QUINN ET AL.: IMPRINTING AND HOMING IN COHO SALMON 



Table 1 . — Summary of cotio salmon experimental treatments, Indicating 

 the date (In 1986) wtien fish were exposed to different water sources or 

 moved. UW refers to UW hatchery water. CW refers to dechlorlnated 

 city water at the UW hatchery, SP refers to lake water at the Seward 

 Park hatchery, Iss refers to the Issaquah Creek hatchery, and LkU 

 refers to the Lake Union release site. 



weight = 26 g), unlike the UW coho. which 

 smelted in their first spring. Those with their 

 right fin clipped (Group 4) were trucked in two 

 gi'oups of 5,000 fish each to the Lake Union site 

 and were released on 19 March. Those with the 

 left ventral fin clipped (Group 5) were returned 

 to the hatchery pond and released from the 

 hatchery with the normal production fish on 9 

 April. 



Recovery of Returning Adults 



It was anticipated that most experimental 

 coho escaping the fisheries would return to the 

 hatcheries at UW, SP, or Iss, primarily in 1987. 

 Coho salmon of the UW population almost all 

 return in the second fall after their release 

 (Brannon et al. 1982) and few precocious males 

 ("jacks") occur. A trap to recover salmon re- 

 turning to the SP hatchery was built in sum- 

 mer 1987; therefore no jack (1986) returns would 

 have been collected that year, but the UW and 

 Iss hatcheries were operating in 1986 to collect 

 jacks. All hatcheries were also open in 1988 for 

 salmon returning in the third fall after release. 

 In addition to these primary recovery sites, the 

 National Marine Fisheries Service (NMFS) op- 

 erates a small hatchery on the opposite side of 

 the ship canal. While no salmon released from 

 NMFS were expected to return in 1987, the 

 hatchery trap was operating and salmon enter- 

 ing it were checked. Some salmon released in 

 Lake Union (where there is no hatchery or 



spawning ground) might have been expected to 

 enter the NMFS facility if they had not im- 

 printed on the UW hatchery. 



RESULTS 



Analysis of the historical data revealed that 

 from 1979 to 1985, 5,465 coho salmon with coded 

 wire tags from UW and Iss were recovered at 

 these two hatcheries. Of 4,696 tagged UW coho 

 salmon recovered, only two (0.049f) strayed to 

 Iss. Similarly, of 769 tagged Iss coho, only one 

 (0.13%) entered the UW hatchery. Thus, vir- 

 tually no straying takes place between these two 

 hatcheries when coho are reared and released at 

 the hatcheries. 



Only one jack from the UW-SP transfer 

 groups (from Group 2) was recovered in 1986 at 

 the UW hatchery, indicating that the absence of 

 a return trap at SP did not bias the data signifi- 

 cantly (Table 2). Group 1, exposed to UW water 

 and released into Lake Union, returned exclu- 

 sively to the UW hatchery (34/34). Group 2, 

 which had not directly experienced UW water 

 but had been reared at SP and released into 

 Lake Union returned priinarily to the UW 

 hatchery (Table 2) but seven salmon were re- 

 covered at SP. Group 3 fish, reared in the same 

 manner as Group 2 fish but released froin SP, 

 returned exclusively to SP. 



In 1986 and 1987', 73 fish with chpped ventral 

 fins were recovered at the UW and Iss hatch- 

 eries. Group 5, reared and released from Iss 



771 



