Assessment of Nearshore Artificial Reefs in Okaloosa County, Florida by Volunteers Using Side Scan Sonar

摘要

The sea floor in the western panhandle region of Florida consists mainly of unconsolidated sediments, causing the counties in this area to support the creation of artificial reefs to provide habitat for local fish populations. Several issues have emerged with these sites, including inaccurate coordinates for the original deployment of materials, movement of reef materials by hurricane wave action, structure failure, and deterioration. Emerald Coast Reef Association, a local group of fishers and divers, partnered with Florida Sea Grant Extension to conduct a side scan sonar survey of selected nearshore reefs in Okaloosa County during 2005. This article summarizes survey methods using recent innovations in side scan sonar technology as well as the survey results. Information systems in conjunction with the use of low-frequency side scan sonar allowed for accurate location of previously deployed reef materials. High-frequency scanning further refined reef material location and was used to evaluate reef condition. Side scan sonar surveys provided the foundation for future monitoring activities such as video and diving assessments. A number of the structures detected during the survey illustrate valuable lessons for artificial reef deployment and management. Care in the placement of reef materials during deployment needs to be prioritized in order for structures to function as they were originally designed. Cylindrical objects need to be deployed in deeper waters and modified to improve storm stability. Reef deployments made during the era of Long Range Navigation may not have been recorded accurately compared to today's standards. Accurately calibrated navigational instruments and professional records are essential tools for future reef managers. Our experience from these surveys also indicates it may not be necessary to locate all lost reefs, even though fishermen and divers may benefit. Previous research studies suggest that lost reefs are utilized as de facto refugia, potentially benefiting fisheries stocks. Nearshore, however, it is prudent to manage all reef structures closely due to the presence of natural reefs, trawling activity, and navigational lanes. The success of this survey suggests skilled volunteer groups can play a larger role inartificial reef management and monitoring. The capacity to execute these types of projects at the local level complements traditional research information from universities and government entities and is of great value to local artificial reef program managers.