Test Condition 2 --Shallow horizontal 

 orifice vs. shallow vertical orifice 



None of the three mean percentages tested 

 for Chinook salmon, steelhead trout, and coho 

 salmon differed significantly from 50 percent 

 (table 2). Chinook salmon and steelhead trout 

 demonstrated a trend toward use of the verti- 

 cal orifice in three of the four replicates. 

 In the exception (second replicate), this en- 

 trance pattern was reversed, and slightly- 

 more fish of both species entered the hori- 

 zontal orifice. This reversal contributed 

 appreciably to the nonsignificance of the mean 

 percentages. Only two replicates were run 

 with coho salmon. Although more fish passed 

 through the vertical orifice than the hori- 

 zontal orifice the difference was not signifi- 

 cant. 



Table 2 — Average percentages ^ of aaljnonlds entering orifices in test 

 condition 2 — shallow horizontal orifice vs. shallow vertical orifice 



[Asterisk, significant at 95-percent level; MS, not significant; mean 

 percentages with neither designation not tested] 



^ Direct observations during a basic time unit of 2 days were combined to 

 form a response measurement called "average percentage" (see text for 

 details). 



Test Condition 3 — Shallow horizontal 

 orifice vs. deep horizontal orifice 



Table 3, --Average percentages^ of salmonids entering orifices in test 

 condition 3 — shallow horizontal orifice vs. deep horizontal orifice 



[Asterisk, significant at 95-percent level; NS, not significant; mean 

 percentages with neither designation not tested] 



^ Direct observations during a basic time unit of 2 days were combined to 

 form a response measurement called "average percentage" (see text for 

 details). 



Table 4. --Average percentages^ of salmonids entering orifices in test 

 condition ^--shallow vertical orifice vs. deep vertical orifice 



[Asterisk, significant at 95-percent level; MS, not significant; mean 



percentages with neither designation not tested] 



^ Direct observations during a basic time unit of 2 days were conbined to 

 fonn a response measurement called "average percentage" (see text for 

 details). 



tended toward the shallow depth. In the third 

 replicate, however, steelhead were almost 

 equally distributed between the two depths. 

 Coho salmon demonstrated a trend toward 

 the 9-foot depth. 



Significantly more than 50 percent of the 

 Chinook salmon and steelhead trout entered 

 the shallow horizontal orifice (table 3). 

 Although more coho salmon entered the 

 shallow than the deep orifice, the two repli- 

 cates totaling 136 fish failed to show signifi- 

 cant departures from 50 percent. 



Test Condition 4 — Shallow Vertical 

 Orifice vs. Deep Vertical Orifice 



None of the mean percentages for chinook 

 salmon, steelhead trout, and coho salmon 

 departed significantly from 50 percent (table 

 4). Although the trend for chinook salmon 

 was toward the shallow orifice in all repli- 

 cates, the strength of the trend differed 

 widely among replicates. The majority of 

 steelhead trout in the first two replicates 



Lateral Orientation of Fish in the 

 Experimental System 



In all replicates for all species except one 

 (test 2, replicate 2) for steelhead trout, the 

 percentage of salmonids entering any given 

 orifice was greater when that orifice was on 

 the south side of the introductory pool than 

 when it was on the north. Table 5 shows re- 

 mainders obtained by subtacting the percent- 

 age of salmonids entering a given orifice 

 on the north from the percentage of those 

 entering the same orifice where it was on the 

 south side during each 2-day test period. 

 Means of the remainders for each species 

 were significantly greater (95-percent level) 

 than zero (t-tests). Bias toward the south 

 side of the system reduced the number of 

 measurements by half because it required 



