How many fisheries are overfished, and what does that mean?

Answer: 34.2% of fisheries are overfished, comprising 22.7% of seafood.

According to the United Nations Food and Agriculture Organization (FAO), the world’s authority on fisheries, 34.2% of fisheries are overfished.

The number of overfished fisheries has been slowly creeping up since the 1980s, but the proportion of overfished fisheries is not necessarily a good indicator of seafood sustainability.

Fisheries are not the same size

Say there are two fisheries: one produces 1 ton of fish from an overfished population and the other produces 99 tons of fish from a sustainable population. 50% of fisheries in that example are overfished, despite 99% of the catch being sustainable. In reality, the 34.2% of overfished stocks produce 22.3% of wild-caught seafood, a number that is still too high, but not indicated by simply reporting the proportion of overfished stocks.

Fishery managers focus effort and enforcement on larger stocks to ensure that a larger proportion of consumed seafood is sustainable.

The definition of “overfished” is not the same as “overfishing”

Stocks are classified as overfished when their population is below the level that would maximize harvest. “Overfished” says nothing about if a population is declining or not, it simply indicates the population is below a target level that maximizes harvest. Many stocks have been overfished for decades and provide viable fisheries, but they are overfished because it is estimated they could have produced more yield.

FAO considers a population of fish that is below 80% of its target biomass to be overfished. That definition fails to capture the current fishing pressure on the stock, a much better indicator of current and future sustainability. For example, a stock at target biomass that is experiencing overfishing would not be considered overfished by FAO, but its sustainability would be highly threatened. At the same time, a severely depleted stock that is recovering due to better management and ending overfishing, would still be considered overfished until it crosses the 80% threshold. Most fishery scientists would consider that fishery sustainable while it recovers. Overfishing—or too much fishing pressure on a stock, is generally a better indicator of fishery sustainability than if a population is overfished.

Data is incomplete

A final consideration is that, though FAO compiles the most complete data on fishing around the world, there are several places that do not have the scientific or management capacity to monitor their fisheries. Underdeveloped parts of Asia and Africa do not have good data on their fisheries and probably have significant amounts of overfishing and depleted stocks.

Country of origin is generally the best indicator of seafood sustainability. If a country monitors their fisheries well, its seafood is probably sustainable.

global trends in fisheries over time

Common fisheries misinterpretations

Strange terminology, like the overfished vs overfishing example above, has led to several problems in how fisheries statistics are communicated. The most common mistake is conflating sustainable and unsustainable fisheries due to old FAO definitions. Many years ago, FAO called stocks at target levels producing maximum sustainable yield “fully-exploited.” 

A fully-exploited fishery is the goal of fishery management—a stock is sustainably producing the most amount of food that it can. However, the term itself has a deeply negative connotation and led to many non-fishery scientists thinking “fully-exploited” was bad, rather than the goal. Common reporting on fisheries statistics included lines like, “over 90% of fisheries are either over or fully exploited.”

FAO had enough of people misinterpreting their statistics, so they changed the terminology used to describe fisheries. “Fully-fished” is now “maximally sustainably fished” and the use of “exploited” is being phased out in other definitions, e.g. over-exploited to overfished; under-exploited to underfished.

How should fishery statistics be communicated?

Communication about the status of fish stocks needs to include proper context.

The most complete data shows that, globally, 66% of monitored fisheries are at biologically sustainable levels producing 78.7% of consumed seafood. The 34% of fisheries below sustainable levels produce 22.3% of seafood.

The number of stocks experiencing overfishing is just as important as the number of stocks across the overfished threshold—if that data is available, it should also be reported.

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Learn more about Sustainable Seafood below.