Study ID 190

St. Croix. USVI Fish Assessment and Monitoring Data (2002 - Present) (NOAA-CCMA)

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Realm: Marine
Climate: Tropical
Biome: Tropical seas
Central latitude: 17.756969
Central longitude: -64.604258
Duration: 10 years, from 2001 to 2010

28017 records

247 distinct species

Across the time series Halichoeres bivittatus is the most frequently occurring species

Citation(s):

"St. Croix, USVI Fish Assessment and Monitoring Data (2002 - Present)", (2007) Silver Spring, MD Publisher: NOAAs Ocean Service, National Centers for Coastal Ocean Science (NCCOS). National Oceanic and Atmospheric Association (NOAA)-National Ocean Service (NOS)-National Centers for Coastal Ocean Science (NCCOS)-Center for Coastal Monitoring and Assessment (CCMA)-Biogeography Team. Available at: http://www.iobis.org/mapper/?dataset=1673, accessed 2012.

Methods

The basis for this work is the nearshore benthic habitats maps (less than 100 ft depth) created by NOAAs Biogeography Program in 2001 and NOS bathymetry models. Using ArcView GIS software. the digitized habitat maps are stratified to select sampling stations. Sites are randomly selected within these strata to ensure coverage of the entire study region and not just a particular reef or seagrass area. At each site. fish. macro-invertebrates. and benthic composition information is then quantified following standardized protocols. By relating the data collected in the field back to the habitat maps and bathymetric models. BT is able to model and map species level and community level information. These protocols are standardized throughout the US Caribbean to enable quantification and comparison of reef fish abundance and distribution trends between locations.Site selection begins by stratifying NOAA's nearshore benthic habitat maps into predetermined habitat strata. Utilizing ArcGIS. sites are then randomly selected within strata throughout the region. Using a handheld GPS unit. the boat captain navigates to previously selected sites. A weighted buoy is dropped to mark any site where live boating is necessary. Once on site. divers are deployed and maintain contact with each other throughout the entirecensus. One diver is responsible for collecting data on the fish communities utilizing the belt transect visual census technique. The belt transect diver obtains a random compass heading prior to entering the water and records the compass bearing (0-360o) on the data sheet. On site. no attempt to avoid structural features within a habitat such as a pile of conch shells. a sand patch or a tire in a seagrass or sand area should be made as these features affect fish communities and are real features of the habitats. Visibility at each site must be sufficient to allow for identification of fish at a minimum of 2m away. Once reasonable visibility is ascertained. the diver attaches a tape measure to the substrate and allows it to roll out as progress is made along the chosen compass heading for a distance of 25m. The transect should take 15 minutes regardless of habitat type or number of animals present. This allows more mobile animals the opportunity to swim through the transect. and standardizes the samples collected to allow for comparisons. As the tape roles out at a relatively constant speed. the diver records all fish species to the lowest taxonomic level possible that come within 2m of either side of the transect. Each survey is 100m2 in area (25m length X 4m width). To decrease the total time spent writing. four letter codes are used that consist of the first two letters of the genus name followed by the first two letters of the species name. In the rare case that two species have the same four-letter code. letters are added to the species name until a difference occurs. If the fish can only be identified to the family or genus level then this is all that is recorded. If the fish cannot be identified to the family level then no entry is necessary. The number of individuals per species is tallied in 5cm size class increments up to 35cm using visual estimation of fork length. If an individual is greater than 35cm. then an estimate of the actual fork length is recorded. Prior to 2002. fork lengths of fish greater than 35 cm were not always recorded. Although the habitat should not be altered in any manner by lifting or moving structure. the observer should record fish seen in holes. under ledges and in the water column. To identify. enumerate. or locate new individuals a diver may move off the centerline of the transect as long as they stay within the 4m transect width and do not look back along area already covered. The diver is allowed to look forward toward the end of the transect for the distance left along the transect (i.e. if the diver is at meter 15. he can look 10 meters distant. but if he is at meter 23. he can only look 2 meters ahead). This diver also takes photos of fishes to document color patterns and phases of the different species.Data Caveats: Overtime. some changes were made to the stratified random site selection process as follows: 1) Habitat strata initially consisted of hard bottom. sand. and seagrass. Sand and seagrass strata were subsequently combined into one soft bottom strata at all three locations (Puerto Rico. St. Croix. and St. John). This action was taken after the February 2002 mission to Puerto Rico. 2) A small subset of sites were resampled during each mission through June 2002 in Puerto Rico and October 2002 in St. Croix. These station names contain the letter 'P' indicating they are permanent stations. 3) The sample area in St. Croix has increased over time. Initially. samples were collected within historic Buck Island National Monument boundaries as well as outside up to a distance of 0.5 km from those boundaries. In February 2002 the sampling effort was increased to include the entire expanded monument boundaries. Finally in April 2003 the effort was increased again to include areas outside of the Monument for control sites. This area is now almost entirely enclosed within the East End Marine Park of St. Croix. 4) The habitat map utilized to stratify the samples in St. Croix was changed from the original habitat map created with a 1 acre minimum mapping unit to one with a 100m2 minimum mapping unit beginning with the April 2003 mission.Process_Date: 200202 Unit of abundance = IndCountInt, Unit of biomass = NA