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Plankton Surveys

Mission: Sample fish eggs, larvae and juveniles, their zooplankton predators and prey, and measure the physical properties of their pelagic habitat in order to provide a time series of fishery-independent estimates of relative abundance, as well as, ecosystem-relevant data on early life history and ecology, habitat, and recruitment characteristics of both fishery and non-fishery species

SEAMAP Plankton Sampling

• Three surveys are conducted yearly to assess the occurrence, abundance and geographic distribution of the early life stages of fishes, as well as, to measure primary productivity and pelagic habitat properties across the Gulf of Mexico. The purpose of these collections is to build a long term fishery independent database on the resource species important to the economy of the Gulf of Mexico.
  • Winter surveys focus on grouper and tilefish species from the continental shelf, shelf edge and deep Gulf waters.
  • Spring surveys focus on bluefin tuna and covers the entire U.S. Gulf of Mexico and in more recently the southern Gulf and the Caribbean Sea in cooperation with scientists from Mexico
  • Fall surveys focus on fall spawning fishes such as king and Spanish mackerel, red drum and snappers.
• Sampling is conducted with bongo nets, neuston nets, CUFES, MOCNESS, and Methot trawls.
• Water properties and Chl a concentration are assessed at each station using a standard CTD cast and benchtop fluorometry.
• Plankton samples are preserved at sea and returned to the Laboratory for analysis. Initial sample sorting and identification of fish larvae and invertebrate zooplankton are conducted at the Sea Fisheries Institute, Plankton Sorting and Identification Center, Gdynia and Szczecin, Poland.

SEAMAP Plankton Sampling
SEAMAP (SouthEast Area Monitoring and Assessment Program) State and Federal Cooperative Research Program

SEAMAP Stations in the Gulf of Mexico
Photo Credit: SEFSC

Plankton samples are collected with fine mesh nets at stations throughout the U.S. Gulf of Mexico during annual SEAMAP surveys (1982 to present). These samples yield data on abundance and distribution of fish eggs, larvae and invertebrate (non-fish) zooplankton. Data for select species are used in fishery stock assessments to index size of adult populations. Ocean water properties are measured at each plankton station in order to describe the pelagic habitat of fish larvae and their planktonic predators and prey.

Bongo Net (61 cm) Photo Credit: SEFSC

Neuston Net (1x2 m) Photo Credit: SEFSC

CTD and Water Sampler Photo Credit: SEFSC

SEAMAP Larval Indices

Fish populations in the Gulf of Mexico are monitored by the National Marine Fisheries Service using data from both fishery-dependent (recreational and commercial catches) and fishery-independent (NMFS resource surveys) sources. The numbers of fish larvae in SEAMAP plankton samples dating back to the 1970s & 1980s are one type of fishery-independent data source. Larval abundance and/or presence/absence data are considered to be important indicators of the size of spawning populations of Atlantic bluefin tuna, red snapper and king mackerel. Data from annual resource surveys such as SEAMAP allow NMFS scientists to follow long term trends in populations and to judge how effective management policies instituted by the Gulf of Mexico Fishery Management Council are in restoring and maintaining viable fishery stocks.

Bluefin Tuna (Thunnus thynnus) Larval Abundance Graph
Credit: SEFSC


Red Snapper (Lutjanus campechanus) Larval Abundance Graph
Credit: SEFSC


King Mackerel (Scomberomorus cavalla) Larval Abundance Graph
Credit: SEFSC

Tuna Spawning and Larval Habitat Studies

Tuna
Photo Credit: SEFSC


Tuna Larvae
Photo Credit: SEFSC

The Western stock of the Atlantic bluefin tuna (Thunnus thynnus) spawn exclusively in the Gulf of Mexico during the month of May. Annual plankton surveys generate indices of larval abundance that are used to determine the number of individual adult tuna in this stock. Directed sampling of tuna eggs and larvae in the vicinity of oceanographic features as seen from satellite imagery is a recent addition to this survey. These new data will help elucidate the reliance of tuna on oceanographic frontal boundaries.

Satellite View of Gulf of Mexico
Photo Credit: SEFSC

Ichthyoplankton (fish eggs and larvae) of the Gulf of Mexico

Ichthyoplankton Specialist
Photo Credit: SEFSC

The fundamental data, on which SEAMAP larval indices of abundance are derived, are supplied by ichthyoplankton specialists who sort, identify, count and measure fish larvae captured in SEAMAP plankton samples. Microscopic examinations are conducted at the Plankton Sorting and Identification Center of Gdynia and Szczecin, Poland and the Southeast Fisheries Science Center, Mississippi and Miami Laboratories.

Larval Fish
Photo Credit: SEFSC
Larval Snapper
Photo Credit: SEFSC

CUFES/TSG (Continuous Underway Fish Egg Sampler/Thermosalinograph)

The CUFES (inset picture) is a plankton sampling device used to collect fish eggs and zooplankton at a fixed depth below the ship. Water is drawn up through the ship's sea chest and sampled at fixed time intervals while the ship is underway. The presence of fish eggs in these near-surface samples reflect spawning locations; and in combination, CUFES, and TSG data are used to examine the influence of physical ocean properties on plankton.

CUFES Map
Photo Credit: SEFSC

Expanding Plankton Sampling

The MOCNESS (multiple opening closing net and environmental sensing system) allows Plankton Unit scientists to sample discrete depths in the water column and to gather the most extensive set of data on vertical distribution of fish larvae yet assembled from the Gulf. Recently added to the suite of ichthyoplankton samplers is the Methot trawl. This gear samples postlarvae and juvenile fishes not captured in the slower towed bongo and neuston nets. Data on the vertical distribution of fish eggs and larvae are critical to understanding their vulnerability to industrial seawater intakes and outlets; while juvenile fish abundance data are vital to understanding variation in recruitment to fisheries.

1 m MOCNESS
Photo Credit: SEFSC
5 m² Methot Trawl
Photo Credit: SEFSC

Primary Production

The chlorophyll a (chl-a) concentration in water samples from three depths is measured at sea with a benchtop fluorometer. Chl-a concentrations reflect the primary production of phytoplankton in the ocean. The relationships between fish larvae, their zooplankton prey and chl-a concentrations can be used to understand annual variations in growth and survival rates of larval fish, and lead to a better understanding of the dynamics of the Gulf of Mexico ecosystem.

Chlorophyll A (chl-a) Concentration
Credit: SEFSC

Invertebrate Zooplankton

Shrimp
Photo Credit: SEFSC
Zooplankton
Photo Credit: SEFSC

SEAMAP Fall 2003 Plankton Survey: Bongo Adundance

The invertebrate (non-fish) fraction of SEAMAP plankton samples provides data on distribution and abundance of decapod crustacean larvae of economically and ecologically important species. A recent OAR-NOAA study, funded through the Northern Gulf Institute, brings together university zooplankton ecologists and Plankton Unit scientists to investigate zooplankton composition and abundance over the 27 year SEAMAP time series and to relate this information to changes in regional climate and the Gulf of Mexico ecosystem.