Density Effects on Subyearling Fall Chinook Salmon During Hatchery Rearing in Raceways with Oxygen Supplementation and After Release
Abstract To determine the effects of hatchery rearing density on fall Chinook Salmon Oncorhynchus tshawytscha released as age-0 subyearlings, we experimentally reared fish at densities of 200,000, 300,000 and 400,000 fish per raceway in Michigan-style raceways that employ oxygen supplementation to achieve high density rearing. The study was conducted for two release years at a maximum raceway density of 52.3 kg/m3 and a maximum loading of 0.92 kg·L−1·min−1. At the end of hatchery rearing there was no significant difference in weight in either release year and Fulton's condition factor was similar in the first year. In the second release year condition factors were significantly different; the low-density group had significantly lower values and the high-density group had significantly higher values. Following release into the Umatilla River, Oregon, out-migration survival and travel time to John Day Dam on the Columbia River was monitored by using passive integrated transponder tags in a subsample of each...