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Density of red snapper on artificial and natural reefs off Texas using Simrad EK-80 towed hydroacoustic echosounder from 2018-09-18 to 2019-10-27

Authors: Wetz, Jennifer J. and Greg W. Stunz
Published On: Apr 05 2023 20:42 UTC
DOI: https://doi.org/10.7266/JWV4HKZV
UDI: NO.x835.000:0016
Project Information

Funded By:
National Oceanic and Atmospheric Administration

Research Group:
Estimating the Absolute Abundance of Red Snapper in the U.S. Gulf of Mexico

Point of Contact

Jennifer Wetz
Texas A&M University-Corpus Christi / The Harte Research Institute for Gulf of Mexico Studies
jennifer.wetz@tamucc.edu

Data Collection Period
2018-09-18
to
2019-10-27
Theme keywords

hydroacoustics, natural banks, artificial reefs, red snapper, ROV, fish density, hydroacoustic echosounder

ISO 19115-2 Metadata
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Abstract:

Density estimates of red snapper on natural and artificial reefs off Texas from 2018-09-18 to 2019-10-27. Visual surveys on a subset of sites were used to calculate a species abundance and this proportion was then used to calculate the number of red snapper based on the hydroacoustic data.

Suggested Citation:

Wetz, Jennifer J. and Greg W. Stunz. 2023. Density of red snapper on artificial and natural reefs off Texas using Simrad EK-80 towed hydroacoustic echosounder from 2018-09-18 to 2019-10-27. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/JWV4HKZV

Purpose:

To calculate the number of red snapper on natural and artificial reefs off Texas.

Data Parameters and Units:

Natural and Unconsolidated Column Headings Site Unique site where survey was completed. Formatted YYYYMMDD_ReefSite_SurveySite_Set. Most reef sites had multiple surveys conducted on them at different locations Survey_date Date of survey in MM/DD/YYYY Longitude Survey centroid longitude in decimal degrees Latitude Survey centroid latitude in decimal degrees Survey_method Method used to count RS. Total abundance was estimated using data collected with a 70KHz single frequency split-beam transducer and scaled to RS abundance using paired species composition from ROV visual surveys Habitat_score An integer score of 1 to 3: 1) indicates unconsolidated (sand/mud/ shell) 2) indicates some natural relief but no hard bottom relief or sparse rubble; generally applied when a site did not have true hardbottom relief, but was also not unconsolidated 3) indicates presence of hardbottom relief Area_Surveyed Area surveyed in m2 Total_Fish_Counted Total fish counted in survey based on acoustic data Red_Snapper_Counted Red Snapper over the age of 2 counted on a single survey RS_per_100m2 Red Snapper Density per 100m2. Calculated as RS counted / Area Surveyed (m2) *100 Proportion_RS Proportion of total fish abundance comprising Red Snapper Mean_Visibility Mean Visibility (in meters) of the survey within layers (10m vertical depth bins) where RS were encountered DepthZone Depth grouping variable including: Shallow: 10-40m Mid: 40-100m Deep: 100-160m Artificial Column Headings Site Unique site where survey was completed. Formatted YYYYMMDD_ReefSite_SurveySite_Set. Most reef sites had multiple surveys conducted on them at different locations Identifier The original numeric identifier from the sampling list provided. Identifier was left as NA since none of the artificial reefs sampled were included in the sampling list provided Survey_date Date of survey in MM/DD/YYYY Longitude Survey centroid longitude in decimal degrees Latitude Survey centroid latitude in decimal degrees Survey_method Method used to count RS. Total abundance was estimated using data collected with a 70KHz single frequency split-beam transducer and scaled to RS abundance using paired species composition from ROV visual surveys Structure_type Nature of the artificial structure surveyed including the number and structure type of what was surveyed Structure_Category A structure type grouping variable for structure type broken into 3 categories: Oil and gas structure: Oil and gas structures including standing and decommissioned platforms and deck structures Fabricated Materials: Low relief, generally concrete materials including pyramids, concrete culverts, railroad ties, etc. Vessel: reefed ships, barges, and vessels Tonnage Estimate of the total tons of material in the structure to be used to classify structures in to s/m/l/xl categories; Tonnage not provided for oil and gas structures because of the XL size of the structures Total_Fish_Counted Total fish counted in survey based on acoustic data Red_Snapper_Counted Red Snapper over the age of 2 counted on a single survey. Red Snapper Counted is reported as RS/single structure when a structure was greater than 50m from another structure and as RS/structure complex when more than one structure was included in a survey because structures were less than 50m apart and they could not be differentiated in acoustic profiles and abundance was lost due to the acoustic shaddow between structures Proportion_RS Proportion of total fish abundance comprising Red Snapper Mean_Visibility Mean Visibility (in meters) of the survey within layers (10m vertical depth bins) where RS were encountered Structure_Size Classification of the size of the artificial structure sampled broken into 2 categories Small: low relief, small footprint structures like prefabricated pyramids, concrete culverts, and wellheads Large: high relief, large footprint structures like oil and gas platforms and vessels DepthZone Depth grouping variable including: Shallow: 10-40m Mid: 40-100m Deep: 100-160m

Methods:

ROV videos were used to determine species composition on various habitat types (artificial and natural reefs). Simrad EK80 was towed hydroacoustic echosounder for determining the number of fish on a particular site.

Instruments:

Simrad EK-80 towed hydroacoustic echosounder