NOTES: Predator Recognition and Avoidance by Larval Razorback Sucker and Northern Hog Sucker

Abstract

The razorback sucker Xyrauchen texanus is an endangered catostomid endemic to the mainstream Colorado River, which originally supported a limited number of piscivorous fishes. Recent attempts to recover razorback suckers by reintroducing them into their native range have not been successful, likely due to predation on the naive young suckers by nonnative fishes. We tested razorback sucker larvae singly and in groups to determine their ability to recognize and avoid predators. We related their performance to that of northern hog sucker Hypentelium nigricans, a species that evolved in a predator-rich fish community. All larvae of both species recognized a predator attack when they were close to the predator and avoided the attack by fleeing or hiding. Single sucker larvae of both species improved their rate of avoidance with age, but northern hog suckers had a significantly higher initial avoidance rate than did razorback suckers. Groups of larval suckers of both species did not improve predator avoidance with age as rapidly as did single larvae. These results suggest an inherent difference in predator avoidance between species from predator-rich and predator-poor communities rather than a differential improvement with age. Recovery of razorback suckers by reintroducing them into historic riverine habitats will be limited by the presence of nonnative fishes.