The queen conch is an important cultural component and an extremely valuable coral reef fishery resource throughout the Caribbean, historically second only to the spiny lobster. Comparisons of past studies with current densities from these areas continue to show that queen conch populations are depletd although we may be seeing small signs of increase. This data set investigates the population status of queen conch around St. John, U.S. Virgin Islands, through mark and recapture, habitat availability and utilization, sonic tracking, and seasonal migration studies to provide needed information for improved management.
The intent of this project is to investigate possible causes of the lack of recovery of queen conch, particularly juvenile, populations around St. John.
ground condition
See Access Constraints.
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https://www.ncei.noaa.gov/data/oceans/coris/data/NOAA/nmfs/1873/locations_of_tagged_queen_conch.jpg
Not applicable.
These data consist of multiple tagging locations of queen conch in several bays around St. John. Also included is habitat use, movement and migration information from visual surveys and long-term acoustic tracking, and environmental data such as temperature and salinity.
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.
Temp = temperature in degrees Celsius; D.O. = dissolved oxygen in mg/L; depth = water depth in meters; sal = salinity in parts per thousand; shell length = total length of each conch measured in millimeters; lip = lip thickness of each conch measured in millimeters.
NOAA/NMFS/SEFSC/Galveston Laboratory/Fishery Ecology Branch
While every effort has been made to ensure that these data are accurate and reliable within the limits of the currrent state of the art, NOAA cannot assume liability for any damages caused by errors or omissions in the data, nor as a result of the failure of the data to function on a particular system. NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.
