NOTE Olson and Quinn Vertical and horizontal movements of adult Oncorhynchus tshawytscha 



175 



*Apf"~v\ 





- FISH DEFTH ■+■ WATER DEFTH 



Fish 6 9/02/ B7 



1 ^f^ <s ~ Y v hfiV^^''^tJJL 



<* ** 



- FISH DEPTH -♦- WATEH DEPTH 



1S10 1610 

 TIME (Hr m&i) 



1010 2010 



Figure 2 



Track maps of vertical movements by Fish 4 and 5 within the 

 Columbia River estuarv. 



Fish 4 



Salinity (o/oo) or Temperature (C) 

 10 15 20 25 30 35 



10 20 30 40 50 60 70 80 90 100 

 Number of Observations 



further upstream during a high tide compared with a 

 preceding or subsequent low tide. Similarly, Groot et 

 al. (1975) found that sockeye salmon tracked in the 

 Skeena River estuary tended to drift with the current. 

 They also observed that during ebb tides, some fish 

 exited the estuary and relatively few fish made any 

 net movement upriver. Average ground speeds were 

 slightly higher for Columbia River chinook (2.41 km/h) 

 than the Skeena River sockeye ( 1.81 km/h in 1969 and 

 2.25 km/h in 1970), but these differences may merely 

 reflect the tidal current regimes of the two estuaries. 



Previous tagging studies have demonstrated that de- 

 lays in estuaries of about one month are common in 

 Pacific salmon (Wendler 1959, Verhoeven & Davidoff 

 1962, Vernon et al. 1964). Based on the period when 

 marked fall chinook salmon are captured in the Co- 

 lumbia River commercial gillnet fishery, lower river 

 tules delay in the estuary but upriver brights pass 

 through relatively rapidly (Donald 0. Mclssac, Oreg. 

 Dep. Fish Wildl., Portland, pers commun.). The move- 

 ment of tracked fish with tidal currents and the lack 

 of substantial net upriver progress support the hy- 

 pothesis that fall chinook may spend an indeterminate 

 amount of time holding within the estuary prior to 

 upstream movements. 



Tracked chinook displayed two vertical movement 

 patterns: swimming close to the bottom, or a combi- 

 nation of swimming in midwater and close to the bot- 

 tom. Time spent near the bottom may have been an 

 alternative stock-specific behavioral pattern for tracked 

 fish, or may have been influenced by stress from the 

 capture and tagging procedure. Sockeye salmon tracked 

 in deeper waters and for longer 

 periods than the present study 

 demonstrated characteristic ver- 

 tical and horizontal movements 

 about 1 h after release (Quinn et 

 al. 1989). Stressed fish would be 

 expected to show lethargic verti- 

 cal and horizontal movements, 

 and, as such, fish in the present 

 study were considered to be be- 

 having normally because all fish 

 demonstrated substantial verti- 

 cal movements during portions of 

 their tracks. 



The vertical distribution of 

 salmon in estuaries may be in- 



Figure 3 



Mean temperature and salinity 

 depth profiles and depth distribu- 

 tions for tracks of Fish 4 and 5. 

 Dotted lines indicate 1SD. 



Fish 5 



Salinity (o/oo) or Temperature (C) 

 10 15 20 25 30 35 



50 100 150 200 250 300 350 

 Number ot Observations 



