Fish Stock Assessment Report
Quarterly summary of the activities of the national stock assessment enterprise.
NOAA Fisheries uses stock assessments to monitor the condition of nearly 500 fish stocks and stock complexes (groups of similar stocks managed together). Stock assessments are scientific efforts that involve data collection, data processing, and mathematical modeling that estimate the health and size of a fish stock, measure how fishing affects the stock, and project harvest levels that achieve the largest sustainable long-term yield. This page provides an annual report, broken out by fiscal year (October 1 – September 30) and quarter, detailing NOAA Fisheries’ planned and completed stock assessments.
Stock assessments are the backbone of sustainable fisheries management. Fishery managers use the results of assessments to evaluate the status of fish stocks and set annual catch limits (ACLs). An ACL is the largest amount of fish that commercial and recreational fisheries can sustainably harvest from a stock in one year. They help prevent overfishing (catching too many fish) from occurring and help fishers to catch the maximum number of fish over the long-term. NOAA Fisheries works with its partners in each management area to conduct stock assessments, but does not assess all managed stocks each year. Each region rotates the stocks it assesses based upon the availability of data, the complexity of available data, the structure and diversity of local fisheries, its available resources, and the regional processes for scheduling, reviewing, and using stock assessment results in management.
NOAA Fisheries sorts stocks into two general categories for tracking and reporting purposes. It tracks the stocks with higher levels of commercial, recreational, or ecological value as components of the Fish Stock Sustainability Index (FSSI). NOAA Fisheries prioritizes FSSI stocks for assessments that make use of its most advanced techniques and tools. NOAA Fisheries also conducts stock assessments of many stocks not on the FSSI list (non-FSSI stocks) in order to provide the necessary management advice for them.
Completed and Planned Assessments
NOAA Fisheries completed 187 stock assessments during the 2019 fiscal year (October 1 – September 30). That included 83 assessments of FSSI stocks and 104 assessments of non-FSSI stocks. The tables below show the regional breakdown of this year’s planned and completed FSSI and non-FSSI stock assessments:
Table of FY19 Planned Assessments
Stock Assessment Model and Type
NOAA Fisheries groups its stock assessment activities based upon the types of data they use, the structure of the model they use, the effort required to complete them, and their final products.
Stock Assessment Models
Stock assessment models evaluate important aspects of fish biology that shape a stock’s current and future condition:
- Abundance – The total amount of fish in a stock, over time
- Reproduction & Growth – The amount of fish and biomass added to a stock each year
- Mortality – The number of fish that die due to natural or man-made causes (e.g., fishing) each year
NOAA Fisheries uses a variety of models to conduct stock assessments. When stock assessment scientists conduct an assessment they identify and develop appropriate models based upon the available data. Those models fit into one of six general categories based upon their data requirements and products:
- Aggregate biomass dynamics
- Virtual population dynamics
- Statistical catch-at-length
- Statistical catch-at-age
Data-limited and index-based methods are the most basic model types used by NOAA Fisheries. They provide simplified catch advice when there are limited stock-level data. Data requirements for these methods include the total catch of a stock over time or a survey-based index of total stock abundance. NOAA Fisheries has catch data available for the majority of the stocks it assesses.
The remaining modeling methods are more complex and require additional data such as the length composition (number of fish at each length category) or age composition (number of fish at each age) of a stock. These models utilize these data and advanced statistical techniques to provide comprehensive advice to fishery managers. That advice allows managers to set harvest targets, select appropriate control rules, and determine stock status.
A stock status determination includes evaluations of whether or not a stock is undergoing overfishing (being harvested above sustainable levels), overfished (has a population below a healthy level), or approaching an overfished state (is likely to become overfished in the next two years.
Stock assessment results can only be used in management after reviewers evaluate them for accuracy. When a stock assessment successfully completes its review, it is certified as the “best scientific information available”. Occasionally, a stock assessment will fail its review and have its results rejected. The results of rejected assessments are not suitable for use in fisheries management.
Stock Assessment Types
Stock assessments are a process intended to produce a product (management advice). The amount of effort involved in the stock assessment process and the product created by it varies around the United States. Because stock assessments are major scientific efforts, some regions conduct intermediate analyses that update ACLs in between assessments. As a result, stock assessment activities can be subdivided into two general categories:
- Operational Stock Assessments -- Analyses conducted to provide scientific advice to fishery managers. These are NOAA Fisheries’ principal assessment-related activities and include efforts to create new assessment models and efforts that update existing models with the most recent data. At minimum, operational stock assessments make ACL recommendations. Those with more complex models also inform decisions related to stock status.
- Stock Monitoring Updates – Activities that provide stock management advice to fishery managers between operational stock assessments. These analyses involve re-running the latest model (completed during an operational stock assessment) and/or forecast with updated catch information to develop new catch advice.
Stock Assessment Program Performance
NOAA Fisheries monitors the performance of its stock assessment enterprise over time. One major measure of the enterprise’s performance is the percentage of FSSI stocks with “adequate” stock assessments. Adequate stock assessments are defined as stock assessments that:
- Provide a model-derived estimate of total stock abundance, and
- Were completed within the last five years
NOAA Fisheries scientific surveys are the primary method used to collect data on the number of fish in a given stock. These fishery-independent surveys, conducted aboard NOAA ships, chartered commercial fishing vessels, or by collaborative partners (e.g. research universities or state governments), follow a statistical sampling design that measures abundance throughout a stock’s range. During them, scientists measure the numbers of each stock of fish in a given area. Many sock assessments rely on the data collected by scientific surveys.
NOAA Fisheries completed 48 scientific surveys during fiscal year 2019. Of those, 28 were conducted aboard NOAA ships, and 20 were conducted aboard chartered commercial vessels or partner vessels.
Table of FY19 Planned Surveys
Table of FY19 Completed Surveys
Archive and More Information
To view reports on NOAA Fisheries’ stock assessment activities from previous years please visit our reports archive.
To view information specific to a particular region or science center, please visit its web page:
Northwest Fisheries Science Center (West Coast)
Southwest Fisheries Science Center (West Coast)
Northeast Fisheries Science Center (Greater Atlantic)