Ledgerwood et al.: Diel sampling of migratory juvenile salmomds in Columbia River estuary 



77 



particularly in deep areas of low current 

 velocity. This premise is supported by 

 studies on water velocity (Blahm 1974) and 

 the movement rates of marked juvenile 

 salmon released below Bonneville Dam and 

 recovered at Jones Beach (Dawley et al. 

 1986) (Table 3). In all cases, fish migration 

 speeds from release site to capture in the 

 estuary were less than water velocity 

 (Dawley et al. 1986). 



In conclusion, the most appropriate 

 times and locations for sampling to attain 

 maximum CPSs are as follows: Subyear- 

 ling chinook salmon, sunrise to early after- 

 noon nearshore; yearling chinook salmon, 

 sunrise to early afternoon midriver; year- 

 ling coho salmon, midmorning to early 

 evening nearshore and sunrise to early 

 afternoon midriver; juvenile steelhead, 

 noon to early evening midriver. 



Acknowledgment 



The authors acknowledge Dr. Theodore 

 Blahm (deceased) for providing inspiration 

 and encouragement while conducting this 

 study. 



Citations 



20 



10 



Allen, R. 



1965 Juvenile fish collector operation at Lake 

 Mayfield July 1, 1964 to June 30, 1965. Report 

 to Bureau of Commercial Fisheries. Contract 

 14-17-0001-1357. Wash. Dep. Fish., Olympia, 

 23 p. 



Blahm, T.H. 



1974 Gas supersaturation research, Prescott 

 Facility-1974. Report to U.S. Army Corps of 

 Engineers, Contract DACW57-74-F-0414. 

 Alaska Fish. Sci. Cent., Natl. Mar. Fish. Serv., 

 NOAA, Seattle, WA 98112, 34 p. 



Dawley, E.M., R.D. Ledgerwood, and A.L. Jensen 



1985 Beach and purse seine sampling of juve- 

 nile salmonids in the Columbia River estuary 

 and ocean plume, 1977-1983; Vol. I. Proce- 

 dures, sampling effort, and catch data. NOAA 

 Tech. Memo. NMFS F/NWC-74, Alaska Fish. 

 Sci. Cent., Natl. Mar. Fish. Serv., NOAA, 

 Seattle, WA 98112, 260 p. 



Dawley, E.M., R.D. Ledgerwood, T.H. Blahm, C.W. Sims, 

 J.T. Durkin, R.A. Kirn, A.E. Rankis, G.E. Monan, and 

 F.J. Ossiander 



1986 Migrational characteristics, biological observations, and 

 relative survival of juvenile salmonids entering the Columbia 

 River estuary, 1966-1983. Report to Bonneville Power Admin- 

 istration, Portland, Oregon. Contract DE-A179-848BP39652. 

 Alaska Fish. Sci. Cent., Natl. Mar. Fish. Serv., NOAA, 



30 



20 



10 



CUMULATIVE YEARS 

 30 r 



SUBYEARLING CHINOOK SALMON 



o Beach Seine 189 d 

 ■• Purse Seine 145 d 

 * Diel Sampling 3 d 



I I I I I I I I I I 



40 r 



30 



20 



10 



SUBYEARLING CHINOOK SALMON 



20 



10 





 40 



COHO SALMON 



I I I 



J I 4 - I 



40 r 



30 



YEARLING CHINOOK SALMON 



30 - 



20 



10 

 40 



COHO SALMON 



J I I l__l 



30 



20 



10 



STEELHEAD 



* (46) 



J_ 



0600 



0900 

 Hours 



1200 



0600 



0900 

 Hours 



1200 



Figure 3 



Percent total catch of juvenile salmonids during morning hour sampling at 

 Jones Beach, Columbia River (1979-83) compared with diel sampling results 

 (mean value per time interval and 95% confidence limits); d = total number 

 of sampling days used for each estimate. 



Seattle, WA 98112, 256 p. 

 Durkin, J.T. 



1982 Migration characteristics of coho salmon {Oncorhynehus 

 kisutch) smolts in the Columbia River and its estuary. In Ken- 

 nedy, V. (ed.), Estuarine comparisons, p. 365-375. Academic 

 Press, NY. 

 Durkin, J.T., and D. L. Park 



1967 Purse seine for sampling juvenile salmon. Prog. Fish- 

 Cult. 29:56-59. 



