CORAL REEF EVALUATION REPORT

Transcription

1 2012 CORAL REEF EVALUATION REPORT Reef Check Bahamas Team Members: Lakeshia Anderson, Frederick Arnett, Ancilleno Davis, Jared Dillet, Lindy Knowles and Krista Sherman February 3, 2012

2 Executive Summary Two Reef Check Surveys were conducted at Mike s Reef, New Providence, Bahamas on February 1, The team consisted of Lakeshia Anderson (BNT), Frederick Arnett (DMR), Ancilleno Davis (TNC), Jared Dillet (DMR), Lindy Knowles (BNT) and Krista Sherman (BNT). The team was divided into pairs to complete fish, invertebrate and substrate surveys. This team used the Reef Check EcoDiver protocol to collect data ( Mike s Reef is within the proposed South West Marine Managed Area. Both survey sites are a part of a contiguous reef system. Fish surveys showed that commercially important species (groupers, snappers and grunts) were in lower abundances when compared to non-target fish species (parrotfish and butterflyfish). When comparing the two invertebrate and impact assessment surveys, the only noticeable difference was the gorgonian counts which could be related to edge effects. Anthropogenic impacts were low on both transects. Even though 76% of the surveyed portion of Mike s Reef consisted of non-living components, the low macroalgal coverage (due to grazing pressure by high parrotfish densities) could mean that there is suitable area for coral recruitment. However, live hard corals cover was 10% suggesting that there may be other factors preventing coral recruitment to the area not related to substrate type e.g. edge effects. This was the first complete Reef Check survey to be conducted within the proposed boundaries of the South West Marine Managed Area in New Providence, Bahamas. The data represented in this report provide baseline information on the status of coral reef health in the area surveyed on Mike s Reef. Additional surveys are required to document changes in the area and obtain a more detailed understanding of coral reef health. 1

3 Table of Contents Executive Summary... 1 Table of Figures... 3 Introduction... 4 Methods... 4 Site Description... 4 Fish belt transect... 4 Invertebrate belt transect... 5 Substrate line transect... 6 Results... 6 Site Description... 6 Fish Abundance... 7 Invertebrates & Impacts... 8 Benthic Coverage Discussion & Conclusion Fish Abundance Invertebrates and Impacts Benthic Coverage Acknowledgements References

4 Table of Figures Figure 1. Diagram of a transect line. This 100 m line is divided into four 20 m segments with a 5 m gap in between them to ensure sample independence Figure 2. Divers swam in an S-shaped pattern to search for the indicator invertebrates inside cracks or crevices on the reef Figure 3. Map of survey site Mike s Reef and the surrounding area off of New Providence, Bahamas Figure 4. Average abundance of Reef Check indicator fish on Mike's Reef. The bars represent the average abundance per 100 m 2 and error bars are reported as standard deviation Figure 5. Average abundance of Reef Check indicator invertebrates on Mike's Reef. The bars represent the average abundance per 100 m 2 and error bars are reported as standard deviation Figure 6. The bars represent the level of perceived impacts ranked on a scale from 0-3. Error bars are reported as standard deviation Figure 7. Comparison of mean percentage cover of living and non-living reef components per 100 m 2 on Mike's Reef East and West. Error bars represent standard deviation Figure 8. Combined percent coverage of living and non-living reef components on Mike's Reef Figure 9. Combined mean percentage cover of living and non-living reef components per 100 m 2 on Mike's Reef East and West. Error bars represent standard deviation

5 Introduction On Wednesday, 1 st February, 2012 a group of marine scientists from The Nature Conservancy, The Bahamas National Trust and The Bahamas Department of Marine Resources performed the first of what is hoped to be a series of Reef Check survey dives on Mike s Reef off southwestern New Providence. The survey group members were Frederick Arnett and Jared Dillet of DMR, Ancilleno Davis of TNC, and Lakeshia Anderson, Lindy Knowles and Krista Sherman of BNT. With the exception of Mr. Knowles, the group had been previously trained in Reef Check methodologies and was participating in a Training of the Trainers workshop. Upon completion of the workshop, Mr. Knowles will be trained by one of his aforementioned peers to become a Reef Check Eco Diver. Mike s Reef is located 3.2 km off the southwestern coast of New Providence (Figure 3). The reef was chosen because it is a popular, well used site for recreational divers and receives daily visitors almost year-round. The site is also used for recreational and small scale commercial fishing. Mike s Reef is located within the proposed Western New Providence Managed Marine Area and is an ideal site for comparison to other, less used reefs (e.g. marine reserves) within The Bahamas. Two surveys were completed using the Reef Check methodology and the findings are presented below. Methods Two Reef Check Surveys were conducted at Mike s Reef, New Providence, Bahamas on February 1, The team consisted of Lakeshia Anderson, Frederick Arnett, Ancilleno Davis, Jared Dillet, Lindy Knowles and Krista Sherman. The team was further divided into pairs to complete fish, invertebrate and substrate surveys. Two transects were laid in a N-S orientation at 35 feet depth more than 5 m apart. Site Description Anecdotal, observational, historical, location (using a hand-held GPS) and other socioeconomic data were recorded on the Reef Check Site Description Form. Fish belt transect Four 5 m wide (centered on the transect line) by 20 m long segments were sampled for fish species typically targeted by fishermen, aquarium collectors and others. Fish seen up to 5 m above the line was included (Figure 1). The indicator fish have been selected because they are, ecologically important species, typically shot out of reefs by spearfishing and caught using handlines. Size minimums have been placed on two families of food fish (> 30 cm for Grouper, > 20 cm for Parrotfish). Grouper and parrotfish smaller than these limits were not counted. Other 4

6 indicator fish included snappers, grunts, butterflyfish and lionfish. No PVC pipes were used to assist with size class estimations based on diver experience with size class estimations. However, novices should utilize this or another method of calibration. Each diver assigned to count fish swam slowly along the transect counting the indicator fish. The diver then stopped every 5 m, and waited one minute for indicator fish to come out of hiding before proceeding to the next 5 m stop point. The fish were counted while swimming and while stopped along the entire length of each 20 m transect. This was a combined timed and area restricted survey: four segments x 20 m long x 5 m wide = 400 m 2. As with each of the surveys, there were four 5 m gaps where no data was collected. The entire 400 m 2 belt transect was completed in one hour. Figure 1. Diagram of a transect line. This 100 m line is divided into four 20 m segments with a 5 m gap in between them to ensure sample independence. Invertebrate belt transect The same four 5 m wide by 20 m long segments were used to sample for invertebrate species typically targeted as food species or collected as curios. The invertebrate survey is similar to the fish survey, however, the diver did not stop every 5 m but each diver swam slowly in an S- shaped pattern along the transect counting the indicator invertebrates (Figure 2). The indicator invertebrates included pencil urchins, Flamingo tongue, Trumpet triton, gorgonians (sea fans or sea whips), Diadema sp., Banded coral shrimp, West Indian sea egg or collector urchins, and Spiny lobster or crawfish. Reef impacts including coral disease, coral bleaching, coral damage and trash were also recorded. 5

7 Figure 2. Divers swam in an S-shaped pattern to search for the indicator invertebrates inside cracks or crevices on the reef. Substrate line transect The same transect line as the fish and invertebrate belt transects was used, but points were sampled at each 0.5 m interval along the tape to determine the substrate types on the reef. Substrate categories included rock (RC), hard coral (HC), soft coral (SC), recently killed coral (RKC), nutrient indicator algae (NIA), sponges (SP), rubble (RB), sand (SD), silt (SI) and other (OT) sessile organisms that do not fall into the above categories. During this survey, the total number of hard corals with diseases or bleaching was also noted. Results Site Description Mike s Reef is located on the southwest side of New Providence ( N and W) and has an average depth of 40 feet (Figure 3). The reef can be characterized as a medium to high profile reef adjacent to a gorgonian hard bottom and sandy area. Mooring buoys maintained by Stuart Cove s Dive Bahamas reduce anchor damage as the area is heavily used by recreational divers. The area is also used for subsistence fishing. 6

8 Figure 3. Map of survey site Mike s Reef and the surrounding area off of New Providence, Bahamas. Fish Abundance A total of 40 parrotfish, 10 butterflyfish, 3 groupers, 1 Nassau grouper and 2 grunts per 100 m 2 were observed at Mike s Reef East. No snappers or moray eels were observed. In comparison a total of 20 parrotfish, 10 butterflyfish, 1 grouper and 6 snappers per 100 m 2 were observed at Mike s Reef West, but no Nassau grouper, grunts or moray eels were observed. Arithmetic means and standard deviations were calculated based on the total number of fish observed per segment (Figure 4). 7

9 Average Abundance +-SD Average Abundance of Indicator Fish on Mike's Reef Butterflyfish: Chaetodontidae Grunts: Haemulidae Snappers: Lutjanidae Nassau Grouper Groupers: Other Scaridae Parrotfish: Scaridae Moray Eels: Muraenidae West East Figure 4. Average abundance of Reef Check indicator fish on Mike's Reef. The bars represent the average abundance per 100 m 2 and error bars are reported as standard deviation. Invertebrates & Impacts A total of 116 gorgonians, 4 Banded coral shrimp, 3 Flamingo tongue, 2 lobsters and 1 Diadema urchin per 100 m 2 were observed at Mike s Reef East. On Mike s Reef West, a total of 41 gorgonians, 2 Banded coral shrimp 1 Diadema urchin and 3 pencil urchins per 100 m 2 were observed (Figure 5). Coral damage on Mike s Reef East and West ranged from low to medium and mainly consisted of boat or anchor damage, discarded fishing gear and other trash (Figure 6). 8

10 Average abundance +-SD 35 Average Abundance of Invertebrates on Mike's Reef West East Banded Coral Shrimp Diadema Pencil Urchin Collector urchin Triton's Trumpet Flamingo Tongue Gorgonians Spiny Lobster Figure 5. Average abundance of Reef Check indicator invertebrates on Mike's Reef. The bars represent the average abundance per 100 m 2 and error bars are reported as standard deviation. 9

11 Lvel of Perceived Coral Impacts +-SD Frequency of Coral Impacts on Mike's Reef 1.8 West East Damage:Boat or Anchor Damage:Dynamite Damage: Other Trash: fishing gear Trash: general Figure 6. The bars represent the level of perceived impacts ranked on a scale from 0-3. Error bars are reported as standard deviation. Benthic Coverage At Mike s Reef East an average of 40% rock (RC), 16% sponge (SP), 13% hard coral (HC), 11% sand (SD), 10% rubble (RB), 2% nutrient indicator algae (NIA), 1% other (OT) and 1% silt (SI) were counted. Comparatively, Mike s Reef West had an average coverage of 28% rock (RC), 8% sponge (SP), 7% hard coral (HC), 34% sand (SD), 22% rubble (RB) and 2% nutrient indicator algae (NIA). No soft corals (SC) or recently killed corals (RKC) were observed under the survey points at either Mike s Reef East or West. No silt (SI) or other (OT) substrate reported for Mike s Reef West (Figure 7). Benthic living and non-living components comprised 31.25% and 68.75% cover respectively of Mike s Reef East. Benthic living and non-living components comprised 16.25% and 83.75% cover respectively of Mike s Reef West (Figure 8). 10

12 Average percent cover +-SD When benthic coverage data of living and non-living components were combined for both transects on Mike s Reef, averages of 36.9% rock (RC), 11.6% sponge (SP), 10% hard coral (HC), 22.8% sand (SD), 15.9% rubble (RB), 1.9% nutrient indicator algae (NIA), 0.3% other (OT) and 0.6% silt (SI) were calculated (Figure 9). 50 Percent Coverage of Substrate on Mike's Reef East West HC SC RKC NIA SP RC RB SD SI OT Figure 7. Comparison of mean percentage cover of living and non-living reef components per 100 m 2 on Mike's Reef East and West. Error bars represent standard deviation. 11

13 Percentage Cover Comparison of Live Cover on Mike's Reef West East Total living Total non-living Figure 8. Combined percent coverage of living and non-living reef components on Mike's Reef. 12

14 Average Percent Cover +-SE Combined Percent Cover of Substrate from Mike's Reef East and West HC SC RKC NIA SP RC RB SD SI OT Figure 9. Combined mean percentage cover of living and non-living reef components per 100 m 2 on Mike's Reef East and West. Error bars represent standard deviation. Discussion & Conclusion Fish Abundance Results from the combined fish surveys indicated that targeted fisheries species like groupers, snappers and grunts are in lower abundance than non-targeted species such as parrotfish and butterflyfish. Moray eels are typically found in low abundance. These results are consistent with the current protection level of this area, which is non-existent. These are preliminary results from a single study and additional surveys on other portions of Mike s Reef across larger time scales are needed to make recommendations. Invertebrates and Impacts Gorgonians were the most abundant Reef Check indicator invertebrate observed at Mike s Reef along the transects. This may be due to high water flow-through in the area and the location of the transects on Mike s Reef. Mean gorgonian abundance on Mike s Reef West was lower on Mike s Reef East and this may be due to the distance between the transects and the reef edge. Mike s Reef East was closer to the reef edge. Assuming the transect areas are representative of the entire reef; lobster abundance could be low due to subsistence or recreational fishing 13

15 pressure. The low Diadema abundance observed during this study is typical of the region following the 1980s epidemic from which only shallow areas are beginning to recover. The other Reef Check indicator species are currently not of economic importance. Impacts related to coral bleaching and disease were low (<5%). Anthropogenic impacts were also low (<1 on the 0-3 perceived impact scale) despite the fact that the area is heavily used by recreational divers. This may be indicative of local dive tour operator management (e.g. active trash removal and mooring buoys) of the area. Benthic Coverage Even though 76% of the surveyed portion of Mike s Reef consisted of non-living components, the low macroalgal coverage (due to grazing pressure by high parrotfish densities) could mean that there is suitable area for coral recruitment. However, live hard corals cover was 10% suggesting that there may be other factors preventing coral recruitment to the area not related to substrate type e.g. edge effects. This was the first complete Reef Check survey to be conducted within the proposed boundaries of the South West Marine Managed Area in New Providence, Bahamas. The data represented in this report provide baseline information on the status of coral reef health in the area surveyed on Mike s Reef. Additional surveys are required to document changes in the area and obtain a more detailed understanding of coral reef health. Acknowledgements We would like to thank Dr. Ruben Torres (Reef Check Dominican Republic) for invigilating the Training of Trainer s Workshop for The Bahamas. This workshop was funded through the GEF/UNEP (Global Environment Facility/United Nations Environment Programme) Full Size Project (FSP) through the National Executing Agency the Bahamas Environment Science and Technology (BEST) Commission and supporting National Implementation Support Programme (NISP) agencies. These agencies include the Bahamas National Trust, The Nature Conservancy, the Department of Marine Resources and the BEST Commission. Thanks to Stuart Cove s Dive Bahamas for providing field logistical support. References 14