Growth, smoltification, and smolt-to-adult return of spring chinook salmonfrom hatcheries on the Deschutes River, Oregon

The relationship between smoltification and smelt-to-adult return (SAR) of spring chinook salmon Oncorhynchus tshawytscha from the Deschutes River, Or egon, was examined for four release groups in each of three successive year s. Fish were reared, marked with coded wire tags, and released from Round B utte Hatchery, Pelton Ladder rearing facility, and Warm Springs National Fi sh Hatchery. Smolt releases occurred in nearly the same place at similar ti mes, allowing a direct comparison of SAR to several characters representing smolt quality. Return rates varied significantly among facilities, varying over an order of magnitude each year. The highest average SAR was from Pel ton Ladder, the lowest was from Warm Springs. Each of the characters used a s metrics of smoltification-fish size, spring growth rate (February-April), condition factor, plasma hormone concentration (thyroxine, cortisol, and i nsulin-like growth factor-I [IGF-I]), stress challenge, gill Na+,K+-ATPase activity, and liver glycogen concentration-varied significantly among facil ities and seasonally within hatchery groups. However, only spring growth ra te, gill ATPase activity, and plasma IGF-I concentration showed significant relationships to SAR. These characters and SAR itself were consistently lo wer for fish released from Warm Springs Hatchery than for fish from Round B utte Hatchery and Pelton Ladder. This demonstrates that differences in the quality of fish released by facilities may have profound effects on subsequ ent survival and suggests that manipulations of spring growth rate may be u sed to influence the quality of smolts released from facilities.