In an adaptation that allows Dolly Varden trout to survive for nearly 11 months without food, the intestinal tracts of the fish change in response to food availability, according to recent research. Researchers found that for five weeks during the summer salmon run, the fish gorge on as much as half a pound of salmon eggs per day, increasing their weight by 50% and super-sizing their intestinal tracts to four times the size seen in the nonfeeding season.