Abstract:

Catch and individual measurements from all organisms captured on bottom longline surveys in Coastal Alabama, Mississippi, and the Chandeleur Islands in 2015. Bottom longline gear type consists of 1.85 km (1 nm) of 4 mm monofilament (545 kg test) set with 100 gangions. Gangions are composed of a longline snap and a 15/0 circle hook, baited with Atlantic mackerel (Scomber scombrus). Each gangion is made of 3.66 m of 3 mm (320 kg test) monofilament. Sampling occurs twice per year (spring and fall), three days per season. All organisms were enumerated by species, measured (to the nearest mm fork length), weighed (to the nearest kg), tagged, and released.

Suggested Citation:

Drymon, Marcus. 2018. Bottom longline surveys of elasmobranchs and teleosts in Coastal Alabama, Mississippi, and the Chandeleur Islands in 2015. Distributed by: Gulf of Mexico Research Initiative Information and Data Cooperative (GRIIDC), Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7RN35X3

Publications:

Seubert, E. A., Hussey, N., Powers, S. P., Valentine, J. F., & Drymon, J. M. (2019). Assessing trophic flexibility of a predator assemblage across a large estuarine seascape using blood plasma stable isotope analysis. Food Webs, 21, e00132. doi:10.1016/j.fooweb.2019.e00132

Purpose:

Our purpose was to assess the species diversity of apex and mesopredators across the Northern Gulf of Mexico and measure any shifts in community assemblages, as well as note any residual effects from the Deepwater Horizon oil spill.

Data Parameters and Units:

Year: year data were collected, Cruise ID: ID for the cruise that contains date of the cruise, Station ID: station ID where data were collected, Station Grid ID: ACER grid ID, Date: month, date, year when data were collected, Season: season when data were collected, Fish ID: Individual ID assigned to each individual containing vessel code, station ID, and individual fish number, Species: species common name, Standard length: on bony fish, the straight line distance from the tip of the snout to the beginning of caudal fin rays, measure in millimeters, Precaudal Length: on sharks, the straight line distance from the tip of the snout to the precaudal pit, 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 natural lies, measure 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, Weight: weight of the individual, measured in kilograms, Fish Sex: sex of each elasmobranch can be determined externally and internally for finfish, Stage: for sharks, maturity can be determined externally in males and internally in females and finfish, rated as immature, transitional, or mature, Start Set Time: Start time at beginning of longline set (HHHH), Start Set Depth: depth at beginning of set (meters), Start Set Longitude: longitude at beginning of longline set (decimal degree), Start Set Latitude: latitude at beginning of longline set (decimal degree), 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), Fish Comment (character)

Methods:

The ACER bottom longline 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 20m depth and the other block is inshore of the Chandeleur Islands, Dauphin Island, and the Ft. Morgan Peninsula. For each season of sampling, a minimum of two stations/grids from each block are randomly chosen using a randomized number generator, which produces a station within the block coordinates. Each block is sampled twice a year, once in spring and once in fall during ACER sampling. Bottom longline surveys are conducted on the R/V E.O. Wilson and the R/V Alabama Discovery out of the Dauphin Island Sea Lab. All bottom longline sampling is conducted during daylight hours.

Individual Files: