Recovery of Queen Conch in the U. S. Virgin Islands

Three field expeditions per year were completed beginning in May 2005 and ending in September 2010, each lasting from 10-14 days. During each sampling period, we haphazardly surveyed each bay for the presence of queen conch. The majority of these surveys were conducted by snorkel, but occasional SCUBA surveys were completed. At each conch's location we measured dissolved oxygen, salinity, depth, water temperature, air temperature, and wind speed. Spatial coordinates were collected using a portable wide area augmentation system-enabled global positioning system (WAAS GPS) unit. Siphonal (shell) length and lip thickness were measured with vernier calipers. Upon initial capture each conch was tagged with a uniquely numbered disk or T-bar anchor tag by drilling a small hole adjacent to the lip of the shell and injecting the tag through the hole. A small drop of super glue secured the tag in place until the conch deposited new material permanently integrating the tag into the shell. High resolution determination of habitat type at each conch's location was completed by centering a 1-m2 quadrat over the conch and visually identifying all benthic organisms contained within the quadrat. Vemco model VR2 omnidirectional hydrophone receivers were deployed throughout each study site such that an array of overlapping detection zones was created corresponding with changes in benthic habitat structure. Range tests were performed at each location on several occasions until a maximum range of tag detection was established. Locations were tested and adjusted accordingly to ensure adequate overlap in zones between neighboring receivers. Hydrophones were mounted on steel tie-down anchors, sunk approximately 1 m into the sediment such that the receiver base rested just above the sediment surface. Receivers were secured to the anchor with a combination of cable ties, hose clamps, and a padlock to minimize the possibility of equipment loss from vandalism or natural events. During the course of the project, we deployed 12 hydrophones in Fish Bay, 4 in No Name Bay, 5 in Brown Bay, and 5 in Coral Bay. HOBO temperature loggers (Onset Computer Corp.) were deployed at each hydrophone location, as well as several surface locations throughout each bay. Prior to deploying acoustic tags, varying sizes and maturity categories of queen conch were selected to effectively represent the composition of the population at large. Individuals matching the chosen size classes were randomly captured and tagged with Vemco V7-4L-R64K acoustic transmitters (20.5 mm length, 7 mm diameter) with a time interval of 60-180 seconds and an average life expectancy of 220 days. Tags were cemented using Liquid Roc 700 Acrylic Twin Tube epoxy (MKT Fastening, LLC) onto the highest portion of the spire where signal transmission was least likely to be obstructed. After the epoxy had cured (10-15 minutes) conch were returned to their exact location, marked previously by a fluorescent flag. On each field trip data files were downloaded from the receivers using an underwater cable. Temperature loggers were downloaded by temporarily removing them from the anchors, downloading, and replacing them in their previous location. After 12 months of continuous deployment receivers were removed from their anchors, cleaned, and batteries replaced to ensure no gaps in data collection. Data files were converted to MS Excel spreadsheets and transferred into ArcView 9.1. Spatial locations of tagged conch were overlayed onto categorized NOAA benthic habitat maps (NOAA/NCCOS Biogeography Program) to examine distributions through habitat types. Movement patterns and position estimates for queen conch with acoustic tags were interpreted from locational data collected on capture/recapture and detection patterns in hydrophone data.