MARKING SOCKEYE SALMON SCALES 

 BY SHORT PERIODS OF STARVATION 



by 



Richard L. Major and Donovan R. Craddock 



Fishery Research Biologists 



Bureau of Commercial Fisheries 



U, S. Fish and Wildlife Service 



Seattle, Washington 



ABSTRACT 



Experiments conducted at the Leavenworth, Wash., national fish hatchery in 

 1959 and 1960 demonstrated that the scale pattern of Columbia River sockeye salmon 

 Oncorhynchus nerka can be recognizably modified by a short period of starvation. 

 Modification was obtained with little mortality. Starved fish readily resumed feeding; 

 and although they did not make up for lost growth, they regained their robustness and 

 outward vigor. 



The tests were the first in a series to determine whether a starvation-marking 

 technique can be developed as a means of separating wild from hatchery-reared 

 sockeye salmon. 



INTRODUCTION 



Seaward migrations of sockeye salmon 

 Oncorhynchus nerka 1 from Lake Wenatchee, 

 Wash,, are composed of both wild and hatch- 

 ery-reared fish. Both types of migrants are 

 progeny of the same parent stock, some of 

 which spawned naturally while others were 

 spawned artificially. Artificially spawned eggs 

 are hatched, and the fish reared to finger- 

 ling size at the nearby Leavenworth hatchery 

 operated by the U. S. Fish and Wildlife Serv- 

 ice. Hatchery-reared young are planted in 

 the lake in the fall where they are subject to 

 mixing with the wild fish. Young sockeye either 

 migrate seaward in the spring of the second 

 or third year of life or remain in the lake 

 to complete their life cycle in fresh water, 

 in which case they are called "kokanee." 



The difficulty in separating wild from hatch- 

 ery-reared fish hampers efforts to evaluate 

 either natural or hatchery production to the 

 migrant stage, or to measure the contribution 

 of either type to the kokanee population. A 

 means is needed, therefore, to readily and 

 accurately distinguish wild from hatchery 

 fish captured in the seaward migration and in 

 the kokanee sport fishery. 



Efforts to discover a built-in identification 

 characteristic by the comparison of known 

 wild and hatchery samples' were unsuccess- 

 ful in 1957 and 1958. In addition to intensively 

 examining the scales, which are known to 



iSockeye intheColumbia River are also called 

 back." 



'blue- 



»The origin of the samples was known in this case be- 

 cause the hatchery fish were taken directly from the 

 hatchery ponds and the wild sample consisted of fish in 

 their second year that were captured in the lake prior to 

 the planting of the hatchery fish. 



