AbStr3Ct. — Beach and purse 

 seine catches at Jones Beach, River 

 kilometer 75, were used to examine 

 diel movement patterns of juvenile 

 chinook salmon Oncorhynchus tsha- 

 wytscha, coho salmon 0. kisutch, and 

 steelhead 0. mykiss as they migrated 

 downstream in the Columbia River 

 estuary. The patterns were moni- 

 tored during five 24-hour periods in 

 1978, 1979, and 1980, and compared 

 with patterns obtained from exten- 

 sive morning-hour sampling con- 

 ducted during 1979-83. Diel catch 

 patterns were generally consistent 

 among the sampling periods and 

 there was reasonable agreement 

 with morning-hour sampling. How- 

 ever, diel movement was different 

 than that reported for salmonids in 

 other river systems and in other loca- 

 tions in the Columbia River. The 

 times and lateral position of greatest 

 downstream movement which pro- 

 vided the largest catches of salmonid 

 juveniles were as follows: sunrise to 

 early afternoon nearshore for sub- 

 yearling chinook salmon, sunrise to 

 early afternoon midriver for yearling 

 chinook salmon, midmorning to early 

 evening nearshore and sunrise to 

 early afternoon midriver for coho 

 salmon, and noon to early evening 

 midriver for steelhead. Decreased 

 movement during darkness was ap- 

 parent for all salmonids. No relation- 

 ship between tidal cycle and catch 

 was evident from either beach or 

 purse seine sampling. 



Diel Sampling of Migratory 

 Juvenile Salmonids in the 

 Columbia River Estuary 



Richard D. Ledgerwood 



Coastal Zone and Estuarine Studies Division 



Northwest Fisheries Science Center, National Marine Fisheries Service, NOAA 



2725 Montlake Boulevard East. Seattle. Washington 981 12-2097 



Frank P. Thrower 



Auke Bay Laboratory. Alaska Fisheries Science Center 

 National Marine Fisheries Service, NOAA 

 P.O. Box 210155. Auke Bay. Alaska 99821 



Earl M. Dawley 



Coastal Zone and Estuarine Studies Division 



Northwest Fisheries Science Center, National Marine Fisheries Service, NOAA 



2725 Montlake Boulevard East. Seattle, Washington 981 12-2097 



Manuscript accepted 24 July 1990. 

 Fishery Bulletin, U.S. 89:69-78 (1991). 



Successful and cost-effective timing 

 and survival studies for juvenile salm- 

 on and steelhead are dependent on 

 understanding migratory behavior 

 as well as sampling effectiveness. 

 Literature regarding the migratory 

 behavior of juvenile Pacific salmon 

 Oncorhynchus spp. and steelhead O. 

 mykiss indicates a wide variation in 

 diel movement patterns, from great- 

 est movement during daylight hours 

 (Sims et al. 1976) to greatest move- 

 ment at night (Smith et al. 1968) (see 

 also Table 1). Catches used for the 

 reported observations were obtained 

 using an assortment of sampling 

 equipment in large and small rivers 

 and reservoirs during a range of tur- 

 bidity conditions. Juveniles captured 

 varied in life stage from emergent fry 

 to migrating smolt. It was difficult to 

 determine from some of the litera- 

 ture whether the greatest catches 

 represented increased fish movement 

 or times of greatest susceptibility to 

 sampling equipment. 



Personnel of the National Marine 

 Fisheries Service conducted a sam- 

 pling program at Jones Beach, Co- 

 lumbia River, kilometer (Rkm) 75, to 

 examine diel movement patterns of 

 juvenile chinook salmon 0. tshawy- 



tscha, coho salmon O. kisutch, and 

 steelhead in the upper Columbia River 

 estuary. The objective was to estab- 

 lish the optimum time of day and 

 lateral location for the most effective 

 sampling of these fish during the 

 peak of the spring migration. Also, 

 this program was to provide data to 

 compare with previous sampling re- 

 sults at Jones Beach which indicated 

 midriver orientation of yearling fish, 

 shore orientation of subyearling fish, 

 and substantially decreased move- 

 ment of shore-oriented migrants at 

 night (Dawley et al. 1986). 



Methods 



Diel migration patterns were moni- 

 tored using beach and/or purse seines 

 during five 24-hour periods: 18-19 

 May 1978, 14-15 June 1978, and 

 14-15 May 1980 for beach seine; and 

 10-11 May 1979, 23-24 May 1979, 

 and 14-15 May 1980 for purse seine. 

 Sampling dates were based on peaks 

 of juvenile salmonid migrations 

 recorded in other years (1966-83) at 

 Jones Beach (Dawley et al. 1986). 



Purse seining was conducted mid- 

 river from the north edge of the ship 

 channel toward Puget Island; beach 



69 



