VREELAND ET AL.: HOMING BEHAVIOR OF MARKED COHO SALMON 



DISCUSSION 



Hatchery returns (see Table 3) indicate that 

 there is little straying of the LV-marked coho salm- 

 on released in Youngs Bay to hatcheries in the 

 area or back to the parent hatchery (Little White 

 Salmon). Only five LV-marked fish were recovered 

 at the four hatcheries near Youngs Bay. Only 4 

 LV-marked coho returned to Little White Salmon 

 Hatchery in 1970 and 1971, while 355 RV-marked 

 fish returned to the hatchery. 



Catches of marked coho also suggest that they 

 home to the area of release (Table 6). An estimated 

 504 LV-marked coho were caught in the Youngs 

 Bay gill-net fishery in 1970 and 1971. Only 12 RV- 

 marked fish were estimated to have been caught in 

 the bay. For 1970 and 1971 combined, the estimat- 

 ed Columbia River gill-net catch of LV- and RV- 

 marked coho was 267 and 1,162, respectively. Of 

 the 267 LV coho caught, about 45% were taken in 

 Zone 1; 30% in Zone 2; and 25% in Zones 3 through 

 5. This means that about 75% of the LV-marked 

 coho caught in the Columbia River were caught in 

 waters adjacent to Youngs Bay. Since few LV- 

 marked fish returned to Little White Salmon 

 Hatchery or hatcheries in the area, it is reasonable 

 to assume that these fish were bound or searching 

 for the area of release. 



These catches and hatchery returns gave an in- 

 dication that the coho homed to the area of release 

 with little straying. With few exceptions, the LV- 

 marked coho released in Youngs Bay returned to 

 the Youngs Bay area, and the RV-marked coho 

 released at Little White Salmon Hatchery were 

 bound for or returned to the hatchery. 



Other investigators have reported various 

 degrees of straying and homing tendencies of 

 transported fish. Ellis and Noble (1960) reported 

 returning fall chinook salmon from Klickitat 

 Salmon Hatchery released in the lower Columbia 

 River showed a greater tendency to stray than 

 chinook released at the hatchery. Few of the 

 transported chinook returned to the hatchery. 



Wagner (1969) found that steelhead trout smolts 

 trapped on the Alsea River and transported 

 downstream returned as adults to an upstream 

 trap in fewer numbers than untransported 

 steelhead trout. This was probably due to the 

 transported steelhead straying into tributaries as 

 they moved upstream. From this and other studies 

 (Wagner 1967), he concluded that the homing 

 imprint in definitely influenced by stocking site 

 and that capturing and transferring smolts during 



their downstream migration may cause gaps in 

 imprinting. These gaps could result in delayed 

 adult upstream migration. The duration of the 

 delay probably depends on the strength of up- 

 stream stimuli. 



Experiments conducted at hatcheries in Oregon, 

 Washington, and California have shown that a 

 majority of the chinook salmon, coho salmon, or 

 steelhead trout released as smolts in an area with 

 no downstream migration prior to hauling return 

 to the area of release as adults. Studies at Ice 

 Harbor Dam on the Snake River, 538 km above the 

 Columbia River mouth (334 miles), indicated that 

 chinook transported from Ice Harbor to below 

 Bonneville Dam, a distance of 304 km (189 miles), 

 returned as adults to Ice Harbor with little stray- 

 ing (Ebel et al. 1972). 



These studies and our data suggest that coho 

 salmon released in an area to create or enhance a 

 fishery would home back to that area. 



When examining the contribution of the RV- 

 and LV-marked coho salmon to the fisheries 

 sampled, it appears that the RV group released at 

 Little White Salmon Hatchery had better survival 

 than the LV group released at Youngs Bay. The 

 total catch of RV-marked 1968-brood coho in 1970 

 and 1971 was 1,176 or 11.7 per 1,000 released com- 

 pared to 778 LV coho caught or 7.7 per 1,000 

 released. However, a good comparison between 

 the recoveries of the two groups cannot be made 

 because of incomplete sampling. The ocean 

 fisheries and Columbia River sport fishery were 

 not sampled for LV- or RV-marked coho, and the 

 Youngs Bay sport fishery was sampled only sparse- 

 ly in 1970. Catches of LV- and RV-marked fish in 

 these fisheries could alter the contribution of 

 either or both groups significantly. 



A good comparison of the contribution of the 

 two groups is also hampered by the difference in 

 size and time of release of the groups. The LV- 

 marked coho were released in Youngs Bay on 23, 

 27, and 29 April 1970, at 49.9 fish/kg (22.6/pound). 

 The RV-marked coho were released at Little 

 White Salmon Hatchery 2 wk later on 12 May and 

 at a larger size, 40.1 fish/kg (18.2/pound). This 

 later release of larger fish could have improved the 

 survival of the RV-marked coho. 



A third factor inhibiting comparisons of the 

 contributions of the RV and LV groups is hauling 

 mortality. Tests have indicated that post-trans- 

 port mortality may have a noteworthy effect on 

 transported fish (Ebel et al. 1972). It is not known 

 if the procedures used in this study to transport 



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