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Fishery-Independent Indices of Abundance in the Southeast Region

Learn about relative abundance indices for fish and shrimp from data collected during fishery-independent surveys conducted by the Southeast Fisheries Science Center and partners.

The Southeast Abundance of Fish and Shrimp (SEAFiSh) data visualizer provides access to relative abundance indices from data collected during fishery-independent surveys conducted in the southeastern U.S. Atlantic (South Atlantic) and Gulf of Mexico. These indices, updated annually, can inform users of current trends in relative abundance for managed species and can be incorporated into stock assessment reports and other interim reports.

Text: "SEAFiSh Southeast Abundance of Fish and Shrimp Data Visualizer", NOAA Fisheries logo, and cartoon images of a fish, shrimp, some coral and seaweed, and four plotted data points
The Southeast Abundance of Fish and Shrimp Data Visualizer, or SEAFiSh, displays trend information for 25 species in the Gulf of Mexico and 18 species in the southeastern U.S. Atlantic.

Explore the SEAFiSh data visualizer

What is a Relative Index of Abundance?

An index of abundance is a measure of the size of a population or sub-unit of the population, usually presented as a function of time. The gear types we use may not perfectly measure absolute abundance, or the exact number of fish in a given area. For example, fish traps and longline gears do not catch all the fish in their area of deployment—only a sample. Therefore, we interpret our abundance estimates relative to each other, and refer to them as relative indices of abundance. For example, if our abundance estimate for a focal species in one year was 20 percent higher than the estimate from the previous year, we would conclude that the abundance of that species had increased by 20 percent between the two years, but we may not know the true, or absolute, abundance value for either year.

Where the Data Come From

NOAA Fisheries’ Southeast Fisheries Science Center and our partners in the southeast region conduct several annual fishery-independent surveys from which the relative abundance indices are built. One of our largest partners in the region is the Southeast Area Monitoring and Assessment Program. SEAMAP is a collaborative effort between federal, state, and university programs. It is designed to collect, manage, and distribute fishery-independent data throughout the region. 

The surveys collect data on a number of commercially and recreationally important species throughout the Southeast region. Data from the following surveys are used to generate the relative abundance indices of abundance: 

  • Southeast Fisheries Science Center Bottom Longline Survey
  • SEAMAP Summer and Fall Groundfish Surveys
  • SEAMAP Spring and Fall Plankton Surveys
  • SEAMAP Reef Fish Video Survey
  • South Atlantic Trap-Video Survey

Purpose of the Indices

The relative abundance indices provided are annually updated snapshots of trends in abundance for selected species of interest. Each index is only part of the data used in stock assessments and is only applicable to the portion of the population that is sampled during the individual survey used to generate that index. Indices of abundance are not indicative of official stock status determinations (overfished and overfishing, or lack thereof), which are made through stock assessments that require additional information such as life history parameters, landings, and length and age compositions. Stock assessments for federally managed species in the Southeast region are performed through the Southeast Data, Assessment, and Review process.

How to View Indices of Abundance

Use the Southeast Abundance of Fish and Shrimp Data Visualizer to see the indices for managed fish and shrimp species in the Southeast Region. The tool provides indices for 25 species in the Gulf of Mexico and 18 species in the South Atlantic. Species include numerous snapper, grouper, amberjack, triggerfish, mackerel, sharks, shrimp, and more.

A plot shows 'standardized CPUE' for late juvenile and adult mutton snapper in the South Atlantic
Caption: An example of what you see in the Southeast Abundance of Fish and Shrimp (SEAFiSh) Data Visualizer. CPUE: Catch per unit effort. Credit: NOAA Fisheries

What to Know Before Using These Data

For those species assessed under SEDAR, the relative abundance indices accessible through the data visualizer were generated using the model structure and variables from the most recent stock assessment model for each species. Working paper links are available for reference within the data visualizer to provide additional information on how each index of abundance was constructed. 

We also produce indices of abundance for a subset of non-SEDAR assessed species to provide additional information to managers and regional fishery management councils:

  • Graysby
  • White grunt
  • Almaco jack
  • Lionfish
  • Sand tilefish

Abundance indices for these species are calculated using data from the South Atlantic Trap-Video Survey. Although these species have not been assessed under SEDAR, the methodology for generating indices of abundance is similar to those used for red snapper and gray triggerfish.

The relative abundance indices presented in the Visualizer are based on the most current dataset available for each survey. All indices in SEAFiSh have undergone rigorous quality assurance checks, including comparison with previous indices of abundance to ensure consistency. Minor differences in the index values and 95 percent confidence limits may exist between the current version and older versions of the data due to data corrections made during routine quality assurance checks.


Explore the SEAFiSh data visualizer


Last updated by Southeast Fisheries Science Center on July 10, 2024