Wells 0, n53 35 30 、 20 15 10 5 0 70 20304050607080901d0 Percent(%)Hematocrit 40 5=1.14 25 15 10 6 81012 46820 Hemoglobin-g/dcl blood heo91ointhgheat8eeteeaadtandaraeieoatoh0sae0so"guen 22
3001 - 3060 May 11, 1979 Steelhead Wells Figure 4. --Frequency histogram for hematocrit and hemoglobin values for the Wells (Winthrop) Hatchery steelhead in 1979. Number of fish sampled (n), mean hemoglobin and hematocrit values (x), and standard deviations (s) are also given. 22
Histopathology The major pathological conditions encountered in the Wells (Winthrop) Hatchery steelhead were increased numbers of lymphocytes and epithelial hypertrophy in gill tissue (Table 6). Seawater Adaptation At entry to seawater,Wells-Winthrop Hatchery steelhead were primarily of transitional stage fish,based upon external characteristics.The cumulative mortality within 30 days of seawater residence attributable to osmoregulatory dysfunction was 734.Vibriosis accounted for most of the other mortalities for the remainder of the study.The presence of precocious males was not a problem in this test group. The survival to test completion (193 days)was only 5s (Table 7). Tucannon Hatchery Steelhead Gill Na+-K+ATPase The gill Na+-K+ATPase profile of summer-run steelhead from the Tucannon Hatchery in fresh water was qualitatively similar to that observed in 1978 with a distinct peak in enzyme activity in early May (Figure 5) followed by a sharp decline.A typical pulse of Na+-K+ATPase activity was observed when these fish were transferred to seawater at Manchester. Little change occurred until the fourth day when activity began to rise (Figure 5).Fish held at the hatchery and sampled just 5 days after release of the main group averaged 17.2 cm fork length and weighed 43.1 g. This was down from the average lengths and weights of 19.5 cm and 65.9 g,respectively,at the same time in 1978. Plasma Electrolytes The summary data for plasma electrolytes at the time of release are listed in Table 3. The mean values for Na,K,and cl of the Tucannon 33
Histopathology The major pathological conditions encountered in the Wells (Winthrop) Hatchery steelhead were increased numbers of lymphocytes and epithelial hypertrophy in gill tissue (Table 6). Seawater Adaptation At entry to seawater, Wells-Winthrop Hatchery steelhead were primarily of transitional stage fish, based upon external characteristics. The cumulative mortality within 30 days of seawater residence attributable to osmoregulatory dysfunction was 73%. Vibriosis accounted for most of the other mortalities for the remainder of the study. The presence of precocious males was not a problem in this test group. The survival to test completion (193 days) was only 5% (Table 7). Gill Na+-K+ ATPase Tucannon Hatchery Steelhead The gill Na+-K+ ATPase profile of summer-run steelhead from the Tucannon Hatchery in fresh water was qualitatively similar to that observed in 1978 with a distinct peak in enzyme activity in early May (Figure 5) followed by a sharp decline. A typical pulse of Na+-K+ ATPase activity was observed when these fish were transferred to seawater at Manchester. Little change occurred until the fourth day when activity began to rise (Figure 5). Fish held at the hatchery and sampled just 5 days after release of the main group averaged 17.2 cm fork length and weighed 43.1 g. This was down from the average lengths and weights of 19.5 cm and 65.9 g, respectively, at the same time in 1978. Plasma Electrolytes The summary data for plasma electrolytes at the time of release are listed in Table 3. The mean values for Na, K, and Cl of the Tucannon 23
—Freshwater ATPase 188 day --Seawater ATPase. T 10 6 9 19 9 Ap 979 Figure 5.--Gill Na+-K+ATPas ard deviations)of 24
Figure 5.--Gill Na+-K+ ATPase activity (means and standard deviations) of the Tucannon Hatchery steelhead in fresh water and seawater. 24
Hatchery steelhead fall within the expected ranges for rainbow trout. There was little difference in the mean cl and K values between 1978 and 1979 (Table 3).In 1978,43.3 of the Tucannon Hatchery samples were below the minimum range reported for K in rainbow trout. The plasma Na and K profiles of the Tucannon Hatchery steelhead in both fresh and seawater appeared to be within normal ranges (Figure 6). There was a typical rise in Na and K followed by a drop within the first week after transfer to the seawater pens,and a return to normal in the surviving fish after this initial stress period. Hematology The summarized data of the hematocrit and hemoglobin values for the Tucannon Hatchery steelhead are presented in Figure 7 and Table 3.The mean hematocrit was slightly higher in 1979 than in 1978 and the mean hemoglobin value was slightly lower than the 1978 mean. Viral Screening The National Fisheries Research Center (USFWS)reported all Tucannon Hatchery steelhead samples tested as negative for IPN virus. Ranger Research Laboratories reported IPN virus in 1 out of 12 pooled samples tested. Indirect Fluorescent Antibody Test for Bacterial Kidney Disease Only 1 out of 60 Tucannon Hatchery steelhead sampled (1.78)was found to have BKD organisms in an anterior kidney smear. Histopathology The major pathological conditions encountered in the Tucannon Hatchery steelhead were lymphocytic infiltration and epithelial hypertrophy in gill tissue,and a 538 incidence of ciliated protozoan parasites in the olfactory sac (Table 6).Total mortality during rearing in the hatchery
Hatchery steelhead fall within the expected ranges for rainbow trout. There was little difference in the mean Cl and K values between 1978 and 1979 (Table 3). In 1978, 43.3% of the Tucannon Hatchery samples were below the minimum range reported for K in rainbow trout. The plasma Na and K profiles of the Tucannon Hatchery steelhead in both fresh and seawater appeared to be within normal ranges (Figure 6). There was a typical rise in Na and K followed by a drop within the first week after transfer to the seawater pens, and a return to normal in the surviving fish after this initial stress period. Hematology The summarized data of the hematocrit and hemoglobin values for the Tucannon Hatchery steelhead are presented in Figure 7 and Table 3. The mean hematocrit was slightly higher in 1979 than in 1978 and the mean hemoglobin value was slightly lower than the 1978 mean. Viral Screening The National Fisheries Research Center (USFWS) reported all Tucannon Hatchery steelhead samples tested as negative for IPN virus. Rangen Research Laboratories reported IPN virus in 1 out of 12 pooled samples tested. Indirect Fluorescent Antibody Test for Bacterial Kidney Disease Only 1 out of 60 Tucannon Hatchery steelhead sampled (1.7%) was found to have BKD organisms in an anterior kidney smear. Histopathology The major pathological conditions encountered in the Tucannon Hatchery steelhead were lymphocytic infiltration and epithelial hypertrophy in gill tissue, and a 53% incidence of ciliated protozoan parasites in the olfactory sac (Table 6). Total mortality during rearing in the hatchery 25
250 12.5 Frethwater samples --0----Seawater samples 200 10.0 5150 7.5 10 na K+Meq/l.(x Plasma Kt 2.5 19 9 19 June 41979 steelhead t sculture at Manchester. Tucannon Hatchery and during seaw 26
Figure 6. --Mean plasma Na+-K+ levels in Tucannon Hatchery steelhead sampled in fresh water at Tucannon Hatchery and during seawater culture at Manchester. 26