Evaluation of Inventory Procedures for Hatchery Fish. III. Nonrandom Distributions of Chinook Salmon in Raceways

Abstract

Abstract Juvenile chinook salmon Oncorhynchus tshawytscha reared at Willamette Hatchery, Oakridge, Oregon, showed nonrandom distributions in both modified Burrows raceways and Michigan raceways. When fish were reared in Burrows raceways at densities of 10–15 kg/m3, largest fish tended to reside near the upstream end of the raceway, but when fish were crowded for sampling, smaller fish were found at the upstream end, and larger fish were found at the downstream end. In Michigan raceways, fish near release size occupied six compartments formed by baffles. Smallest fish were usually found in the upstream and downstream compartments, while largest fish were in the middle compartments. Fish sizes were compared between fish sampled by dip net with and without crowding in all experimental raceways. Only 9 of 49 measurements showed statistical differences in weight between the two methods. We conclude that juvenile chinook salmon distribute in modified Burrows raceways and Michigan raceways in a nonrandom manner,...