Population Assessments

Stock assessments are the scientific foundation of successful and sustainable fishery harvest management. Stock assessments measure the impact of fishing on fish and shellfish stocks. They project harvest levels that maximize the number of fish that can be caught every year while preventing overfishing (removing too many fish), protecting the marine ecosystem, and where necessary, rebuilding overfished (depleted) stocks.

Each stock assessment produces a report that provides fishery managers with a scientific basis for setting sustainable harvest policies under the authority of the Magnuson-Stevens Fishery Conservation and Management Act. Under the Act, we partner with eight regional fishery management councils to manage nearly 500 fishery stocks. NOAA Fisheries provides scientific guidance to resource managers by addressing fundamental questions including:

• What target harvest rate (percent removal per year) best balances resource conservation and use?
• Has a stock declined into an overfished condition?
• Does a stocks recent harvest rate exceed sustainable levels (i.e., is overfishing occurring)?

Stock assessments also support ecosystem-based fisheries management via integrated ecosystem assessments.

Stock Assessments 101

To learn more about the basics of the fisheries stock assessment process, read our Stock Assessments 101 series:

• Data Required to Assess Fish Stocks
• Stock Assessment Models
• More About Models
• Ecosystem Factors
• Future of Stock Assessments

Collecting Data

Along with our regional, state, and international partners, we conduct an average of 175 stock assessments annually. This includes more than 85 assessments of stocks included in the Fish Stock Sustainability Index, which is used to measure the performance of the most commercially and recreationally important fisheries.

We collect and store fish stock assessment results and related information in the Species Information System. A new public portal allows users to view and download stock assessment summaries and results. We also produce National Fish Assessment reports on a quarterly basis with up-to-date summaries on the status of NOAA Fisheries assessment activities for federally-managed fish stocks.

Stock Assessment Prioritization

We provide the scientific information that supports the management of approximately 500 fish stocks. However, we only have data and resources to assess about 200 stocks each year. Stock assessment prioritization allows us to work with regional partners to decide which stocks are assessed each year.

Stock assessment prioritization considers stocks managed under federal fishery management plans as well as non-federal stocks that might also be assessed by our regional fisheries science centers. This process considers:

• First-time assessments for previously unassessed stocks.
• Updating existing assessments using established methods and data types.
• Upgrading assessments to use new types of data and methods.

We developed the prioritization process during several years of collaboration with partners. The result is a national framework for prioritizing stocks. Each region uses this framework to help determine assessment targets and priorities to best meet those targets.

Species Information System

The Species Information System database is the central repository for regional and national fish stock information across NOAA Fisheries and includes stock assessment results and related information used to determine stock status. The database also has a public version, the Stock Status, Management, Assessment, and Resource Trends (Stock SMART) web portal that provides easy access for anyone to view and download summaries and results from stock assessments since 2005.

Regional Stock Assessments

Interested in specific regional stock assessments?

• Alaskan/North Pacific Stocks
• Pacific Islands Stocks
• Pacific Highly Migratory Species
• Other Pacific Stocks
• Atlantic Highly Migratory Species
• Northeast Stocks
• Southeast Stocks

Or take a deeper dive and learn more about our stock assessment programs at our science centers:

• Alaska Fisheries Science Center | Status of Stocks and Multispecies Assessment Program | Marine Ecology and Stock Assessment Program
• Pacific Islands Fisheries Science Center | Fisheries Research and Monitoring Division
• Northwest Fisheries Science Center | Population Ecology | Mathematical Biology and Systems Monitoring
• Southwest Fisheries Science Center | Stock Assessment Programs
• Northeast Fisheries Science Center | Population Dynamics Branch
• Southeast Fisheries Science Center | Sustainable Fisheries Division

Improving Stock Assessments

Stock Assessment Training

We also support the development of future and current stock assessment scientists. Programs focused on training the next generation of scientists in stock assessment and other relevant career fields include the QUEST Program and NOAA Fisheries-Sea Grant Fellowship Program. We also provide current stock assessment scientists with resources and opportunities for continued education and training in the evolving skills necessary for next generation stock assessments through in-person and online workshops.

We publish marine mammal stock assessment reports, which contain information about geographic range, population size and trends, productivity rates, and estimates of mortality. Marine mammals under our jurisdiction include whales, dolphins/porpoises, and seals/sea lions. The reports are prepared in consultation with one or more of three regional scientific review groups, and drafts are available for public review and comment.

Each year, we review reports for strategic stocks of marine mammals. For non-strategic stocks, we review reports every three years, or when new information becomes available. If the reviews show that the status of the stock has changed or can be assessed more accurately, we revise the report in consultation with the scientific review groups and after public review and comment.

The U.S. Fish and Wildlife Service also prepares stock assessment reports for marine mammals under their jurisdiction including manatees, polar bears, sea otters, and walruses. Some reports include information on multiple stocks.

NOAA Fisheries and U.S. Fish and Wildlife Service prepare reports only for marine mammal stocks that occur in waters under U.S. jurisdiction, as stated in the Marine Mammal Protection Act. We do not prepare reports for marine mammal stocks worldwide.

Conducting Assessments

Data collection, analysis, and interpretation are conducted through marine mammal research programs at each of our regional fisheries science centers and by other researchers. Data are collected in a variety of methods, including aerial and ship-based surveys, acoustic monitoring, photo identification studies, biopsy sampling for genetic studies, and tagging. 

The Marine Mammal Protection Act provides only general descriptions of the kinds of information that must be included in stock assessment reports. For example, the reports require a "minimum population estimate," which means we have "reasonable" assurance there are at least the estimated number in the population.
Each marine mammal stock assessment report includes:

• A description of the stock's geographic range.
• A minimum population estimate
• Current population trends.
• Current and maximum net productivity rates.
• "Potential biological removal" levels.
• Status of the stock.
• Estimates of annual human-caused mortality and serious injury by source.
• Descriptions of other factors that may be causing a decline or impeding the recovery of strategic stocks.

How Many Marine Mammal Stock Assessment Reports Are Reviewed or Prepared Annually?

The first stock assessment reports prepared in 1995 included about 165 reports on marine mammal stocks in U.S. waters:

• Approximately 60 reports in the Atlantic Ocean and Gulf of America.
• Approximately 60 reports along the Pacific Coast of the continental United States and Hawaii.
• Roughly 35 reports in Alaska and the North Pacific.
• Roughly 10 reports for manatees, polar bears, sea otters, and walrus in U.S. waters (prepared by U.S. Fish and Wildlife Service).

The number of reports may vary from year to year because stock identification is subject to change. Marine mammal stocks may be added or removed from the regional list of compiled reports due to changes in distribution.

Using Assessments for Management and Conservation

We use marine mammal stock assessment reports to:

• Identify and evaluate the status of marine mammal populations and the effects of human activities upon them.
• Evaluate the population level effects when authorizing the "take" of marine mammals incidental to human activities.
• Design and conduct appropriate conservation measures.
• Classify fisheries on the Marine Mammal Protection Act List of Fisheries.
• Evaluate the progress of each fishery in reducing its incidental mortality and serious injury to insignificant levels approaching a zero mortality and serious injury rate.

Improving Assessments

For marine mammal stock assessments, the Marine Mammal Protection Act provides only general guidance on assessment methods and on the content of the reports. To include values for the required elements in the reports, NOAA Fisheries and U.S. Fish and Wildlife Service translated qualitative concepts into quantitative terms. After building a scientific foundation through simulation modeling, we proposed guidelines for selecting specific values to include in the reports. The guidelines received review and comments by the public and scientific review groups.  

View the Guidelines for Assessing Marine Mammal Stocks for information on the background, decisions, and default values that go into developing the stock assessment reports.

Additionally, we work with partners to develop and evaluate analytical products and applications to improve population assessments.

To disseminate results and increase national coordination and collaboration in conducting assessments, we support and organize protected species assessment workshops biennially. Other workshops address specific technical topics and advance various protected species science initiatives with direct relevance to management actions. Similarly, various dedicated working groups encourage dissemination of best practices and latest advances in the field.

Population assessments provide the foundation for evaluating the status of and threats to marine mammals, sea turtles, and fish protected under the Endangered Species Act and to plan and implement species recovery and conservation actions.
Marine resource managers require accurate and precise information on a species or stock’s population structure, life history characteristics and vital rates, abundance, and threats (particularly those caused by human activities). This information informs agency decisions related to:

• A species’ listing status under the Endangered Species Act. 
• Federal or federally-funded activities that might impact a species or its habitat.
• Acceptable bycatch levels.
• Scientific research and incidental take permits issued to agencies, scientific and academic institutions, and industry.

Information included in endangered species population assessments is vital to how we support and advise state and tribal-managed coastal areas. It also allows us to provide scientific and policy leadership to regional and international bodies such as multi-state marine fishery commissions, U.S. fishery management councils, international fishery management organizations, and the Convention on International Trade in Endangered Species of Wild Fauna and Flora.

Improving Assessments

We provide funding support to our agency scientists as well as university, federal, and state partners to improve sea turtle population assessments through a competitive, peer-reviewed process. Funds are awarded based on relevance to management concerns and scientific research priorities.

For assessing acoustic impacts on endangered species, we also provide funding through a competitive, peer-reviewed process to support research conducted by NOAA scientists and partners.

We have established the National Protected Species Toolbox Initiative to support the development of analytical products and applications that aim to investigate impacts and consequences of human and environmental disturbance on endangered and threatened marine life and other protected species.