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About Tuna Stock Growth

A fish stock consists of all of the fish of a given type that live in a fishery. Our model studies the yellowfin tuna stock in the Mindoro area of the Philippines, a biomass of roughly 20,000 tonnes of fish.1

Key Parameters and Observables

A fishery is said to be fully exploited when fished at Maximum Sustainable Yield. A fishery is said to be overfished when more fish are removed then are able to repopulate, leading to the collapse of the stock. Today, roughly 90% of worldwide fisheries are either fully exploited or overfished. 2

Click here to learn more about the outcomes of a fully exploited fishery

Click here to learn more about the outcomes of an overfished stock

Modeling Notes

We based our model of fish stocks off of the Gordon-Schaefer model.3 Gordon-Schaefer is a basic approach to modeling fish stock change which does not take into account, for example, changing ecological conditions that might lead to the carrying capacity changing over time, or the ages of the fish being caught and removed from the reproductive cycle. The goal of this fishery model is to investigate the interactions in the value chain, not the complexities of fish stock changes, and Gordon-Schaefer provides a reasonable model of the fish stock component of the fishery value chain.

Change the slider below to see how it affects fish stocks


When neither over- not under-fishing, fish stocks stabilize at maximum sustainable yield.

When under-fishing, fish stocks grow over time.

When over-fishing, fish stocks collapse.