KIHSLINGER, Rebecca L.; NEVITT, Gabrielle A.; Univ. of California, Davis: Examining effects of the early rearing environment on the development of phenotype in steelhead alevins.

The early rearing environment plays a critical role in the development and expression of phenotype. This vital role is frequently underestimated in captive rearing or hatchery situations. Hatcheries consistently produce fish that are behaviorally and physiologically different from their wild counterparts. How these differences get established, however, is not known. This study examined the role of the structural environment on the development of behavior of steelhead (Onchorhynchus mykiss) hatchlings (‘alevins’). Since they are experiencing rapid neural and somatic growth, alevins are likely to be influenced by their environment. To assess the affects of the structural environment on behavioral development, fish were reared in three control and three structurally enriched tanks (Mexican Beach Pebble, 10 cm in diameter). Two thousand fish per tank were hatched in situ, and reared until emergence. Tanks were monitored with video to assess behavior and fish were weighed and measured at emergence. Results indicate that fish reared in environments that containing cobble structure are significantly heavier (H(1, N = 180) = 30.65, p < 0.001) and longer (H(1, N = 180) = 15.57694, p < 0.001) at emergence than fish reared without structure. Alevins in tanks with cobble structure tended to associate with the cobbles whereas alevins in the control tanks clumped in corners and along the sides of the tank, or distributed themselves evenly throughout the tank. There was an increase in the number of moving fish per unit time in control tanks compared to tanks with structure. Future studies will examine if the early rearing environment influences neural development.