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. Previous years' reports are stored in our archive.
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 its processes for scheduling, conducting, 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) to provide necessary management advice.
Completed and Planned Assessments
NOAA Fisheries anticipates completing 180 stock assessments during fiscal year 2021 (October 1, 2020 – September 30, 2021). This includes 86 assessments of FSSI stocks and 94 assessments of non-FSSI stocks. NOAA Fisheries completed nine FSSI stock assessments and two non-FSSI stock assessments during quarter 3 (April 1, 2021 – June 30, 2021). This brings the current totals for fiscal year 2021 to 48 FSSI stock assessments and 78 non-FSSI stock assessments. The tables below show the regional breakdown of this year’s planned and completed FSSI (Table 1) and non-FSSI (Table 2) stock assessments.
Table 1: FY21 Planned and Completed FSSI Stock 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 stock-level data are limited. 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. They utilize those 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 that produces management advice as a product. That management advice estimates sustainable harvest levels that maximize fishery removals while protecting stocks’ long-term health. Data-limited and index-based models provide advice based upon the analysis of observed trends in catch data or fishery-independent survey data. More advanced models both evaluate the current condition of a stock and develop projections that estimate a stock’s future condition. Managers can use those projections to update harvest guidance in the years between stock assessments.
Each NOAA Fisheries region rotates its portfolio of stock assessments annually. That rotation includes both the stocks being assessed and, for stocks managed using advanced models, the extent of their assessments. Because stock assessments that use advanced models are major scientific efforts, most regions conduct intermediate analyses (stock monitoring updates) between stock assessments to keep management advice current. As a result, stock assessment activities can be subdivided into two general categories (Figure 3):
- 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. 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 is working hard to navigate the uncertainties created by the COVID-19 pandemic and the unique challenges those are creating for Fishery-Independent Surveys. More information is available here.
NOAA Fisheries completed 12 scientific surveys during quarter 3 of fiscal year 2021 (April 1, 2021 – June 30, 2021). Nine of the quarter 3 surveys were conducted aboard NOAA ships and three aboard chartered vessels. This brings the total for fiscal year 2021 up to 17 scientific surveys, including 13 surveys conducted aboard NOAA ships and four conducted aboard chartered vessels.
Table 3: FY21 Planned and Completed NOAA Vessel Surveys
Table 4: FY21 Planned and Completed Chartered Surveys
Archive and More Information
To view current and historical records of stock assessments please visit our Stock Status, Management, Assessment, and Resources Trends (Stock SMART) tool.
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)