Influence of reward level on vertical distribution and growthof rainbow trout Oncorhynchus mykiss fed on demand with self-feeders
The influence of reward level on vertical distribution and growthwas examined in rainbow trout fed on demand with self-feeders. Groupsof 15 trout with initial body weight of 140 g were maintainedat 14°C and feed access was restricted to a 12-h photophase.The trout received three reward levels with triplicates: 0.051 (low),0.089 (medium) and 0.267 g/kg fish/triggeractuation (high). Vertical distribution in the higher reward groupswas generally more even than that in the lower-reward groups, butthe behavioral characteristics of some individuals in a group couldplay an important role in determining vertical distribution. Moreover,no fish including the individuals responsible for trigger actuation,occupied the vicinity of a trigger. The small groups of 15 troutreceiving the medium-reward level obtained as much feed and grewas fast as the high-reward groups, but this was not the case forthe low-reward groups.
Document Type: Research Article
Affiliations: Department of Biosciences, Teikyo Universityof Science and Technology, Uenohara, Yamanashi 409-0193, Japan
Publication date: April 1, 2003