LOCAL POPULATIONS AND MIGRATION IN RELA- 

 TION TO THE CONSERVATION OF PACIFIC 

 SALMON IN THE WESTERN STATES 

 AND ALASKA* 



By WILLIS H. RICH 



DEPAETMENT OF BIOLOGY, STANFORD UNIVERSITY, CALIF., AND DEPARTMENT OF RESEARCH, 

 FISH COMMISSION OF OREGON 



The study of the migrations of the salmon 

 of Alaska and the Pacific states has been 

 actuated by the conviction that a knowledge 

 of the movements of these fish is essential to 

 the formation of a sound conservation pro- 

 gram. The conservation of any species may 

 be defined as the maintenance of the abun- 

 dance of that species at a level that, with due 

 regard for the requirements of the future, 

 appears to be the most desirable from the 

 point of view of Man. Such maintenance 

 of a population, whether of mice or men or 

 of fishes, requires that the births and deaths 

 shall be equal over a period of time. It is 

 the function of conservation efforts to pro- 

 duce this condition and it is the function of 

 conservation research to provide the infor- 

 mation necessary to guide these efforts. 



The requirements of practical conserva- 

 tion demand a knowledge of the fluctuations 

 in the birth and death rates and of the events 

 and forces that may cause fluctuations in the 

 birth-death ratio. But any study of the 

 factors affecting the birth-death ratio must 

 take into consideration (1) the extent to 

 which the species is broken up into self- 

 sustaining groups; (2) the fluctuations in 

 the birth-death ratio of each independent 

 group at each stage in the life-history ; and 

 (3) the causes of these fluctuations, again 

 for each independent group and for each life 

 phase because these causes need not be and 

 often are not the same for all of the popula- 

 tion groups that go to make up the species. 



In the conservation of any natural, bio- 

 logical resource it may, I believe, be con- 

 sidered self-evident that the population must 

 be the unit to be treated. By population I 

 mean an effectively isolated, self-perpetuat- 



* Contribution No. 1, Department of Eesearch, 



ing group of organisms of the same species 

 regardless of whether they may or may not 

 display distinguishing characters and re- 

 gardless of whether these distinguishing 

 characters, if present, be genetic or environ- 

 mental in origin. Given a species that is 

 broken up into a number of such isolated 

 groups or populations, it is obvious that the 

 conservation of the species as a whole re- 

 solves into the conservation of every one of 

 the component groups; that the success of 

 efforts to conserve the species will depend, 

 not only upon the results attained with any 

 one population, but upon the fraction of the 

 total number of individuals in the species 

 that is contained within the populations af- 

 fected by the conservation measures. On 

 the other hand, the conservation of a species 

 that is not so broken up into isolated, self- 

 perpetuating groups obviously presents en- 

 tirely different problems, simpler in some 

 ways, more difficult in others. More general 

 conservation measures may be effective for 

 such species. These population groups 

 have commonly been termed by biologists on 

 the Pacific coast "races," entirely without 

 any implication that the groups show de- 

 monstrable and heritable differences. It is 

 true that, in certain instances, the popula- 

 tion groups do show demonstrable and 

 heritable differences but it is also true that 

 in many other cases no such differences have 

 been shown. The latter is not surprising in 

 view of the fact that there are certainly 

 scores or hundreds of such population 

 groups in each of the five species of the genus 

 Oncorhynehus. 



It is apparent then that one of the first 

 requirements of a sound conservation pro- 

 Fish Commission of Oregon. 

 45 



