Minnows

Low Temperature Effects on Minnows (Phoxinus phoxinus) and juvenile Atlantic Salmon (Salmo salar) Studies have shown that freshwater minnows and juvenile Atlantic Salmon become nocturnal with increased low temperature. To determine if these species are nocturnal at low temperatures, counts of individual fishes would be taken by how many fishes are observed during the daytime taking refuge underneath rocks. Also, by observing how many individuals are active at nighttime. At a warmer day time temperature …

…So if a fish was out during the day and a bird is hunting it, the fish would not be as fast and escape becomes more difficult. By taking refuge during the day, the two fishes avoid predation. And by coming out at night to feed, their slowed down movement won't cost them their lives. It may be a little bit more difficult to catch prey but they could worry a lot less about predators.