RESULTS AND DISCUSSION OF HATCHERY STEELHEAD SURVEYS Chelan Hatchery (Transferred to Leavenworth Hatchery)Steelhead Gill Na+-K+ATPase Since the phenomenon of elevation in gill sodium,potassium stimulated ATPase (Na+-K+ATPase)activity was first reported to be associated with Parr-smolt transformation in steelhead (Zaugg and Wagner 1973)and in in coho salmon,0.kisutch,(Zaugg and McLain 1970),numerous experiments have been conducted to verify these results and extend observations to other species.As a result,it has been conclusively shown that the rise in gill Na+-K+ATPase activity is one of the many physiological changes which occur at the time of Parr-smolt transformation. The average gill Na+-K+ATPase activity of Chelan Hatchery steelhead sampled in 1979 at Leavenworth Hatchery was not substantially different from 1978 (Table 3).Gill Na+-K+ATPase showed only a small rise in late April (Figure 1)with a peak mean value of 9.4.The absence of a greater increase in activity may have resulted from water temperatures which remained at the upper limit (13C)for good smoltification during late April and May (Zaugg et al.1972).The average fork length (20.8 cm) was similar to 1978 (21.0 cm),but the average weight (98.1 g)was up from 1978(79.4g). Plasma Electrolytes A compilation of data on rainbow trout by Miles and Smith (1968)and Hickman et al.(1964)suggests expected normal or near normal plasma electrolyte values in fresh water of 130 to 172 meq (milliequivalents)/1 for Nat,1.4 to 6.0 meq/l for K+,and 111 to 155 meq/l of cl-. Table 4 lists some known values for steelhead trout from available published literature,including data for the Dworshak Hatchery steelhead RESULTS AND DISCUSSION OF HATCHERY STEELHEAD SURVEYS Chelan Hatchery (Transferred to Leavenworth Hatchery) Steelhead Gill Na+-K+ ATPase Since the phenomenon of elevation in gill sodium, potassium stimulated ATPase (Na+-K+ ATPase) activity was first reported to be associated with Parr-smolt transformation in steelhead (Zaugg and Wagner 1973) and in in coho salmon, 0. kisutch, (Zaugg and McLain 1970), numerous experiments - have been conducted to verify these results and extend observations to other species. As a result, it has been conclusively shown that the rise in gill Na+-K+ ATPase activity is one of the many physiological changes which occur at the time of Parr-smolt transformation. The average gill Na+-K+ ATPase activity of Chelan Hatchery steelhead sampled in 1979 at Leavenworth Hatchery was not substantially different from 1978 (Table 3). Gill Na+-K+ ATPase showed only a small rise in late April (Figure 1) with a peak mean value of 9.4. The absence of a greater increase in activity may have resulted from water temperatures which remained at the upper limit (13°C) for good smoltification during late April and May (Zaugg et al. 1972). The average fork length (20.8 cm) was similar to 1978 (21.0 cm), but the average weight (98.1 g) was up from 1978 (79.4 g). Plasma Electrolytes A compilation of data on rainbow trout by Miles and Smith (1968) and Hickman et al. (1964) suggests expected normal or near normal plasma electrolyte values in fresh water of 130 to 172 meq (milliequivalents)/l for Na+, 1.4 to 6.0 meq/l for K+, and 111 to 155 meq/l of Cl-. Table 4 lists some known values for steelhead trout from available published literature, including data for the Dworshak Hatchery steelhead 9