2007-221 - Laserfiche WebLink

Home Browse Search

ATTACHMENTA SCOPE OF SERVICES INDIAN RIVER COUNTY ARTIFICIAL. REEF MONITORING GRANT INTRODUCTION In this project, the grantee will employ and evaluate new methods for assessing nearshore natural and artiflclal reef structure and function. The results will be applicable for refinement of beach nourishment programs and development of more ecologically appropriate structures used to mitigate for loss of hard bottom structure In the near-share region as well as Improved assessment of beach rencurishment Impacts on natural nearshore communitles, The approach will combine traditional visual , video and digital photographic assessment of selected habitats along with a suite of techniques that hold significant promise for analyzing the physical structure and biological characteristics of the habitats. Efforts will focus on several natural near-shore reef structures along the Indian River County coastline and on a 5 acre mitigation reef constructed by the County over the last few years. These new techniques Include two different very high resolution sonar sensors. In addition, direct assessment of fishes will be performed using existing fishery sampling procedures that are not normally applied In the coastal zone. Reef sites to be examined include: 1 ) Mitigation reef, constructed of 42,500 tons of limestone boulders and 25 Reef Balls (3500 Ib size). This reef is located along reference markers R 91 .5 to R94 in Indian River county, and the geographic boundaries of the reef are: NW corner: 270 37.735'N x 800 20.886 W NE corner: 27° 37.742'N x 80° 20.866' W SW corner: 270 37.261 'N x 80° 20,687' W SE corner; 270 37.268'N x 80° 20.666' W 2) Natural reef sites, sectors 1 and 21 located from R-5 to R-22 In Indian River County, There are six sites within this area that are of specific Interest to the County, along transects from Inshore edge of hardbottom habitat extending 150m offshore at R-5, R-6,51 R-81 R-9.51 R-10.5, and R-22. The high resolution sonar systems are the RoxAnn7m system for acoustic ground discrimination and seabed mapping, and the DIDSONT"' system for assessment of the abundance and size distribution of fishes and turtles Inhabiting the region. The RoxAnnT" system will be mounted on a small vessel for acoustical high-resolution mapping of the selected near-shore bottom areas. Sand, bare rock, rock with fleshy macroalgal growth, rock with filamentous algal growth, encrusting sponges, and worm rock are expected to produce clear patterns of acoustic returns due to the differences in hardness and roughness of the surfaces. Other categorles that become apparent from the patterns In the acoustic data will also be surveyed and ground-truthed to identify corresponding bottom type. Using an acoustic means of determining bottom type removes our reliance on clear water and calm seas for aerial photography and direct diver observations, thus allowing us to map bottom areas and quantify benthlo habitats throughout the year to evaluate Intra-annual variation In burial and exposure of reef area. Use of the RoxAnnTM will initially be coupled with standard diver-operated survey techniques, including quadrat analysis using digital photography, so we anticipate conducting Initial operations under calm sea conditions (<2' sea height or less in the near shore region). The DIDSONM sonar is a high-frequency sonar, Initially developed for port security applications, that Is rapidly finding many applications In fishery biology. This sonar uses focused nearly-parallel sound beams to generate highly detailed "pictures" of stationary structures and moving organisms. Recent trials of the DIDSONT ,' sonar in the Indian River Lagoon and St. Johns River demonstrated the ability to count, measure and observe the behavior of fish as small as 2' anchovies against a rock background to as large STATEMENT ON DISCLOSURE