Productivity and Susceptibility Analysis

The National Standard 1 guidelines advise fishery managers to consider the vulnerability of a fish stock to becoming overfished when developing annual catch limits. The National Standard 1 guidelines define the vulnerability of a stock based on two things:

• Productivity – the capacity of the stock to produce its maximum sustainable yield and to recover if the population is depleted.
• Susceptibility to the fishery – the potential for the stock to be impacted by the fishery through direct capture as well as indirect impacts, such as bycatch.

NOAA Fisheries formed a working group to develop a methodology that could be applied broadly across many fisheries to determine the vulnerability of a stock. After examining a number of risk assessment methods, the working group chose the Productivity and Susceptibility Assessment (PSA) because it can be based on qualitative data, has a history of use in other fisheries, and is recommended by several organizations and work groups as a reasonable approach for determining risk.

This methodology scores the stock’s productivity and susceptibility to determine its overall vulnerability:

• Stocks with a low productivity score and a high susceptibility score are highly vulnerable to overfishing.
• Stocks with a high productivity score and a low susceptibility score are less vulnerable to overfishing.

NOAA Fisheries produced a variety of guidance aimed at helping fishery managers better understand how to use and calculate the vulnerability of the stock when setting annual catch limits:

• Vulnerability Evaluation Work Group – Extended Abstract (Patrick & Spencer)
• Use of Productivity and Susceptibility Indices to Determine Stock Vulnerability, with Example Applications to Six U.S. Fisheries – NOAA Tech Memo, October 2009 (Patrick et al.)
• Using productivity and susceptibility indices to assess the vulnerability of United States fish stocks to overfishing – Fishery Bulletin, 2010 (Patrick et al.)
• Vulnerability Worksheet
• NOAA Fisheries Toolbox - PSA Application
• Advanced Graphics - Vulnerability Plotting Tutorial