Effect of Quality of the Spawning Bed on Growth and 

 Development of Pink Salmon Embryos and Alevins 



By 



RALPH A. WELLS, Medical Doctor 



U.S. Army Hospital 

 Fairbanks, Alaska 99701 , 



and 



WILLIAM J. McNEIL, Head, Pacific Fisheries Laboratory 



Department of Fisheries and Wildlife 

 Oregon State University, Newport, Oregon 97365 



ABSTRACT 



Among three segments of the spawning ground in Sashin Creek, southeastern 

 Alaska, the largest and fastest developing embryos and alevins of pink salmon, 

 Oncorhynchus gorbuscha , came fronn spawning gravels characterized by high levels 

 of dissolved oxygen in intragravel water. The high oxygen levels occurred in a 

 stream segment which has a relatively steep grade and coarse materials in the bed. 

 No differences in water temperature were observed among the three segments. 



INTRODUCTION 



Pacific salmon bury their eggs in gravel 

 beds of streams where the developing em- 

 bryos and alevins are protected from ex- 

 posure to predation, light, and turbulent water. 

 Unfortunately, conditions in the spawning beds 

 are not always adequate for optimum growth 

 and development. 



Effects of environmental stresses on growth 

 and development of eggs and alevins have been 

 studied in the field, in the laboratory, and with 

 artificial populations in streams. The studies 

 of natural populations have yielded information 

 on environmental factors that sometimes limit 

 survival in spawning beds, but aside from ob- 

 servations on the body size of newly emerged 

 fry, little attention has been given in field 

 studies to the effects of stress on growth and 

 development. 



This paper describes the growth and de- 

 velopment of embryos and alevins of pink 

 salmon, Oncorhynchus gorbuscha , in natural 

 spawning beds of different quality in Sashin 

 Creek, a small stream in southeastern Alaska. 



STUDY AREA 



BCF (Bureau of Commercial Fisheries) is 

 studying the ecology of salmon spawning beds 

 in Sashin Creek between the ocean and an im- 

 passable falls about 1,000 m. upstream. The 

 creek drains a small ( 1 3. 5-km.^ ) watershed on 



Baranof Island about 100 km. south of Sitka. 

 The ecological studies have been concentrated 

 in three segments that together include about 

 96 percent of the total spawning ground. In this 

 report the three segments, which are con- 

 tinuous over 890 m. of stream channel, are 

 designated as "upper" (220 m. long), "middle" 

 (270 m.), and "lower" (400 m.). The upper 

 segment has a relatively steep grade (0.7 

 percent) and coarse materials in the bed; the 

 middle segment has an intern-iediate grade 

 (0.3 percent) and medium-sized materials; 

 and the lower segment has a relatively shallow 

 grade (0. 1 percent) and fine materials. The con- 

 trasting ecological conditions resulting from 

 these different grades and streambed materials 

 make Sashin Creek an excellent stream for a 

 comparative study of populations of salmon 

 eggs and alevins in a natural environment. 



Dissolved oxygen and temperature of the 

 intragravel water are two of the principal 

 criteria used to assess the quality of a spawn- 

 ing bed. These two criteria were measured in 

 Sashin Creek with standpipes driven at many 

 random locations within three segments of the 

 spawning bed (table 1 ). The upper segment, 

 where the grade is steep and the bed materials 

 are coarse, often had a higher content of dis- 

 solved oxygen in the intragravel water than did 

 the middle and lower segments (table 1). These 

 differences were particularly evident when 

 waterflows were low and water temperatures 



