A new study by two University of Washington researchers may have found an answer to how some fish species can go long periods of time with very little food.

According to National Geographic, biologists Johnny Armstrong and Morgan Bond studied a population of Dolly Varden trout in Alaska’s Chignik Lake, and discovered that trout had the ability to change the size of their stomachs.

The scientists first came upon the mystery when discovering that Chignik Lake held very little food for the trout. So how could the population not only survive, but thrive? The answer comes in the form of an annual salmon spawning, whose eggs provide the trout with a nutritious and high-energy meal. But what about the time between the salmon runs? Do the trout just tighten their belts and wait patiently for next year?

Armstrong and Bond believe so. Measurements of trout before and after the annual salmon egg feast found that trout stomachs were bloated to 2.6 times their original size. This is not just a stretching of the gut like a post-Thanksgiving sit down, but rather the result of trout building larger organs in anticipation of the salmon run. Peripheral organs such as the intestines and liver were also enlarged. In food-scarce environments, the trout would shrink these organs back to preserve energy.

This ability allows the trout to survive long periods of time without much food. The new study could also be used by wildlife departments in planning salmon stocking. It was previously feared that salmon harvesting could hurt trout populations, but the study proposes that due in part to this flexibility, Dolly Varden trout can bear the wait for the next round of salmon.

You can read the study here.

Image courtesy U.S. Fish and Wildlife

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