714 



Fishery Bulletin 97(3), 1999 



probably spawn at this non-natal site. We also tagged 

 and released chinook salmon to compare the behav- 

 ior of salmon that originated elsewhere (the sock- 

 eye) with that of salmon that presumably originated 

 from the hatchery (the chinook). 



Methods 



The UWH is located approximately 10 km from Puget 

 Sound, Washington, on the north side of Portage Bay, 

 in the Lake Washington system (Fig. 1). It produces 

 chinook and coho but not sockeye salmon. However, 

 an average of eight sockeye salmon (range 4-18) en- 

 tered the pond each fall during the years of this study 

 (1992-97). Over this period, the Lake Washington 

 system has had a mean total sockeye escapement of 

 175,893 (range 122,415-400,000).^ The main spawn- 

 ing areas within the watershed are the Cedar River, 

 Issaquah Creek, and Bear Creek, and all sockeye 

 salmon spawn in the watershed upstream from the 

 UWH outfall (Fig. 1; Hendry et al., 1996), principally 

 in October and November. 



During the years of our study, an average of 1299 

 chinook salmon (range 458-2229) entered the UWH, 

 principally from early October through mid-Novem- 

 ber. Analysis of coded wire tagging (CWT) data has 

 revealed a very high fidelity of UW salmon for the 



1 Egan, R. 1998. Washington Department of Fish and Wild- 

 life. 600 Capitol Way North. Olympia. WA 98501. Personal 

 commun. 



hatchery, and very low levels of straying of non-na- 

 tal chinook salmon into the UWH (»99% of the fish 

 entering the hatchery had been released from it; 

 Quinn and Dittman, 1992). We therefore assumed 

 that chinook salmon entering the hatchery had been 

 produced there but a few might have been produced 

 elsewhere. 



Twice each week during the fall, the UWH pond 

 was partially drained and all the salmon were seined 

 into a small area. All sockeye salmon and a 

 subsample of the chinook salmon (in 1994-96) were 

 transferred from the seine to a live box in the pond. 

 These fish were tagged with a T-bar tag on each side 

 in the musculature just below the dorsal fin and 

 quickly released within 10 m of the ladder leading 

 into the hatchery. All tagged chinook salmon were 

 males ( 1 year olds in 1994; 2 year olds in 1995 and 

 1996) and releases were spread throughout the 

 course of the run. Returning tagged fish of both spe- 

 cies were recaptured during the seining of the pond. 

 Those in good condition were released once more out- 

 side the hatchery but those with extensive fungus on 

 their bodies were sacrificed. Fish that returned a third 

 time were killed, regardless of their condition. 



Results 



Between 1992 and 1997, 48 sockeye salmon (28 males 

 and 20 females) entered the UW hatchery and were 

 tagged and released (Table 1). The percentage of 

 these fish that returned to the hatchery varied from 

 0% to 37.5% among years with an overall mean of 

 20.87c (Table 1). Of the ten sockeye salmon that re- 

 turned after their first displacement and that were 

 displaced a second time, five (50%) returned again. 

 The sex ratio of the sockeye salmon stra3dng into the 

 hatchery (58% males) was similar to that of those 

 returning after displacement (60% males). 



From 1994 to 1996, 132 male chinook salmon were 

 tagged and released from the UWH (Table 1). The 

 proportion of chinook salmon that returned after dis- 

 placement did not differ among the three years 

 ( x'-=0.0 15, 2 df P>0.99, overall mean=77% , Table 1 ). 

 The percentage of sockeye salmon returning after 

 displacement was much smaller than that of the 

 chinook salmon (20.8% vs. 77.3%; X^=48.5, 1 df, 

 P<0.005). Of the chinook salmon that returned after 

 release, 65% returned a second time. 



Figure 1 



Map of the Lake Washington drainage, showing locations of the 

 University of Washington (UW) hatchery and the major tributaries 

 used by spawning sockeye salmon. Insert indicates the drainage's 

 location in northwest Washington. 



Discussion 



Our finding that most of the sockeye entering the 

 UWH appeared to be proving or exploring rather than 



