reviewed in this article. But it has been found 

 for several species for which both morphomet- 

 ric and tagging data are available that groups 

 that were judged to be "distinct" on the basis of 

 morphometric studies were found to have con- 

 siderable intermixture when a tagging experi- 

 ment was performed (Tester, 1948; Roedel, 

 1952) . It is now realized that morphometric 

 differences are evidence that a population is 

 not homogeneous throughout its range; but the 

 amount of intermixture can only be determined 

 if certain special conditions are satisfied by the 

 data. The problem is discussed by Royce and 

 by Widrig and Taft in other papers in this 

 series. 



This paper will review some of the work 

 done on "subpopulations" of Pacific marine 

 fishes . The species which will be dealt with 

 are the Pacific herring, Clupea pallasi ; yellow - 

 fin tuna, Neothunnus macropterus ; albacore, 

 Germo alalunga; Pacific mackerel, Pneumato- 

 phorus diego; northern anchovy, Engraulis 

 mordax; anchovetta, Cetengraulis mysticetus ; 

 nehu, Stolephorus purpureus and Australian 

 anchovy, Engraulis australis. Subpopulation 

 studies on the Pacific sardine are dealt with in 

 another paper in this series; the Pacific halibut 

 is omitted because the "studies of racial char- 

 acters" mentioned in the introductory report on 

 Pacific halibut (Thompson and Herrington, 1930: 

 ll)i' have never been published. 



"racial" studies. The term "population" has 

 been used usually to designate the aggregate of 

 individuals in particular localities; no worker 

 has restricted the term to the definition given 

 by Marr. There are similar differences in 

 meaning attached to other terms, particularly 

 to "stock and "race". In reviewing research 

 done on "subpopulations of Pacific fishes I have 

 found it expedient to employ at times the termi- 

 nology used by the authors of the papers being 

 discussed. 



STUDIES DEALING WITH SUBPOPULATIONS" 

 OF PACIFIC COAST FISHES 



Pacific herring , Clupea pallasi 



The Pacific Herring is, in many respects, 

 an ideal species on which to conduct subpopula- 

 tion studies . The species is a demersal spawner, 

 depositing its eggs on seaweed and eel grass 

 near shore. The fish are thus concentrated at 

 the time of spawning and can be caught and tagged 

 on the spawning grounds . The species migrates 

 offshore or along shore to feed, and in British 

 Columbia at least, the herring is not fished dur- 

 ing the feeding period. The fishery takes place 

 during the inshore return of the herring to the 

 spawning grounds . If the spawning runs main- 

 tain a high degree of integrity, the herring 

 population could be made up of a large number 

 of separate stocks . 



In the papers which will be reviewed, 

 there has been no consistency in terminology. 

 Most commonly, the studies have been called 

 1/ Tag return s from the early tagging experi- 

 ments on Pacific halibut (tagging in 1925 and 

 1926 south of Cape Spencer, 1926 and 1927 

 north and west of Cape Spencer) showed that 

 the immature fish tagged to the south of Cape 

 Spencer were recovered near the areas of re- 

 lease with an average distance of recovery 

 spot from release spot of only 22 miles . The 

 mature fish tagged on the Yakutat spawning 

 grounds and Portlock Bank were recovered 250 

 miles from the tagging spot, on the average . 

 Only one fish tagged to the south of Cape Spencer 

 was recaptured above Cape Spencer, and about 

 5 percent of the fish tagged in the western area 

 were recaptured below Cape Spencer; evidence 

 of the heterogeneity of the halibut stocks . 



The early work on "races" of herring at- 

 tempted to show separateness of herring stocks 

 by structural differences in meristic and mor- 

 phometric characters. In this approach, American 

 investigators were following techniques that had 

 been pioneered by European workers in "racial" 

 studies of Atlantic herring. The indirect approach 

 was used because of the difficulty in conducting 

 tagging experiments on herring. Marking experi- 

 ments on herring were considered impractical, 

 both because of the high mortality that would re- 

 sult from handling them in tagging, and because 

 of the difficulty of recovering tagged members 

 in a fishery where fish could not be individually 

 examined on recapture (most herring are re- 

 duced to fish meal and oil) . 



The problem of an effective means of tag- 

 ging herring and recovering the tags was finally 



45 



