FISHERY BULLETIN: VOL. 70, NO. 1 



Table 3. — Regression of (log W^ — log Wq) on time for Group I fish. 

 The approximate 95 "Jf confidence interval estimates of h are taken from 

 the confidence limits of log (1 + h). 



Sub- 

 group 



Regression equation 



95% confidence 

 limits of log (I + A) 



Approximate 95% 



confidence limits 



of A 



la (log If^ - log W^) = 0.01 168< 



lb (log IV ^- log (Cg) = 0.011 18« 



Ic (log »'j — log ffp) = 0.01006< 



Id (log ;fj - log W^) = 0.00945< 



le (log Jfj - log W^) = 0.00880i 



0.01168 ± 0.00099 

 0.01118 ± 0.00084 

 0.01006 ± 0.00087 

 0.00945 It 0.00077 

 0.00880 ± 0.00042 



2.7 ± 0.2%/day 



2.6 ± 0.2%/day 



2.3 ± 0.2%/day 



2.2 ± 0.2%/day 



2.1 ± 0.1%/day 



of growth. Reduced growth may come about in 

 part because the young salmon expend more en- 

 ergy to maintain an osmotic homeostasis in 

 water of high salinity than in water of low sa- 

 linity. 



Chinook salmon blood is isotonic with water 

 of salinity between 10 and 13'/r (Coche, 1967). 

 Houston (1959) thought that the increased ener- 

 gy demands for osmoregulation combined with 

 possible inhibition of electrolyte-sensitive com- 

 ponents of the neuromuscular system might con- 

 tribute to reduced growth of young salmon in 

 water of high salinity. There is the further 

 possibility that endocrine systems which are as- 

 sociated with osmoregulation and growth in 

 water of high salinity are not fully functional 

 in premigratory juvenile salmon (Saunders and 

 Henderson, 1970). 



O Subgroup la (h = 2.7% /day) 

 Subgroup le (h=2 l7o/day) 



~ 3 



E 



2 2 



28 



42 



56 



I 



70 



Time (days after first weighing) 



Figure 2. — Calculated growth curves for chinook salmon 

 from subgroups la and le as calculated from equation 

 (1). The observed growth is plotted to illustrate cor- 

 respondence with calculated curves, "h" is the com- 

 pounded daily increment of body weight. 



The acclimation of premigratory chinook, 

 coho, and sockeye salmon to seawater may find 

 future applications in aquaculture. Possibilities 

 include the early release of young salmon from 

 hatcheries into open ocean pastures to reduce 

 costs of feeding and handling and to increase 

 hatchery production. Other possibilities are to 

 pen young salmon in saltwater bays or estuaries 

 (Garrison, 1965; Mahnken et al., 1970) or to 

 place them in raceways receiving waste salt 

 water from coastal thermal-electric stations 

 (McNeil, 1970). 



Large-scale aquaculture systems, similar to 

 one under development in the Canadian Maritime 

 Provinces (Gunstrom, 1970), would most likely 

 benefit from early acclimation of juvenile salmon 

 to seawater. The release of premigratory ju- 

 venile chinook salmon acclimated to seawater 

 should also be tested at hatcheries equipped with 

 seawater pumping systems. The eflFects of early 

 acclimation on ocean survival is unknown, but 

 the greater availability of food and space in the 

 ocean than in freshwater conceivably would pro- 

 vide potential advantages to juvenile salmon 

 which had been acclimated to seawater. 



ACKNOWLEDGMENTS 



Research on acclimation of juvenile salmon 

 to seawater is administered by the Oregon State 

 University Agricultural Experiment Station. 

 Funds are provided by the National Oceanic and 

 Atmospheric Administration's Sea Grant Pro- 

 gram (Contract No. GH97) and National Ma- 

 rine Fisheries Service (Project No. AFC-55). 



We wish to express our appreciation to Robert 

 Courtright, Director of the Oregon State Uni- 

 versity Port Orford Marine Research Labora- 



122 



