softbottom habitats (sand and seagrasses). Small hotspots of high coral cover area are encircled.

b)

c)

a)

3 - Results
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 16

Figure 16. Spatial distributions of benthic components at all transects in the study region (northeastern St. Croix) between 2001 and 

2006. (a) Macroalgal cover (including filamentous algae/cyanobacteria; (b) algal turf cover; and (c) crustose coralline algal cover.

b)

c)

a)

3 - Results
p. 17

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

a)

Figure 17. Spatial distributions of coral cover for individual coral species at all transects in the study region (northeastern St. Croix) 

between 2001 and 2006. (a) Diploria strigosa, (b) Montastraea annularis and (c) Montastraea cavernosa. White areas inside the 

mapped region denote softbottom habitats (sand and seagrasses). Small hotspots of high coral cover are encircled.

b)

c)

3 - Results
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 18

Figure 18. Spatial distributions of coral cover for individual coral species at all transects in the study region (northeastern St. Croix) 

between 2001 and 2006. (a) Siderastrea siderea and (b) Porites astreoides. White areas inside the mapped region denote softbottom 

habitats (sand and seagrasses). Small hotspots of high coral cover are encircled.

b)

a)

3 - Results
p. 19

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

3.1.4 Temporal patterns in benthic cover

Mean live coral cover was higher inside than outside 

BIRNM for all sampling seasons and years (Figure 19). 

A dramatic decline in live coral cover due to a mass coral 

bleaching event in October 2005 was recorded outside 

BIRNM during the October 2005 sampling season and 

the subsequent April 2006 and October 2006 seasons. 

The decline inside BIRNM was not detected until the 

following year (October 2006).

Examination of differences in mean values for selected 

dominant plant biota inside and outside BIRNM over 

eight field missions from 2003 to 2006 (e.g., since the 

sampling design included the two management domains) 

also revealed some distinct temporal trends. Mean 

macroalgal cover was higher outside BIRNM for six of 

eight sampling periods (Figure 20). Spring macroalgal 

cover declined in abundance from 2003 to 2006 both 

inside and outside BIRNM, but exhibit higher cover in 

the fall. Algal turf cover was generally lower in the fall 

than spring, yet appeared similar in abundance inside 

and outside across seasons and years (Figure 20). In 

contrast, filamentous cyanobacterial/algal cover was 

markedly higher in the fall than in spring and was highly 

variable across years with greatest abundance observed 

in October 2005 (Figure 20).

Further more detailed examination of temporal trends 

in benthic components will be the focus of a separate 

future report.

Inside BIRNM

Outside BIRNM

Figure 19. Seasonal and inter-annual patterns of live coral cover inside and outside BIRNM over a four year sampling period. Error bars 

indicate + SE.

Healthy coral Recently bleached coral Turf and filamentous algae over bleached coral

3 - Results
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 20

Inside BIRNM

Outside BIRNM

a)

b)

c)

Figure 20. Seasonal and inter-annual patterns of marine plant cover inside and outside BIRNM over a four year sampling period: (a) 

macroalgae, (b) filamentous algae/cyanobacteria and (c) algal turf. Fil. algal/cyano.= filamentous algal/cyanobacterial. Error bars indicate + SE.

3 - Results
p. 21

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

3.1.5 Mapping threatened Acropora species inside and outside BIRNM

Since 1980, populations of Acropora cervicornis (staghorn coral) and A. palmata (elkhorn coral) have declined by up to 

98% throughout their range and localized extirpations have occurred due to combinations of stressors including disease, 

hurricanes and coral bleaching (Figure 21). In BIRNM, white-band disease and several major hurricanes have reduced 

live elkhorn coral cover by over 80 percent since the 1970s and 1980s. In 1999, NOAA National Marine Fisheries Service 

(NMFS) added elkhorn coral to the candidate species-list of the Endangered Species Act (ESA), but it was not until May 

2006 that staghorn coral and elkhorn coral were formally listed as threatened species under the ESA. According to the 

Act, a species is considered endangered if it is in danger of extinction throughout all or a significant portion of its range 

or if it is likely to become an endangered species within the foreseeable future. In response to the designation, NMFS 

proposed in February 2008 to designate critical habitat areas for Acropora species throughout the U.S territories based 

on best available information on species distributions and habitat parameters (Federal Register 50 CFR Parts 223 and 

226, February 6, 2008). Critical habitat was defined by Section 3 of the ESA (and further by 50 CFR 424.02(d)) and is 

paraphrased here as: (i) specific areas essential to the conservation of the species; and (ii) areas which may require 

special management considerations or protection; and (iii) specific areas outside the geographical area occupied by the 

species that are determined essential for the conservation of the species.

Within the BIRNM, NPS staff identified 2,492 A. palmata colonies greater than 1 m in size at 455 of 617 random survey 

sites (Mayor, 2005). In addition, CCMA-BB documented the presence of A. palmata at 32 of 815 hardbottom sites within 

the BIRNM and at 11 of 430 sites within the EEMP. The distribution of A. palmata is almost entirely confined to relatively 

shallow waters (<12 m or approximately 35 ft) with most colonies observed in waters less than 10 m on the exposed 

seaward side of Buck Island within BIRNM. The presence and absence of A. palmata in the study region of northeastern 

St. Croix is shown in Figure 22. A. cervicornis is considerably rarer in the study region than was A. palmata. CCMA-BB 

CREM surveys recorded the presence of A. cervicornis at 12 of 815 hardbottom sites within the BIRNM and at two of 430 

sites within the EEMP, but they did not observe any colonies at 39 other sites visited in northeast St. Croix. In general, 

A. cervicornis has received much less attention by researchers than A. palmata, although for both species more data 

are required to adequately assess the distribution and occurrence of the species in the USVI. Due to the relatively well 

defined environmental conditions that support A. palmata establishment and growth (i.e., wave exposed shallow water 

hardbottom areas with good circulation and low exposure to sedimentation and fresh water incursions) it should be 

possible to develop predictive models that will help fill in the data gaps by providing species distribution maps.

Figure 21. Two types of Acropora species recorded in the study region (northeastern St. Croix): Acropora palmata (left) and A. 

cervicornis (right).

3 - Results
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 22

Figure 22. Spatial distribution of Acropora palmata (red circles) and A. cervicornis (yellow circles) in St. Croix, U.S. Virgin Islands. Open 

circles indicate survey sites where Acropora corals were not observed. Source of Data: Mayor (2005) and NOAA Biogeography Branch 

database http://www8.nos.noaa.gov/biogeo_public/query_main.aspx

3 - Results
p. 23

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Blue tang (A. coeruleus) and 

A. palmata

Bar jacks (C. ruber) Red hind (E. guttatus)

3.2 Fish communities, groups and species

3.2.1 Fish community metrics

Fish biomass over colonized hardbottom habitat was significantly higher inside BIRNM for all (1) fish species combined 

and (2) all herbivorous fish (Figure 23). In contrast, mean biomass of piscivorous fish was lower inside BIRNM for all 

habitat types, although only significantly so over unvegetated sandy sediments (Figure 23). No significant difference was 

detected between inside and outside BIRNM for fish biomass over seagrasses.

Fish diversity (number of species, Shannon diversity and Taxonomic diversity) was highest over colonized hardbottom 

and lowest over unvegetated sediments and no differences were found between inside and outside BIRNM (Figure 24). 

In the study area overall, however, more fish species/species groups have been observed inside BIRNM than outside 

(201 inside and 182 outside).

3.2.2 Fish community composition

nMDS plots and ANOSIM tests indicated that fish community composition between hard and soft habitat types was 

significantly different and well separated (Figure 25). Dissimilarities between sand and seagrasses were less distinct 

with considerable overlap (Table 8). Pairwise comparisons between the individual hardbottom habitat types revealed that 

fish communities were barely separable with substantial overlap. Highest dissimilarity existed between linear reefs and 

scattered coral. Fish community composition of aggregated patch reefs, linear reefs and colonized pavement were not 

significantly different (Table 8).

Much overlap was also found in fish community composition when also considering management domains. “R” values 

were very low (e.g., high similarity) when comparing the dominant softbottom habitat types inside versus outside BIRNM 

and even lower when comparing like hardbottom habitat types inside versus outside BIRNM (Figure 26 and Table 9). 

Although the null hypotheses of no difference was rejected (p=<0.05) for pairwise hardbottom habitat types, this is likely 

to be indicative of the high sample size rather than ecologically meaningful differences. The R value is a better relative 

indicator of the amount of dissimilarity between groups and is thus given greater emphasis here.

3.2.3 Fish groups

For all selected fish species groups and families (all Lutjanidae. [snapper], all Haemulidae. [grunts], all Scaridae [parrotfish], 

large-bodied Serranidae [groupers] species), mean density and biomass were highest on colonized hardbottom sites 

(Figure 26). Highest density and biomass were recorded for parrotfish. The most frequently observed species of parrotfish, 

with highest biomass were the redband parrotfish (Sparisoma aurofrenatum), the stoplight parrotfish (Sparisoma viride) 

and the striped parrotfish (Scarus iseri; Table 10). When management domains were considered, parrotfish exhibited 

significantly higher mean biomass inside BIRNM over colonized hardbottom.

Assemblage of Acanthuridae species

3 - Results
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 24

Inside BIRNM

Outside BIRNM

*

*

*

a)

b)

c)

Figure 23. Comparison of mean (+ SE) values inside versus 

outside BIRNM for: (a) biomass of all species; (b) biomass of 

all herbivores; and (c) biomass of all piscivores including sharks 

and rays. Asterisks (*) indicate a statistically significant difference 

between inside and outside.

Inside BIRNM

Outside BIRNM

a)

b)

c)

Figure 24. Comparison of mean (+ SE) values inside versus 

outside BIRNM for: (a) number of fish species; (b) ShannonWeiner diversity (H’) using abundance data; and (c) taxonomic 

diversity using presence-absence data. Asterisks (*) indicates a 

statistically significant (p=<0.05) difference between inside and 

outside.

3 - Results
p. 25

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Figure 25. Non-metric multidimensional ordination based on 

between site similarity in fish community composition using 

species biomass data. (a) Community similarities by habitat 

structure; (b) community similarities by dominant softbottom 

habitat type inside versus outside BIRNM; and (c) community 

similarities by dominant hardbottom habitat types inside versus 

outside BIRNM.

a)

b)

c)

Table 8. Results of ANOSIM test for significant difference in fish 

community composition using species biomass between samples 

grouped by habitat type. R<0.25 = barely separable; R<0.05 = 

overlapping, but clearly different. Asterisks (*) indicates null 

hypothesis of no difference rejected at p=<0.05. Agg= aggregated, 

Ind= individual.

Habitat pairs ANOSIM R

Between major habitat types

Global - all pairs* 0.80

Sand and Seagrass* 0.19

Sand and Colonized Hard* 0.83

Seagrass and Colonized Hard* 0.84

Amongst Colonized Hard

Global - all pairs* 0.19

Linear reef and Scattered coral/rock* 0.31

Colonized pavement and Patch reef (Ind)* 0.29

Colonized pavement and Linear reef* 0.18

Colonized pavement and Scattered coral/rock* 0.28

Patch reef (Agg) and Linear reef <0.01

Colonized pavement and Patch reef (Agg)* 0.13

Patch reef (Ind) and Linear reef* 0.14

Patch reef (Agg) and Scattered coral/rock* 0.17

Patch reef (Ind) and Scattered coral/rock* 0.11

Patch reef (Agg) and Patch reef (Ind) 0.04

Table 9. ANOSIM test for significant difference in fish community 

composition using species biomass between samples grouped 

by habitat type and management domain (inside/outside BIRNM). 

R<0.25 = barely separable; R<0.05 = overlapping, but clearly 

different. Asterisks (*) indicates null hypothesis of no difference 

rejected at p=<0.05.

Habitat pairs

ANOSIM 

R

Sand Inside and Sand Outside 0.06

Seagrass Inside and Seagrass Outside 0.07

Col. pavement Inside and Col. pavement Outside* 0.04

Patch reef Inside and Patch reef Outside 0.05

All colonized hard Inside and All Colonized hard Outside* 0.04

3 - Results

Grouper were almost entirely found over colonized hardbottom, with very few individuals over seagrasses (Figure 26). 

Neither mean density nor mean biomass were significantly different inside versus outside BIRNM. The most frequently 

observed species of grouper were the coney (Cephalopholis fulva) at 32.4% of transects, red hind (Epinephelus guttatus) 

at 18.1% of transects and graysby (Cephalopholis cruentata) at 4.2% of transects (Appendix C). All other species of 

large-bodied serranids were relatively rare within the surveyed region. For example, only one tiger grouper (Mycteroperca

tigris), three Nassau grouper (Epinephelus striatus) and three yellowfin grouper (Mycteroperca venenosa) were observed 

in 1,275 surveys over six years (Appendix C).
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 26

*

*

*

d)

Inside BIRNM

Outside BIRNM

*

*

a)

b)

c)

Figure 26. Comparison of mean (± SE) density and biomass inside versus outside BIRNM for: (a) grouper, (b) snapper, (c) grunt and 

(d) parrotfish. Asterisks (*) indicate a statistically significant difference between inside and outside.

3 - Results
p. 27

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Table 10. Twenty most frequently observed species in the CREM Buck Island survey area. For full species list see Appendix C. Fish 

surveys from http://ccmaserver.nos.noaa.gov/ecosystems/coralreef/reef_fish/protocols.html.

Species name Common name

Total 

occurrence

% 

occurrence

Total 

abundance

Mean 

abundance

(+ SE)

Total 

biomass, 

kg

Mean 

biomass, kg 

(+ SE)

Halichoeres bivittatus Slippery dick 933 73.2 24752 19.4 (1.8) 97.96 0.08 (<0.01)

Thalassoma bifasciatum Bluehead wrasse 777 60.9 32001 25.1 (1.2) 46.06 0.04 (<0.01)

Acanthurus bahianus Ocean surgeonfish 762 59.8 8601 6.7 (0.36) 540.37 0.42 (0.04)

Sparisoma aurofrenatum Redband parrotfish 669 52.5 4887 3.8 (0.18) 240.21 0.19 (0.01)

Stegastes partitus Bicolor damelfish 624 48.9 10202 8.0 (0.44) 17.76 0.01 (<0.01)

Acanthurus coeruleus Blue tang 595 46.7 8597 6.7 (0.65) 904.14 0.71 (0.08)

Halichoeres garnoti Yellowhead wrasse 586 46.0 4658 3.7 (0.19) 34.69 0.03 (<0.01)

Sparisoma viride Stoplight parrotfish 460 36.1 2456 1.9 (0.11) 331.90 0.26 (0.02)

Scarus iseri Striped parrotfish 434 34.0 4761 3.7 (0.28) 74.27 0.06 (<0.01)

Halichoeres maculipinna Clown wrasse 432 33.9 2176 1.7 (0.11) 10.19 0.01 (<0.01)

Cephalopholis fulva Coney 413 32.4 1391 1.1 (0.07) 193.13 0.15 (0.01)

Stegastes leucostictus Beaugregory 378 29.6 3991 3.1 (0.25) 12.88 0.01 (<0.01)

Carangoides ruber Bar jack 364 28.5 1735 1.4 (0.17) 57.87 0.05 (<0.01)

Haemulon flavolineatum French grunt 357 28.0 1944 1.5 (0.26) 107.19 0.08 (<0.01)

Serranus tigrinus Harlequin bass 349 27.4 713 0.56 (0.03) 5.55 0.00 (<0.01)

Holocentrus rufus Longspine squirrelfish 321 25.2 574 0.45 (0.03) 65.19 0.05 (<0.01)

Scarus taeniopterus Princess parrotfish 318 24.9 1713 1.3 (0.10) 72.30 0.06 (<0.01)

Coryphopterus glaucofraenum Bridled goby 302 23.7 1670 1.3 (0.11) 1.49 0.00 (<0.01)

Pseudupeneus maculatus Spotted goatfish 297 23.3 915 0.72 (0.08) 72.22 0.06 (<0.01)

Microspathodon chrysurus Yellowtail damselfish 272 21.3 1158 0.91 (0.08) 77.58 0.06 (<0.01)

Inside BIRNM

Outside BIRNM

Figure 27. Comparison of mean (± SE) density and biomass inside versus outside BIRNM for sharks and rays. Asterisks (*) indicate a 

statistically significant difference between inside and outside.

Yellowtail snapper (Ocyurus chrysurus) was the most commonly observed lutjanid recorded at 20.4% of transects; 

mahogany snapper (Lutjanus mahogoni) at 3.4% and schoolmaster snapper (Lutjanus apodus) at 3.3% (Appendix C). 

Thirteen species of grunt (Haemulidae) were identified, with French grunt (Haemulon flavolineatum) the most commonly 

observed at 28% of transects followed by bluestriped grunt (Haemulon sciurus) at 4.3% of transects and tomtate (Haemulon

aurolineatum) at 4.2% of transects (Appendix C).

Snapper and grunt density were higher outside BIRNM in all habitat types, although the difference was only statistically 

significant for colonized hardbottom. Mean biomass of snapper over colonized hardbottom and seagrasses was slightly 

higher inside BIRNM, but was not significantly different to the outside 

(Figure 26). Biomass of grunts, however, was significantly higher over 

colonized hardbottom outside BIRNM (Figure 26). Sharks and rays 

exhibited highest mean density and biomass over unvegetated sandy 

sediments (Figure 27). Although, only observed infrequently across 

the region, mean shark and ray density was higher over sand inside 

BIRNM than outside, but mean biomass was higher outside than inside 

BIRNM. None of the differences were significantly different. In total, 

40 rays were recorded: three spotted eagle rays (Aetobatus narinari), 

37 southern stingrays (Dasyatis americana), and nine nurse sharks 

(Ginglymostoma cirratum; Appendix C). Nurse shark (Ginglymostoma cirratum)

3 - Results
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 28

3.2.4 Individual species

In the northeastern St. Croix study region, 201 fish species from 56 families have been positively identified using visual 

census and underwater photography. A further 26 fish types were identified to family only. Only selected species are 

examined at the individual species level herein, including species of special interest to NPS, those that were potentially 

threatened by overfishing and those that were dominant components of the fish community across the region. 

Mean biomass for the two most abundant grouper species was higher inside BIRNM, with biomass and abundance of 

coney being significantly higher over colonized hardbottom habitat types inside (Figure 28).

None of the three most abundant snapper species were significantly different when comparing biomass and density 

inside versus outside BIRNM (Figure 29). Although not statistically significant, mean biomass of yellowtail snapper was 

markedly higher inside than outside, particularly over colonized hardbottom. Of note, was that yellowtail snapper were 

observed in all three major habitat types. In contrast, schoolmaster snapper and gray snapper (Lutjanus griseus) were 

found primarily over colonized hardbottom habitat types. 

In general, French grunt and bluestriped grunt density and biomass were higher outside BIRNM (Figure 30). This was 

statistically significant for French grunt biomass and bluestriped grunt density. Assessment of differences for grunt, 

however, is hampered by the fact that 3,419 grunts were identified only to family; primarily small juveniles that can be very 

similar in appearance between species.

For abundant herbivore species, blue tang (Acanthurus coeruleus) and striped parrotfish biomass were significantly 

higher inside BIRNM over colonized hardbottom (Figure 31). Redband parrotfish density and biomass was very similar 

inside and outside BIRNM. Comparatively few individuals of the abundant herbivores were observed over seagrasses or 

sand.

*

Inside BIRNM

Outside BIRNM

a)

b)

Figure 28. Comparison of mean (± SE) density and biomass inside versus outside BIRNM for two grouper species: (a) coney (C. fulva) 

and (b) red hind (E. guttatus). Asterisks (*) indicate a statistically significant difference between inside and outside.

3 - Results
p. 29

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Inside BIRNM

Outside BIRNM

a)

b)

c)

Figure 29. Comparison of mean (± SE) density and biomass inside versus outside BIRNM for three snapper species: (a) yellowtail 

snapper (O. chrysurus), (b) schoolmaster (L. apodus) and (c) gray snapper (L. griseus). Asterisks (*) indicate a statistically significant 

difference between inside and outside.

3 - Results
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 30

*

Inside BIRNM

Outside BIRNM

a)

b)

*

Figure 30. Comparison of mean (± SE) density and biomass inside versus outside BIRNM for two grunt (Haemulidae) species: (a) 

French grunt (H. flavolineatum) and (b) bluestriped grunt (H. sciurus). Asterisks (*) indicate a statistically significant difference between 

inside and outside.

French grunts (Haemulon flavolineatum)

3 - Results
p. 31

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Inside BIRNM

Outside BIRNM

a)

b)

c)

*

*

*

Figure 31. Comparison of mean (± SE) density and biomass inside versus outside BIRNM for three numerically dominant herbivore 

species: (a) blue tang (A. coeruleus), (b) striped parrotfish (S. iseri) and (c) redband parrotfish (S. aurofrenatum). Asterisks (*) indicate 

a statistically significant difference between inside and outside.

3.2.5 Spatial distribution patterns and species habitat associations

Twenty-five or more fish species were recorded at 100 sites, 62 of these high fish species richness sites were located 

within BIRNM and 38 were located outside BIRNM, but within 2 km of the current boundary. Fish species richness 

(number of species) hotspots were associated with shallow-water hardbottom habitat types and were located both within 

and outside BIRNM (Figure 32). The largest continuous area of high fish species richness existed around the eastern 

end of the Buck Island fringing reef comprising an interspersion of patches of linear reef, patch reef, colonized pavement 

and scattered coral. This included much of the area of the original “marine garden” zones. A second region of high fish 

species richness, however, also existed to the south of Buck Island immediately south of BIRNM, along the northern shore 

of St. Croix. This area comprised a similar range of hardbottom habitat types including linear reef, patch reef, colonized 

pavement and scattered coral, extending east to west alongside large expanses of seagrasses on both the north and 

south sides. Overlaying these high fish species richness sites on the NOAA benthic habitat map and measuring proximity 

3 - Results
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 32

Figure 32. Interpolated spatial surfaces representing (a) number of fish species; (b) herbivorous fish biomass; and (c) piscivorous fish 

biomass using 1,275 samples.

b)

c)

a)

3 - Results
p. 33

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Figure 33. Spatial distributions of juvenile and adult (a) coney (C. fulva) and (b) red hind (E. guttatus) in northeastern St. Croix.

from sampling point to nearest seagrass beds revealed that approximately 80% of all high (=>30 species) fish species 

richness sites on coral reefs were within 200 m of seagrass beds.

The spatial distribution of herbivore biomass as represented by interpolation of transect data revealed a distinctive area 

of high herbivore biomass over much of the hardbottom habitat in the region, but especially high at the eastern end of the 

Buck Island fringing reef and to the north of Buck Island over scattered coral and branching coral dominated pavement 

(Figure 32). Lowest herbivore biomass was over sand and seagrasses farthest from hardbottom, creating an interior effect 

in the spatial surface of herbivore biomass over softbottom habitat types. High herbivore biomass was also estimated for 

the coral reefs along the northern shore of St. Croix, south of Buck Island.

Piscivore biomass was biased toward high biomass hotspots created by sharks (e.g. large-bodied fish predators). 

Otherwise, no distinctive hotspots were seen. Large areas of low piscivore biomass existed around the north shore of 

Buck Island and at several inshore locations along the north shore of St. Croix (Figure 32).

Spatial distributions for juveniles and adults of specific fish species show some individualistic species-specific and lifestage specific patterns. Coney juveniles and adults were widespread across hardbottom habitats, with both utilizing 

similar habitat types (Figure 33). Highest mean density for juveniles and adults was recorded for the most structurally 

complex coral reef habitat types including colonized pavement (0.75 and 1.83/100 m2), linear reef (0.63 and 0.63/100 

m2) and aggregated patch reef (0.31 and 0.54/100 m2; Figure 34). Juveniles and adults also were observed over less 

rugose reef rubble (0.52 and 0.61/100 m2) and scattered coral and rock habitat types (0.45 and 0.53/100 m2). Very few 

coney were observed over seagrasses and sand (0 and <0.01/100 m2). Red hind were less abundant than coney over 

the large expanse of coral reef north of Buck Island, with distributions more closely associated with complex coral reef 

habitat types fringing Buck Island, and areas south and east of BIRNM (Figure 34). Highest mean density for adults was 

recorded for colonized pavement (0.31/100 m2), patch reefs (0.23/100 m2) and scattered coral and rock (0.19/100 m2). 

Juvenile densities were highest for colonized pavement (0.36/100 m2), scattered coral/rock (0.27/100 m2) and reef rubble 

(0.23/100 m2; Figure 34).

a)

b)

3 - Results
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 34

b)

a) Juveniles/Subadults

Adults

Figure 34. Mean (+ SE) density for juvenile/subadult and adult by observer habitat type for (a) 

coney (C. fulva) and (b) red hind (E. guttatus). 

3 - Results
p. 35

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Figure 35. Spatial distribution of juvenile and adult: (a) yellowtail snapper (O. chrysurus), (b) schoolmaster (L. apodus) and (c) gray 

snapper (L. griseus) in northeastern St. Croix.

a)

b)

c)

3 - Results

Juvenile yellowtail snapper were associated with all benthic habitat types, with highest mean density over patch reefs 

(0.94/100 m2) and seagrasses (0.88/100 m2). Spatially, juveniles were most abundant in shallow inshore waters around 

Buck Island and along the north coast of St. Croix outside BIRNM (Figure 35 and Figure 36). Adults used a similar range 

of habitat types, but were less frequently observed and occurred in lower densities. Highest adult densities were recorded 

for aggregated patch reefs (0.33/100 m2). Juvenile schoolmaster snapper and gray snapper were infrequently observed in 

the study region (Figure 36 and Appendix C). Adults were slightly more abundant than juveniles, but relatively localized in 

distribution to the north shore of Buck Island and several locations along the St. Croix shoreline (Figure 35). Schoolmaster 

snapper adults were observed in all hardbottom habitat types, with highest density in aggregated patch reefs (0.29/100 

m2

) and linear reefs (0.18/100 m2; Figure 36). Mean density of adult gray snapper was highest in patch reefs (0.01/100 

m2).
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 36

b)

a)

c)

Juveniles/Subadults

Adults

Figure 36. Mean (+ SE) density for juvenile/subadult and adult by observer habitat type 

for: (a) yellowtail snapper (O. chrysurus), (b) schoolmaster (L. apodus) and (c) gray 

snapper (L. griseus).

3 - Results
p. 37

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Figure 37. Spatial distributions of juvenile and adult: (a) French grunt (H. flavolineatum), (b) bluestriped grunt (H. sciurus) and (c) white 

grunt (H. plumierii) in northeastern St. Croix.

a)

b)

c)

3 - Results

French grunt were the most widely distributed of the haemulids (Figure 37), found in all hardbottom habitat types (Figure 

38). Similar habitat associations and spatial distributions were observed for both juveniles and adults, which exhibited 

highest densities over aggregated patch reefs (5.13 and 0.9/100 m2), patch reefs (3.1 and 1.4/100 m2), scattered coral/

rock (2.67 and 0.57/100 m2) and linear reef (2.60 and 1.08/100 m2). Highest occurrence was recorded around the 

shallow fringing mosaic of habitats surrounding Buck Island (Figure 37). The majority of bluestriped grunt and white grunt 

(Haemulon plumierii) were found either in close proximity to Buck Island or to the south of Buck Island in shallow water 

hardbottom habitats that exist in close proximity to seagrasses. Very few individuals were found in the northern portion 

of the mapped BIRNM (Figure 37). Highest densities of juvenile and adult bluestriped grunt (0.60 and 0.67/100 m2

) and 

white grunt (4.35 and 0.51/100 m2) were observed over patch reefs (Figure 38).
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 38

b)

a)

c)

Juveniles/Subadults

Adults

Figure 38. Mean (+ SE) density for juvenile/subadult and adult by observer habitat 

type for: (a) French grunt (H. flavolineatum), (b) bluestriped grunt (H. sciurus) and (c) 

white grunt (H. plumierii).

3 - Results
p. 39

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Figure 39. Spatial distributions of juvenile and adult: (a) blue tang (A. coeruleus), (b) ocean surgeonfish (A. bahianus), (c) redband 

parrotfish (S. aurofrenatum) and (d) striped parrotfish (S. iseri) in northeastern St. Croix.

a)

b)

c)

d)

3 - Results
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 40

Juvenile and adult blue tang, ocean surgeonfish (Acanthurus bahianus) and redband parrotfish were distributed widely 

across the study area, sharing the same habitat types (Figure 39 and Figure 40). Although present in all habitat types 

except macroalgal beds, highest densities of juvenile and adult blue tang were associated with structurally complex 

hardbottom habitats including aggregated patch reefs (4.08 and 17.88/100 m2), linear reef (3.56 and 20.04/100 m2) and 

patch reef (2.46 and 10.6/100 m2). Adult and juvenile ocean surgeonfish were also very widespread across hardbottom 

habitat types, with highest density of adults recorded for colonized pavement (3.49/100 m2) and aggregated patch reefs 

(3.3/100 m2) and highest density of juveniles was recorded for linear reef (12.86/100 m2), colonized pavement (7.79/100 

m2), aggregated patch reefs (5.21/100 m2), reef rubble (7.2 /100 m2) and scattered coral/rock (7.03/100 m2; Figure 40). 

Visual comparison of adult to juvenile ratios for the two acanthurids revealed that adult blue tang were more abundant 

than juveniles, while juvenile ocean surgeonfish were more abundant than adult ocean surgeonfish.

Highest densities of juvenile and adult redband parrotfish were associated with aggregated patch reef (6.83 and 2.72/100 

m2), linear reef (3.70 and 2.12/100 m2), patch reef (3.41 and 2.59/100 m2) and colonized pavement (3.50 and 2.38/100 m2; 

Figure 40). Juvenile and adult striped parrotfish were more restricted in distribution with highest densities of adults and 

juveniles close to Buck Island and also with high densities of juveniles along the nearshore fringing reef parallel to Teague 

Bay (Figure 39). Although observed in all habitat types, densities of juveniles and adults were highest over aggregated 

patch reef (11.64 and 3.06/100 m2), linear reef (9.47 and 1.59/100 m2) and patch reef (6.55 and 0.84/100 m2; Figure 40).

Spatial distributions for other species are shown in Appendix D.

a)

d)

b)

c)

Juveniles/Subadults

Adults

Figure 40. Mean (± SE) density for juvenile/subadult and adult by observer habitat type for: (a) blue tang (A. coeruleus), (b) ocean 

surgeonfish (A. bahianus), (c) redband parrotfish (S. aurofrenatum) and (d) striped parrotfish (S. iseri).

3 - Results
p. 41

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Table 11. Summary information on selected species from five key fish families showing maximum size observed in the study region 

(northeastern St. Croix) compared with maximum known size for the species and the proportion of juveniles found inside and outside 

BIRNM based on n=453 samples outside BIRNM and 431 inside BIRNM from 2003-2006. Maximum known fish size and size at first 

maturity are from FishBase (http://www.fishbase.org). TL= total length; FL= fork length

Species Common name

Approx. size 

class at first 

maturity*

Max. known 

size, TL

Max. size

 observed St. 

Croix, FL

% juveniles

Inside BIRNM Outside BIRNM

Serranidae

C. fulva Coney 15-20 41 30-35 35.1 35.2

E. guttatus Red hind 20-25 76 45 47.4 61.2

Lutjanidae

O. chrysurus Yellowtail snapper 20-25 86.3 60 56.6 81.4

L. apodus schoolmaster 20-25 67.2 45 35.3 22.9

Haemulidae

H. flavolineatum French grunt 15-20 30 30-35 65.7 73.4

H. plumierii White grunt 15-20 53 30-35 12.0 20.5

H. sciurus Bluestriped grunt 15-20 46 30-35 0.0 55.6

Acanthuridae

A. bahianus Ocean surgeonfish 15-20 38.1 30-35 73.8 77.8

A. chirurgus Doctorfish 10-15 39 25-30 33.2 38.6

A. coeruleus Blue tang 10-15 39 20-25 15.4 43.9

Scaridae

S. iseri Striped parrotfish 15-20 35 30-35 81.9 91.9

S. taeniopterus Princess parrotfish 15-20 35 30-35 50.3 64.2

S. aurofrenatum Redband parrotfish 15-20 28 30-35 64.7 63.9

S. viride Stoplight parrotfish 15-20 64 50 74.7 87.4

3 - Results

3.2.6 Fish size class frequency distributions and maximum lengths

The body lengths of the largest individuals of several common groupers, snappers and grunts observed in the study 

region were less than the maximum size recorded for the species (Table 11). For example, the largest red hind was 

approximately 60% of the maximum known adult size for that species. The largest yellowtail snapper was approximately 

70% of the maximum known, schoolmaster snapper 66%, white grunt 56-66%, and bluestriped grunt 65-76%. Even when 

factoring in the relatively small difference between fork length and total length these individuals were between 20-40% 

less than maximum size. In contrast, the longest parrotfish and surgeonfish were estimated at or near maximum size.

Size frequency distribution for all grouper species on hardbottom habitat types combined was approximately normal (e.g., 

a bell shaped distribution) both inside and outside BIRNM, with very few newly settled individuals (<5 cm FL) and very 

few large adults (>35 cm FL; Figure 41). Snappers exhibit a slightly flatter distribution slightly skewed towards a higher 

frequency of small and medium length fish. A higher frequency of large snapper were found inside BIRNM (Figure 41). 

Grunts and parrotfish exhibited a more strongly skewed size frequency distribution towards a higher frequency of the 

smallest size classes, this pattern was particularly strong for grunts outside BIRNM (Figure 41). Comparatively few large 

adults were observed either inside or outside BIRNM. Surgeonfish were more normally distributed inside BIRNM, with 

size frequency distribution outside skewed towards a higher frequency of smaller size classes.

At the species level, highest frequency of coney and red hind individuals occurred for subadults and small mature adults, 

with very few small juveniles or large adults. This pattern was similar to the size-frequency distribution for all grouper 

combined (Figure 42). Yellowtail snapper outside BIRNM showed a more skewed distribution than inside, with a higher 

frequency of juveniles and subadults and a greater decrease in frequency with larger size classes of subadults and 

adults (Figure 42). Schoolmaster snapper distribution was skewed in the opposite direction towards a higher frequency of 

small mature adults both inside and outside BIRNM. Very low frequency of the smallest juvenile (<5 cm) or largest adult 

(>35) schoolmaster snapper were recorded in the study area (Figure 42). French grunt and bluestriped grunt exhibited 

very different distributions inside versus outside BIRNM, with French grunt slightly skewed towards higher frequency of 

large juveniles and subadults inside BIRNM and towards higher frequency of small juveniles outside (Figure 42). Overall, 

blue tang and ocean surgeonfish showed similar near-normal size class distributions. Bluestriped grunt exhibited higher 

frequency of mature adults inside and higher frequency of juveniles and subadults outside.

Blue tang exhibit a peak in frequency for small adults and ocean surgeonfish exhibit a peak for subadults (Figure 43). 

In contrast, redband parrotfish and striped parrotfish showed a strongly skewed distribution, with high frequency of the 

smallest juveniles (<5 cm) and gradual decline with size with very few of the largest adults (Figure 43). Similar patterns 

existed for populations inside and outside BIRNM.
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 42

Inside BIRNM

Outside BIRNM

e) surgeonfish

c) grunts d) parrotfish

a) grouper b) snapper

Figure 41. Length frequency histograms for key fish families over hardbottom sites inside and outside BIRNM: (a) grouper, (b) snapper, 

(c) grunts, (d) parrotfish and (e) surgeonfish.

3 - Results
p. 43

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

a) coney Inside BIRNM

Outside BIRNM

c) yellowtail snapper

e) French grunt

b) red hind

d) schoolmaster

f) bluestriped grunt

Figure 42. Size class frequency histogram for selected fish species over hardbottom sites inside and outside BIRNM. (a) Coney (C. 

fulva), (b) red hind (E. guttatus), (c) yellowtail snapper (O. chrysurus), (d) schoolmaster (L. apodus), (e) French grunt (H. flavolineatum) 

and (f) bluestriped grunt (H. sciurus).

3 - Results
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 44

Inside BIRNM

Outside BIRNM

c) redband parrotfish d) striped parrotfish

a) blue tang b) ocean surgeonfish

Figure 43. Size class frequency histogram for selected fish species over hardbottom sites inside and outside BIRNM. (a) Blue tang (A. 

coeruleus), (b) ocean surgeonfish (A. bahianus), (c) redband parrotfish (S. aurofrenatum), and (d) striped parrotfish (S. iseri).

3.2.7 Comparison of fish densities and species presence between 1979 and 2001-2006

The most conspicuous difference between fish surveyed in 1979 and those surveyed from the same general area (within 

500 m of Buck Island) over two decades later was the absence of Nassau grouper (E. striatus), tiger grouper (M. tigris) 

and yellowfin grouper (M. venenosa) from the 2001-2006 data (Table 12). In contrast, smaller species of grouper such as 

red hind (E. guttatus) and coney (C. fulva) had increased in density since 1979. Overall, parrotfish also have increased 

in density since 1979 as have French grunt (Haemulon flavolineatum) and white grunt (H. plumierii), but not bluestriped 

grunt (H. sciurus). Snappers showed very mixed differences between the two survey periods, with a decrease in schoolmaster snapper (L. apodus) and mahogany snapper (L. mahogoni) and an increase in yellowtail snapper (O. chrysurus) 

and mutton snapper (Lutjanus analis; Table 12 ). Other commercially targeted species such as queen triggerfish (Balistes 

vetula), spotted goatfish (Pseudupeneus maculatus), yellow goatfish (Mulloidichthys martinicus) and bar jacks (Carangoides ruber) also increased since 1979. Threespot damselfish (Stegastes planifrons), a potential indicator of live coral 

cover, was substantially lower in 2001-2006 than in 1979.

3 - Results

Fish assemblages around dead Acropora palmata and 

Millepora colony
p. 45

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Table 12. Comparison of mean density for a range of key fish species from 1979 (n=147) 

and 2001-2006 (n=184) monitoring periods within 500 m surrounding Buck Island. Source: 

Gladfelter and Gladfelter, 1980; CCMA-BB reef fish database

Species

Mean density 1979 Mean density 2001-2006 

Change /100m2 /100m2

Serranidae

Epinephelus striatus 0.01 Absent -0.01

Epinephelus guttatus 0.08 0.18 +0.1

Mycteroperca venenosa 0.001 Absent -0.001

Mycteroperca tigris 0.02 Absent -0.02

Cephalopholis. fulva 0.01 0.30 +0.3

Lutjanidae

Lutjanus apodus 0.28 0.16 -0.12

Lutjanus griseus 0.01 0.08 +0.07

Ocyurus chrysurus 0.17 0.24 +0.07

Lutjanus mahogoni 0.33 0.29 -0.04

Lutjanus analis 0.004 0.06 +0.06

Haemulidae

Haemulon flavolineatum 2.49 2.89 +0.4

Haemulon sciurus 0.28 0.14 -0.14

Haemulon plumierii 0.21 0.22 +0.01

Scaridae

Scarus vetula 0.38 1.21 +0.83

Sparisoma aurofrenatum 0.23 1.50 +1.27

Sparisoma viride 0.92 0.79 -0.13

Scarus guacamaia 0.01 0.07 +0.06

Sparisoma rubripinne 0.13 0.24 +0.11

Other

Stegastes planifrons 4.09 2.18 -1.19

Balistes vetula 0.01 0.02 +0.01

Carangoides ruber 1.12 2.07 +0.95

Mulloidichthys martinicus 0.53 0.98 +0.45

Pseudupeneus maculatus 0.13 0.44 +0.31

3 - Results

3.2.8 Synoptic overview of inter-annual trends in mean fish metrics (2003-2006)

Presented here is a synoptic overview of inter-annual changes in summary statistics (mean and SE) for 39 fish metrics 

at the level of species, family, trophic group and community using data from both the whole study area and inside and 

outside BIRNM separately. The intention is to assist in highlighting potential trends that may be emerging even within the 

relatively short term monitoring data currently available. The synopsis is presented for: (1) the entire study area; (2) inside 

BIRNM; and (3) outside BIRNM.

Study area

Across the entire study area, mean biomass of bluestriped grunt, density of striped parrotfish and biomass of yellowtail 

snapper exhibited a year after year decline across three consecutive years (Table 13). Striped parrotfish density and 

bluestriped grunt biomass was significantly (p=<0.01) lower in 2003 than 2006. Although mean yellowtail snapper 

biomass declined over the study period too the difference was not significant. In contrast, mean herbivore density and 

biomass of redband parrotfish increased year after year across three consecutive years, with 2003 significantly higher 

than 2006. Other metrics were less consistent in the directionality of change. For instance, five metrics exhibited at least 

two consecutive years of increase, 15 exhibited at least two consecutive years of decrease and 19 showed no distinctive 

direction in inter-annual change (Table 13).

Inside BIRNM

Inside BIRNM, no metric exhibited three consecutive years of decline. Declines for at least two consecutive years, however, 

were documented for coney biomass, gray snapper density and biomass, all grunt density and biomass including French 

grunt density and biomass. In contrast, year after year increases for three consecutive years were documented for fish 

density (all species combined), with 2005 and 2006 density significantly higher than 2003 (Table 14 and Appendix E). 

Parrotfish biomass was also higher but not significantly (p=>0.05) different between years. In addition, increases inside 

BIRNM for at least two consecutive years were documented for herbivore density, parrotfish biomass, including redband 

parrotfish biomass and striped parrotfish biomass. Red hind density and all snapper density also increased. Overall, 

seven metrics exhibited at least two years of consecutive decline, seven exhibited increases and 25 showed no clear 

directionality (Table 14).
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 46

Table 13. Summary statistics (mean + SE) for a range of fish variables grouped by year (2003-2006) for the study region (northeastern 

St. Croix). Blue arrow = two consecutive years of increase; Orange arrows = two consecutive years of decrease. Double arrows indicate three consecutive years. Multidirectional change is indicated by the label “variable”.

Fish variable

2003 2004 2005 2006

Mean SE Mean SE Mean SE Mean SE Change

Community metrics

Number of species 14.2 0.5 13.4 0.6 14.2 0.5 14.4 0.4

Shannon diversity 1.8 0.04 1.7 0.05 1.8 0.04 1.8 0.0 Variable

Taxonomic diversity (pres/abs) 57.4 0.7 57.4 0.8 58.0 0.7 59.6 0.7

Density (all species combined) 115.5 5.8 115.2 7.4 132.9 6.7 148.8 7.6

Biomass 4371.1 497.8 5705.6 704.7 3444.7 273.1 5160.3 476.8 Variable

Herbivore density 44.8 2.6 45.1 3.7 53.7 3.3 56.2 3.6

Herbivore biomass 1773.5 206.1 3156.7 582.7 1806.5 182.0 2326.6 358.7 Variable

Piscivore density 4.5 0.5 4.3 1.2 4.0 0.4 5.5 0.7

Piscivore biomass 1015.9 162.7 1044.7 288.7 759.0 167.2 1173.5 231.9 Variable

Serranidae

Grouper density 1.5 0.2 0.9 0.1 1.9 0.2 1.8 0.2 Variable

Grouper biomass 317.0 68.2 243.9 42.6 219.6 30.8 263.6 28.1

Coney (C. fulva) density 1.2 0.2 0.7 0.1 1.5 0.2 1.4 0.1 Variable

Coney (C. fulva) biomass 231.3 63.3 173.8 35.4 131.0 20.5 175.3 22.3

Red hind (E. guttatus) density 0.2 0.05 0.2 0.0 0.4 0.1 0.4 0.1 Variable

Red hind (E. guttatus) biomass 79.5 15.2 59.6 21.9 75.2 18.1 77.1 13.7 Variable

Lutjanidae

Snapper density 0.9 0.2 0.7 0.1 0.6 0.1 1.2 0.3

Snapper biomass 193.2 47.0 198.8 71.3 136.4 30.6 195.5 50.8 Variable

Yellowtail snapper (O. chrysurus) density 0.7 0.2 0.4 0.1 0.5 0.1 0.8 0.2 Variable

Yellowtail snapper (O. chrysurus) biomass 77.0 16.1 57.6 21.2 50.1 18.7 48.7 9.9

Schoolmaster snapper (L. apodus) density 0.1 0.0 0.09 0.05 0.04 0.01 0.1 0.0

Schoolmaster snapper (L. apodus) biomass 20.9 13.8 40.6 23.8 16.2 7.3 22.4 9.6 Variable

Gray snapper (L. griseus) density 0.04 0.03 0.01 0.01 0 0 0.1 0.1 Variable

Gray snapper (L. griseus) biomass 12.2 9.1 2.5 1.8 0 0 25.7 25.6

Haemulidae

Grunt density 10.3 2.9 8.1 3.8 2.1 0.6 4.5 1.9

Grunt biomass 418.7 93.9 283.2 67.1 123.1 45.1 202.4 41.4

French grunt (H. flavolineatum) density 2.7 0.9 1.1 0.3 1.0 0.3 2.0 0.9

French grunt (H. flavolineatum) biomass 135.9 28.4 103.1 18.9 44.1 8.5 86.1 15.8

Bluestriped grunt (H. sciurus) density 0.5 0.2 0.1 0.0 0.1 0.0 0.0 0.0

Bluestriped grunt (H. sciurus) biomass 82.9 36.5 42.7 22.0 11.3 6.2 7.8 4.1

Scaridae

Parrotfish density 16.1 1.1 13.8 1.2 14.8 1.1 13.1 0.9 Variable

Parrotfish biomass 646.2 70.4 837.1 118.4 718.0 80.6 827.5 115.4 Variable

Redband parrotfish (S. aurofrenatum) density 3.7 0.4 2.4 0.3 5.4 0.5 4.7 0.4 Variable

Redband parrotfish (S. aurofrenatum) biomass 181.3 22.0 199.6 32.8 203.5 22.1 254.9 31.8

Striped parrotfish (S. iseri) density 4.4 0.5 3.4 0.6 3.1 0.5 2.0 0.3

Striped parrotfish (S. iseri) biomass 59.9 10.9 50.6 11.1 31.2 5.8 45.7 13.8

Other species

Blue tang (A. coeruleus) density 4.1 0.8 8.3 1.8 6.8 1.0 6.9 1.9 Variable

Blue tang (A. coeruleus) biomass 443.8 134.0 1199.5 308.5 483.9 106.0 788.5 248.8 Variable

Sharks and Rays density 0.03 0.01 0.01 0.01 0.03 0.01 0.05 0.02 Variable

Sharks and Rays biomass 435.9 381.9 41.2 39.6 43.4 31.4 148.6 88.3 Variable

3 - Results
p. 47

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Table 14. Summary statistics (mean + SE) for a range of fish variables grouped by year (2003-2006) inside BIRNM, northeastern St. 

Croix. Blue arrow = two consecutive years of increase; Orange arrows = two consecutive years of decrease. Double arrows indicate 

three consecutive years. Multidirectional change is indicated by the label “variable”.

Fish variable

2003 2004 2005 2006

Mean In SE In Mean In SE In Mean In SE In Mean In SE In Change

Community metrics

Number of species 14.65 0.74 13.13 0.81 14.74 0.66 14.91 0.59 Variable

Shannon diversity 1.80 0.07 1.58 0.07 1.77 0.06 1.84 0.06 Variable

Taxonomic diversity (pres/abs) 55.91 1.27 55.35 1.53 57.14 1.16 60.00 0.84 Variable

Density (all species combined) 111.75 7.34 128.63 10.68 147.95 10.14 150.64 10.24

Biomass 4520.20 542.35 6188.42 1261.80 4106.78 379.82 5985.86 773.23 Variable

Herbivore density 46.34 4.38 55.51 6.91 64.22 5.43 61.43 5.42

Herbivore biomass 2567.12 390.94 4641.46 1177.32 2690.23 332.21 3520.99 697.34 Variable

Piscivore density 4.68 0.79 3.27 0.92 3.70 0.40 5.72 1.12 Variable

Piscivore biomass 970.10 201.34 479.55 102.22 594.25 105.95 831.62 141.42 Variable

Serranidae

Grouper density 1.84 0.38 0.92 0.19 2.21 0.33 1.90 0.23 Variable

Grouper biomass 426.91 135.70 198.97 58.64 206.06 37.86 324.03 47.55 Variable

Coney (C. fulva) density 1.65 0.37 0.74 0.18 1.84 0.30 1.63 0.22 Variable

Coney (C. fulva) biomass 358.96 128.08 158.96 56.73 122.72 21.28 231.44 38.87

Red hind (E. guttatus) density 0.15 0.04 0.18 0.06 0.31 0.07 0.24 0.04

Red hind (E. guttatus) biomass 60.01 18.80 38.06 14.17 82.24 26.62 82.46 22.03 Variable

Lutjanidae

Snapper density 0.56 0.10 0.27 0.07 0.58 0.14 0.75 0.21

Snapper biomass 154.03 45.73 76.84 34.09 159.13 52.69 228.58 81.98 Variable

Yellowtail snapper (O. chrysurus) density 0.39 0.08 0.20 0.06 0.44 0.13 0.31 0.07 Variable

Yellowtail snapper (O. chrysurus) biomass 75.49 25.11 44.77 28.39 58.72 32.31 54.53 14.93 Variable

Schoolmaster snapper (L. apodus) density 0.03 0.02 0 0 0.08 0.03 0.05 0.02 Variable

Schoolmaster snapper (L. apodus) biomass 16.13 11.36 0 0 32.86 14.93 33.93 18.85 Variable

Gray snapper (L. griseus) density 0.04 0.04 0.01 0.01 0 0 0.01 0.01

Gray snapper (L. griseus) biomass 18.00 18.00 1.89 1.89 0 0 0.26 0.26

Haemulidae

Grunt density 2.49 0.61 1.15 0.28 0.99 0.23 2.42 1.20

Grunt biomass 180.51 53.39 119.77 31.46 77.53 21.42 221.49 58.89

French grunt (H. flavolineatum) density 1.16 0.34 0.85 0.24 0.77 0.19 1.81 1.06

French grunt (H. flavolineatum) biomass 63.91 10.93 57.58 15.05 44.39 10.61 114.66 23.44

Bluestriped grunt (H. sciurus) density 0.06 0.02 0.04 0.02 0.05 0.03 0.02 0.01 Variable

Bluestriped grunt (H. sciurus) biomass 14.12 5.70 22.71 12.56 12.44 8.25 10.27 7.45 Variable

Scaridae

Parrotfish density 13.73 1.39 11.54 1.37 16.55 1.83 15.44 1.35 Variable

Parrotfish biomass 909.42 125.44 997.91 214.23 1039.05 145.55 1261.63 225.00

Redband parrotfish (S. aurofrenatum) density 3.24 0.50 1.67 0.28 5.22 0.73 5.61 0.58 Variable

Redband parrotfish (S. aurofrenatum) biomass 175.43 30.79 136.37 37.07 221.33 30.47 304.39 55.36

Striped parrotfish (S. iseri) density 3.41 0.61 2.37 0.63 4.52 0.97 2.97 0.58 Variable

Striped parrotfish (S. iseri) biomass 72.06 19.86 38.14 14.57 42.93 10.05 83.89 27.88

Other species

Blue tang (A. coeruleus) density 6.29 1.57 13.65 3.60 11.18 1.99 10.92 3.76 Variable

Blue tang (A. coeruleus) biomass 818.37 272.97 2091.38 638.73 874.25 210.59 1305.35 504.49 Variable

Sharks and Rays density 0.03 0.02 0 0 0.03 0.02 0.07 0.03 Variable

Sharks and Rays biomass 100.50 71.75 0 0 84.21 64.25 126.96 85.60 Variable

3 - Results
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 48

Table 15. Summary statistics (mean + SE) for a range of fish variables grouped by year (2003-2006) outside BIRNM, northeastern St. 

Croix. Blue arrow = two consecutive years of increase; Orange arrows = two consecutive years of decrease. Double arrows indicate 

three consecutive years. Multidirectional change is indicated by the label “variable”.

Fish variable

2003 2004 2005 2006

Mean Out SE Out Mean Out SE Out Mean Out SE Out Mean Out SE Out Change

Community metrics

Number of species 13.79 0.67 12.43 0.78 13.68 0.69 13.78 0.66 Variable

Shannon diversity 1.82 0.06 1.72 0.07 1.76 0.05 1.67 0.06 Variable

Taxonomic diversity (pres/abs) 58.79 0.83 58.51 0.93 58.70 0.79 59.31 1.03 Variable

Density (all species combined) 119.08 8.99 100.73 11.89 119.08 8.65 146.80 11.21 Variable

Biomass 3540.57 412.35 4918.35 806.26 2793.13 387.51 4284.39 561.44 Variable

Herbivore density 43.71 2.88 33.39 3.64 43.89 3.81 50.84 4.71 Variable

Herbivore biomass 1051.65 135.51 1607.58 307.11 961.77 124.16 1158.73 199.61 Variable

Piscivore density 4.25 0.74 5.40 2.38 4.33 0.62 5.34 0.79 Variable

Piscivore biomass 1070.27 256.58 1704.56 624.65 913.07 313.03 1503.03 431.69 Variable

Serranidae

Grouper density 1.20 0.21 0.70 0.15 1.61 0.22 1.78 0.24

Grouper biomass 213.22 36.57 297.83 71.38 224.39 47.82 207.83 31.45

Coney (C. fulva) density 0.81 0.16 0.47 0.12 1.09 0.18 1.11 0.18

Coney (C. fulva) biomass 110.21 24.02 194.08 51.59 140.02 34.87 125.58 23.13

Red hind (E. guttatus) density 0.33 0.08 0.19 0.09 0.39 0.08 0.57 0.11

Red hind (E. guttatus) biomass 98.15 23.84 91.41 46.23 67.08 24.99 69.78 16.88 Variable

Lutjanidae

Snapper density 1.32 0.39 1.09 0.28 0.58 0.12 1.57 0.46

Snapper biomass 233.31 81.46 181.72 64.75 105.80 31.36 156.75 62.33

Yellowtail snapper (O. chrysurus) density 0.94 0.30 0.61 0.19 0.44 0.12 1.18 0.39

Yellowtail snapper (O. chrysurus) biomass 79.74 21.03 49.39 28.51 32.34 17.57 37.97 12.03

Schoolmaster snapper (L. apodus) density 0.07 0.06 0.18 0.11 0.01 0.01 0.06 0.02 Variable

Schoolmaster snapper (L. apodus) biomass 25.76 24.96 83.09 52.40 0.29 0.29 8.79 5.53 Variable

Gray snapper (L. griseus) density 0.04 0.03 0.01 0.01 0 0 0.21 0.21

Gray snapper (L. griseus) biomass 6.82 5.62 3.53 3.53 0 0 49.88 49.88

Haemulidae

Grunt density 17.87 5.62 15.10 8.33 3.22 1.08 6.52 3.59

Grunt biomass 650.30 174.85 354.92 96.83 166.04 86.32 156.63 51.25

French grunt (H. flavolineatum) density 4.23 1.72 1.11 0.40 1.27 0.53 2.16 1.56 Variable

French grunt (H. flavolineatum) biomass 206.13 54.14 131.15 34.57 42.22 13.23 58.95 21.42

Bluestriped grunt (H. sciurus) density 0.89 0.37 0.05 0.04 0.09 0.07 0.01 0.01 Variable

Bluestriped grunt (H. sciurus) biomass 149.13 70.93 27.31 20.55 10.28 9.23 1.99 1.99

Scaridae

Parrotfish density 18.58 1.61 14.40 2.09 13.25 1.22 10.82 1.19

Parrotfish biomass 407.44 63.93 600.81 122.72 409.99 64.85 406.83 57.24

Redband parrotfish (S. aurofrenatum) density 4.06 0.56 2.57 0.47 5.60 0.77 3.86 0.57 Variable

Redband parrotfish (S. aurofrenatum) biomass 189.60 31.85 213.25 51.02 184.58 32.24 212.55 33.74 Variable

Striped parrotfish (S. iseri) density 5.37 0.80 3.90 1.08 1.79 0.38 1.02 0.28

Striped parrotfish (S. iseri) biomass 49.33 10.28 44.36 16.26 19.90 5.90 6.00 2.27

Other species

Blue tang (A. coeruleus) density 2.09 0.34 2.98 0.77 2.62 0.43 2.93 0.67 Variable

Blue tang (A. coeruleus) biomass 97.01 28.60 371.83 116.34 112.93 22.53 260.31 84.41 Variable

Sharks and Rays density 0.02 0.01 0.01 0.01 0.02 0.01 0.03 0.02 Variable

Sharks and Rays biomass 13.70 8.58 3.51 3.51 4.53 4.01 171.17 152.96 Variable

3 - Results
p. 49

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Outside BIRNM

Outside BIRNM, declines over three consecutive years were recorded for striped parrotfish and for grunt biomass 

including bluestriped grunt biomass, with 2005 and 2006 values significantly lower (p=<0.05) than 2003 (Table 15 and 

Appendix E). Unlike inside BIRNM, no metric exhibited three consecutive years of increase. Declines recorded for at 

least two consecutive years were considerably more widespread, with decreases in mean metric value for all major fish 

families, including: all grouper biomass; coney biomass; red hind density and biomass; all snapper density and biomass; 

yellowtail snapper density and biomass; gray snapper density and biomass; grunt density and biomass; French grunt and 

bluestriped grunt biomass; parrotfish density and biomass, including striped parrotfish density and biomass (Table 15). 

Overall, 17 metrics exhibited at least two consecutive years of decline, three metrics increased over two years, and 19 

showed no clear directionality (Table 15). Interestingly, many of the fish metrics that showed a declining trend between 

2003 and 2005, then showed a substantial increase in 2006.

3.2.9 Seasonal and inter-annual patterns in fish community metrics

Mean fish density was markedly lower 

over hardbottom habitat types during the 

spring sampling season than during the fall 

sampling season (Figure 44). Table 16 shows 

that all of the most abundant fish species in 

the study region were more abundant in fall 

than spring. Greatest differences were found 

for the three most abundant fish species 

bluehead wrasse (Thalassoma bifasciatum), 

slippery dick (Halichoeres bivittatus) and 

bicolor damselfish (Stegastes partitus).

As a result of this distinct seasonal 

difference, temporal change was examined 

separately for: (1) March/April; and (2) 

October sampling periods.

Figure 44. Mean (+ SE) density for all species combined by sampling season for 

both inside and outside BIRNM. 

Table 16. Spring and fall total abundance and mean (+ SE) density for the 20 most abundant fish species across 

the study region (northeastern St. Croix).

Species Common name

Spring total 

abundance

Spring mean 

density (+SE)

Fall total 

abundance

Fall mean 

density (+SE)

Thalassoma bifasciatum Bluehead wrasse 9525 15.1 (0.9) 22476 34.9 (2.2)

Halichoeres bivittatus Slippery dick 9710 15.4 (3.4) 15042 23.4 (1.3)

Stegastes partitus Bicolor damselfish 3500 5.5 (0.5) 6702 10.4 (0.7)

Acanthurus bahianus Ocean surgeonfish 3670 5.8 (0.4) 4931 7.7 (0.5)

Acanthurus coeruleus Blue tang 3737 5.9 (0.8) 4860 7.5 (1.1)

Sparisoma aurofrenatum Redband parrotfish 1820 2.9 (0.2) 3067 4.8 (0.3)

Scarus iseri Striped parrotfish 2212 3.5 (0.3) 2549 4.0 (0.4)

Halichoeres garnoti Yellowhead wrasse 1660 2.6 (0.2) 2998 4.7 (0.3)

Stegastes leucostictus Beaugregory 1537 2.4 (0.3) 2454 3.8 (0.4)

Chromis cyanea Blue chromis 1426 2.3 (0.4) 1895 2.9 (0.5)

Haemulon aurolineatum Tomtate 1052 1.7 (0.9) 1581 2.5 (1.9)

Xyrichtys martinicensis Rozy razorfish 1231 2.0 (0.6) 1351 2.1 (0.4)

Sparisoma viride Stoplight parrotfish 968 1.5 (0.1) 1488 2.3 (0.2)

Decapterus macarellus Mackerel scad 820 1.3 (0.5) 1499 2.3 (0.9)

Halichoeres maculipinna Clown wrasse 743 1.2 (0.1) 1433 2.2 (0.2)

Clepticus parrae Creole wrasse 827 1.3 (0.5) 1333 2.1 (1.2)

Haemulon flavolineatum French grunt 687 1.1 (0.2) 1257 2.0 (0.5)

Stegastes diencaeus Longfin damselfish 930 1.5 (0.2) 940 1.5 (0.2)

Scarus taeniopterus Princess parrotfish 711 1.1 (0.1) 1002 1.6 (0.1)

Cephalopholis fulva Coney 604 1.0 (0.1) 787 1.2 (0.1)

3 - Results
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 50

a)

b)

c)

Inside BIRNM

Outside BIRNM

Figure 45. Seasonal and inter-annual (2003-2006) change in mean (+ SE) fish biomass inside and outside BIRNM for: (a) all fish 

biomass; (b) herbivorous fish biomass; and (c) piscivorous fish biomass.

3 - Results

Between 2003 and 2006, mean density increased in both sampling seasons. Mean fish biomass was higher inside BIRNM 

for six of eight sampling seasons and mean herbivore biomass was higher inside BIRNM in all seasons and years. 

Piscivore biomass was higher outside in six out of eight sampling seasons (Figure 45). Furthermore, spring piscivore 

decreased inside, while increasing outside BIRNM between 2003 and 2006.

In contrast, the number of fish species and value of diversity indices varied very little across years except for a slight 

decrease during 2004, although mean values were marginally higher in fall 2005 and 2006 than fall 2003 and 2004 

(Figure 46).
p. 51

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Inside BIRNM

Outside BIRNM

Figure 46. Seasonal and inter-annual (2003-2006) change in mean (+ SE) fish diversity inside and outside BIRNM.

3 - Results

3.2.10 Seasonal and inter-annual patterns in fish groups and species

Mean grouper biomass was higher in spring than fall sampling seasons, particularly within BIRNM, although spring 

biomass declined inside BIRNM from 2003 to 2005 (Figure 47a). Spring snapper biomass also was greater than fall 

and increased gradually from 2003 to 2006 inside BIRNM, but appeared to decrease outside over the same time period 

(Figure 47b). Grunt and parrotfish biomass also was greater in spring than fall, but not for all years. In general, grunt 

biomass decreased outside BIRNM between 2003 and 2006 and remained relatively consistently low inside (Figure 

47c). Parrotfish biomass was higher inside BIRNM for all sampling seasons and all years (Figure 47d). Spring biomass 

appeared fairly consistent across years, but fall biomass increased year upon year inside BIRNM.

Coney mean biomass was higher inside BIRNM for five of eight sampling seasons, but showed a dramatic decline 

from 2003 to 2005 in the spring sampling season (Figure 48a). Fall biomass was lower than spring and highly variable 

within season. Red hind biomass was lower than coney biomass and highly variable across seasons and years, with 

similar inside/outside biomass patterns (Figure 48b). Yellowtail snapper mean biomass in spring was higher inside than 

outside for all years (Figure 49a). Other snapper species were highly variable and not abundant enough to determine any 

meaningful temporal patterns between season and years (Figure 49).
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 52

Inside BIRNM

Outside BIRNM

a)

b)

c)

d)

Figure 47. Seasonal and inter-annual (2003-2006) change in mean (+ SE) fish biomass inside and outside BIRNM for: (a) groupers, (b) 

snappers, (c) grunts and (d) parrotfish.

3 - Results
p. 53

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Inside BIRNM

Outside BIRNM

a)

b)

Figure 48. Seasonal and inter-annual (2003-2006) change in mean (+ SE) fish biomass inside and outside BIRNM for (a) coney (C. 

fulva) and (b) red hind (E. guttatus).

Red hind (Epinephelus guttatus) 

3 - Results
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 54

Inside BIRNM

Outside BIRNM

a)

b)

c)

Figure 49. Seasonal and inter-annual (2003-2006) change in mean (+ SE) fish biomass inside and outside BIRNM for: (a) yellowtail 

snapper (O. chrysurus), (b) schoolmaster (L. apodus) and (c) gray snapper (L. griseus).

Yellowtail snapper (Ocyurus chrysurus)

3 - Results
p. 55

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Inside BIRNM

Outside BIRNM

a)

b)

Figure 50. Seasonal and inter-annual (2003-2006) change in mean (+ SE) fish biomass inside and outside BIRNM for (a) French grunt 

(H. flavolineatum) and (b) bluestriped grunt (H. sciurus).

Mean biomass of French grunts and bluestriped grunts outside BIRNM declined year after year from 2003 to very low levels 

in 2006 (Figure 50). Inside BIRNM, biomass increased for French grunt and varied little between years for bluestriped 

grunt.

Herbivore mean biomass in spring was higher inside BIRNM for all species (blue tang, striped parrotfish and redband 

parrotfish) and almost all years (Figure 51). In addition, spring biomass for all species examined was higher in spring than 

in fall. For both seasons biomass was highly variable among years and no obvious trend was observed.

Assemblage of juvenile, subadult and adult grunts (Haemulidae) on a patch reef. 

3 - Results
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 56

Inside BIRNM

Outside BIRNM

a)

b)

c)

Figure 51. Seasonal and inter-annual (2003-2006) change in mean (+ SE) fish biomass inside and outside BIRNM for: (a) blue tang (A. 

coeruleus), (b) redband parrotfish (S. aurofrenatum) and (c) striped parrotfish (S. iseri).

3 - Results
p. 57

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

3.3 Macroinvertebrate spatial distribution patterns and species-habitat associations

3.3.1 queen conch (Strombus gigas)

A total of 736 queen conch were observed in the study region (northeastern St. Croix) between 2004 and 2006, of which 

72.3% were juveniles (i.e., no flared lip). Highest mean density of both juveniles and adults were recorded in seagrass 

beds inside BIRNM (Figure 52). The maximum number of individuals at any one survey site (100 m2

) was 59, recorded 

from a seagrass bed inside BIRNM. Overlay of distributions on the benthic habitat map showed a concentration of juveniles 

in seagrasses directly in the sheltered leeward side of Buck Island. Adults showed a similar distribution (Figure 53), albeit 

less concentrated and at lower densities revealing that adult and juvenile S. gigas were not spatially segregated. Sixty 

percent of sites with juveniles present also had adults present. Comparison of estimates of sighting frequency (Figure 

54) show that S.gigas juveniles and adults were markedly more common in northeastern St. Croix than for St. John or 

southwestern Puerto Rico and comparison of area-weighted abundance for the three islands highlights the importance of 

the St. Croix seagrass beds in supporting a queen conch population of regional significance. 

Comparison of estimates of sighting frequency (Figure 54) show that S.gigas juveniles and adults were markedly more 

common in northeastern St. Croix than for St. John or southwestern Puerto Rico and comparison of area-weighted 

abundance for the three islands highlights the importance of the St. Croix seagrass beds in supporting a queen conch 

population of regional significance (Table 17).

Juveniles

Adults

Inside BIRNM

Outside BIRNM

3 - Results

Figure 52 Mean (± SE) density for (a) juvenile and adult queen conch (S. gigas) by 

habitat type, and (b) all queen conch inside and outside BIRNM by dominant habitat 

types in the study region (northeastern St. Croix) between 2004 and 2006.
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 58

Figure 53. Spatial distributions of (a) juvenile (immature) and (b) adult (mature) queen conch (S. gigas) density in the study region 

(northeastern St. Croix) between 2004 and 2006.

3 - Results

Figure 54. Sighting frequency of sexually immature (juvenile), mature (adult), 

and all queen conch from three study sites in the U.S. Caribbean: Southwest 

Puerto Rico; northeastern St. Croix and St. John. Sighting frequency was 

calculated as the percentage of sampled sites where at least one juvenile or 

adult conch was observed. Source: Jeffrey and Monaco, 2007.

Table 17. Estimates of total queen conch abundance (number of individuals) by life stage for three 

islands in the U.S. Caribbean (2004-2006). Source: Jeffrey and Monaco, 2007.

Island

Size of study 

area (ha)

% of area 

sampled

# of 

surveys Life stage

Estimated 

abundance Range of estimate

Puerto Rico 157,348 < 0.01 394 Immature 1,100,248 236,943 - 1,963,553 

Mature 204,645 34,698 - 374,591 

Total 1,304,893 271,641 - 2,338,144 

St. Croix 32,014 0.02 624 Immature 1,933,950 1,025,084 - 2,842,815 

Mature 835,005 493,204 - 1,176,805 

Total 2,768,954 1,518,288 - 4,019,620 

St. John 4,697 0.11 505 Immature 169,838 39,019 - 300,656 

Mature 72,832 26,576 - 119,087 

Total 242,669 65,596 - 419,743
p. 59

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

3.3.2 Long-spined sea urchin (Diadema antillarum)

D. antillarum was observed at approximately 10% 

of sites (38 out of 364) surveyed between October 

2005 and November 2006. Mean density across the 

study region was 0.03 (± 0.01 SE) per 1 m2

. Maximum 

density recorded at any individual site was 4.2 m2. 

Visual assessment of spatial distributions of abundance 

revealed that very few D. antillarum were using the 

coral reef ecosystems around Buck Island between 

2005 and 2006 (Figure 55) and D. antillarum densities 

were considerably higher on hardbottom habitat types 

outside BIRNM than inside (Figure 55). Highest densities 

were observed in the nearshore environments within 

the EEMP on colonized bedrock, colonized pavement 

and macroalgal beds in close proximity to extensive 

seagrass beds (Figure 56). Figure 55. Spatial distribution of long-spined urchins (Diadema 

antillarum) in the study region (northeastern St. Croix) between 2005 

and 2006. 

Juveniles

Adults

Inside BIRNM

Outside BIRNM

Figure 56. Mean (± SE) density for long-spined sea urchin (Diadema antillarum) by (a) 

habitat type and (b) inside and outside BIRNM (northeastern St. Croix) between 2005 

and 2006.

3 - Results
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 60

3.3.3 Historical comparison of Diadema abundance

In 1979, Gladfelter (1980) carried out daytime surveys 

and recorded a peak density of 10.6 per m2

 on pavement 

areas at the northwest end of Buck Island ,between 5 

and 10 per m2 in the lagoonal patch reef south of island 

and 5-8.3 m2 on the bank barrier reef at the eastern tip 

of the island. A few years earlier, Ogden et al. (1972) 

recorded mean D. antillarum densities of between 0.81 

and 4.08 per m2 on patch reefs in Teague Bay (Figure 

57).

In contrast, between 2005 and 2006, mean density of 

D. antillarum was recorded at 0.03 m2 across the study 

region and presence of D. antillarum. Of particular 

importance was the observation of only five D. antillarum

individuals over hardbottom habitats in the lagoon and 

bank barrier reef areas (n=43 transects or 4,300 m2

surveyed within 500 m of Buck Island) between October 

2005 and November 2006. However, sea urchin 

densities were higher in lagoonal and back reef areas 

outside BIRNM along the northeastern coastline of St. 

Croix.

D. antillarum, October 2005

Figure 57. The changing abundance of Diadema antillarum in (a) the 

lagoon and on bank barrier coral reefs within 500 m of Buck Island 

and (b) Teague Bay and adjacent nearshore lagoonal environments 

showing little to no recovery in over two decades since the mass 

mortality event. Source: Ogden, 1972; Gladfelter, 1980; CCMA-BB.

3.3.4 Caribbean spiny lobster (Panulirus argus)

A total of 24 spiny lobster (Panulirus argus) were recorded over 

hardbottom areas from 2003 to 2006, including two in 2003 

from two sites; eight in 2005 from six sites and 14 in 2006 from 

five sites (Table 18). There were no lobsters observed in 2004. 

Fifteen spiny lobsters were observed inside BIRNM and nine 

outside. The highest densities at individual sites were observed 

in patch reef and colonized pavement habitat types dominated 

by branching corals (three and nine lobsters respectively). Five 

lobsters were observed over scattered coral/rock in sand habitat 

type. No lobsters were observed on softbottom sites. However, 

the abundance of lobsters detected using existing techniques is 

very likely to be an underestimate 

of abundance. Lobsters are cryptic 

and crevice dwelling animals that 

are best surveyed using dedicated 

lobster census techniques and 

supplemented with night time surveys 

when some lobsters are more active 

and therefore more visible. These 

data should not be used to estimate 

spiny lobster populations in the study 

region.

P. argus, March 2007

Table 18. Abundance of spiny lobster (Panulirus argus) in 

hard and soft habitats of the study region and inside and 

outside BIRNM (northeastern St. Croix) between 2003 and 

2006.

Habitat Location

Year Types Inside Outside Total

2003

Hard 0 2 2

Soft 0 0 0

Overall 0 2 2

2004

Hard 0 0 0

Soft 0 0 0

Overall 0 0 0

2005

Hard 4 4 8

Soft 0 0 0

Overall 4 4 8

2006

Hard 11 3 14

Soft 0 0 0

Overall 11 3 14

Total 15 9 24

3 - Results
4 - Discussion

4. Discussion

This report demonstrates quantitatively and spatially that the benthic environment inside BIRNM was significantly different 

to the outside (Tables 5, 6 and 7). The results show conclusively that the abundance of key benthic components, at both 

the 1 m2 spatial scale (quadrat sampling unit) and at the 100 m radius spatial scale (e.g., surrounding seascape unit), were 

significantly different inside. For instance, nine of 14 biotic variables measured within quadrats set over hardbottom habitat 

sites and seven of nine seascape metrics (amount and richness of habitat types) were significantly different inside versus 

outside BIRNM. Seascapes inside BIRNM were more diverse and had on average a higher area of colonized hardbottom 

and lower area of seagrasses surrounding transects. Furthermore, visual examination of interpolated distribution maps 

clearly showed that a greater spatially continuous area of high coral cover, coral species richness and rugosity was 

contained within the boundary of BIRNM consistent with objectives of the marine protected area designation. The existing 

BIRNM boundary broadly follows the boundary between medium-high coral cover and medium-low coral cover as depicted 

in the spatial interpolation. In addition, higher coral cover for all major scleractinian families was recorded inside BIRNM 

and coral reefs inside also had a higher ratio of live coral cover to macroalgal cover than coral reefs outside BIRNM. 

Such information may serve as a useful indicator for change detection, with the coral-macroalgal ratio being an important 

benthic relationship relevant to faunal communities and indicative of the functional status of the environment.

Although coral reef structure has been modified by several major 

events since the original National Monument designation and the 

special recognition of the “marine gardens” in 1961, the area around 

the eastern tip of Buck Island remains distinctive in both biological and 

geomorphological structure. The spatial data contained in the report 

characterizes this area as having high live coral cover, high rugosity, 

high coralline algal cover, high fish species richness, high biomass of 

herbivorous fish and high density for many fish species. The relevance 

of coralline algae is related to its function in providing an important 

food source for some fish including parrotfish and physical structure 

and chemical cues promoting the settlement and metamorphosis of 

many invertebrates including some coral larvae. The distinct biological 

features of the eastern tip of Buck Island suggest that the area could 

function as refugia for several benthic organisms. If true, then because 

of prevailing northeasterly winds and circulatory patterns, the area may 

be an important source of larvae for corals and other benthic organisms in down stream areas. Hardbottom areas inside 

BIRNM exhibited a significantly higher ratio of coral to macroalgae than did hardbottom areas outside. This may be 

indicative of greater top-down control of macroalgae due to grazing pressure since hardbottom areas inside BIRNM also 

have significantly higher herbivore biomass, particularly parrotfish and surgeonfish than similar outside areas.

In addition to the well-recognized and extensive hardbottom areas north and east of Buck Island within BIRNM, an 

additional area was found to support high coral species richness and fish species richness along the northeast coastline 

of St. Croix. The linear reef and adjacent colonized pavement extends east-west from Teague Bay to Coakley Bay and 

now falls within the EEMP no-take zone and recreation zone (Appendix A, Figure A1). This extensive fringing coral reef 

may also offer important habitat to fish moving from nearshore seagrass and patch reef environments to coral reefs 

as part of ontogenetic transitions in habitat use. More focused research including acoustic tracking may elucidate on 

the connectivity between nearshore lagoonal environments and coral reefs both inside and outside BIRNM. Very little 

is known about fish movement patterns in the study region and data from an acoustic tracking project would provide 

important information on connectivity. For example, is the reason for low abundance of the large size classes of grouper, 

snapper and grunt due to emmigration out from the study region to deeper waters or mortality? A multi-year broadscale 

acoustic tracking study has the capability to answer this question. 

Extensive areas with high coral species richness, high cover for Montastraea cavernosa and M. annularis, high fish 

species richness and high abundance for several fish species including 

coney (C. fulva), rock beauty (Holacanthus tricolor) and queen triggerfish 

(Balistes vetula) occurred along the northernmost edge of the benthic 

habitat map. This indicates that important deeper water habitat is likely 

to exist beyond the scope of this report, requiring further benthic habitat 

mapping effort combined with deeper water visual census to capture 

data on fish communities.

In comparative investigation of management domains for the purpose of 

evaluating efficacy (e.g., inside versus outside protected areas), caution 

is required since clear differences are evident in benthic habitat that will 

likely explain some of the patterns in faunal distributions independently 

of management practices. However, this does not obviate the usefulness 

of comparative analyses, since differences and similarities that exist 

within or between management domains provide valuable information 

p. 61

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Crustose coralline algae

queen triggerfish (Balistes vetula)
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 62

in support of local decision-making processes for the selected regions of interest. Future assessments could, however, 

usefully attempt to partition out the relative influence of differences in habitat from the effects of management actions.

Fish species, family/trophic group and communities inside and outside BIRNM

As expected, fish community composition was most dissimilar between linear reefs and scattered coral or rock, habitat 

types that are known to differ markedly in structural complexity and areal extent. Unexpectedly, fish communities 

associated with aggregated patch reefs, linear reefs and colonized pavement were so similar as to be barely separable. 

These habitat types were considered distinct to the human observer when classifying the benthic structure, yet for the 

fish communities the differences were not significant. This may have implications for the level of thematic accuracy 

required when delineating benthic habitat in the construction of benthic maps for fish-habitat studies. Considerable cost 

savings may result from delineation of fewer classes of hardbottom. Further studies using high resolution Light Detection 

and Ranging (LiDAR) bathymetry should provide useful information on the structural variability within existing NOAA 

benthic habitat types and will help to understand the implications of benthic structural types for fish. Furthermore, fish 

communities associated with the same habitat types inside and outside BIRNM were very similar and indistinguishable. 

Examination of more subtle differences in community composition between strata may require additional multivariate 

analytical techniques.

Several individual fish metrics were significantly higher on colonized 

hardbottom habitats inside than outside BIRNM including fish 

biomass (all fish combined), herbivore biomass, parrotfish biomass, 

shark and ray biomass, coney density and biomass, blue tang (A. 

coeruleus) density and biomass and striped parrotfish (S. iseri) 

biomass. Comparatively fewer fish metrics were significantly higher 

outside, but included ecologically important predator groups such as 

piscivore biomass, snapper density and grunt density and biomass. 

The greater biomass of piscivorous fish outside BIRNM probably 

relates more to habitat preferences of relatively infrequently occurring 

sharks and rays (over unvegetated sediments) than any indication 

of MPA performance. Similarly, higher grunt density and biomass 

outside BIRNM likely relates more to the abundance of shallow 

nearshore hardbottom environments in close proximity to seagrass beds than MPA performance. Interpretation of these 

patterns highlights the importance of using spatially explicit census data.

Size frequency histograms revealed some differences in size structure inside versus outside BIRNM for grunts and 

snapper, with: (1) a higher frequency of large bodied snapper inside BIRNM; (2) a greater decrease in frequency of large 

subadult and adult yellowtail snapper (O. chrysurus) with increasing size outside BIRNM; (3) a higher frequency of large 

juvenile and subadult French grunt inside BIRNM; and (4) higher frequency of small juveniles outside (Figures 42 and 

43). These differences may reflect differences in environment or management/fishing pressure or both, but nevertheless 

data indicate that a larger proportion of the mature adult snapper and grunts are occurring inside the protected area than 

outside.

Interestingly, very few of the largest and very few of the smallest size 

classes were observed for grouper and snapper. For small juveniles, 

this suggests that either: (1) the study region is not a primary 

settlement area for groupers and snappers; or (2) newly settled 

juveniles exist, but are not being detected by the belt transect survey 

technique due to cryptic coloration or hiding behavior thus providing 

false absences. For large adults, this suggests that either: (1) large 

adults do not use the study area and may perhaps inhabit deeper 

unsurveyed waters by day; (2) large adults exist, but are not being 

detected by the belt transect survey technique due to avoidance 

behavior thus providing false absences; or (3) large adults are being 

removed from the system by fishing. Additional targeted survey work 

may be required to determine the locally important areas for both 

newly settled juveniles and large-bodied mature adults.

Spatial distributions and fish-habitat associations

Although mean densities varied widely between habitat types, with many of the most abundant fish across the study 

region found in highest densities over hardbottom habitat types, most utilized multiple habitat types including seagrasses 

and sand. This has implications for the way species-habitat relationships are understood and managed and further study 

may provide insight into fish resource use patterns and predictions on resilience to change, with many species having 

evolved sufficient plasticity to exploit a diverse range of structurally distinct habitat types. In addition, many of the juveniles 

of the most abundant species used the same habitat types as adults and the two life-stages were often found to coexist in 

the same areas of the study area. This pattern is in contrast to results for the same species elsewhere (e.g., southwestern 

Southern stingray (Dasyatis americana)

Stoplight parrotfish (Sparisoma viride) and longfin damselfish 

(Stegastes diencaeus)

4 - Discussion
p. 63

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Puerto Rico) that have shown a cross-shelf or water depth related size distribution or have reported juveniles using 

spatially discrete areas as nursery before undertaking ontogenetic habitat shifts to preferred adult habitat. This difference 

in pattern observed in northeastern St. Croix further highlights the flexibility or plasticity in resource utilization patterns for 

fish using heterogeneous coral reef ecosystems.

Visual assessment of density distributions for the two abundant species 

of grouper (red hind [E. guttatus] and coney) around northeastern St. 

Croix suggest different habitat use patterns, with high coney density 

being widespread over the contiguous colonized hardbottom areas 

(much of which is inside BIRNM) and high densities of red hind found 

mostly to the south of Buck Island (many outside BIRNM). These areas 

of highest red hind density are also close to the interface between 

seagrasses and extensive areas of colonized hardbottom which 

may relate to direct or indirect utilization of seagrasses presence of 

seagrasses or some other covarying environmental variable such as 

wave exposure (Kendall et al., 2004b). Almost all species examined 

here were found at higher densities on hardbottom habitat types than 

seagrasses or other softbottom, however, surveys were conducted 

during daylight hours and many of these species may use seagrasses 

during nocturnal foraging excursions. Thus, the low densities of fish associated with seagrasses should not be used 

in evaluation of relative habitat importance without complimentary information on resource use activity within the daily 

home range that includes examination of diel migrations. This is particularly relevant to many grunts which are known to 

make use of seagrasses adjacent to coral reefs as a nighttime feeding ground. Furthermore, most of the coral reefs with 

high species richness were within 200 meters of seagrass beds. Several studies have demonstrated links between fish 

distribution on coral reefs and proximity to seagrass beds suggesting that many species may benefit from complementary 

and supplementary resources provided by seagrasses in close proximity (Grober-Dunsmore, 2007; Pittman et al., 2007) 

to coral reefs. However, not all coral reef sites in close proximity to seagrasses supported high fish richness, thus it is 

likely that the interaction between multiple environmental variables including surface rugosity determine such complex 

spatial patterns.

Spatial distribution data on selected species may also provide valuable information that can be used as indicators for 

habitat structure, health, and in combination with temporal data, as a tool in change detection. For example, the threespot 

damselfish (Stegastes planifrons), which exhibits a strong preference for select taxa of live coral (e.g., Agaricia spp., 

Acropora spp. and Montastraea spp.) and through feeding promotes high algal diversity, may function as a useful indicator 

of healthy and structurally complex coral reefs. In the northeastern St. Croix study region, highest densities of threespot 

damselfish were found around the eastern tip of Buck Island within BIRNM and the fringing reef outside BIRNM extending 

east-west along the northeast coast of St. Croix (Appendix D).

Temporal trends in fish and benthic habitat

With respect to temporal trends, hardbottom benthic habitat exhibited a 

higher cover of filamentous algae/cyanobacteria and macroalgae, and 

lower turf algae in fall than in spring. A peak in filamentous cyanobacteria/

algae was recorded for October 2005, a season with anomalously high 

water temperature that also resulted in a mass coral bleaching event. 

Highest algal turf was recorded for spring 2006, which may be linked to 

the algal colonization of dead coral colonies that is commonly observed 

after a bleaching event. Across years, macroalgae cover shows some 

indication of decline both inside and outside BIRNM between 2003 and 

2006. This was especially evident for spring sampling seasons and 

may indicate increased grazing from a concurrent increase in density 

of herbivorous fish in the region as a whole and particularly larger (e.g. 

higher biomass) parrotfish inside BIRNM (see below). Another important 

observation that emerged from a seasonal comparison of fish density 

was the markedly higher abundance of fish in fall than in spring. This 

seasonal pattern was also noted by Simpson (1979) and attributed to the influence of summer recruitment. Still, little is 

known about the spatio-temporal characteristics of the life-history patterns for even the most common fish in the study 

region and Simpson’s (1979) statement that “knowledge of spawning and recruitment of fishes is still rudimentary” is still 

pertinent today.

Synoptic overview of inter-annual differences in mean metric values both inside and outside BIRNM showed no consistent 

decline for any of the 39 fish metrics inside BIRNM, but increases every year between 2003 and 2006 were recorded for 

density of all fish and mean biomass of parrotfish. In contrast, increases for the entire sampling period were not evident 

outside BIRNM, instead considerable and consecutive decline was apparent for grunt biomass, especially bluestriped 

grunt (H. sciurus) and density and biomass of stripped parrotfish. Grunts and parrotfish are all readily captured in baited 

trap and net fisheries, and thus are highly susceptible to extraction from the ecosystem. Results here suggest that target 

Seagrasses and macroalgae habitat

4 - Discussion

Bleached Diploria strigosa with turf and cyanobacteria 

overgrowth.
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 64

species may receive some protection within BIRNM and that may account for the absence of continuous decline and the 

apparent increases during the sampling period between 2003 and 2006. If BIRNM retains fish species within its boundary 

and the existing legislated protection is enforced effectively, then biomass and abundance of fish would be expected to 

increase since the commencement of no-take regulations in 2003. Accumulation of biomass at detectable levels, however, 

may require longer term monitoring data. This is particularly likely for grouper since many grouper are comparatively slow 

growing and some such as the Nassau grouper are late maturing (i.e., approximately 50 cm length). This together with 

the fact that many grouper and snapper aggregate to spawn make them particularly vulnerable to fishing pressure and 

slower in recovery of viable populations.

Interestingly, many of the fish variables that showed a decline between 

2003 and 2005 then showed an increase (sometimes substantial) in 

2006, for example, coney biomass, piscivore density, grunt biomass 

and French grunt (H. flavolineatum) biomass inside BIRNM. This may 

be indicative of: (1) the beginning of a response to increased protection; 

(2) an artifact of random sampling; or (3) part of variable fluctuations 

driven by other ecological factors (e.g., predation pressure, changing 

habitat quality etc.). It is known that greater voluntary compliance began 

in 2003 and this was then supplemented with law enforcement patrols 

from 2004. Thus, if fishing pressure was an important determinant of 

fish abundance and biomass the recovery would not be expected to 

be detectable for several years after compliance. Further long term 

monitoring will be required to reveal the direction of apparent upturns 

reported in 2006 at the end of this portion of the monitoring data.

When comparing inside with outside BIRNM, neither groupers nor snappers exhibited any consistent increases or declines 

over the entire sampling period (2003-2006), yet at the scale of the entire study area, yellowtail snapper biomass declined 

year upon year. This trend warrants concern and requires further monitoring since yellowtail snapper mean is a highly 

valuable commercial species and important ecological component of the ecosystem, being found in all habitat types in 

the study region. Furthermore, breakout of data by spring season revealed apparent downward directional trends inside 

BIRNM for density of yellowtail snapper, coney, gray snapper (L. griseus) and piscivore biomass (2003-2005). No obvious 

trend for the same species existed during fall and this may relate to seasonal differences in the influx and outflow of fish 

to BIRNM. Acoustic tracking may provide useful information on the seasonal fish movement patterns.

The multi-level and multi-resolution analyses in this report showed that direction of trend and subsequent interpretation of 

results varied with temporal grouping or resolution. An apparent inter-annual trend for a single season and management 

domain may not be apparent when both seasons are combined, or when management domains are combined. In 

addition, density and biomass may exhibit different patterns over time. It is important, therefore, that future temporal 

characterizations using summary statistics be undertaken at multiple levels of temporal resolution (season, year), as well 

as biological resolution (species, family, trophic group, community) and management domain resolution (inside, outside, 

region).

Overall, the majority of fish biomass was highly variable between years and therefore long term monitoring is required to 

elucidate further on the direction of change and particularly to track the declining trends in several key fish species and 

groups.

Connection between life history and vulnerability to fishing

Fisheries management organizations and fishers themselves need to be more aware of the relationship between fish life 

history characteristics and vulnerability to fishing. The apparent decline of three species of large-bodied and late maturing 

grouper (tiger, yellowfin and Nassau grouper) in the study region highlights the vulnerability of some species that were 

once of significant commercial value to the local fishery. Species with larger body size, higher longevity, higher age at 

maturity, and lower growth rate are generally considered to have higher vulnerability to fishing (Jennings et al., 1999; 

Dulvy and Reynolds, 2002; Dulvy et al., 2003).

Evidence that fishing pressure may have been responsible for some 

observed declines in abundance comes from analytical methods used 

to estimate extinction vulnerability to fishing which have classified 

tiger grouper and Nassau grouper as having HIGH to VERY HIGH 

vulnerability and yellowfin grouper as MODERATE to HIGH vulnerability 

based on body size and other biological characteristics (FishBase: 

http://www.fishbase.org; Cheung et al., 2005; Table 19). These species 

are also thought to mature late, with tiger grouper estimated to mature 

at approximately half its maximum size at an age of between 6.5-9.5 

years. As such all three species have low resilience to fishing with a 

minimum population doubling time calculated at between 4.5-14 years 

(Table 19). In contrast, the smaller-bodied grouper (red hind and coney) 

Diver collecting fish data

E. striatus (Nassau grouper)

4 - Discussion
p. 65

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

which are now more abundant in the study region have LOW to MODERATE vulnerability and medium resilience to fishing 

with an estimated population doubling time of between 1.4-4.4 years. For instance, the maximum body size for red hind 

is 76 cm TL, yet maturity has been recorded for fish at 25 cm FL (three years of age).

Distribution of macroinvertebrates

Long-spined sea urchins

Dramatic shifts in the distribution and abundance of the long-spined sea urchin (Diadema antillarum) were evident when 

comparing present day distributions (2005-2006) with historical distributions recorded in the 1970s. Comparison with 

historical density estimates indicated that 1970s/early 1980s densities were substantially higher than in 2005-2006. 

Gladfelter (1980) stated “Diadema antillarum is a conspicuous member of the Buck Island fauna” and Ogden et al. (1972) 

note that “on certain patch reefs in the vicinity of Teague Bay Reef, the grazing activities of this sea urchin have all but 

eliminated the growth of large benthic algae”. Furthermore, high abundance of sea urchins was thought to have been 

responsible for the high abundance of sea urchin predators observed within the original BIRNM, including black margate 

(Anisotremus surinamensis), Spanish grunt (Haemulon macrostomum), caesar grunt (Haemulon carbonarium) and queen 

triggerfish; Gladfelter et al., 1977). In contrast, between 2001 and 2006, only two black margate were observed across the 

study region, however, caesar grunt, Spanish grunt and queen triggerfish were relatively abundant. 

Even though differences occurred in the survey methods between studies in 1970s and 2005-2006, the evidence is 

clear that D. antillarum no longer plays such an important role as an “ecosystem engineer” in the coral reef ecosystems 

of northeastern St. Croix. This decline is likely to have contributed in part to the status of macroalgal/cyanobacterial/

turf dominated coral reefs that currently exist over much of the study region. The 

likely cause of these changes was the reported sea urchin die-off that occurred in 

1983 and 1984 throughout the Caribbean region resulting in an estimated 95-99% 

mortality rate (Lessios et al., 1984; Carpenter, 1988). Carpenter (1988) reported 

that five days after the mass mortality event in St. Croix, algal biomass increased 

by 20% and herbivorous removal of algal biomass decreased by 50%, although an 

increase in the rate of grazing by herbivorous fishes was also observed suggesting 

that exploitative competition for food was occurring between D. antillarum and 

some herbivorous fish species (Carpenter, 1988). In areas of the Caribbean where 

fishing had reduced the number of herbivorous fish, the growth and persistence 

of macroalgae increased (Lessios, 1988). It appears that recovery to pre-disease 

levels of density have not yet occurred in the BIRNM region even after more than 

two decades since the mass mortality event. 

In other areas of the Caribbean (e.g., Jamaica) populations of sea urchins appear to be showing signs of a recovery 

(Edmunds and Carpenter, 2001). In St. Croix, however, the high amounts of macroalgal cover on hardbottom areas and 

the small number of D. antillarum survivors (some of which may be relatively isolated from one another) may impede 

population recovery in the region. The ecological consequences of such low sea urchin abundance have not been evaluated 

for the coral reef ecosystems of BIRNM and surrounding areas. Furthermore, the dynamics of larval connectivity and 

other factors affecting recruitment are not well known for the region. However, at several shallow water sites (< 3 m) in 

Teague Bay lagoon, sea urchin densities were relatively high and this may be related to water depth and substratum type, 

with high densities observed at two colonized bedrock sites. Studies in St. Croix and elsewhere indicate that lagoonal 

and sheltered back reef areas may function to promote recovery in D. antillarum populations (Miller et al., 2003; Debrot 

and Nagelkerken, 2006) Further investigation is needed to determine the environmental factors that correlate with the 

observed spatial patterns in sea urchin occurrence and abundance and to determine if a recovery is occurring. Lessios 

(2005) recommended that assessment of sea urchin recovery should be are conducted using consistent survey methods 

that also include use of permanent transects due to the highly clustered distributions that are typically observed.

It is likely that 1970s populations were a result of explosive release due to predator removal by the fishery and were 

ecologically unsustainable thereby facilitating the exceptionally rapid spread of disease throughout the Caribbean. 

Table 19. Life history characteristics and vulnerability to fishing for three large-bodied species and two smaller-bodied species of 

grouper. Vulnerability is based on maximum size and the von Bertalanffy growth parameter (K) used by Cheung et al., 2005. Population 

doubling time is based on calculations by Musick et al., 2000 as reported in FishBase.

M. tigris M. venenosa E. striatus C. fulva E. guttatus

Tiger grouper Yellowfin grouper Nassau grouper Coney Red hind

Max. size (cm) 101 TL 100 TL 122 TL 41 TL 76 TL

Length first maturity (cm) 46 - 55 TL 51 FL 48 FL 16 FL 25 FL

Age first maturity (Y) 6.5-9.5 ? ? ? 3

Pop. doubling time (Y) 4.5-14 4.5-14 4.5-14 1.4-4.4 1.4-4.4

Vulnerabilty (index) High-Very High (74.9) Mod.-High (49.7) High-Very High (71.9) Low-Mod. (32.5) Moderate (41.5)

D. antillarum

4 - Discussion
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 66

Biological populations are naturally dynamic, yet questions regarding the optimum densities of sea urchin populations for 

a healthy coral reef ecosystem remain unanswered and future changes in sea urchin abundance must be monitored in 

order to determine if recovery is occurring and whether management intervention may be required.

Queen conch

Due to overfishing in many regions of the Caribbean and Florida, queen conch (Strombus 

gigas) has been listed in Annex II of the Cartagena Convention’s Protocol Concerning 

Specially Protected Areas and Wildlife (SPAW Protocol) as a species that may be used 

on a rational and sustainable basis and that requires protective measures. Because of 

this recognition, the United States proposed queen conch for listing in Appendix II of 

the Convention on International Trade in Endangered Species of Wild Fauna and Flora 

(CITES) in 1992; this proposal was adopted, and queen conch became the first largescale fisheries product to be regulated by CITES (see http://www.nmfs.noaa.gov/pr/

species/invertebrates/queenconch.htm). In the U.S. Caribbean, the queen conch fishery 

is regulated under the auspices of the CFMC.

The coral reef ecosystems of BIRNM and adjacent seascapes support regionally 

significant populations of juvenile and adult queen conch (S. gigas). The large expanse 

of seagrasses between Buck Island and St. Croix coastline are key resources supporting 

conch populations. However, very little is known about the historical densities to determine if present day populations 

are relatively large or small. This is important since according to the NOAA Office of Protected Resources, queen conch 

abundance is declining throughout the species’s range as a result of overfishing. Conch are an important food resource 

for the Virgin Islands and are known to be harvested from the Buck Island region, yet the extent and impact of the local 

conch fishery is undocumented. Infilling of this substantial knowledge gap may require collaboration with local fishers to 

ascertain levels of exploitation and to manage for ecologically sustainable levels of extraction.

S. gigas looking out of shell

4 - Discussion
References

p. 67

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

References

Anderson, M., H. Lund, E.H. Gladfelter, and M. Davies. 1986. Ecological community type maps and biological community descriptions 

for Buck Island Reef National Monument and proposed marine park sites in the British Virgin Islands. U.S. National Park Service and 

Virgin Islands Resource Management Cooperative Report. 236 pp.

Bythell, J.C., E.H. Gladfelter, W.B. Gladfelter, K.E. French, and Z. Hillis. 1989. Buck Island Reef Monument- changes in modern reef 

community structure. pp. 145-153. In: D.K. Hubbard (ed.). Terrestrial and marine geology of St. Croix, U.S. Virgin Islands. Special 

Publication No. 8. Teague Bay, St. Croix, West Indies Laboratory. 213 pp. http://www.aoml.noaa.gov/general/lib/CREWS/Cleo/St.%20

Croix/salt_river164.pdf.

Bythell, J.C., M. Bythell, and E.H. Gladfelter. 1993. Initial results of a long-term coral reef monitoring program: Impact of Hurricane Hugo 

at Buck Island Reef National Monument, St. Croix, U.S. Virgin Islands. J. Exp. Mar. Biol. Ecol. 172(1-2): 171-183.

Caribbean Fishery Management Council (CFMC). 1985. Fishery Management Plan, Final Environmental Impact Statement, and Draft 

Regulatory Impact Review, for the Shallow-Water Reeffish Fishery of Puerto Rico and the U.S. Virgin islands. Caribbean Fishery 

Management Council and National Marine Fisheries Service. 178 pp. http://www.caribbeanfmc.com/SCANNED%20FMPS/REEF%20

FISH/REEF-FISH%20FMP.htm.

Carpenter, R.C. 1988. Mass Mortality of a Caribbean Sea Urchin: Immediate Effects on Community Metabolism and Other Herbivores. 

Proceedings of the National Academy of Sciences. 85(2): 511-514. 

Cheung, W.W.L., T.J. Pitcher, and D. Pauly, 2005. A fuzzy logic expert system to estimate intrinsic extinction vulnerabilities of marine 

fishes to fishing. Biol. Conserv. 124: 97-111. 

Clark, R.D., C.F.G. Jeffrey, K. Woody, Z. Hillis-Starr, and M.E. Monaco. In press. Spatial and temporal patterns of coral bleaching 

around Buck Island Reef National Monument, St. Croix, U.S. Virgin Islands. Bull. Mar. Sci.

Clarke, K.R. and R.M. Warwick. 1994. Change in marine communities: an approach to statistical analysis and interpretation, 1st edition. 

Plymouth Marine Laboratory, Plymouth. 144 pp.

Clarke, K.R. and R.M. Warwick. 1998. A taxonomic distinctness index and its statistical properties. J. Appl. Ecol. 35: 523-531.

Clarke, K.R. and R.M. Warwick. 1999. The taxonomic distinctness measure of biodiversity: weighting of step lengths between hierarchial 

levels. Mar. Ecol. Prog. Ser. 194: 21-29.

Debrot, A.O. and I. Nagelkerken. 2006. Recovery of the long-spined sea urchin Diadema antillarum in Curçao (Netherlands Antilles) 

linked to lagoonal and wave sheltered shallow rocky habitats. Bull. Mar. Sci. 79(2):415-424.

Dulvy, N.K. and J.D. Reynolds. 2002. Predicting extinction vulnerability in skates. Conserv. Biol.16 (2): 440-450. 

Dulvy, N.K., Y. Sadovy, and J.D. Reynolds. 2003. Extinction vulnerability in marine populations. Fish and Fisheries 4: 25-64. 

Edmunds, P.J. and R.C. Carpenter. 2001. Recovery of Diadema reduces macroalgal cover and increases the abundance of juvenile 

corals on a Caribbean reef. Proceedings of the National Academy of Science. 98: 5067–5071.

Faith, D.P., P.R. Minchin, and L. Belbin. 1987. Compositional dissimilarity as a robust measure of ecological distance. Vegetatio 68: 

57-68.

Gladfelter, E.H. 1980. Aspects of population dynamics and ecological impact of the sea urchin Diadema antillarum. In: E.H. Gladfelter 

and W.B. Gladfelter (eds.). Chapter 5: Environmental studies of Buck Island Reef National Monument III, St. Croix, U.S. Virgin Islands. 

West Indies Laboratory, Fairleigh Dickinson University. St. Croix, U.S. Virgin Islands. 116 pp.

Gladfelter, W.B., E.H. Gladfelter, R.K. Monahan, J.C. Ogden, and R.F. Dill. 1977. Environmental studies of Buck Island Reef National 

Monument. National Park Service Report. Washington, DC. 144 pp. http://www.aoml.noaa.gov/general/lib/CREWS/Cleo/St.%20Croix/

salt_river164.pdf.

Grober-Dunsmore, R., T.K. Frazer, W.J. Lindberg, and J. Beets. 2007. Reef fish and habitat relationships in Caribbean seascapes: the 

importance of reef context. Coral Reefs 26(1): 210-216.

Hughes, T.P. 1994. Catastrophes, Phase-Shifts, and Large-Scale Degradation of a Caribbean coral reef. Science 265(5178): 1547-

1551.

Jeffrey, C. and M. Monaco. 2007. Domain (island) wide estimates of queen conch (Strombus gigas) abundance for three U.S. 

Caribbean Islands based on habitat-derived densities. SEDAR Report SEDAR14-AW3. Prepared by Biogeography Branch, Center for 

Coastal MOnitoring and Assessment, NOAA National Centers for Coastal Ocean Science. Prepared for Southeast Fisheries Sicence 

Center, NOAA National Marine Fisheries Service. St. Thomas, U.S. Virgin Islands. 11 pp. http://www.sefsc.noaa.gov/sedar/download/

S14AW03%20conch%20Habitatbasedanalysis.pdf?id=DOCUMENT

Jennings, S., J.D. Reynolds, and N.V.C. Polunin. 1999. Predicting the vulnerability of tropical reef fishes to exploitation with phylogenies 

and life histories. Conserv. Biol. 13(6): 1466-1475.
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 68

Kendall, M.S., C.R. Kruer, K.R. Buja, J.D. Christensen, M. Finkbeiner, R. Warner, and M.E. Monaco. 2002. Methods used to map the 

benthic habitats of Puerto Rico and the U.S. Virgin Islands. NOAA Technical Memorandum 152. Silver Spring, MD. http://ccma.nos.

noaa.gov/ecosystems/coralreef/usvi_pr_mapping.html.

Kendall, M.S., J.D. Christensen, and Z. Hillis-Starr. 2003. Multi-scale data used to analyze the spatial distribution of French grunts, 

Haemulon flavolineatum, relative to hard and soft bottom in a benthic landscape. Environ. Biol. Fish. 66: 19-26.

Kendall, M.S., T. Battista, and Z. Hillis-Starr. 2004b. Long term expansion of a deep Syringodium filiforme meadow in St. Croix, U.S. 

Virgin Islands: the portential role of hurricanes in the dispersal of seeds. Aquat. Bot. 78: 15-25.

Kendall, M.S., J.D. Christensen, C. Caldow, M. Coyne, C.F.G. Jeffrey, M.E. Monaco, W.Morrison, and Z. Hillis-Starr . 2004a. The 

influence of bottom type and shelf position on biodiversity of tropical fish inside a recently enlarged marine reserve. Aquatic. Conserv. 

Mar. Freshw. Ecosyst. 14: 113-132.

Legendre, P. and L. Legendre. 1998. Numerical Ecology, 2nd English edition. Developments in Environmental Modelling 20 Series . 

Elsevier Science Publishing. Amsterdam, The Netherlands. 870 pp. 

Lessios, H. 2005. Diadema antillarum populations in Panama twenty years following mass mortality. Coral Reefs 24(1):125-127.

Lessios, H.A. 1998. Mass mortality of Diadema antillarum in the Caribbean: what have we learned? Ann. Rev. Ecol. Syst. 19: 371-

393.

Lessios, H., D.R. Robertson, and J.D. Cubit. 1984. Spread of Diadema mass mortality through the Caribbean. Science 226(4672): 

335-337.

Magurran, A.E. 1988. Ecological diversity and its measurement. Princeton University Press. Princeton, NJ. 192 pp.

Mayor, P. 2005. Distribution and abundance of elkhorn coral, Acropora palmata, at Buck Island Reef National Monument in 2004. Buck 

Island Reef National Monument, National Park Service, U.S. Department of the Interior. 28 pp. 

Menza, C., J. Ault, J. Beets, C. Bohnsack, C. Caldow, J. Christensen, A. Friedlander, C. Jeffrey, M. Kendall, J. Luo, M.E. Monaco, S. 

Smith, and K. Woody. 2006. A guide to monitoring reef fish in the National Park Service’s South Florida/Caribbean Network. NOAA 

Technical Memorandum NOS NCCOS 39. Silver Spring, MD. 166 pp. http://ccma.nos.noaa.gov/news/feature/FishMonitoring.html.

Miller, J. South Florida / Caribbean Network, National Park Service. St. John, U.S. Virgin Islands. Personal communication.

Miller, R.J., A.J. Adams, N.B. Ogden, J.C. Ogden, and J.P. Ebersole. 2003. Diadema antillarum 17 years after mass mortality: is 

recovery beginning on St. Croix? Coral Reefs 22: 181-187.

Musick, J.A., M.M. Harbin, S.A. Berkeley, G.H. Burgess, A.M. Eklund, L. Findley, R.G. Gilmore, J.T. Golden, D.S. Ha, G.R. Huntsman, 

J.C. McGovern, S.J. Parker, S.G. Poss, E. Sala, T.W. Schmidt, G.R. Sedberry, H. Weeks, and S.G. Wright. 2000. Marine, estuarine, 

and diadromous fish stocks at risk of extinction in North America (exclusive of Pacific salmonids). Fisheries 25: 6-30. 

Ogden, J.C., D. Helm, J. Peterson, A. Smith, and S. Weisman (eds.). 1972. An ecological study of Teague Bay Reef, St. Croix, U.S. 

Virgin Islands. West Indies Laboratory, St. Croix, U.S. Virgin Islands. Special Publication 1: 50 pp.

Ogden, J.C., D.P. Abbott, and I.A. Abbott. 1973. Studies on the activity and food of the echinoid Diadema antillarum Philippi on a West 

Indian patch reef. West Indies Lab, St. Croix, U.S. Virgin Islands. Special Publication 2: 96 pp.

Pittman, S.J., C. Caldow, S.D. Hile, and M.E. Monaco. 2007. Using seascape types to explain the spatial patterns of fish in the 

mangroves of SW Puerto Rico. Mar. Ecol. Prog. Ser. 348: 273-284

Rogers, C.S., T. Suchanek, and F. Pecora. 1982. Effects of Hurricanes David and Federic (1979) on shallow Acropora palmata reef 

communities: St. Croix, USVI. Bull. Mar. Sci. 32: 532-548.

Rogers, C., V. Garrison, and R. Grober-Dunsmore. 1997. A fishy story about hurricanes and herbivory: seven years of research on a 

reef in St John, US Virgin Islands. pp. 555-560. In: H.A. Lessios and I.G. Macintyre (eds.). Proceedings of the 8th International Coral 

Reef Symposium, Vol. 1. Panama City, Panama. 1040 pp.

Rogers, C.S. and J. Beets. 2001. Degradation of marine ecosystems and decline of fishery resources in marine protected areas in the 

U.S. Virgin Islands. Environ. Conserv. 84: 312-322.

Warwick, R.M. and K.R. Clarke. 1995. New ‘biodiversity’ measures reveal a decrease in taxonomic distinctness with increasing stress. 

Mar Ecol. Prog. Ser. 129: 301-305.

References
p. 69

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Appendix A

Figure A1. Map of the East End Marine Park and park zoning. 

Source: http://www.stxeastendmarinepark.org/about.htm

Appendix A
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 70Appendix B

Table B1. USVI finfish landings as a proportion of the total finfish landings 

reported for the U.S. Caribbean in 1980. Listed are the most commonly 

landed species and species groups. Data from the Caribbean Fisheries 

Management Council (CFMC, 1985).

Species/Species group Fish Family

USVI % of 

total landings 

U.S. Caribbean

Grunts Haemulidae 0.47

Groupers Serranidae 13.91

Goatfish Mullidae 0.99

Parrotfish Scaridae 5.83

Lane snapper (L. synagris) Lutjanidae 0.03

Yellowtail snapper (O.chryusurus) Lutjanidae 2.89

Triggerfishes Balistidae 29.68

Squirrelfishes Holocentridae 4.84

Mutton snapper (L. analis) Lutjanidae 0.13

Other snappers Lutjanidae 1.04

Hogfish Labridae 1.06

Trunkfish Ostraciidae 0.08

Appendix B
p. 71

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Appendix C

Appendix C

Table C1. Fish species list and summary data on occurrence, abundance and biomass (2001-2006) for the study region (northeastern 

St. Croix).

Family

Species name Common name

% occurrenceTotal occurrenceTotal

abundance

Mean abundance Total

biomass, g

Mean biomass, g

 (+ SE) (+ SE)

Acanthuridae

Acanthurus bahianus Ocean surgeonfish 59.8 762 8601 6.7 (0.36) 540368.5 423.8 (37.0)

Acanthurus chirurgus Doctorfish 11.8 150 652 0.51 (0.06) 48646.1 38.2 (5.7)

Acanthurus coeruleus Blue tang 46.7 595 8597 6.7 (0.65) 904137.1 709.1 (83.8)

Acanthurus UNK SURGEONFISH sp 0.1 1 1 <0.01 (<0.01) 0.8 <0.01 (<0.01)

Apogonidae

Apogon binotatus Barred cardinalfish 0.1 1 1 <0.01 (<0.01) 7.7 <0.01 (<0.01)

Apogon maculatus Flamefish 0.2 2 2 <0.01 (<0.01) 8.1 <0.01 (<0.01)

Apogon quadrisquamatus Sawcheek cardinalfish 0.5 6 22 0.02 (<0.01) 10.1 <0.01 (<0.01)

Apogon townsendi Belted cardinalfish 0.5 7 16 0.01 (<0.01) 29.0 0.02 (0.02)

Apogon UNK CARDINALFISH sp 0.3 4 7 <0.01 (<0.01) 46.8 0.04 (0.03)

Astrapogon puncticulatus Blackfin cardinalfish 0.1 1 1 <0.01 (<0.01) 0.5 <0.01 (<0.01)

Astrapogon stellatus Conchfish 0.2 3 4 <0.01 (<0.01) 2.0 <0.01 (<0.01)

Aulostomidae

Aulostomus maculatus Trumpetfish 6.3 80 107 0.08 (0.01) 9163.9 7.2 (1.0)

Balistidae

Balistes vetula Queen triggerfish 8.5 108 208 0.16 (0.02) 175978.6 138.0 (19.6)

Melichthys niger Black durgon 4.4 56 158 0.12 (0.02) 118235.5 92.7 (21.4)

Belonidae

Ablennes hians Flat needlefish 0.2 2 51 0.04 (0.04) 1891.0 1.5 (1.5)

Blenniidae

Ophioblennius macclurei Redlip blenny 9.0 115 368 0.29 (0.04) 1442.1 1.1 (0.18)

Parablennius marmoreus Seaweed blenny 0.1 1 4 <0.01 (<0.01) 1.2 <0.01 (<0.01)

Bothidae

Bothus lunatus Peacock flounder 2.3 29 32 0.03 (<0.01) 5391.4 4.2 (1.5)

Bothus ocellatus Eyed flounder 0.6 8 9 <0.01 (<0.01) 224.7 0.18 (0.10)

Bothus UNK FLOUNDER sp 0.5 6 6 <0.01 (<0.01) 13.4 0.01 (<0.01)

Callionymidae

Paradiplogrammus bairdi Lancer dragonet 1.1 14 20 0.02 (<0.01) 49.2 0.04 (0.02)

Carangidae

Carangoides bartholomaei Yellow jack 0.5 6 22 0.02 (<0.01) 33344.3 26.2 (17.8)

Caranx crysos Blue runner 12.8 163 1064 0.83 (0.12) 369852.4 290.1 (53.4)

Caranx hippos Crevalle jack 0.2 2 2 <0.01 (<0.01) 2218.8 1.7 (1.3)

Caranx latus Horse-Eye jack 0.2 2 7 <0.01 (<0.01) 1822.9 1.4 (1.1)

Carangoides ruber Bar jack 28.5 364 1735 1.4 (0.17) 57872.9 45.4 (8.6)

Caranx UNK JACK sp 0.1 1 1 <0.01 (<0.01) 389.1 0.31 (0.31)

Decapterus macarellus Mackerel scad 2.9 37 2319 1.8 (0.51) 136084.3 106.7 (30.6)

Decapterus UNK SCAD sp 0.3 4 244 0.19 (0.13) 6799.1 5.3 (2.9)

Selar crumenophthalmus Bigeye scad 0.1 1 24 0.02 (0.02) 2182.9 1.7 (1.7)

Chaenopsidae

Acanthemblemaria aspera Roughhead blenny 0.2 2 3 <0.01 (<0.01) 0.6 <0.01 (<0.01)

Acanthemblemaria maria Secretary blenny 0.2 2 2 <0.01 (<0.01) 0.4 <0.01 (<0.01)

Acanthemblemaria spinosa Spinyhead blenny 0.1 1 1 <0.01 (<0.01) 0.2 <0.01 (<0.01)

Acanthemblemaria UNK TUBE BLENNY sp 0.1 1 6 <0.01 (<0.01) 1.2 <0.01 (<0.01)

Chaenopsis limbaughi Yellowface pikeblenny 2.0 26 123 0.10 (0.03) 266.2 0.21 (0.09)

Chaenopsis ocellata Bluethroat pikeblenny 2.0 26 54 0.04 (0.01) 241.0 0.19 (0.06)

Chaenopsis UNK PIKEBLENNY sp 0.4 5 8 <0.01 (<0.01) 21.3 0.02 (<0.01)

Emblemaria pandionis Sailfin blenny 0.3 4 7 <0.01 (<0.01) 1.4 <0.01 (<0.01)

Chaetodontidae

Chaetodon capistratus Foureye butterflyfish 15.4 196 385 0.30 (0.02) 9481.2 7.4 (1.2)

Chaetodon ocellatus Spotfin butterflyfish 0.7 9 14 0.01 (<0.01) 283.1 0.22 (0.14)

Chaetodon sedentarius Reef butterflyfish 1.2 15 22 0.02 (<0.01) 624.8 0.49 (0.17)

Chaetodon striatus Banded butterflyfish 7.0 89 147 0.12 (0.01) 4940.0 3.9 (0.79)

Prognathodes aculeatus Longsnout butterflyfish 0.5 7 9 <0.01 (<0.01) 151.4 0.12 (0.06)

Cirrhitidae

Amblycirrhitus pinos Redspotted hawkfish 1.3 17 22 0.02 (<0.01) 24.8 0.02 (<0.01)

Clupeidae

Clupeidae UNK HERRING sp 0.1 1 70 0.05 (0.05) 3.4 <0.01 (<0.01)

Jenkinsia UNK HERRING sp 0.1 1 50 0.04 (0.04) 2.4 <0.01 (<0.01)
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 72

Table C1 cont...

Family

Species name Common Name

% occurrenceTotal occurrence

Total

abundance

Mean abundance Total

biomass, g

Mean biomass, g

 (+ SE) (+ SE)

Congridae

Heteroconger longissimus Brown garden eel 1.5 19 1711 1.3 (0.66) 46379.3 36.4 (18.8)

Dactylopteridae

Dactylopterus volitans Flying gurnard 0.1 1 3 <0.01 (<0.01) 330.6 0.26 (0.26)

Dasyatidae

Dasyatis americana Southern stingray 2.2 28 37 0.03 (<0.01) 10064.2 7.9 (2.3)

Diodontidae

Chilomycterus antennatus Bridled burrfish 0.1 1 1 <0.01 (<0.01) 395.5 0.31 (0.31)

Diodon holocanthus Balloonfish 0.7 9 10 <0.01 (<0.01) 1196.3 0.94 (0.44)

Diodon hystrix Porcupinefish 0.7 9 10 <0.01 (<0.01) 9898.9 7.8 (3.9)

Echeneidae

Echeneis naucrates Sharksucker 0.7 9 11 <0.01 (<0.01) 8529.7 6.7 (2.5)

Engraulidae

Engraulidae UNK 0.1 1 1 <0.01 (<0.01) 0.2 <0.01 (<0.01)

Gerreidae

Eucinostomus gula Silver jenny 0.2 3 10 <0.01 (<0.01) 616.2 0.48 (0.32)

Eucinostomus melanopterus Flagfin mojarra 0.2 2 6 <0.01 (<0.01) 115.1 0.09 (0.07)

Eucinostomus UNK MOJARRA sp 0.1 1 13 0.01 (0.01) 668.4 0.52 (0.52)

Gerres cinereus Yellowfin mojarra 6.9 88 162 0.13 (0.02) 7597.4 6.0 (1.1)

Ginglymostomatidae

Ginglymostoma cirratum Nurse shark 0.5 7 9 <0.01 (<0.01) 37663.9 29.5 (12.1)

Gobiidae

Coryphopterus dicrus Colon goby 1.3 16 19 0.01 (<0.01) 12.5 <0.01 (<0.01)

Coryphopterus eidolon Pallid goby 0.1 1 1 <0.01 (<0.01) 0.7 <0.01 (<0.01)

Coryphopterus glaucofraenum Bridled goby 23.7 302 1670 1.3 (0.11) 1490.4 1.2 (0.12)

Coryphopterus lipernes Peppermint goby 0.2 2 5 <0.01 (<0.01) 3.3 <0.01 (<0.01)

Coryphopterus personatus/hyalinus Masked/Glass goby 1.7 22 639 0.50 (0.28) 418.8 0.33 (0.19)

Ctenogobius saepepallens Dash goby 1.1 14 68 0.05 (0.03) 44.6 0.03 (0.02)

Elacatinus chancei Shortstripe goby 0.5 7 20 0.02 (<0.01) 5.0 <0.01 (<0.01)

Elacatinus evelynae Sharknose goby 6.4 81 143 0.11 (0.02) 35.8 0.03 (<0.01)

Elacatinus multifasciatus Greenbanded goby 0.1 1 1 <0.01 (<0.01) 0.3 <0.01 (<0.01)

Elacatinus prochilos Broadstripe goby 1.8 23 45 0.04 (0.01) 11.3 <0.01 (<0.01)

Elacatinus saucrus Leopard goby 0.1 1 1 <0.01 (<0.01) 0.3 <0.01 (<0.01)

Elacatinus UNK GOBY sp 0.1 1 1 <0.01 (<0.01) 0.3 <0.01 (<0.01)

Gnatholepis thompsoni Goldspot goby 14.6 186 690 0.54 (0.07) 298.7 0.23 (0.07)

Gobiidae UNK GOBIES 0.2 2 2 <0.01 (<0.01) 1.3 <0.01 (<0.01)

Microgobius carri Seminole goby 0.1 1 1 <0.01 (<0.01) 0.2 <0.01 (<0.01)

Nes longus Orangespotted goby 0.4 5 8 <0.01 (<0.01) 68.9 0.05 (0.04)

Priolepis hipoliti Rusty goby 0.1 1 1 <0.01 (<0.01) 0.4 <0.01 (<0.01)

Grammatidae

Gramma loreto Fairy basslet 4.0 51 154 0.12 (0.02) 131.7 0.10 (0.03)

Haemulidae

Anisotremus surinamensis Black margate 0.2 2 2 <0.01 (<0.01) 2048.1 1.6 (1.3)

Anisotremus virginicus Porkfish 0.2 3 3 <0.01 (<0.01) 850.7 0.67 (0.38)

Haemulon album White margate 0.2 2 5 <0.01 (<0.01) 2840.8 2.2 (2.1)

Haemulon aurolineatum Tomtate 4.2 53 2633 2.1 (1.1) 109702.8 86.0 (32.2)

Haemulon carbonarium Caesar grunt 1.8 23 130 0.10 (0.03) 22569.4 17.7 (6.5)

Haemulon chrysargyreum Smallmouth grunt 1.2 15 201 0.16 (0.07) 5190.1 4.1 (2.1)

Haemulon flavolineatum French grunt 28.0 357 1944 1.5 (0.26) 107188.4 84.1 (7.5)

Haemulon macrostomum Spanish grunt 1.0 13 54 0.04 (0.02) 2954.0 2.3 (1.5)

Haemulon melanurum Cottonwick 0.5 6 209 0.16 (0.16) 15919.8 12.5 (11.5)

Haemulon parra Sailors choice 0.2 2 3 <0.01 (<0.01) 377.4 0.30 (0.27)

Haemulon plumierii White grunt 3.5 45 468 0.37 (0.26) 64316.4 50.4 (17.7)

Haemulon sciurus Bluestriped grunt 4.3 55 199 0.16 (0.04) 42646.6 33.4 (8.4)

Haemulon striatum Striped grunt 0.1 1 1 <0.01 (<0.01) 43.9 0.03 (0.03)

Haemulon UNK GRUNT sp 4.1 52 3419 2.7 (0.78) 9538.7 7.5 (3.8)

Holocentridae

Holocentrus adscensionis Squirrelfish 11.8 150 349 0.27 (0.05) 48639.6 38.1 (6.3)

Holocentrus rufus Longspine squirrelfish 25.2 321 574 0.45 (0.03) 65191.6 51.1 (4.2)

Myripristis jacobus Blackbar soldierfish 3.5 45 127 0.10 (0.04) 13899.2 10.9 (4.3)

Sargocentron vexillarium Dusky squirrelfish 0.6 8 13 0.01 (<0.01) 448.2 0.35 (0.16)

Appendix C
p. 73

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Table C1 cont...

Family

Species name Common name

%

occurrence

Total

occurrence

Total

abundance

Mean abundance Total

biomass, g

Mean biomass, g

 (+ SE) (+ SE)

Inermiidae

Inermia vittata Boga 0.5 7 490 0.38 (0.19) 6365.2 5.0 (2.9)

Kyphosidae

Kyphosus sectator Chub (Bermuda/Yellow) 0.5 6 20 0.02 (<0.01) 10739.8 8.4 (4.6)

Labridae

Bodianus rufus Spanish hogfish 6.4 81 149 0.12 (0.02) 14514.0 11.4 (2.1)

Clepticus parrae Creole wrasse 3.5 45 2160 1.7 (0.67) 65470.5 51.3 (17.7)

Halichoeres bivittatus Slippery dick 73.2 933 24752 19.4 (1.8) 97962.0 76.8 (5.8)

Halichoeres cyanocephalus Yellowcheek wrasse 0.7 9 9 <0.01 (<0.01) 656.0 0.51 (0.29)

Halichoeres garnoti Yellowhead wrasse 46.0 586 4658 3.7 (0.19) 34689.8 27.2 (1.8)

Halichoeres maculipinna Clown wrasse 33.9 432 2176 1.7 (0.11) 10193.3 8.0 (0.78)

Halichoeres pictus Rainbow wrasse 1.8 23 164 0.13 (0.04) 483.3 0.38 (0.12)

Halichoeres poeyi Blackear wrasse 16.7 213 650 0.51 (0.05) 3592.1 2.8 (0.33)

Halichoeres radiatus Puddingwife 21.1 269 503 0.39 (0.03) 5361.9 4.2 (1.2)

Lachnolaimus maximus Hogfish 0.4 5 6 <0.01 (<0.01) 115.5 0.09 (0.05)

Thalassoma bifasciatum Bluehead wrasse 60.9 777 32001 25.1 (1.2) 46055.3 36.1 (1.7)

Xyrichtys martinicensis Rosy razorfish 13.6 174 2582 2.0 (0.34) 12572.0 9.9 (2.4)

Xyrichtys novacula Pearly razorFish 0.3 4 6 <0.01 (<0.01) 40.6 0.03 (0.02)

Xyrichtys splendens Green razorfish 11.8 150 598 0.47 (0.08) 3050.0 2.4 (0.54)

Xyrichtys UNK RAZORFISH sp 0.2 3 23 0.02 (0.01) 6.2 <0.01 (<0.01)

Labrisomidae

Malacoctenus aurolineatus Goldline blenny 0.9 11 23 0.02 (<0.01) 15.6 0.01 (<0.01)

Malacoctenus boehlkei Diamond blenny 0.1 1 1 <0.01 (<0.01) 0.2 <0.01 (<0.01)

Malacoctenus gilli Dusky blenny 0.4 5 9 <0.01 (<0.01) 2.2 <0.01 (<0.01)

Malacoctenus macropus Rosy blenny 4.7 60 129 0.10 (0.02) 87.4 0.07 (0.01)

Malacoctenus triangulatus Saddled blenny 10.4 132 265 0.21 (0.02) 77.7 0.06 (0.01)

Malacoctenus UNK LABRISOMIDS 0.5 6 8 <0.01 (<0.01) 2.9 <0.01 (<0.01)

Malacoctenus versicolor Barfin blenny 1.1 14 14 0.01 (<0.01) 10.4 <0.01 (<0.01)

Lutjanidae

Lutjanus analis Mutton snapper 3.2 41 49 0.04 (<0.01) 81134.4 63.6 (15.1)

Lutjanus apodus Schoolmaster 3.3 42 81 0.06 (0.02) 30045.2 23.6 (6.0)

Lutjanus buccanella Blackfin snapper 0.1 1 1 <0.01 (<0.01) 1.5 <0.01 (<0.01)

Lutjanus griseus Gray snapper 1.2 15 53 0.04 (0.02) 12823.5 10.1 (5.3)

Lutjanus jocu Dog snapper 0.2 2 2 <0.01 (<0.01) 7404.6 5.8 (5.4)

Lutjanus mahogoni Mahogany snapper 3.4 43 129 0.10 (0.03) 13467.7 10.6 (2.4)

Lutjanus synagris Lane snapper 2.3 29 60 0.05 (0.01) 5485.8 4.3 (1.2)

Lutjanus UNK SNAPPER sp 0.1 1 1 <0.01 (<0.01) 0.4 <0.01 (<0.01)

Ocyurus chrysurus Yellowtail snapper 20.4 260 741 0.58 (0.06) 73934.6 58.0 (7.0)

Malacanthidae

Malacanthus plumieri Sand tilefish 10.7 137 232 0.18 (0.02) 66683.8 52.3 (6.3)

Megalopidae

Megalops atlanticus Tarpon 0.1 1 1 <0.01 (<0.01) 37379.9 29.3 (29.3)

Microdesmidae

Ptereleotris helenae Hovering goby 0.8 10 29 0.02 (0.01) 39.5 0.03 (0.02)

Monacanthidae

Aluterus scriptus Scrawled filefish 0.2 3 3 <0.01 (<0.01) 153.5 0.12 (0.11)

Cantherhines macrocerus Whitespotted filefish 0.4 5 6 <0.01 (<0.01) 734.9 0.58 (0.35)

Cantherhines pullus Orangespotted filefish 1.7 22 26 0.02 (<0.01) 1157.9 0.91 (0.36)

Monacanthus ciliatus Fringed filefish 1.1 14 14 0.01 (<0.01) 23.2 0.02 (<0.01)

Monacanthus tuckeri Slender filefish 1.5 19 24 0.02 (<0.01) 44.4 0.03 (0.01)

Monacanthus UNK FILEFISH sp 0.2 3 3 <0.01 (<0.01) 1.5 <0.01 (<0.01)

Mullidae

Mulloidichthys martinicus Yellow goatfish 7.3 93 344 0.27 (0.05) 69054.0 54.2 (16.5)

Pseudupeneus maculatus Spotted goatfish 23.3 297 915 0.72 (0.08) 72224.9 56.6 (6.8)

Muraenidae

Enchelycore nigricans Viper moray 0.1 1 1 <0.01 (<0.01) 253.1 0.20 (0.20)

Gymnothorax funebris Green moray 0.1 1 1 <0.01 (<0.01) 52.9 0.04 (0.04)

Gymnothorax miliaris Goldentail moray 0.2 2 2 <0.01 (<0.01) 6.7 <0.01 (<0.01)

Gymnothorax moringa Spotted moray 0.2 3 3 <0.01 (<0.01) 2063.0 1.6 (1.2)

Gymnothorax UNK MORAY EEL sp 0.1 1 1 <0.01 (<0.01) 0.6 <0.01 (<0.01)

Gymnothorax vicinus Purplemouth moray 0.2 2 2 <0.01 (<0.01) 373.1 0.29 (0.22)

Muraenidae UNK 0.1 1 1 <0.01 (<0.01) 18.6 0.01 (0.01)

Appendix C
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 74

Table C1 cont...

Family

Species name Common name

%

occurrence

Total

occurrence

Total

abundance

Mean abundance Total

biomass, g

Mean biomass, g

 (+ SE) (+ SE)

Myliobatidae

Aetobatus narinari Spotted eagle ray 0.2 3 3 <0.01 (<0.01) 26717.4 21.0 (16.1)

Ogcocephalidae

Ogcocephalus nasutus Shortnose batfish 0.1 1 1 <0.01 (<0.01) 0.5 <0.01 (<0.01)

Ophichthidae

Myrichthys breviceps Sharptail eel 0.1 1 1 <0.01 (<0.01) 1000.0 0.78 (0.78)

Myrichthys ocellatus Goldspotted eel 0.3 4 4 <0.01 (<0.01) 130.5 0.10 (0.06)

Ophichthus ophis Spotted Snake eel 0.1 1 2 <0.01 (<0.01) 42.4 0.03 (0.03)

Opistognathidae

Opistognathus aurifrons Yellowhead jawfish 3.5 44 145 0.11 (0.03) 710.6 0.56 (0.13)

Opistognathus macrognathus Banded jawfish 0.3 4 7 <0.01 (<0.01) 16.2 0.01 (<0.01)

Ostraciidae

Acanthostracion polygonius Honeycomb cowfish 0.5 6 7 <0.01 (<0.01) 1620.8 1.3 (0.65)

Acanthostracion quadricornis Scrawled cowfish 0.2 2 3 <0.01 (<0.01) 199.8 0.16 (0.14)

Lactophrys bicaudalis Spotted trunkfish 0.5 7 7 <0.01 (<0.01) 1566.0 1.2 (0.62)

Lactophrys trigonus Trunkfish 1.1 14 15 0.01 (<0.01) 4200.4 3.3 (1.2)

Lactophrys triqueter Smooth trunkfish 4.1 52 55 0.04 (<0.01) 7529.1 5.9 (1.1)

Paralichthyidae

Syacium UNK SAND FLOUNDER sp 0.2 3 3 <0.01 (<0.01) 113.5 0.09 (0.08)

Pempheridae

Pempheris schomburgkii Glassy sweeper 0.3 4 40 0.03 (0.02) 609.0 0.48 (0.30)

Pomacanthidae

Holacanthus ciliaris queen angelfish 0.6 8 10 <0.01 (<0.01) 2662.5 2.1 (1.3)

Holacanthus tricolor Rock beauty 6.0 76 94 0.07 (<0.01) 9185.6 7.2 (1.5)

Pomacanthus arcuatus Gray angelfish 1.0 13 16 0.01 (<0.01) 8538.6 6.7 (4.5)

Pomacanthus paru French angelfish 2.5 32 45 0.04 (<0.01) 15188.9 11.9 (3.9)

Pomacentridae

Abudefduf saxatilis Sergeant major 5.2 66 202 0.16 (0.03) 7497.3 5.9 (1.5)

Abudefduf taurus Night sergeant 0.2 2 2 <0.01 (<0.01) 256.9 0.20 (0.14)

Chromis cyanea Blue chromis 17.3 220 3321 2.6 (0.30) 18487.0 14.5 (2.0)

Chromis multilineata Brown chromis 6.4 81 812 0.64 (0.11) 7800.1 6.1 (1.4)

Microspathodon chrysurus Yellowtail damselfish 21.3 272 1158 0.91 (0.08) 77577.9 60.8 (6.8)

Stegastes adustus Dusky damselfish 16.8 214 1544 1.2 (0.12) 11375.4 8.9 (1.1)

Stegastes diencaeus Longfin damselfish 20.7 264 1870 1.5 (0.13) 18510.1 14.5 (1.8)

Stegastes leucostictus Beaugregory 29.6 378 3991 3.1 (0.25) 12877.4 10.1 (0.86)

Stegastes partitus Bicolor damselfish 48.9 624 10202 8.0 (0.44) 17761.2 13.9 (1.2)

Stegastes planifrons Threespot damselfish 15.9 203 1221 0.96 (0.10) 12604.7 9.9 (1.1)

Stegastes variabilis Cocoa damselfish 8.9 114 343 0.27 (0.04) 1788.7 1.4 (0.33)

Priacanthidae

Heteropriacanthus cruentatus Glasseye snapper 0.2 2 2 <0.01 (<0.01) 314.9 0.25 (0.19)

Scaridae

Cryptotomus roseus Bluelip parrotfish 18.1 231 1968 1.5 (0.17) 13233.5 10.4 (1.6)

Scarus guacamaia Rainbow parrotfish 0.3 4 14 0.01 (<0.01) 3907.1 3.1 (1.8)

Scarus iseri Striped parrotfish 34.0 434 4761 3.7 (0.28) 74268.8 58.3 (5.8)

Scarus taeniopterus Princess parrotfish 24.9 318 1713 1.3 (0.10) 72301.0 56.7 (5.3)

Scarus UNK PARROTFISH sp 0.5 6 103 0.08 (0.04) 466.9 0.37 (0.22)

Scarus vetula Queen parrotfish 13.4 171 489 0.38 (0.04) 133281.4 104.5 (12.0)

Sparisoma atomarium Greenblotch parrotfish 13.7 175 845 0.66 (0.08) 1900.2 1.5 (0.46)

Sparisoma aurofrenatum Redband parrotfish 52.5 669 4887 3.8 (0.18) 240212.9 188.4 (10.0)

Sparisoma chrysopterum Redtail parrotfish 5.5 70 118 0.09 (0.01) 16052.8 12.6 (2.6)

Sparisoma radians Bucktooth parrotfish 17.5 223 1181 0.93 (0.11) 3764.1 3.0 (0.61)

Sparisoma rubripinne Yellowtail parrotfish 6.8 87 198 0.16 (0.03) 36043.3 28.3 (6.1)

Sparisoma UNK PARROTFISH Genus 0.4 5 7 <0.01 (<0.01) 9.9 <0.01 (<0.01)

Sparisoma viride Stoplight parrotfish 36.1 460 2456 1.9 (0.11) 331900.0 260.3 (24.1)

Sciaenidae

Equetus lanceolatus Jackknife-fish 0.1 1 1 <0.01 (<0.01) 2.5 <0.01 (<0.01)

Equetus punctatus Spotted drum 0.4 5 5 <0.01 (<0.01) 1078.1 0.85 (0.59)

Pareques acuminatus Highhat 0.3 4 8 <0.01 (<0.01) 2.3 <0.01 (<0.01)

Scombridae

Scomberomorus regalis Cero 0.9 11 11 <0.01 (<0.01) 13666.4 10.7 (4.2)

Appendix C
p. 75

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Table C1 cont...

Family

Species name Common name

%

occurrence

Total

occurrence

Total

abundance

Mean abundance Total

biomass, g

Mean biomass, g

 (+ SE) (+ SE)

Scorpaenidae

Scorpaena plumieri Spotted scorpionfish 0.3 4 4 <0.01 (<0.01) 1015.8 0.80 (0.44)

Scorpaena UNK SCORPIONFISH sp 0.2 2 2 <0.01 (<0.01) 113.6 0.09 (0.09)

Serranidae

Alphestes afer Mutton hamlet 0.3 4 4 <0.01 (<0.01) 896.1 0.70 (0.50)

Cephalopholis cruentata Graysby 4.2 53 81 0.06 (0.01) 9010.6 7.1 (1.3)

Cephalopholis fulva Coney 32.4 413 1391 1.1 (0.07) 193131.3 151.5 (15.0)

Epinephelus adscensionis Rock hind 0.4 5 7 <0.01 (<0.01) 6562.3 5.1 (4.2)

Epinephelus guttatus Red hind 18.1 231 379 0.30 (0.02) 89106.8 69.9 (6.9)

Epinephelus striatus Nassau grouper 0.2 2 3 <0.01 (<0.01) 1267.8 0.99 (0.81)

Hypoplectrus chlorurus Yellowtail hamlet 1.2 15 19 0.01 (<0.01) 235.5 0.18 (0.06)

Hypoplectrus guttavarius Shy hamlet 0.1 1 1 <0.01 (<0.01) 4.1 <0.01 (<0.01)

Hypoplectrus indigo Indigo hamlet 0.1 1 1 <0.01 (<0.01) 19.5 0.02 (0.02)

Hypoplectrus nigricans Black hamlet 1.1 14 16 0.01 (<0.01) 146.5 0.11 (0.05)

Hypoplectrus puella Barred hamlet 1.4 18 31 0.02 (<0.01) 234.7 0.18 (0.06)

Hypoplectrus unicolor Butter hamlet 0.7 9 12 <0.01 (<0.01) 88.7 0.07 (0.03)

Hypoplectrus UNK HAMLET sp 0.4 5 5 <0.01 (<0.01) 43.5 0.03 (0.02)

Mycteroperca tigris Tiger grouper 0.1 1 1 <0.01 (<0.01) 2200.4 1.7 (1.7)

Mycteroperca venenosa Yellowfin grouper 0.1 1 3 <0.01 (<0.01) 684.7 0.54 (0.54)

Rypticus saponaceus Greater soapfish 0.1 1 1 <0.01 (<0.01) 29.1 0.02 (0.02)

Serranus baldwini Lantern bass 3.7 47 112 0.09 (0.02) 187.2 0.15 (0.04)

Serranus tabacarius Tobaccofish 3.5 45 75 0.06 (0.01) 796.5 0.62 (0.20)

Serranus tigrinus Harlequin bass 27.4 349 713 0.56 (0.03) 5553.1 4.4 (0.59)

Serranus tortugarum Chalk bass 0.2 3 9 <0.01 (<0.01) 3.2 <0.01 (<0.01)

Sparidae

Calamus calamus Saucereye porgy 0.1 1 2 <0.01 (<0.01) 101.4 0.08 (0.08)

Sphyraenidae

Sphyraena barracuda Great barracuda 4.5 58 61 0.05 (<0.01) 263227.7 206.5 (37.9)

Sphyraena picudilla Southern sennet 0.1 1 300 0.24 (0.24) 344915.6 270.5 (270.5)

Syngnathidae

Acentronura dendritica Pipehorse 0.1 1 1 <0.01 (<0.01) 0.2 <0.01 (<0.01)

Cosmocampus elucens Shortfin pipefish 0.2 3 5 <0.01 (<0.01) 1.5 <0.01 (<0.01)

Hippocampus reidi Longsnout seahorse 0.1 1 1 <0.01 (<0.01) 0.6 <0.01 (<0.01)

Hippocampus UNK PIPEFISH sp 0.1 1 2 <0.01 (<0.01) 1.3 <0.01 (<0.01)

Synodontidae

Synodus intermedius Sand diver 2.9 37 41 0.03 (<0.01) 3906.8 3.1 (0.89)

Tetraodontidae

Canthigaster rostrata Sharpnose puffer 15.1 192 287 0.23 (0.02) 1059.6 0.83 (0.12)

Sphoeroides spengleri Bandtail puffer 2.5 32 36 0.03 (<0.01) 181.3 0.14 (0.04)

Sphoeroides testudineus Checkered puffer 0.2 2 5 <0.01 (<0.01) 70.4 0.06 (0.04)

Appendix C
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 76Appendix D

a)

b)

d)

c)

Figure D1. Spatial distributions of juvenile and adult: (a) bluehead wrasse (T. bifasciatum), (b) queen triggerfish (B. vetula), (c) rock 

beauty (H. tricolor) and (d) slippery dick (H. bivittatus) in northeastern St. Croix.

Appendix D
p. 77

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Figure D2. Spatial distributions of juvenile and adult (a) princess parrotfish (S. taeniopterus) and (b) stoplight parrotfish (S. viride) in 

northeastern St. Croix.

a)

b)

Appendix D
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 78Appendix D

e)

a)

c)

b)

d)

Figure D3. Spatial distributions of juvenile and adult: (a) threespot damselfish (Stegastes planifrons), (b) foureye butterflyfish (Chaetodon 

capistratus), (c) spotfin butterflyfish (Chaetodon ocellatus), (d) banded butterflyfish (Chaetodon striatus) and (e) great barracuda 

(Sphyraena barracuda) in northeastern St. Croix.
p. 79

Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

Appendix E

Appendix E Fish density / 100 m2

a) Inside BIRNM Grunt biomass (g/100 m2

) c) Outside BIRNM S. iseri density (100 m2

)

e) Outside BIRNM

Parrotfish biomass (g/100 m2

)

b) Inside BIRNM H. sciurus biomass (g/100 m2

)

d) Outside BIRNM S. iseri biomass (g/100 m2

)

f) Outside BIRNM

Figure E1. Raw census data grouped by year of survey for fish metrics that exhibited an increase or decline every year over the study 

period (2003-2006). The horizontal blue line connects the mean (+ SE) for each year. (a) Fish density (all species) increased gradually inside BIRNM, with 2005 and 2006 densities significantly higher than 2003; (b) Mean parrotfish biomass increased inside BIRNM 

from 2003 to 2006, but with no significant difference between years; (c) grunt biomass decreased each year outside BIRNM, with 2005 

and 2006 biomass significantly lower than 2003; (d) bluestriped grunt (H. sciurus) biomass decreases each year outside BIRNM, with 

2005 and 2006 biomass significantly lower than 2003; (e) striped parrotfish (S. iseri) density decreased each year outside BIRNM, with 

2005 and 2006 biomass lower than 2003; and (f) striped parrotfish (S. iseri) biomass decreased each year outside BIRNM, with 2006 

biomass significantly lower than 2003 and 2004.
Fish assemblages and benthic habitats of the Buck Island Reef National Monument and the surrounding seascape

p. 80Acknowledgements

Acknowledgements

Many thanks to our partners in the field including the many NPS scientists that contributed to data collection and logistical 

support enabling many successful missions over six years and to the NOAA Coral Reef Conservation Program, NCCOS 

CSCOR and NCCOS CCMA for funding the Biogeography Branch’s CREM project. A special thanks to Mr. John Christensen 

on the initial formulation of sample design and data analysis in support of CREM. In addition, we thank our colleagues at 

the U.S. Virgin Islands Department of Planning and Natural Resources for their contributions to the monitoring study. 



United States Department of Commerce

Carlos M Gutierrez

Secretary

National Oceanic and Atmospheric Administration

Vice Admiral Conrad C Lautenbacher, Jr. USN (Ret.)

Under Secretary of Commerce for Ocean and Atmospheres

National Ocean Service

Jack H Dunnigan

Assistant Administrator