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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.

Overfishing

Is when the rate of removal from stock is too high. A priority for the United States is ending overfishing so that all stocks can rebuild and be sustained at optimal levels.

Overfished

Is when the population is too low, or below a prescribed threshold. A population can be overfished but be managed under a rebuilding plan that over time returns the population to optimal levels.

Taking Stock of Environmental Changes

Environmental changes play a large role in what happens to a fish stock in our waters. 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.

For example, in the Bering Sea off the coast of Alaska, scientists are seeing decreases in Tanner crab populations, which led to the recent determination that the species is overfished. Scientists are finding that the primary driver of this decrease is not fishing pressure but rather changes in the crab’s habitat.

They saw that, since the first formal surveys of southern Tanner crab in the early 1970s, the eastern Bering Sea populations have fluctuated greatly, with peaks in abundance (or biomass) in 1975, 1990, and 2007. But since 2007, the number of mature male Tanner crabs declined substantially and fell below a threshold in 2009 that led to its overfished status. NOAA scientists are assessing whether this population drop might have been influenced by climate impacts such as increased seawater temperature and ocean acidification.

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.