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The United States Virgin Islands TERRITORIAL CORAL REEF MONITORING PROGRAM ANNUAL REPORT 2024 Hollander ENR, Krampitz NM, Ennis RS, Heidmann SL, Kadison E, Smith TB INDEX ii A collaboration between: The Center for Marine and Environmental Studies, University of the Virgin Islands The Division of Coastal Zone Management, USVI Department of Planning and Natural Resources The Coral Reef Conservation Program, National Oceanic and Atmospheric Administration Special Thanks To: Arrington B, Brandt ME, Byrne I, Dade LM, Durdall A, Gretta A, Hobbs T, Jobsis P, McKague V, Maxin S, Nemeth R, Olinger L, O’neill G, Parr SW, Quetel J, Shelby A, Swan A, Tierney C, and Tonge R. INDEX iii © 2026 Cite As: Hollander ENR, Krampitz NM, Ennis RS, Heidmann SL, Kadison E, Smith TB (2026) The United States Virgin Islands Territorial Coral Reef Monitoring Program. 2024 Annual Report. University of the Virgin Islands, United States Virgin Islands 69 pp INDEX iv INDEX OF FIGURES VI INDEX OF TABLES VIII OUR VISION 1 OBJECTIVES 1 EXECUTIVE SUMMARY 2 CORAL REEFS OF THE VIRGIN ISLANDS: MANGEMENT ACTIONS NEEDED 2 CORAL REEFS OF THE VIRGIN ISLANDS: POSITIVE SIGNS 5 IMPACTS, SCOPE, AND COMPARISONS OF THE 2023 AND 2024 CONSECUTIVE CORAL BLEACHING EVENTS 8 SEA SURFACE TEMPERATURES AND CORAL THERMAL STRESS 8 CORAL BLEACHING RESPONSE 9 CORAL SPECIES RESPONSE 12 CORAL COVER LOSS 16 INTRODUCTION 21 OBJECTIVES FOR MONITORING CORAL REEFS 24 METHODS 27 BENTHIC ASSESSMENTS 27 FISH CENSUS 33 TERRITORIAL CORAL REEF MONITORING SUMMARY 35 BENTHIC COMMUNITIES AND CORAL REEF HEALTH 35 FISH COMMUNITIES 46 SPECIAL INTEREST FISH: NASSAU GROUPER AND INVASIVE LIONFISH 57 BLACK SPINED SEA URCHIN DIADEMA ANTILLARUM 60 INDEX v LITERATURE CITED 65 INDEX vi Index of Figures Figure 1. Partially bleached and recovering colony of Siderastrea siderea at Flat Cay, St. Thomas (Nov. 12, 2005). .................................................................................................................................................................................................................... 3 Figure 2. 1982 – 2025 sea surface temperature (left axis ,blue line), and degree heating weeks (right axis, red line) for the USVI. ............................................................................................................................................................................................. 9 Figure 3. Mean coral paling and bleaching prevalence and extent at each TCRMP site in 2005, 2019, 2023, and 2024. Prevalence is the proportion of the community showing some level of paling and stark white bleaching. Extent is the mean proportion of the colony area affected by paling or bleaching. Note that some sites in 2005 were not sampled at the peak of heat stress. .................................................................................................................................... 11 Figure 4: The bleaching and paling prevalence and extent of tissue affected for the most common TCRMP coral species across the 2023 and 2024 bleaching events. ..................................................................................................................... 14 Figure 5. Time series showing the stark and deadly effects of the 2023 bleaching event on an Orbicella faveolata at the St Croix Castle TCRMP site. This coral is over 250 cm in longest diameter and lost about 90% of its tissue. (photo credits: L. Henderson and B. Arrington) ..................................................................................................... 15 Figure 6. Mean coral cover at each TCRMP location during peak bleaching in the fall of 2023, post bleaching spring of 2024, fall of 2024, and post bleaching sampling in the fall of 2025. .................................................................. 18 Figure 7: Absolute change in coral cover (%) at each TCRMP site from 2023 peak bleaching survey to 2025 post bleaching survey. ................................................................................................................................................................................. 19 Figure 8: Relative percent change in coral cover (%) at each TCRMP site from 2023 peak bleaching survey to 2025 post bleaching survey. ..................................................................................................................................................................... 20 Figure 9. A TCRMP research diver (S. Heidmann) on closed circuit rebreather records a roving fish survey at the Salt River Deep wall site, 30m/100’ depth (April 9, 2020; credit: S. Meiling). ........................................................... 25 Figure 10. Locations of Territorial Coral Reef Monitoring Sites in the US Virgin Islands. Boundaries indicate federal and territorial marine protected areas. .............................................................................................................................. 26 Figure 11. A screen grab of benthic video used for the determination of percent cover of coral reef organisms and non-living substrate. ........................................................................................................................................................................... 29 Figure 12. Coral cover (±SE) across St. Thomas and St. John TCRMP monitoring sites from 2002 – spring 2025. .............................................................................................................................................................................................................................. 38 Figure 13. Coral cover (±SE) across St. Croix TCRMP monitoring sites from 2001 – spring of 2025. ...................... 39 Figure 14. Mean hard coral, macroalgal (encrusting and erect), and epilithic algal community (EAC) coverage (±SEM) across all TCRMP sites during sampling from 2002-2024. ........................................................................................ 41 INDEX vii Figure 15. Mean algal coverage (±SEM) across TCRMP monitoring sites from 2005-spring of 2024. ................... 42 Figure 16. Mean benthic cover (±SEM) of gorgonians, sponges, and zooanthids from 2005- 2024 at TCRMP locations. ........................................................................................................................................................................................................... 45 Figure 17. A representative photo of the mesophotic wall sites on St. Croix, characterized by sloping walls, high silt loads, Agaricia spp. coverage, and low fish abundance, biomass, and richness (photo credit: L. Henderson). .............................................................................................................................................................................................................................. 49 Figure 18. Fish abundance (±SE) across St. Thomas and St. John TCRMP monitoring sites from 2003-2024. ... 52 Figure 19. Fish abundance (±SE) across St. Croix TCRMP monitoring sites from 2003-2024. ................................... 53 Figure 20. Mean fish biomass (±SE) across St. Thomas and St. John TCRMP monitoring sites from 2003-2024. .............................................................................................................................................................................................................................. 55 Figure 21. Mean fish biomass (±SE) across St. Croix TCRMP monitoring sites from 2003-2024. .............................. 56 Figure 22. Nassau grouper (Epinephelus striatus) observed while sampling at Grammanik Tiger FSA (photo credit: N.Krampitz). ..................................................................................................................................................................................... 57 Figure 23: Density of Nassau grouper (Epinephelus striatus) per transect effort across all TCRMP sites, 2003 – 2024. ................................................................................................................................................................................................................... 58 Figure 24. Lionfish (Pterois volitans) observed while sampling at Flat Cay, St Thomas (photo credit: E Hollander) ........................................................................................................................................................................................................ 59 Figure 25: Density of lionfish (Pterois volitans) on TCRMP transects from 2011 - 2024. ............................................. 60 Figure 26. Average density (±SE) of the black spined sea urchin (Diadema antillarum) at 33 TCRMP monitoring sites in 2024. ........................................................................................................................................................................... 61 Figure 27. Average density ± SE of Diadema antillarum (Diadema / 100m2) at TCRMP sites from 2002 – 2024. .............................................................................................................................................................................................................................. 62 Figure 28. Average test size of Diadema antillarum (cm) ± SE at TCRMP sites from 2005 – 2024. ......................... 63 INDEX viii Index of Tables Table 1: Summary of heat stress by year and survey period (annual/peak heat stress and post bleaching) across TCRMP sites. Paling and bleaching prevalence is the proportion of corals that exhibited any signs of paling or bleaching, >90% bleaching prevalence is the proportion of corals that showed total stark white bleaching, and extent of paling or bleaching refers to among the corals that were heat stressed, what proportion of the tissue was affected. .................................................................................................................................................. 12 Table 2: Count, paling and bleaching prevalence, and extent of paling and bleaching of Agaricia, Millepora, Orbicella, and Porites genera before, during, and after the consecutive 2023 and 2024 mass bleaching events. .............................................................................................................................................................................................................................. 16 Table 3. TCRMP site reef complex type, location coordinates (decimal degrees; WGS 1984), and depths. ........... 30 Table 4. TCRMP sampling dates for fish, urchin, benthic cover, and coral health at each site. .................................. 31 Table 5: Northern USVI (St Thomas and St John) fish belt data across habitat zones nearshore, offshore, and mesophotic ....................................................................................................................................................................................................... 47 Table 6: St Croix fish belt data across habitat zones nearshore, offshore, and mesophotic ......................................... 48 Table 7: The 2024 species richness for belt transects and roving diver surveys (RDS). ................................................. 50 MISSION STATEMENT 1 To provide critical information on the status and threats to all Virgin Islands coral reef ecosystems in order to increase management effectiveness and improve basic and applied coral reef research OBJECTIVES • Monitor the status and trajectories of coral reefs across a variety of habitats and threats, including land-based sources of pollution & thermal stress • Link changes in coral reef health with specific stressors, indicating specific management interventions most effective for preserving reefs • Integrate assessments of understudied mesophotic coral reef ecosystems and threatened species in the USVI • Provide data, outputs, and advice to stakeholders and create a nexus of information for reef research OUR VISION To provide critical information on the status and threats to all the U.S. Virgin Island’s coral reef ecosystems to increase management effectiveness and improve basic and applied coral reef research EXECUTIVE SUMMARY 2 Executive Summary Coral reefs in the Caribbean are at a crossroads, facing the possibility of further dramatic decline. Management decisions made today will affect the goods and services that coral reefs provide for decades to come. The government of the United States Virgin Islands (USVI), in coordination with the NOAA Coral Reef Conservation Program and the University of the Virgin Islands, implemented the Territorial Coral Reef Monitoring Program (TCRMP). The TCRMP has established baseline conditions and temporal trends of coral reefs and fish populations in the USVI and has identified threats that influence future reef health and development. A major focus of the TCRMP is to provide information that can lead to more effective management strategies that balance the immediate needs of the Virgin Island’s population with the preservation and sustainability of coral reefs and the renewable goods and services they provide. The intent of this report is to distill monitoring data into actionable information that can guide management decisions and inform the public and policy-makers about areas that need further effort. This executive summary presents information on threats to USVI reefs that require management intervention/action as well as positive signs that can inform our understanding of sustainability. CORAL REEFS OF THE VIRGIN ISLANDS: MANGEMENT ACTIONS NEEDED The TCRMP data has identified threats to USVI coral reef ecosystems that need increased management attention if reef corals are to persist in a condition that is equal to or better than current conditions. Coral Reef Bleaching. High thermal stress caused by climate change is currently the greatest threat to USVI coral reef ecosystems. The 2005 coral bleaching event caused the largest loss of coral in the documented history of the USVI, with a 50% decline in coral cover in shallow waters less than 25m/85’ deep (Figure 1)(Smith et al. 2013b; Smith et al. EXECUTIVE SUMMARY 3 2016a). This event surpassed all known modern impacts from physical damage (storms and anchoring), ecosystem changes (fishing and disease), and pollution (terrestrial sediments and toxins). This thermal disturbance was compounded by record heat stress in the fall of 2023 and 2024, with widespread bleaching and community effects that are only now being investigated. Please see `Research Highlights` for more detailed information on this bleaching event. While local management actions cannot remove impacts to reefs from global warming, reefs that are otherwise less stressed by land-based sources of pollution, fishing, and/or physical damage are known to recover more quickly from bleaching. Hence, local management actions that promote seascape-wide coral reef health offer the best strategy for sustainable reefs. We can also identify areas that are naturally more resistant to thermal stress and offer these areas further protection, since they offer insurance against the worst possible future outcomes for USVI reefs. Figure 1. Partially bleached and recovering colony of Siderastrea siderea at Flat Cay, St. Thomas (Nov. 12, 2005). EXECUTIVE SUMMARY 4 Overfishing. There are clear indications that reefs of the USVI are suffering the effects of overexploitation of reef resources. The entire district of St. Croix has an extremely low abundance of commercially important grouper species, including the threatened Nassau grouper (Kadison et al. 2017). In St. John and St. Thomas, many common species have completely or nearly disappeared from nearshore waters in the last 30 years. For example, a study conducted by Rogers et al. (1982) on the southwest coast of St. Thomas found a variety of species that are no longer encountered or are rare, including the black, Nassau, yellowfin, and tiger groupers, as well as the federally protected parrotfish species: blue, midnight, and rainbow. Rebuilding these fish stocks will require knowledge of comprehensive life-history information for target species, a willingness to find strategies to rebuild stocks, and partnerships between commercial and recreational fishers, community stakeholders, and managers. Signs of an increasing recruiting and spawning population of Nassau groupers in the northern USVI and more frequent sightings at TCRMP sites in St. Croix suggests that management actions, including no-take restrictions and protection of spawning aggregation sites, can have tangible, positive effects (Kadison et al. 2010). In addition, recent work under the Deep Coral Reef Monitoring Program, an extension of the spatially randomized National Coral Reef Monitoring Program in depths between 30-50 m (100-165 feet), is finding higher abundances of commercially important species that are rare in shallow waters (Grove et al. 2024; Heidmann et al. 2024). Therefore, for many species viable populations may still exist for rebuilding stocks. Land-Based Source of Pollution. The steep hillsides of the USVI are natural conduits for run-off during heavy rain events and in many instances, there is little interception of materials before they reach the sea and impact coral reefs. When tropical soils are naturally disturbed or altered through human activity, they can erode and release fine- grained silt and clay particles. In the USVI, these fine-grained particles are quickly transported to coral reefs where they can block sunlight, directly smother corals, or increase the growth of organisms that compete with corals for space. There is evidence EXECUTIVE SUMMARY 5 from the TCRMP that terrestrial sediments are having large negative impacts on nearshore coral reefs by increasing mortality of ecologically important corals (Ennis et al. 2016; Henderson et al. 2026) CORAL REEFS OF THE VIRGIN ISLANDS: POSITIVE SIGNS Despite the incredible declines in reef health witnessed since the inception of the TCRMP in 2001, there are many positive signs for the USVI that should be highlighted. These successes offer lessons that can be applied to troubled reefs and may indicate refuge areas where we might “double-down” on current management strategies. Reef Refuges. The USVI is blessed with extensive areas of deep bank and slope reefs that may be buffered from the direct impacts of local pressures (Smith et al. 2019a, b). The mesophotic (pronounced: me-zo-photik; meaning; “middle-light”) reefs of the USVI are the best developed in the Caribbean from what is currently known. Mesophotic Coral Ecosystem (MCE) reefs with high populations of star corals (Orbicella spp.), which are listed as threatened on the United States Endangered Species List (NOAA 2014), form extensive tracts on the south shelf of St. John and St. Thomas, from the British Virgin Islands to Vieques, Puerto Rico. Well-formed, but patchier mesophotic boulder coral reefs also form on the Lang Bank of St. Croix and the northern Puerto Rican Shelf. The lower MCE consists mostly of lettuce corals (primarily Agaricia undata) and form a semi- continuous ring on steep slopes and walls at depths between 50-70m. These reefs are isolated from some, but not all, local impacts but may be susceptible to global climate change (see below). In federal waters some of these areas are wholly or partly protected from fishing of ecologically important species that help maintain reef health. These include the Red Hind Marine Conservation District (est. 1999), the Grammanik Bank Seasonally Closed Area (est. 2005), and the Lang Bank Red Hind Seasonally Closed Area (est. 1993). However, extensively developed mesophotic reef in unprotected territorial waters also exist near the island of French Cap and Sail Rock in St. Thomas. It is important that these EXECUTIVE SUMMARY 6 areas are identified, their threats assessed, and they are incorporated into the territorial and federal management planning process. Rebounding Fisheries Species. There are positive signs of recovery for certain fish species in some areas. A red hind aggregation in the Red Hind Marine Conservation District (MCD) has dramatically rebounded (Nemeth 2005) and at the Grammanik Bank, a multi- species fish spawning aggregation site, there have been increasing numbers of Nassau grouper during annual spawning (Kadison et al. 2010; Jackson et al. 2014). About 875 individuals were seen in 2023-2024 (R. Nemeth, unpub. obs), contrasting the ~100 individuals seen spawning only a decade previously. Recruitment pulses of juvenile Nassau grouper in nearshore environments have also been noted in St. Thomas and St. John (R. Nemeth, unpub. data). Other territorial and federal closed areas in St. Croix, St. John, and St. Thomas are more recently established and thus may not show effects for several years. It has also been recently documented in the National Coral Reef Monitoring Program that larger and more numerous commercially important fish populations are found in deeper areas south of St. Thomas-St. John (Grove et al. 2024, Heidmann et al. 2024). For species that are completely protected from fishing (Nassau grouper and blue, midnight, and rainbow parrotfish), educational campaigns for recreational and commercial fisherman are critical, as awareness of regulations among the USVI residents appears to be lacking (Authors, unpub. obs.). Land-based source of pollution. While development of steep island slopes has continued despite current regulations intended to prevent sediments from entering nearshore waters, research has identified key targets for restoration and some effective habitat restoration best-management practices. Results from TCRMP research suggest that there are certain levels of silt-laden terrestrial run-off that are damaging to corals, providing a target for reductions of sediment in the marine environment (Henderson et al. 2026). Unpaved road segments have been implicated as the worst culprits in the production of sediment-laden run-off (Ramos-Scharrón and MacDonald 2007a, b) and this provides a clear target for where management can be most effectively applied. Restoration of EXECUTIVE SUMMARY 7 watersheds has shown that implementation of best-management practices and control structures can be effective in reducing sedimentation. For example, the American Recovery and Reinvestment Act project “USVI Coastal Habitat Restoration Through Watershed Stabilization” showed promising results (Virgin Islands Resource Conservation and Development Council; P.I. M. Taylor). _____________________________________________________________________________________________________ This report presents results of the 24th year of monitoring on reefs surrounding St. Croix, St. John, and St. Thomas, and includes surveys from annual sampling (2001-2024) as well as an additional post-bleaching benthic sampling that occurred in the early spring 2025. Monitoring sites were distributed across the insular platform in depths from 5 to 63 m (16 – 220’) to capture the diversity of reef types present in the Virgin Islands. Long- term data is presented from 34 sites. While not exhaustive, the TCRMP is generally representative of the geographic areas and variety of reef types in the USVI. Digital video and diver surveys were used to quantify benthic cover and coral health at 15 permanent sites surrounding the island of St. Croix and 19 permanent sites on the Puerto Rican Shelf surrounding the island of St. John and St. Thomas. In addition, at 33 of these sites, sea urchin density and fish community structure were evaluated. The TCRMP website describes the program and houses updated data https://www.vitcrmp.org Data can also be requested directly from the research team by contacting Erin Hollander at erin.hollander@uvi.edu INTRODUCTION 8 Impacts, Scope, and Comparisons of the 2023 and 2024 Consecutive Coral Bleaching Events SEA SURFACE TEMPERATURES AND CORAL THERMAL STRESS The U.S. Virgin Islands experienced unprecedented back-to-back mass bleaching events in 2023 and 2024. Both years experienced the highest levels of heat stress recorded for the US Virgin Islands, leading to the fifth mass bleaching event for the region in the past 20 years (Figure 2). Coral thermal stress, measured as Degree Heating Weeks (DHW), is evaluated by the duration that corals spend above a location-specific bleaching threshold temperature (nominally 29.4°C for sea surface temperatures in the USVI) and magnitude of the deviation above the threshold. DHW values above 8 are expected to lead to mass bleaching, with values above that leading to increasing levels of coral mortality. TCRMP also records in situ temperatures at reef level and has location specific calibrated bleaching threshold values, allowing site-specific estimates of heat stress. Major bleaching recorded by satellite temperatures have occurred in 2005 (DHW=15.5), 2010 (DHW=9.8), 2019 (DHW=8.9), 2023 (DHW = 18.7), and 2024 (DHW = 22.3) (NOAA Coral Reef Watch 2025). The TCRMP site Salt River Deep, St Croix recorded the highest in situ DHW value of 24 in November of 2024 as registered by in situ temperatures and the locally calibrated bleaching threshold. DHW at this site did not drop to 0 until early February 2025. In 2024, the USVI waters also warmed earlier than in previous years, reaching the 8 DHW mark by July. Sea surface temperatures in the USVI have been increasing at a rate of about 0.24°C per decade since the 1980’s, increasing the likelihood of coral thermal stress in the warmest periods of the year (Figure 2). INTRODUCTION 9 Figure 2. 1982 – 2025 sea surface temperature (left axis ,blue line), and degree heating weeks (right axis, red line) for the USVI. The black line is a linear fit of the sea surface temperature showing a 0.024˚C increase in temperature per year (y = 0.0237/year * x - 26.75). Degree heating weeks (DHW) are calculated as the 12-week rolling sum of temperatures exceeding 1°C over the monthly maximum mean temperature, which is estimated at 28.5°C for the USVI (NOAA 2006). DHW values above 4 are associated with the onset of bleaching, and above 8 with the onset of mass bleaching and coral mortality. (Data from Coral Reef Watch, US Virgin Islands virtual station, 5 km product. https://coralreefwatch.noaa.gov/product/vs/data.php) CORAL BLEACHING RESPONSE In response to record breaking heat stress in 2023 and 2024 corals across the territory bleached at high levels (Figure 3). The average prevalence of bleaching and paling remained similar for both years, hovering around 71% of colonies affected on average at a site (Table 1). Furthermore, the extent of the bleaching and paling, estimated as the proportion of tissue affected on a colony, was similar across both 2023 and 2024 at 72.3% and 74.7%, respectively. As expected, weaker thermal stress events in 2010 and 2019 produced more modest bleaching responses; however, among the more severe events in 2005, 2023, and 2024 peak bleaching responses did not always follow the realized thermal stress. The year 2005 had the worst bleaching response even though INTRODUCTION 10 that period had less accumulated thermal stress than 2023 and 2024. This is likely underestimated since not all TCRMP sites were sampled for bleaching at the peak of heat stress in 2005 (see Smith et al. 2016 a,b). This may reflect the impacts of the first very severe thermal stress event in 2005 on a relatively naı̈ve fauna that had more thermally susceptible species and genotypes. It also suggests selective culling and some level of adaptation have led to a slightly more resistant fauna by the 2020’s. Approximately six months after the peak bleaching period, a post bleaching sampling was conducted to assess the effects of the 2024 mass bleaching event. In the post bleaching period in spring 2025, the prevalence of bleached corals decreased from 71 ± 8.2% to 37 ± 14.4%, and the prevalence of severe bleaching (greater than 90% of the coral bleached) decreased from 41.5 ± 13.1% to 4.12 ± 4.69%. However, the extent of both bleaching and paling was comparable from peak bleaching to the post bleaching period; in peak 2024 stress, extent was approximately 74 ± 12.4% of tissue affected and in the post bleaching survey, extent was approximately 61 ± 18.7% of tissue affected. Although prevalence of paling and bleaching declined substantially in the post bleaching sampling, the colonies that remained heat stressed showed similar levels of extent of tissue affected during both the post and peak bleaching periods. INTRODUCTION 11 Figure 3. Mean coral paling and bleaching prevalence and extent at each TCRMP site in 2005, 2019, 2023, and 2024. Prevalence is the proportion of the community showing some level of paling and stark white bleaching. Extent is the mean proportion of the colony area affected by paling or bleaching. Note that some sites in 2005 were not sampled at the peak of heat stress. INTRODUCTION 12 Table 1: Summary of heat stress by year and survey period (annual/peak heat stress and post bleaching) across TCRMP sites. Paling and bleaching prevalence is the proportion of corals that exhibited any signs of paling or bleaching, >90% bleaching prevalence is the proportion of corals that showed total stark white bleaching, and extent of paling or bleaching refers to among the corals that were heat stressed, what proportion of the tissue was affected. Year Period Paling and Bleaching Prevalence >90% Bleaching Prevalence Extent of Paling or Bleaching 2005 Annual 70.72 46.29 88.22 2019 Annual 45.54 23.19 36.30 2023 Annual 70.69 50.55 72.28 2024 Post bleaching 32.98 5.29 50.79 2024 Annual 71.20 41.53 74.79 2025 Post bleaching 36.59 4.13 61.44 CORAL SPECIES RESPONSE There were species-specific responses to the 2023 and 2024 heat stress event in both the severity of bleaching and the pattern across the different events. Coral species most affected by heat stress in 2023 and 2024 included species from the genera of Agaricia, Porites, and Orbicella. However, genera differed in their responses to heat stress, namely in the bleaching and paling prevalence, extent of paled or bleached tissue (percent of colony tissue affected by heat stress), and species percent loss (Figure 4, Table 2). Paling and bleaching prevalence was high across both the 2023 and 2024 events, although coral species exhibited distinct responses (Figure 4). Prevalence and extent were calculated for the most abundant species documented in TCRMP surveys (> 50 INTRODUCTION 13 counts per sampling period). Agaricia and Orbicella species recorded the highest prevalences of paling and bleaching in 2023 (Figure 5). Agaricia species again exhibited the highest prevalence in 2024, suggesting either lack of recovery or high susceptibility to heat stress. In contrast, other species such as Stephanocoenia intersepta and Porites spp. showed a higher prevalence in 2024 than in 2023. Montastraea cavernosa was moderately affected by heat stress with a prevalence of paling or bleaching of approximately 50% for both years. These consecutive bleaching events greatly substantially altered coral assemblages on USVI reefs with strong genus-specific declines in coral abundance, calculated by change in pre bleaching colony counts in 2022 and post bleaching colony counts in spring 2025. Agaricia experienced the greatest reduction in colony counts (68.7%), likely reflecting its high sensitivity to thermal stress and consistently strong bleaching responses during both events. Millepora also declined markedly (42.4%), consistent with its elevated bleaching prevalence and extent during the 2024 event. However, Porites only declined 14.7%. Finally, Orbicella was least affected in terms of abundance (5.3% decline), despite severe bleaching in 2023, which may indicate higher survivorship, partial acclimatization following the initial event, or selective loss of the most susceptible colonies during the first bleaching episode. INTRODUCTION 14 Figure 4: The bleaching and paling prevalence and extent of tissue affected for the most common TCRMP coral species across the 2023 and 2024 bleaching events. INTRODUCTION 15 Figure 5. Time series showing the stark and deadly effects of the 2023 bleaching event on an Orbicella faveolata at the St Croix Castle TCRMP site. This coral is over 250 cm in longest diameter and lost about 90% of its tissue. (photo credits: L. Henderson and B. Arrington) INTRODUCTION 16 Table 2: Count, paling and bleaching prevalence, and extent of paling and bleaching of Agaricia, Millepora, Orbicella, and Porites genera before, during, and after the consecutive 2023 and 2024 mass bleaching events. Count Prevalence Extent Agaricia 2022 - pre heat stress 705 13.19 1.16 2023- global bleaching 715 91.32 76.88 2024 - regional bleaching 308 82.47 57.62 2025 - post heat stress 221 51.47 22.55 Agaricia percent loss: 68.65 Millepora 2022 - pre heat stress 151 7.28 0.75 2023- global bleaching 193 51.30 24.80 2024 - regional bleaching 162 79.63 65.00 2025 - post heat stress 87 16.09 8.55 Millepora percent loss: 42.38 Porites 2022 - pre heat stress 1523 7.22 0.56 2023- global bleaching 1785 59.61 41.22 2024 - regional bleaching 1737 80.42 69.91 2025 - post heat stress 1299 24.40 14.13 Porites percent loss: 14.71 Orbicella 2022 - pre heat stress 815 24.66 1.66 2023- global bleaching 770 89.35 72.36 2024 - regional bleaching 779 60.85 32.23 2025 - post heat stress 772 50.00 27.23 Orbicella percent loss: 5.27 CORAL COVER LOSS TCRMP sites displayed heterogeneous responses to the consecutive bleaching events in 2023 and 2024. With the exception of South Water and South Capella, all sites experienced declines in coral cover (Figure 6). The greatest absolute losses in coral cover INTRODUCTION 17 between the 2023 peak bleaching survey and the 2025 post bleaching survey included Meri Shoal (15.9%), College Shoal East (9.3%), and Castle (7.9%) (Figure 7). At the start of the 2023 bleaching event, Meri Shoal had the greatest coral cover of all TCRMP sites but after the consecutive bleaching events, lost 75.2% of the coral at that site (Figure 8). While the rest of the sites seemingly had a low loss in absolute coral cover (<10%), the proportional loss in coral cover is much greater (Figure 8). For example, Castle exhibited the third-largest absolute decline in coral cover (7.9%), but experienced the greatest proportional loss overall, with 78.6% of coral cover lost across the study period (as shown in Figure 5). Sixteen TCRMP sites, out of 33, lost over 40% of proportional coral cover that was present prior to the 2023 bleaching event. Mutton Snapper FSA had one of the highest DHW (22) in November 2024 which coincided with peak bleaching sampling in 2024. Despite this extreme thermal stress, the prevalence of paling and bleaching at Mutton Snapper FSA in 2024 was the second lowest among all TCRMP sites (55.1%), suggesting that factors beyond DHW alone influence site-level bleaching responses. INTRODUCTION 18 Figure 6. Mean coral cover at each TCRMP location during peak bleaching in the fall of 2023, post bleaching spring of 2024, fall of 2024, and post bleaching sampling in the fall of 2025. INTRODUCTION 19 Figure 7: Absolute change in coral cover (%) at each TCRMP site from 2023 peak bleaching survey to 2025 post bleaching survey. INTRODUCTION 20 Figure 8: Relative percent change in coral cover (%) at each TCRMP site from 2023 peak bleaching survey to 2025 post bleaching survey. INTRODUCTION 21 Introduction The U.S. Virgin Islands consist of three large islands, St. Thomas, St. John and St. Croix, and numerous smaller islands surrounded by a diverse, tropical marine environment that includes coral reefs, seagrass beds, and mangrove forests (Fig. 7). The islands of St. Thomas and St. John lie on the Puerto Rican Shelf, an extensive shallow water platform that connects them to Puerto Rico to the west and the British Virgin Islands to the east. St. Croix lies on an isolated platform sixty-five kilometers to the south of St. Thomas and St. John and separated by the 4000m deep Anegada Passage and the Virgin Islands Trough. This forms an effective barrier to the migration of adult coral reef fishes and invertebrates. The coral reefs of the Virgin Islands represent a wide range of characteristic coral reef habitats of the Caribbean, including patch reefs, fringing reefs, barrier reefs, shelf reefs, and extensive bank and slope mesophotic coral reef ecosystems. The area of a star coral bank mesophotic reef complex south of St. Thomas to Vieques covers more area than all the shallow water coral reefs of the USVI combined (Smith et. al 2019a). The economy of the US Virgin Islands is reliant largely on maintenance of vibrant marine ecosystems. Tourism drives the economy of the Virgin Islands, which are famous for white sand beaches that give way to clean, clear marine waters. The diverse marine life of the coral reefs and other habitats attract thousands of snorkelers and scuba divers each year. Sport fishing on charter boats and private vessels also makes an important contribution to the economy. In addition, the coral reefs and other habitats in the Virgin Islands are essential to the lives of hundreds of thousands of species including economically important whelk, queen conch, spiny lobster, snapper, and grouper. Over three hundred full-time or part-time commercial fishermen work in territorial and federal waters surrounding all three islands (Tobias 1997). In tough economic times and after natural disasters, fishing is an important means of supplemental income or extra protein for many people. INTRODUCTION 22 Over the last few decades, major hurricanes, coral disease outbreaks, mass coral reef bleaching, and invasive species introductions have caused extensive coral mortality to the coral reefs surrounding the Virgin Islands (Gladfelter 1982; Edmunds and Witman 1991; Rogers et al. 1991; Rothenberger et al. 2008; Woody et al. 2008; Miller et al. 2009; Smith et al. 2013b; Brandt et al. 2021). Recovery from these disturbances is hindered by a multitude of human impacts that affect coral reefs, such as overfishing of ecologically important species, physical damage to reef structure, and pollution (Hatcher 1984; Pastorok and Bilyard 1985; Rogers and Garrison 2001; Mumby 2006; Mumby et al. 2006; Mumby and Harborne 2010). Moreover, rapid development of steep island slopes has dramatically increased soil erosion and sedimentation into nearshore waters (Brooks et al. 2007; Gray et al. 2008; Smith et al. 2008), particularly below unpaved road surfaces (Anderson and Macdonald 1998; Ramos-Scharrón and MacDonald 2007a). Chronic sedimentation affects the abundance and diversity of corals and other reef organisms, increases coral stress and susceptibility to diseases and bleaching, and reduces the ability of corals and other reef organisms to recover and regenerate after natural disturbances such as hurricanes (Acevedo and Morelock 1988; Rogers 1990; Nemeth and Sladeck Nowlis 2001; Fabricius 2005; Sabine et al. 2015; Ennis et al. 2016). The first sightings of the invasive Indo-Pacific lionfish (Pterois volitans) occurred in the US Virgin Islands in 2009. This predator can dramatically alter coral reef fish community structure (Cote and Maljkovic 2010) and these alterations may have additional, indirect impacts on benthic communities (Albins and Hixon 2011). In addition, the aggressive and possibly introduced red alga Ramicrusta textilis has increased in abundance at many locations and is killing coral tissue through competitive overgrowth (Bramanti et al. 2017; Edmunds et al. 2019; Hollister et al. 2021; Williams and Edmunds 2021). Stony Coral Tissue Loss Disease (SCTLD), first observed at the Flat Cay monitoring location in early 2019, has led to widespread coral mortality and diversity losses throughout the Virgin Islands over the last several years (Brandt et al. 2021). In addition, losses of the black spined sea urchin to INTRODUCTION 23 an epizootic scutiociliate outbreak in 2022 have greatly reduced the already impacted populations of this key Caribbean herbivore (Hylkema et al. 2023; Hewson et al. 2023). High thermal stress and coral bleaching events affected the northeastern Caribbean in 2005, 2010, 2012, 2019, 2023, and 2024. Prior to 2023, the most severe high sea surface temperature (SST) event occurred in 2005. Degree Heating Weeks (DHW) for this event peaked at 15.4 (NOAA Coral Reef Watch 2025; 5km satellite product) and was associated with severe coral bleaching and mortality (Miller et al. 2009). In the fall of 2023, DHW reached an all-time maximum of 18.7 (NOAA Coral Reef Watch 2025; 5km satellite product), coinciding with observations of wide-spread bleaching and coral mortality in shallow and mesophotic environments. (Authors, unpub. obs.) Recent research developed bleaching threshold temperatures for 24 of the 34 TCRMP monitoring sites dominated by star corals of the genus Orbicella (Smith et al. 2016a). This study concluded that mesophotic reefs of the USVI are unlikely to be long- term climate change refugia because they are not immune to high temperature thermal stress. This is further evidenced by the observed widespread paling and bleaching that occurred at all mesophotic TCRMP sites in both 2023 and 2024 (79% and 72% mesophotic corals paled and bleached, respectively). Earlier events and the species- specific responses of Caribbean corals are summarized in Smith et al. (2013, b) for shallow corals and Smith et al. (2016, a) for shallow and mesophotic corals. Most research around the Virgin Islands has focused on fringing reefs (5 – 30 m depth) located along the shoreline of the three main islands, St. Thomas, St. John, and St. Croix. In contrast, very little information exists for offshore and deeper reef systems, which can be quite extensive. These other reef systems include mid-shelf reefs (5 – 30 m depth) located 2 to 10 km from the shore of the main islands and mesophotic reefs (>30 m depth) located from 0.5 to 15 km offshore along the edge of the insular platform (Armstrong et al. 2002; Armstrong et al. 2006; Armstrong 2007; Menza et al. 2007; Menza et al. 2008; Nemeth et al. 2008; Smith et al. 2010b; Smith et al. 2016b). Distance INTRODUCTION 24 from shore may be a factor in the historical degeneration of coral reef systems in the Virgin Islands (Herzlieb et al. 2005; Calnan et al. 2008; Smith et al. 2008; Sabine et al. 2015; Ennis et al. 2016). A systematic approach to investigating these cross-shelf coral reef systems allows us to evaluate the variable impacts and synergistic effects of natural impacts and human-induced stress that influence the decline or recovery of Caribbean coral reef systems. The first two years of this project (2001 and 2002) concentrated on the fringing reefs surrounding St. Croix. In 2003, monitoring continued at St. Croix reefs and began at reef systems distributed across the insular platform surrounding St. Thomas. In 2004-2006 monitoring continued at reefs surrounding both islands, with additional reefs surrounding St. Thomas added in 2004, 2005, and 2011. Mesophotic coral reef monitoring sites were added to St. Croix during the 2008, 2009, and 2017 monitoring. In 2011, the TCRMP also expanded to include sites established under separate funding that are continued in the core TCRMP monitoring activities funded by USVI DPNR and NOAA CRCP. OBJECTIVES FOR MONITORING CORAL REEFS Effective management is necessary to maintain the resources in the territorial and federal waters of the Virgin Islands in an ecologically and economically sustainable manner. Monitoring programs are essential for successful management because they provide managers with fundamental information with which to make and reinforce decisions. Standards for resource protection can be measured by comparison to baseline data established by monitoring. Monitoring also provides the means to assess the status and trends of ecological resources, allowing managers to determine the effectiveness of current management and to develop effective future management plans. The Territorial Coral Reef Monitoring Program monitors the condition of coral reefs throughout the U.S. Virgin Islands and provides key information to better manage these ecosystems. TCRMP is complimentary to the National Coral Reef Monitoring Program (NCRMP) that started in 2013 and is co-coordinated in the USVI by the University of the Virgin Islands. TCRMP INTRODUCTION 25 focuses on permanent sites and repeatedly samples the same transects to generate the most in-depth metrics of change over time while NCRMP uses a stratified-random sampling design to spread out samples and gain an understanding of change through time, with predictions that can be applied spatially. NCRMP does not currently sample reefs below 30m and therefore misses the dominant habitat in the northern USVI. The Deep Coral Reef Monitoring Program (DCRMP) was instituted in 2019 to sample reef fishes and basic benthic attributes in depths of 30-50 m on hardbottom areas south of St. Thomas and St. John (Grove et al. 2024; Heidmann et al. 2024). However, this program has no long-term sustained funding and sampling ended in 2022. This report presents annual monitoring results from 2001-2024 in St. Croix and from 2003-2024 in St. Thomas and St. John, as well results from a benthic-only post bleaching sampling that occurred at all sites in the spring of 2025. Figure 9. A TCRMP research diver (S. Heidmann) on closed circuit rebreather records a roving fish survey at the Salt River Deep wall site, 30m/100’ depth (April 9, 2020; credit: S. Meiling). INTRODUCTION 26 Figure 10. Locations of Territorial Coral Reef Monitoring Sites in the US Virgin Islands. Boundaries indicate federal and territorial marine protected areas. METHODS 27 Methods BENTHIC ASSESSMENTS The University of the Virgin Islands determined the benthic composition at 34 long-term monitoring sites between 2001 and 2024 (Table 3; Table 4). All data is now available at the TCRMP website and updated annually after quality control: https://www.vitcrmp.org Around St. Croix the following 15 sites were assessed: Buck Island-St. Croix, Buck Island Deep, Cane Bay, Cane Bay Deep, Castle, Eagle Ray, Great Pond, Jacks/Isaacs Bay, Kings Corner, Lang Bank East End Marine Park (Lang EEMP), Lang Bank Red Hind Fish Spawning Aggregation (Lang Hind), Mutton Snapper, Salt River, Salt River Deep, and Sprat Hole. Four of these sites are within the St. Croix East End Marine Park boundary (Castle, Great Pond, Jacks Bay, Lang EEMP), two sites are in a territorially managed area associated with Salt River (Salt River West and Salt River Deep), Buck Island-St. Croix and Buck Island Deep are within National Park Service/National Monument boundaries, two sites are within federal fisheries marine protected areas (Lang Hind, Mutton Snapper), and five sites can be considered mesophotic coral reefs (Buck Island Deep, Cane Bay Deep, Lang Bank EEMP, Lang Hind, Salt River Deep; sensu Ginsburg 2007) . Around St. John/St. Thomas the following 19 sites were assessed: Black Point, Botany Bay, Brewers Bay, Buck Island-St. Thomas, Coculus Rock, College Shoal East, Coral Bay, Fish Bay, Flat Cay, Ginsburgs Fringe, Grammanik Tiger FSA, Hind Bank FSA, Little St. James, Magens Bay, Savana Island, Seahorse Cottage Shoal, Meri Shoal, South Capella, and South Water Island. One site is the within the St. Thomas East End Reserve (Coculus Rock), four sites are within federal fisheries marine protected areas (College Shoal, Ginsburgs Fringe, Grammanik Tiger, Hind Bank), and five sites can be considered mesophotic coral reefs (College Shoal, Ginsburgs Fringe, Grammanik Tiger, Hind Bank, METHODS 28 Meri Shoal). Because of its deep depth, Ginsburgs Fringe at 60-66m was only sampled for benthic cover and occasional fish surveys. Benthic Cover. At each site benthic cover and coral health surveys were conducted along six 10 m long permanent transects marked with steel or brass rods. Video sampling consisted of one diver traversing each transect videotaping the benthic cover using a standard definition digital video camera (prior to 2007) or a high-definition digital camera (after 2007). TCRMP has attempted to continually upgrade video equipment through time to maintain the highest quality imagery possible for benthic analysis. The diver swam at a uniform speed, pointing the camera down and keeping the lens approximately 0.4 m above the substrate at all times. A guide wand or dropper weight attached to the camera housing was used to help the diver maintain the camera a constant distance above the reef. After taping, approximately 20 - 50 non-overlapping images per transect were captured and saved as JPEG files (Figure 11). Captured images represented an area of reef approximately 0.31 m2 (0.64 m x 0.48 m). Coral Point Count with Excel Extension software (Kohler and Gil 2006; prior to 2019) or R Studio (RStudio Team 2015; 2019 onward) was used to superimpose randomly located dots on each image. The number of points varied with the evolution of the video camera systems and was 10 points from 2001-2011, 15 points from 2012-2013, and 20 points from 2014 onwards. The substrate type located under each of the dots was then identified to the most descriptive level possible and entered into a database. Where multiple benthic cover categories fell under a single point, for example macroalgae over bedrock, the upper benthic category was assessed. For each transect, the percent cover of coral, epilithic algae, macroalgae, sponges, gorgonians, and sand/sediment were calculated by dividing the number of random dots falling on that substrate type by the total number of dots for that transect. Epilithic algae (sensu Hatcher and Larkum 1983) are diminutive turfs and filamentous algae without thallus structure that cover all rock surfaces of coral reefs not occupied by larger epibenthic organisms. METHODS 29 Figure 11. A screen grab of benthic video used for the determination of percent cover of coral reef organisms and non-living substrate. METHODS 30 Table 3. TCRMP site reef complex type, location coordinates (decimal degrees; WGS 1984), and depths. Island Site Reef Complex Lat Long Depth (m) St. Croix Buck Island-St. Croix Offshore-Shallow 17.78500 -64.60917 15 Buck Island Deep-St. Croix Offshore-MCE 17.80659 -64.59935 33 Cane Bay Nearshore 17.77388 -64.81350 10 Cane Bay Deep Offshore-MCE 17.77661 -64.81522 38 Castle Offshore-Shallow 17.76278 -64.59743 7 Eagle Ray Offshore-Shallow 17.76150 -64.69880 10 Great Pond Nearshore 17.71097 -64.65221 6 Jacks Bay Nearshore 17.74337 -64.57160 14 Kings Corner Nearshore 17.69116 -64.90008 17 Lang Bank EEMP Offshore-MCE 17.72145 -64.54706 27 Lang Bank Red Hind FSA Offshore-MCE 17.82372 -64.44943 33 Mutton Snapper FSA Offshore-Shallow 17.63660 -64.86240 24 Salt River Deep Offshore-MCE 17.78523 -64.75917 30 Salt River West Nearshore 17.78530 -64.75940 11 Sprat Hole Nearshore 17.73400 -64.89540 8 St. John Coral Bay Nearshore 18.33797 -64.70402 9 Fish Bay Nearshore 18.31417 -64.76408 6 Meri Shoal Offshore-MCE 18.24433 -64.75832 30 St. Thomas Black Point Nearshore 18.34450 -64.98595 9 Botany Bay Nearshore 18.35845 -65.03330 8 Brewers Bay Nearshore 18.34403 -64.98435 7 Buck Island-St. Thomas Offshore-Shallow 18.27883 -64.89833 14 Coculus Rock Nearshore 18.31257 -64.86058 7 College Shoal East Offshore-MCE 18.18568 -65.07677 30 Flat Cay Offshore-Shallow 18.31822 -64.99104 12 Ginsburgs Fringe Offshore-MCE 18.18770 -64.95998 63 Grammanik Tiger FSA Offshore-MCE 18.18901 -64.95630 38 Hind Bank East FSA Offshore-MCE 18.20217 -65.00158 39 Magens Bay Nearshore 18.37425 -64.93438 7 Savana Offshore-Shallow 18.34064 -65.08205 9 Seahorse Cottage Shoal Offshore-Shallow 18.29467 -64.86750 20 South Capella Offshore-Shallow 18.26267 -64.87237 20 South Water Offshore-Shallow 18.28068 -64.94592 20 Little St James Offshore-Shallow 18.29459 -64.83238 17 METHODS 31 Table 4. TCRMP sampling dates for fish, urchin, benthic cover, and coral health at each site. Where there are two dates an asterisk (*) indicates the full fish survey date for St. Thomas-St. John. Only benthic surveys were completed at Ginsburgs Fringe. Only benthic and health surveys were completed during the post bleaching sampling season in spring of 2025. Island Site Annual Survey Sample Date (2024) Post Bleaching Sample Date (2025) St. Croix Buck Island STX 11/11/24 4/11/25 Buck Island STX Deep 11/11/24 4/11/25 Cane Bay 11/12/24 4/16/25 Cane Bay Deep 11/12/24 4/16/25 Castle 11/12/24 4/11/25 Eagle Ray 11/14/24 4/12/25 Great Pond 11/13/24 4/13/25 Jacks Bay 11/13/24 4/15/25 Kings Corner 11/15/24 4/14/25 Lang Bank EEMP 11/13/24 4/15/25 Lang Bank Red Hind FSA 11/16/24 4/13/25 Mutton Snapper FSA 11/15/24 4/14/25 Salt River Deep 11/14/24 4/12/25 Salt River West 11/14/24 4/12/25 Sprat Hole 11/14/24 4/14/25 St. John Coral Bay 8/7/24*, 10/24/24 5/8/25 Fish Bay 8/7/24*, 10/24/24 5/8/25 Meri Shoal 9/12/24*, 11/22/24 3/21/25 St. Thomas Black Point 8/23/24*, 10/11/24 3/26/25 Botany Bay 8/8/24*, 10/17/24 3/19/25 Brewers Bay 9/25/24*, 10/11/24 3/26/25 Buck Island STT 8/23/24*, 10/18/24 3/20/25 Coculus Rock 9/27/24*, 10/18/24 5/8/25 College Shoal East 9/18/24*, 11/21/24 4/8/25 Flat Cay 8/28/24*, 10/22/24 3/27/25 Ginsburgs Fringe 1/17/25; 2/26/25 ----- Grammanik Tiger FSA 8/29/24*, 11/22/24 4/8/25 Hind Bank East FSA 9/5/24*, 11/21/24 3/28/25 Magens Bay 8/8/24*, 10/22/24 3/19/25 Savana 8/8/24*, 10/17/24 3/19/25 Seahorse Cottage Shoal 9/12/24*, 10/29/24 3/20/25 South Capella 9/27/24*, 10/25/24 3/27/25 South Water 8/28/24*, 10/25/24 3/28/25 Little St James 8/23/24*, 10/29/24 3/21/25 METHODS 32 Coral Health. Coral health assessments followed methodologies outlined in Calnan et al. 2008, Smith et al. 2008, and Smith et al. 2013, and are briefly described here. All coral colonies located directly under the transect lines were assessed in situ for signs of mortality and disease following a modified Atlantic and Gulf Rapid Reef Assessment protocol (Kramer et al. 2005). Starting in 2008 all colonies were assessed, regardless of size, in contrast to previous years where only colonies greater than 10 cm in maximum linear dimension were assessed. Partial mortality of coral colonies was broken into two categories: recent and old. Recent partial mortality was characterized visually as skeleton not eroded (fine corallite structure still intact) and bare or with a thin veneer of sheeting or filamentous algae. Recent partial mortality is typically visible for up to three months following tissue loss. Old partial mortality was characterized as skeleton eroded and covered with turf or macroalgae. Old partial mortality is a transition from recent mortality and typically lasts up to 1–6 years (Smith et al. 2008). Diseases were conservatively categorized into recognized Caribbean scleractinian diseases and syndromes that included bleaching, black band disease, dark spots disease, white plague, stony coral tissue loss disease, and yellow band (blotch) disease (following Bruckner 2007). Acroporid corals were extremely rare at the study sites; thus, their associated diseases (white band and white pox) are not presented. Bleaching was assessed as abnormal paling of the colony, and, when present, the severity of the bleaching (paling or total whitening) and the area of the colony affected were assessed. For each transect, the prevalence of coral impairment categories was calculated as the number of colonies with partial mortality, disease, or bleaching divided by the number of colonies assessed. Also, for affected colonies in each transect the average three-dimensional surface area (%), or extent of the colony affected was also estimated for each impairment category. METHODS 33 FISH CENSUS Fish abundance, size, and diversity were recorded using transects and roving diver surveys. There have been changes in protocol through the years to make initial methods more comparable to other regional sampling programs, to increase detection of rare, commercially important species, and to streamline logistics. Fish species’ identity, abundance, and size were assessed along at each site conducted over 15 minutes per transect. Prior to 2009, belt transect were 30 x 2 m in size. Starting in sampling year 2009 belt transects were enlarged to 25 m x 4 m, increasing the survey area however from 2009 through 2011, two surveys were done per replicate, the first counting all non- site attached fish and the return survey along the transect line surveying smaller, site attached fish. In 2012, transects were again modified, and single surveys (25 m x 4 m) were conducted per transect replicate, counting both site attached, and non-site attached fish on a single survey. This change brought TCRMP assessment methodologies in line with NOAA Biogeography Branch methods at that time (Menza et al. 2006; Friedlander et al. 2013). Before 2019 ten transects were conducted at each site. A retrospective analysis showed that nine transects were sufficient to capture within-site variability, and so the number of transects was reduced to nine starting in 2019. All transects were begun at a random location on the site and were laid in a random direction. Fish were sized by fork length recorded into size-bin categories (cm): 1-5, 6-10, 11-20, 21-30, 31-40, etc. up to >150. This sampling strategy is not optimized for noting the presence and abundance of small (<5 cm) gobies and blennies, and the taxa were inconsistently recorded. Roving diver survey (RDS) were also conducted at each site to estimate site fish diversity. Prior to 2016, RDS surveys in water depths less than 25 m were 30 minutes in duration and, because of restrictions in dive length, were 15 minutes in deeper water. Retrospective analysis showed that almost all diversity was captured in the first 15 METHODS 34 minutes of the survey. Therefore, to make deeper sites comparable, the methods were switched to 15 minute RDS at all sites in 2016. In all surveys, all species encountered were recorded except blennies and gobies. Divers also counted the number of Diadema antillarum sea urchins within 1 m on either side of a transect. From 2001 – 2008 this occurred along the 6 – 10 m long benthic transects. Starting in 2009, urchins were assessed along 25 x 2 m belt transects corresponding to the return of the fish transects. The mean number of sea urchins per 100 m2 was calculated for each site. Data from all fish surveys were transcribed to Microsoft Excel and Access spreadsheets and analyzed for descriptive statistics of reef fish assemblage structure. Starting in 2021, data entry occurred in a customized data entry system with built-in quality control parameters. Data presented in individual site summaries represents data collected for the current report period only. Details on date of data collection are outlined in Table 4.