Spatial Distribution of Juvenile Salmonids in the 

 Hanford Reach, Columbia River 



Dennis D. Dauble, Thomas L. Page, and R. William Hanf, Jr. 



ABSTRACT: The cross-sectional distribution of 

 juvenile chinook salmon, sockeye salmon, and 

 steelhead was determined in the Hanford Reach of 

 the Columbia River from July to September 1983 

 and from April to July 1981. Fish were sampled 

 with fyke nets from anchored barges, movable 

 shoreline fyke nets, seines, and with electroshock- 

 ing equipment. Fall chinook salmon from naturally 

 spawning populations and from hatchery releases 

 were the principal species collected in the spring. 

 Zero-age fall chinook salmon occurred primarily in 

 shoreline areas of reduced current velocity but were 

 present throughout the river cross section during 

 their early rearing and outmigration period. Hatch- 

 ery-released fall chinook smolts were less abundant 

 in nearshore areas than were wild fish. Yearling 

 spring chinook salmon, sockeye salmon, and steel- 

 head smolts from upriver areas were collected 

 mainly from the bottom, midchannel zone of the 

 river. Principal downstream movement of all 

 species occurred from 2200 to 0400 [PDTl. Fish 

 collections followed an activity pattern that includ- 

 ed migration, feeding, and resting periods. 



Knowledge of the distribution of migi-ating fish 

 is important both to fisheries managers and to 

 scientists interested in migratory behavior. 

 From a practical standpoint, knowledge of 

 where fish migi-ate may allow technology to be 

 developed with minimal impact on that resource. 

 Information on the location of fish during differ- 

 ent phases of their hfe cycle may also provide 

 clues to specific environmental factors that in- 

 fluence their behavior and ultimately affect their 

 survival (Coutant 1986). Migi-ational character- 

 istics are adapted toward particular life history 

 strategies (Smith 1985); therefore, comparisons 

 of distribution among species or size classes can 

 further our understanding of anadromous fish 

 biology. 



Information on the spatial distribution of ju- 

 venile salmonid outmigrants in nonimpounded 

 waters of the mainstem Columbia River is lim- 



Dennis I>. Dauble, Thomas L. Page, and R. William Hanf, 

 Jr., Environmental Sciences Department, Pacific North- 

 west Laboratory, Richland, WA 99352. 



Manuscript accepted May 1989. 

 Fishery Bulletin. U.S. 87:77.5-790. 



ited to studies of 0-age fall chinook salmon, 

 Oncorhynchus tshawytscha, by Mains and Smith 

 (1964). Investigations of the distribution of mi- 

 gi-ating salmonids in other river systems have 

 been directed at determining the behavior of 

 juveniles during movement from spawning or 

 nursery areas. For example, in the Skeena River 

 drainage in Canada, the lateral distribution of 

 outmigi'ant pink salmon, 0. gorbiischa, and sock- 

 eye salmon, 0. nerka, was positively correlated 

 with current velocity. In contrast, coho, 0. 

 kisutch, and chum, 0. keta. salmon fry were 

 more uniformly distributed across the river 

 (McDonald 1960). Studies with juvenile sockeye 

 salmon in the Newhalen River, AK showed that 

 most fry and smolts were present in the faster 

 midchannel areas and near the surface (Dames 

 and Moore 1982). To our knowledge, no studies 

 have been conducted to quantify and compare 

 the cross-sectional distribution of juvenile sal- 

 monids in lotic environments. 



Descriptions of habitat selection have been 

 conducted for many salmonid species in small 

 stream systems. Most indicate a general rela- 

 tionship between increased fish size and greater 

 water depth and/or current velocity (Hartman et 

 al. 1967; Lister and Genoe 1970; Everest and 

 Chapman 1972; Wankowski and Thorpe 1979). 

 Whether this relationship applies to the spatial 

 distribution of migrating fish in a large river has 

 not been established. 



We report results from field studies conducted 

 in the Hanford Reach of the mid-Columbia River 

 in 1983 and 1984. The Hanford Reach is now the 

 only unimpounded section of the mainstem Co- 

 lumbia River above Bonneville Dam and below 

 the international border (Fig. 1). Our objective 

 was to obtain estimates of the relative cross-sec- 

 tional distribution of juvenile chinook salmon, 

 sockeye salmon, and steelhead, 0. ttiykiss, dur- 

 ing their spring and summer outmigi-ation from 

 upriver spawning and nursery areas. These 

 estimates of distribution were needed to assess 

 the potential for fish to pass through a midriver 

 thermal discharge, located downstream from the 

 study site. Capture locations of fish were also 



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