McCABE ET AL.: INTERRELATIONSHIPS BETWEEN SALMONIDS 



harengus pallasi, and northern anchovy, Engraulis 

 mordax. 



In intertidal areas of the upper estuary, subyearling 

 chinook salmon was the only abundant salmonid 

 species; its importance was considerably reduced 

 by August. 



Catches in intertidal areas of the lower estuary were 

 dominated by nonsalmonids; however, in the inter- 

 tidal areas, subyearling chinook salmon were more 

 important than in the pelagic zone. Although l~rge 

 numbers of salmonids were captured in the pelagic 

 and intertidal areas of the lower estuary (Table 1), 

 their importance was masked by the large number of 

 marine nonsalmonids. 



Thirteen species including yearling chinook salmon 

 were commonly associated with subyearling chinook 

 salmon during at least one of the months in the two 

 seasonal periods in the Columbia River estuary (Ta- 

 ble 2). 



Juvenile coho salmon were captured primarily in 

 pelagic areas; however, they were occasionally collect- 

 ed in intertidal areas (Table 1). Yearling chinook 

 salmon and steelhead in particular were almost ex- 

 clusively in pelagic areas. 



Length characteristics of subyearling chinook 

 salmon and the commonly associated species are 

 shown in Table 3. Most common species in the 

 pelagic zone of the upper estuary were longer than 

 the subyearling chinook salmon, whereas in the 

 pelagic zone of the lower estuary many of the species 

 were shorter or the same. In the intertidal areas of the 

 upper estuary, only starry flounder, Platichthys stel- 

 latus; threespine stickleback, Gasterosteus aculeatus; 

 peamouth, Mylocheilus caurinus; and American 

 shad, Alosa sapidissima, were commonly associated 

 with subyearling chinook salmon and all of their 

 mean lengths were shorter. In intertidal areas of the 

 lower estuary, many of the common species were 



TABLE 2.— Fish associated with subyearling chinook salmon in the Columbia River estuary from March through September 1980. (C= com- 

 monly. O = occasionally, and U = uncommonly associated with subyearlings; * = commonly associated species; J = juveniles; and A = 

 adult.) 



Species 



River lamprey. Lampetra ayresi 



Pacific lamprey. Lampetra tndentata 



White sturgeon, Actpenser transmontanus 

 "American shad, Alosa sapidissima 

 'Pacific herring, C/upea harengus pallasi 

 "Northern anchovy, Engraulis mordax 



Chum salmon (J), Oncorhynchus keta 

 *Coho salmon (J), Oncorhynchus kisutch 



Coho salmon (A) 



Sockeye salmon (J), Oncorhynchus nerka 

 "Chinook salmon (Yr). Oncorhynchus tshawytscha 



Chinook salmon (A) 



Cutthroat trout, Salmo clarki 

 "Steelhead (J), Salmo gairdnen 



Steelhead (A) 



Whitebait smelt, Atlosmerus elongatus 

 "Surf smelt, Hypomesus pretiosus 

 "Longfm smelt. Spirmchus thaleichthys 



Eulachon, Thaleichthys pacificus 



Common carp. Cyprtnus carpio 

 "Peamouth. Mylocheilus caurinus 



Northern squawfish, Ptychocheilus oregonensis 



Largescale sucker, Catostomus macrocheilus 



Pacific hake. Merluccius productus 



Pacific tomcod, Microgadus proximus 

 "Threespine stickleback, Gasterosteus aculeatus 



Yellow perch, Perca flavescens 



Redtail surfperch, Amphistlchus rhodoterus 

 "Shiner perch, Cymatogaster aggregate 



Walleye surfperch, Hyperprosopon argenteum 



Silver surfperch, Hyperprosopon el/ipticum 



Pile perch, Rhacochilus vacca 



Pacific sandfish, Trichodon trichodon 



Snake prickleback, Lumpenus sagttta 



Lingcod, Ophiodon elongatus 



Prickly sculpin, Cottus asper 

 "Pacific staghorn sculpin, Leptocottus armatus 



Speckled sanddab. Cithanchthys stigmaeus 



Butter sole. Isopsetta isolepis 



English sole, Parophrys vetulus 

 "Starry flounder. Platichthys stellatus 



Sand sole, Psettichthys melanostictus 



819 



