Abstract:
Fishes and macroinvertebrates were collected using a 12.8m semi-balloon otter trawl with 4 cm mesh from January 5 to November 1, 2017 in the coastal waters of Alabama and Mississippi, as well as the Chandeleur Islands. Abundance and biomass of all fish and macroinvertebrates taken in the trawls were enumerated by species and weighed to the nearest 0.1g or kg, depending on size.
Suggested Citation:
John Valentine, Charlie Martin, J. Marcus Drymon, Trey Spearman, and Sean Powers. 2018. Trawl surveys of fish and invertebrates in Coastal Alabama, Mississippi, and the Chandeleur Islands, January 5 - November 1, 2017. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N78W3BSF
Purpose:
Our purpose was to collect community-level data of the demersal fish and invertebrate species, looking for shifts in community composition due to remaining effects of oiling years after the oil spill.
Data Parameters and Units:
Year: year data were collected, Project: the project that funded the data collection trip, Cruise ID: id for the cruise that contains date of the cruise, Station ID: station id where data were collected, Grid: grid id, Date: month, date, year when data were collected, Commonname: species common name, Total Count: total count of species in a trawl, Total Combined Biomass: total weight of all species in a trawl in kg, Start Set Time (hhmm), Start Set Depth (meter), Start Set Longitude degree (decimal degree), Start Set Longitude minute (decimal minute), Start Set Latitude degree (decimal degree), Start Set Latitude minute (decimal minute), End Set Time (hhmm), End Set Depth (meter), End Set Longitude degree (decimal degree), End Set Longitude minute (decimal minute), End Set Latitude degree (decimal degree), End Set Latitude minute (decimal minute), Surface Temperature (Celsius), Mid Temperature (Celsius), Bottom Temperature (Celsius), Surface Salinity (psu), Mid Salinity (psu), Bottom Salinity (psu), Surface DO (mg/L), Mid DO (mg/L), Bottom DO (mg/L), Cruise Comment (character), Station Comment (character), Trawl Comment (character)
Methods:
The ACER bottom trawl survey design consists of six sampling blocks stratified by depth (inshore vs. offshore) and region (west, central, east): two blocks surround the Chandeleur Islands, LA, two blocks are west of the Mobile Inlet to the AL/MS border and two blocks are east of the Inlet to the AL/FL border. One block on each side of the sampling area is offshore out to 20 m depth and the other block is inshore of the Chandeleur Islands, Dauphin Island, and the Ft. Morgan Peninsula. For each season of sampling, two grids (stations) from each block are randomly chosen using a randomized number generator, which produces two grids within the block coordinates. Each grid is sampled twice during each survey event, and two surveys occur per year, once in spring and once in fall. During Fall 2017, bottom trawl surveys were conducted on the R/V Alabama Discovery out of the Dauphin Island Sea Lab. Trawl sampling was conducted during daylight hours – between sunrise and sunset. All trawl samples were conducted at speeds ranging from 2.5 to 3 knots and lasted 15 minutes. Catch was sorted on deck to species, and combined biomass and abundance of each species was recorded.
Instruments:
The trawl net was a SEAMAP standard 12.8-m semiballoon otter trawl with a 12.95-m headrope, wooden doors, rollers and a tickler chain. The net was composed of three sections: wings, an intermediate area, and a codend with mesh sizes of 5.08 cm, 3.81 cm, and 4.13 cm, respectively. Chaffing gear (8.89 cm mesh) covered the codend as protection from contact with the bottom.
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