Abstract:

Fishes and macroinvertebrates were collected using a 12.8m semi-balloon otter trawl with 4 cm mesh in Spring and Fall of 2016 in the coastal waters of Alabama and Mississippi, as well as the Chandeleur Islands. Length measurements and individual biomass of a subset of fish and macroinvertebrates taken in the trawls were recorded for each trawl. Length measurements appropriate for each species were recorded to the nearest millimeter, and biomass was recorded to the gram.

Suggested Citation:

John Valentine, Charlie Martin, J. Marcus Drymon, Trey Spearman, and Sean Powers. 2017. Individual Measurements from trawl surveys of fish and invertebrates in Coastal Alabama, Mississippi, and the Chandeleur Islands, March - December, 2016. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7GQ6W01

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, 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, Season: season data collected, Common Name: species common name, Rostrum Length: on shrimps, the distance from the tip of the rostrum to the back of the carapace measured in millimeters, Mantle Length: on squid, the distance from the tip of the mantle to its base measured in millimeters, Carapace Width: on crabs, the distance between the two lateral spines, measured in millimeters, Precaudal Length: on sharks, the straight line distance from the tip of the snout to the pre caudal pit, measured in millimeters, Standard Length: on bony fish, the straight line distance from the tip of the snout to the beginning of caudal fin rays, measured in millimeters, Fork Length: on bony fish and sharks, the straight line distance from the tip of the snout to the fork of the tail, measured in millimeters, Natural Total Length: on bony fish and sharks, the straight line distance from the tip of the snout to the tip of the tail as it naturally lies, measured in millimeters, Stretched Total Length: on bony fish and sharks, the straight line distance from the tip of the snout to the tip of the tail stretched to its farthest distance, measured in millimeters, Disk Width: on skates and rays, the lateral distance across the body, measured in millimeters, Individual Biomass: weight of the individual fish (kg), Start Set Time (time), 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 (time), 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, Station Comment

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 2016, 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 a random subset of up to twenty individuals were chosen for measuring and weighing.

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.

Individual Files: