SEAMAP Resource Surveys

What is SEAMAP

Fishery-independent data, Gulf-wide

SEAMAP is a cooperative State, Federal, and university program for the collection, management, and dissemination of fishery-independent data in the southeastern United States. Its Gulf component runs a suite of long-running surveys, each with its own gear, sampling area, and purpose.

Trawl Surveys

SEAMAP trawl surveys have monitored shrimp and groundfish populations since the Summer survey began in 1982 and the Fall survey began in 1985. Together, they target roughly 650 stations each year across the 9-110 m depth stratum using a standardized 42-ft semi-balloon trawl towed at 2.5 knots.

Summer and Fall Shrimp/Groundfish Survey sampling area map — Summer and Fall Shrimp/Groundfish Survey sampling area across the Gulf.

NMFS statistical zones used for SEAMAP Gulf sampling — NMFS statistical zones used to organize Gulf sampling designs.

Summer Shrimp / Groundfish Survey

The Summer Shrimp/Groundfish Survey targets approximately 350 stations each June and July. Survey data help monitor the size and distribution of penaeid shrimp during or prior to the migration of brown shrimp from bays to the open Gulf, supports evaluation of the Gulf Council's "Texas Closure" management measure, and tracks shrimp and groundfish stocks across the standardized trawl sampling frame.

Processing. Catches are sorted to species, counted, and weighed. When catches are small or not highly diverse, the full catch is processed. Larger catches may be subsampled, while penaeid shrimp, lionfish, Red Snapper, sharks, skates, rays, rare species, and other select species are processed in full when required. During the Summer Shrimp/Groundfish Survey, up to 50 brown, pink, and white shrimp from each trawl are processed for sex, individual length, and individual weight.

Station selection is through a probability-based design where every element in the sampling universe has a known, positive probability of selection, which avoids selection bias and supports valid statistical inference. Selection probability is proportional to geographic surface area. Each NMFS statistical zone is split into shallow (9-37m) and deep (37-110m) depth zones. Approximately 242,328 sq. km are available for sampling within these depth zones. Protected and sensitive areas are removed from the sample universe, and stations are randomly selected with a 5 nautical mile buffer between stations. After excluding sensitive and protected areas, the 2026 available trawling area was approximately 218,034 sq. km.

Sampling is conducted around the clock, and all trawls are towed for 30 minutes. If a tow is longer or shorter, crews document the reason rather than changing towing speed or course solely to force the duration. If the selected station is untrawlable, crews move to the nearest trawlable location. Known hardbottom, sensitive sponge habitat, and similar areas are not sampled. If an artificial reef is nearby, the station may be shifted no more than 1 nautical mile while staying in the same depth and statistical zone when possible.

Environmental data are collected within 1 hour of the trawling event and within 1/2 nautical mile of the SEAMAP sample site. The standard trawl is a 42-ft semi-balloon trawl with 8-ft by 40-in doors, a standard free tickler chain, and a recommended towing speed of 2.5 knots. The resulting time series supports stock assessments for penaeid shrimp, mackerels, snappers, groupers, triggerfish, coastal sharks, and other managed species.

Crew sorting a Shrimp/Groundfish Survey catch aboard the vessel — A Shrimp/Groundfish catch is sorted, counted, and weighed by species aboard the vessel.

Fall Shrimp / Groundfish Survey

The Fall Shrimp/Groundfish Survey targets approximately 300 stations each October and November across the same 9-110 m sampling universe. It estimates abundance and distribution of demersal organisms, obtains length-frequency measurements for major finfish and shrimp species, and links catch patterns with environmental conditions.

Its operational design mirrors the Summer Shrimp/Groundfish Survey. For the Fall Shrimp/Groundfish Survey, shrimp are treated like other finfish and invertebrates with up to 20 shrimp lengths being recorded per station, and sex is recorded for every fifth penaeid shrimp.

Bottom Longline Survey

The SEAMAP Bottom Longline Survey began in 2008 and was standardized in 2015 around the 3-10 m depth contour. Spring (April-May), Summer (June-July), and Fall (August-September) sampling targets roughly 106 stations per season, or 318 stations each year.

One hundred baited gangions are attached at equal distances along a 1.842 km longline, which soaks for one hour, and environmental data are collected at each station. The objective is to collect data on coastal shark and finfish abundance and distribution, supporting assessments for species such as Blacktip Shark, Atlantic Sharpnose Shark, Great Hammerhead Shark, and Red Drum.

Stations are proportionally allocated based upon the area within the 3-10 m depth contour in NMFS statistical zones 3-21. Each statistical zone receives at least two stations per season. Selected locations are buffered by 4 nautical miles to reduce overlap in bait-plume and catch data. If a point is outside the depth stratum or unsafe because of bottom profile, vessel traffic, shoals, or fishing activity, crews may shift up to 4 nautical miles within the same stratum and statistical zone.

Sets are made during daylight. Crews deploy the mainline with 100 gangions carrying 15/0 circle hooks baited with Atlantic Mackerel, spaced about 19 m apart, with bottom weights at the ends and midpoint of the mainline. Soak time is calculated from deployment of the second high flyer to retrieval of the first high flyer, with a target of 60 minutes. High-flyer times and locations, hooks deployed and retrieved, environmental observations, catch, biological measurements, and any operation problems are recorded for each station.

Bottom Longline Survey sampling area map — Bottom Longline Survey sampling area in the 3-10 m depth contour.

Catch Workup

As catch comes onboard, crews record biological data for captured sharks and finfish, including species identification, lengths, sex when visible, condition, weight when practical, and tagging or sample information as needed.

Crew measuring a shark during SEAMAP Bottom Longline Survey catch processing — An Atlantic Sharpnose Shark is measured during the SEAMAP Bottom Longline Survey.

Reef Fish Survey

The Reef Fish Survey began in 1992 on shelf-edge natural reef areas and has evolved into a Gulf-wide stereo-video program for reef fish on natural reefs, artificial reefs, oil and gas platforms, and other structured habitat. Since 2020, the G-FISHER design has unified partner surveys around biologically relevant spatial and habitat strata.

Baited stereo-video camera arrays are deployed during daylight, baited with Atlantic Mackerel and squid, and allowed to soak for at least 35 minutes to capture a continuous video record for species identification, relative abundance, and length measurement. Habitat mapping is conducted at night, and water samples are collected at a subset of stations for eDNA analysis.

Four-camera reef fish survey array hardware — The four-camera baited array used to record reef-fish presence, abundance, and lengths on natural reef habitat.

Camera Array Hardware

The reef-fish survey uses baited video arrays instead of extractive sampling at each camera station. Multiple camera views give analysts overlapping fields of view for identification and length measurement while preserving the reef habitat being surveyed. The resulting data support assessments for snappers, groupers, amberjacks, Gray Triggerfish, Hogfish, and other managed reef species.

Reef Fish Survey sampling area map — Reef Fish Survey sampling area for natural and artificial reef habitats.

Plankton Surveys

SEAMAP plankton surveys have sampled ichthyoplankton across the Gulf since the Spring Plankton Survey began in 1982 and the Fall Plankton Survey began in 1984.

Sampling gear consists of standard 61-cm bongos and a 2 x 1 m neuston net on the larger vessels. Bongos carry 0.335 mm mesh nets with hard or soft cod ends; the neuston net is a 2 x 1 m pipe frame fitted with 0.950 mm mesh.

A 2 x 1 m neuston net towed at the surface to sample plankton.

A standard 61 cm bongo net — A pair of standard 61 cm bongo nets fished on an oblique tow.

SPRING

Spring Plankton Survey

Conducted each April and May, the Spring Plankton Survey collects ichthyoplankton for estimates of the abundance and distribution of early life stages of spring-spawning fishes, especially Atlantic Bluefin Tuna. Hydrographic data, Sargassum observations, and gelatinous plankton observations add habitat context at each station. Data from the SEAMAP Spring Plankton Survey have been used in stock assessments for Atlantic Bluefin Tuna and Skipjack Tuna.

FALL

Fall Plankton Survey

Conducted each August and September, the Fall Plankton Survey estimates the abundance and distribution of eggs, larvae, and small juveniles of Gulf fishes, particularly King and Spanish Mackerel, Red Drum, Red Snapper, other snappers, and sciaenids. The time series supports stock assessments for Red Snapper, Vermilion Snapper, King Mackerel, and Gray Triggerfish.

Larval snapper specimens collected through ichthyoplankton sampling.

Spring Plankton Survey sampling area map — Spring Plankton Survey sampling area.

Fall Plankton Survey sampling area map — Fall Plankton Survey sampling area.

Environmental Data

Hydrographic profiles and surface observations are collected with biological samples so catch and plankton data can be interpreted alongside environmental conditions. A standardized methodology is used across the program, though the sampling equipment varies by vessel.

Weather & Surface

Barometric pressure: Recorded in millibars.
Wave height: Estimated visually, in meters.
Wind speed & direction: Knots, with compass bearing of origin.
Air temperature: Recorded in Centigrade.
Cloud cover: Estimated visually, percent of sky.
Secchi depth: Collected when transmissivity is unavailable.

Water Column Profile

Temperature: CTD profile; handheld thermometer or sonde as backup.
Salinity: CTD profile; bottle samples and salinity instruments as backup.
Chlorophyll: CTD fluorescence where available; extracted samples when collected.
Dissolved oxygen: CTD or in-situ sensor; Winkler titration as backup or QA/QC.
Turbidity: Electronic probe, where available.

The following parameters are measured at the surface, mid-depth, and bottom. For bottom depths greater than 200 m, samples are taken at the surface, 100 m, and 200 m.

When the CTD is operating, it is the primary source for the water-column profile, including temperature, salinity, dissolved oxygen, and available optical measurements such as fluorescence or transmissivity. Backup methods are used when the primary instrument is unavailable or for QA/QC. Water samples may be collected with Niskin bottles for temperature, salinity, dissolved oxygen, or chlorophyll analysis. Handheld thermometers, sondes, refractometers, salinometers, and Winkler titration may be used as alternate or supplemental methods. Secchi depth is collected when transmissivity is unavailable.

A CTD being deployed overboard — A CTD deployed overboard to measure environmental data at the surface, mid-depth, and bottom.

Spatial data

The SEAMAP WebMap

Visualize sampling locations and catch data from the trawl and bottom longline surveys. Designed as a first-pass tool for quickly viewing sampling effort and where species have been caught, with heat-map visualization of important species metrics.

Sampling effortLocations of all trawl and longline sampling stations, with filtering available by survey source, year, and season.

Where species were caughtMap the locations and frequency of catches across the Gulf.

Heat mapsVisualization tool showing relative abundance of fish species.