Bathymetric and Backscatter Analyses of Fisheries R/V ...oceanica.cofc.edu/beamsprogram/images/Photo...
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RESULTS: Classified Backscatter Bathymetric and Backscatter Analyses of Fisheries Habitats Off the Southeast US Coast Sarah J. Shainker and Dr. Leslie Sautter Department of Geology and Environmental Geosciences, College of Charleston ABSTRACT The Marine Resources Monitoring, Assessment, and Prediction (MARMAP) Program of the South Carolina Department of Natural Resources (SCDNR) assesses reef fish off the southeastern US coast. Our mapped region included habitat areas for economically significant reef fish species monitored by MARMAP. Bathymetric and backscatter intensity analyses were conducted on two study sites. The greatest biomass and diversity of fishes are found near rocky outcrops and settling invertebrates at depths of 19 to 55 m. Bathymetry and backscatter analyses allowed for the identification of “hard bottom” rocky outcrops and sand bodies. Profiles were generated to identify rocky versus sandy areas as well as areas of high relief. Hard bottom surfaces with complex morphology may serve as substrate for invertebrates, making them ideal sites for spawning reef fishes. Identifying suitable reef fish habitat areas within these mapped regions may aid in managing fisheries and identifying potential marine protected areas (MPAs). BACKGROUND The Marine Resources Monitoring, Assessment, and Prediction (MARMAP) Program of the South Carolina Department of Natural Resources (SCDNR) conducts assessments of reef fish off the southeastern US coast (DNR). The study sites are located off the coast of Savannah, GA from 25-38 m deep and are within the area monitored by MARMAP. There are rocky outcrops and hard bottom areas which could serve as ideal habitats for snapper and grouper (DNR). Hotspot fish habitats such as these are vulnerable to overexploitation (Wyanski et.al. 2000). This study will conduct sediment analysis of two focus sites to quantify and compare their suitability as fish habitats. METHODS • Multibeam sonar data were collected off the coast of Savannah, GA by CofC BEAMS program aboard the RV Savannah using a Kongsberg EM2040 system. • Data were post-processed using CARIS HIPS 9.0. Bathymetric surfaces and backscatter mosaics were generated. • Grids were overlain on backscatter mosaics to characterize the percentage of soft, medium, and hard sediment. ACKNOWLEDGEMENTS We would like to thank CARIS for Academic Partnership, Dept. of Geology and Environmental Geosciences, School of Science and Math, the crew of the R/V Savannah, and the CofC BEAMS program. LOCATION OF STUDY SITE REFERENCES Koenig, C. C., Coleman, F. C., Grimes, C. B., Fitzhugh, G. R., Scanlon, K. M., Gledhill, C. T., Grace, M. Protection of fish spawning habitat for the conservation of warm-temperate reef-fish fisheries of shelf-edge reefs of Florida. Bulletin of Marine Science 66 (3): 593-616, 2000. Lindeman K.C., Pugliese R., Waugh G.T., & Ault, J.S. Developmental patterns within a multispecies reef fishery: Management applications for essential fish habitats and protected areas. Bulletin of Marine Science 66(3): 929-956, 2000. "MARMAP Program History." Marine Resources Research Institute. South Carolina Department of Natural Resources. Wyanski, D. M., White, D. B., & Barans, C. A. (2000). Growth, population age structure, and aspects of snowy grouper, Epinephelus niveatus, off North Carolina and South Carolina. Fishery Bulletin 98 (1). 1m Swath Angle BASE surface of MARMAP West 1m Swath Angle BASE surface of MARMAP East R/V Savannah • MARMAP East profile A-A’ (Fig. 5A) depicts a rocky ledge, ideal for fish habitat • Profiles B-B’, C-C’, and D-D’ (Fig. 5A and 5B) show scattered, smaller rocky areas and sand bodies • MARMAP East has a higher percentage of hard bottom substrate when compared to MARMAP West FIGURE 3. Classified backscatter surfaces of study sites with percentages of hard, medium and soft substrate for each site. 3d bathymetric surfaces of both sites overlaid with classified backscatter surfaces. 18.5% 54.1% 27.4% Classified Backscatter surface with pie chart showing % of hard, medium and soft substrate. 18.5% 54.1% 27.4% A A’ B B’ 29.8% 60.0% 10.2% 29.8% 60.0% C C’ D D’ 3d bathymetry with draped classified backscatter. VE: 24X Rocky ledge Sand bodies 3d bathymetry with draped classified backscatter. VE: 24X Rocky ledges FIGURE 1. Bathymetric images of study sites, each with a 1m resolution Swath Angle BASE surface. A) MARMAP West B) MARMAP East The inset above shows their location off the Georgia coast. MARMAP East MARMAP West Savannah A. B. MARMAP East MARMAP West MARMAP East MARMAP West Classified Backscatter surface with pie chart showing % of hard, medium and soft substrate. PURPOSE Characterize and compare sites monitored by MARMAP using bathymetric maps, backscatter data, and profiles to identify potential areas of ideal reef fish habitat. DISCUSSION • Ideal spawning habitat is often characterized by hard substrate, including rocky ledges or cliffs (Wyanski et al., 2000). • MARMAP East has a higher percentage of hard bottom substrate when compared to MARMAP West • Both sites have areas with rocky ledges which could serve as ideal fish habitat. • The highest relief rocky ledge on Profile A-A’ is especially ideal: high relief areas aid in spawning by limiting egg predation (Lindeman et al., 2000). • Boxes indicate the most suitable potential habitat areas: these areas should be targeted for ROV dives to identify species present and to more clearly describe substrate types. • Spawning aggregations are sources of high and predictable biomass distributions, so they are often targeted for fishing (Koenig et al., 2000). • MPAs containing spawning areas could be especially effective at restoring populations of fished species (Koenig et al. 2000); so these ideal habitat areas may be suitable for MPA establishment. FIGURE 5. Ideal habitat areas indicated for MARMAP West and East, based on bathymetry and classified backscatter data. MARMAP West MARMAP East RESULTS: Backscatter Intensity FIGURE 2. Backscatter intensity maps for A) MARMAP West and B) MARMAP East. MARMAP West -10 -25 -15 -20 MARMAP East -9 -25 -15 -19 RESULTS: Profiles VE=83x 2900 0 Depth (m) 36.8 34.7 Distance (m) B B’ Distance (m) Depth (m) 0 1600 27.2 24.8 D D’ MARMAP West • Profile C-C’: rocky ledge and sand waves with possible rocky outcrops • Profile D-D’: sand waves and rocky outcrops MARMAP East • Profile A-A’: two rocky ledges indicated by the dark blue areas underneath the profiles • Profile B-B’: rocky ledge and a rocky outcrop area Hard Medium Soft FIGURE 4. Profiles from lines shown on Fig. 3. MARMAP East MARMAP West 25.2 29.8 Depth (m)
Transcript of Bathymetric and Backscatter Analyses of Fisheries R/V ...oceanica.cofc.edu/beamsprogram/images/Photo...
RESULTS: Classified Backscatter
Bathymetric and Backscatter Analyses of Fisheries
Habitats Off the Southeast US Coast Sarah J. Shainker and Dr. Leslie Sautter
Department of Geology and Environmental Geosciences, College of Charleston
ABSTRACT The Marine Resources Monitoring, Assessment, and Prediction (MARMAP) Program of the South Carolina Department of Natural Resources (SCDNR) assesses reef fish off the southeastern US coast. Our mapped region included habitat areas for economically significant reef fish species monitored by MARMAP. Bathymetric and backscatter intensity analyses were conducted on two study sites. The greatest biomass and diversity of fishes are found near rocky outcrops and settling invertebrates at depths of 19 to 55 m. Bathymetry and backscatter analyses allowed for the identification of “hard bottom” rocky outcrops and sand bodies. Profiles were generated to identify rocky versus sandy areas as well as areas of high relief. Hard bottom surfaces with complex morphology may serve as substrate for invertebrates, making them ideal sites for spawning reef fishes. Identifying suitable reef fish habitat areas within these mapped regions may aid in managing fisheries and identifying potential marine protected areas (MPAs).
BACKGROUND The Marine Resources Monitoring, Assessment, and Prediction (MARMAP) Program of the South Carolina Department of Natural Resources (SCDNR) conducts assessments of reef fish off the southeastern US coast (DNR). The study sites are located off the coast of Savannah, GA from 25-38 m deep and are within the area monitored by MARMAP. There are rocky outcrops and hard bottom areas which could serve as ideal habitats for snapper and grouper (DNR). Hotspot fish habitats such as these are vulnerable to overexploitation (Wyanski et.al. 2000). This study will conduct sediment analysis of two focus sites to quantify and compare their suitability as fish habitats.
METHODS • Multibeam sonar data were collected off the coast
of Savannah, GA by CofC BEAMS program aboard the RV Savannah using a Kongsberg EM2040 system.
• Data were post-processed using CARIS HIPS 9.0. Bathymetric surfaces and backscatter mosaics were generated.
• Grids were overlain on backscatter mosaics to characterize the percentage of soft, medium, and hard sediment.
ACKNOWLEDGEMENTS
We would like to thank CARIS for Academic Partnership, Dept. of Geology and Environmental Geosciences, School of Science and Math, the crew
of the R/V Savannah, and the CofC BEAMS program.
LOCATION OF STUDY SITE
REFERENCES Koenig, C. C., Coleman, F. C., Grimes, C. B., Fitzhugh, G. R., Scanlon, K. M., Gledhill, C. T., Grace, M. Protection of fish spawning habitat for the conservation of warm-temperate reef-fish fisheries of shelf-edge
reefs of Florida. Bulletin of Marine Science 66 (3): 593-616, 2000.
Lindeman K.C., Pugliese R., Waugh G.T., & Ault, J.S. Developmental patterns within a multispecies reef fishery: Management applications for essential fish habitats and protected areas. Bulletin of Marine Science
66(3): 929-956, 2000.
"MARMAP Program History." Marine Resources Research Institute. South Carolina Department of Natural Resources.
Wyanski, D. M., White, D. B., & Barans, C. A. (2000). Growth, population age structure, and aspects of snowy grouper, Epinephelus niveatus, off North Carolina and South Carolina. Fishery Bulletin 98 (1).
1m Swath Angle BASE surface of MARMAP West
1m Swath Angle BASE surface of MARMAP East
R/V Savannah
• MARMAP East profile A-A’ (Fig. 5A) depicts a rocky ledge, ideal for fish habitat • Profiles B-B’, C-C’, and D-D’ (Fig. 5A and 5B) show scattered, smaller rocky areas and sand bodies • MARMAP East has a higher percentage of hard bottom substrate when compared to MARMAP West
FIGURE 3. Classified backscatter surfaces of study sites with percentages of hard, medium and soft substrate for each site. 3d bathymetric surfaces of both sites overlaid with classified backscatter surfaces.
18.5%
54.1%
27.4%
Classified Backscatter surface with pie chart showing % of hard, medium and soft substrate.
18.5%
54.1% 27.4%
A
A’
B
B’
29.8%
60.0%
10.2%
29.8%
60.0% C
C’
D
D’
3d bathymetry with draped classified backscatter. VE: 24X
Rocky ledge Sand bodies
3d bathymetry with draped classified backscatter. VE: 24X
Rocky ledges
FIGURE 1. Bathymetric images of study sites, each with a 1m resolution Swath Angle BASE surface. A) MARMAP West B) MARMAP East The inset above shows their location off the Georgia coast.
MARMAP East
MARMAP West
Savannah
A.
B. MARMAP East
MARMAP West
MARMAP East MARMAP West
Classified Backscatter surface with pie chart showing % of hard, medium and soft substrate.
PURPOSE Characterize and compare sites monitored by MARMAP using bathymetric maps, backscatter data, and profiles to identify potential areas of ideal reef fish habitat.
DISCUSSION • Ideal spawning habitat is often characterized by hard substrate, including rocky ledges or cliffs
(Wyanski et al., 2000). • MARMAP East has a higher percentage of hard bottom substrate when compared to MARMAP West • Both sites have areas with rocky ledges which could serve as ideal fish habitat. • The highest relief rocky ledge on Profile A-A’ is especially ideal: high relief areas aid in spawning by
limiting egg predation (Lindeman et al., 2000). • Boxes indicate the most suitable potential habitat areas: these areas should be targeted for ROV dives
to identify species present and to more clearly describe substrate types. • Spawning aggregations are sources of high and predictable biomass distributions, so they are often
targeted for fishing (Koenig et al., 2000). • MPAs containing spawning areas could be especially effective at restoring populations of fished species
(Koenig et al. 2000); so these ideal habitat areas may be suitable for MPA establishment.
FIGURE 5. Ideal habitat areas indicated for MARMAP West and East, based on bathymetry and classified backscatter data.
MARMAP West
MARMAP East
RESULTS: Backscatter Intensity
FIGURE 2. Backscatter intensity maps for A) MARMAP West and B) MARMAP East.
MARMAP West
-10
-25
-15
-20
MARMAP East
-9
-25
-15
-19
RESULTS: Profiles
VE=83x
2900 0 Dep
th (
m)
36.8
34.7
Distance (m)
B B’
Distance (m) Dep
th (
m)
0 1600 27.2
24.8
D D’
MARMAP West • Profile C-C’: rocky
ledge and sand waves with possible rocky outcrops
• Profile D-D’: sand waves and rocky outcrops
MARMAP East
• Profile A-A’: two rocky ledges indicated by the dark blue areas underneath the profiles
• Profile B-B’: rocky ledge and a rocky outcrop area
Hard Medium Soft
FIGURE 4. Profiles from lines shown on Fig. 3.
MARMAP East
MARMAP West 25.2
29.8 Dep
th (
m)
![15 Sediment Gages - USGS · 0.2707 c,S372 Velccty and backscatter seres C] Depth-averaøed streamwise vebcfy RMS Curr.tive u at depths backscatter Depth-averaged backscatter Contour](https://static.fdocuments.us/doc/165x107/5fd8133cbc6723794903cbd2/15-sediment-gages-usgs-02707-cs372-velccty-and-backscatter-seres-c-depth-averaed.jpg)
