Overfishing vs. Overfished: The Same Thing?

When you see the word “overfishing” it’s only natural to think this only applies to, well, fishing. Although fishing adds significant pressure, fish stocks can also become “overfished” for many other reasons, including natural mortality, disease, and environmental conditions. Here’s the breakdown.


A stock that is subject to overfishing has a fishing mortality (harvest) rate that is higher than the rate that produces maximum sustainable yield (MSY). MSY is the largest long-term average catch or yield that can be taken from a stock or stock complex under prevailing ecological, environmental conditions and fishery technological characteristics. 


A stock that is overfished has a biomass level depleted to a degree that the stock's capacity to produce MSY is jeopardized. A population can be overfished but be managed under a rebuilding plan that over time returns the population to a level that can support the MSY.

Taking Stock of Environmental Changes

In addition to fishing pressure, other ecosystem and habitat factors also influence the abundance of fish populations, including climate change, ocean acidification, and other environmental shifts. A fish's environment (habitat) includes physical factors, such as temperature and bottom type, as well as chemical factors, such as oxygen levels and dissolved minerals. The habitat needs for each stage of a fish's life cycle—egg, larvae, juvenile, and adult—vary within the same water body. So changes in these environmental factors can greatly affect the population of a stock. Continued progress in ending overfishing and rebuilding stocks relies on an understanding of these factors.

Checking Our Status

Since 1997, every year NOAA Fisheries reports to Congress the number of stocks that are and are not subject to overfishing, and those that are or are not overfished. The Status of Stocks summarizes the best available science on our stocks. We use this science to aid the management process and ensure appropriate actions are taken. The report documents our national journey toward ending overfishing and rebuilding stocks.