Stock Assessment 101 Series

Stock Assessment 101 Series: Part 1—Data Required for Assessing U.S. Fish Stocks (originally published May 23, 2012 -

Why Do We Conduct Fish Stock Assessments?

NOAA Fisheries’ scientific stock assessments are key to fisheries management. They examine the effects of fishing and other factors to describe the past and current status of a fish stock, answer questions about the size of a fish stock, and make predictions about how a fish stock will respond to current and future management measures (Marine Fisheries Stock Assessment Improvement Plan). Fish stock assessments support sustainable fisheries by providing fisheries managers with the information necessary to make sound decisions.

Why Are Fish Stock Assessments Important?

Fisheries in the United States contribute significantly to the American economy and generate over 1.5 million jobs economy-wide. Healthy fisheries also provide recreational fishing opportunities to millions of Americans. To continue enjoying these benefits, we must carefully manage fish stocks to ensure sustainable use for current and future generations.

Stock assessments provide important science information necessary for the conservation and management of fish stocks. The Magnuson-Stevens Reauthorization Act calls for the best scientific information available to manage U.S. commercial and recreational fisheries. More than 500 fish stocks in the United States are managed under fishery management plans produced by eight regional fishery management councils. Additionally, coastal states and international organizations rely on NOAA Fisheries’ stock assessments for the management of non-federal and joint jurisdiction fish stocks.

Data for Complete Stock Assessments—Catch, Abundance, and Biology

Stock assessments are based on models of fish populations that require three primary categories of information: catch, abundance, and biology. To ensure the highest quality stock assessments, the data used must be accurate and timely.

Catch Data—The amount of fish removed from a stock by fishing.

A national network of fishery monitoring programs continuously collects catch data and makes this information available to stock assessment scientists and managers. Sources of catch data include:

  • Dockside monitoring
  • Logbooks
  • Observers
  • Recreational sampling

Abundance Data—A measure, or relative index, of the number or weight of fish in the stock. Data ideally come from a statistically-designed fishery-independent survey that samples fish at hundreds of locations throughout the stock’s range.

Biology Data—Provides information on growth rates and natural mortality.

Biological data includes information on fish size, age, reproductive rates, and movement. Annual growth rings in fish ear bones are read by biologists in our laboratories. The samples may be collected during fishery-independent surveys or be obtained from observers and other fishery sampling programs. Academic programs and cooperative research with the fishing industry are other important sources of biological data.

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