Surviving such a long time between meals takes a lot of gutsâ€”literally. New research shows that a trout can change the size of its intestinal tract based on the availability of salmon eggs, its favorite food.
For the first four or five years of life, Dolly Varden trout travel to the northern Pacific to feed during the spring and summer, then return to freshwater streams and lakes during winter. After that, the fish stay in fresh water, never returning to the sea for the rest of their 12-year life span.
The trout get one opportunity to feed: When salmon arrive in these waters to spawn. The researchers couldnâ€™t identify any other food source for the trout.
When the researchers calculated how much energy the fish likely obtained from the annual surplus of salmon eggs and compared this with the estimated number of calories the fish would need to survive for an entire year, they found a thousand-calorie deficit.
â€œWe were stumped.Â How could these large fishâ€”the most [fertile] in the whole [Chignik Lake] populationâ€”get enough energy to survive and reproduce in these barren waters?â€ Armstrong said.