Tagging has shown that the runs of 

 herring to the various sounds and 

 inlets along the west coast of Van- 

 couver island form a series of inter- 

 grading populations, each of which 

 exhibit a definite 'homing tendency' 

 but each of which has a relatively small 

 degree of independence. Rough calcu- 

 lations indicate that on the average 

 about 55% of the fish return to the area 

 of spawning, but the remainder, 45%, 

 disperse or 'wander' to other areas. 

 If the five areas are grouped into 3 

 (Area 23-24, Area 25-26, and Area 27), 

 each of which is separated by a prom - 

 inent headland which might act as a 

 barrier to mixing, the calculations 

 indicate that on the average about 70% 

 of the fish return to the area of spawn- 

 ing and 30% wander to other areas . 

 Mixture is greatest between adjacent 

 areas and tends to become progressively 

 less the more widely -separated are the 

 areas. 



The conclusions drawn from a consider- 

 ation of vertebral material are 

 essentially in accord with the above 

 findings, except that the amount of 

 mixing between areas is considerably 

 greater than might have been anticipated 

 from the term 'limited' .... so much so 

 that for practical purposes the series 

 of intergrading 'units' were considered 

 to constitute one major population . 

 (ibid A 17, 419.) 



Royce in a paper in this series uses some 

 of the data of Tester (1949) in showing a condi- 

 tion of nearly complete overlap in vertebral 

 counts from samples of herring off Vancouver 

 Island. He compares the northernmost and 

 southernmost areas and found a p of . 465 . Ex- 

 pressed as S\j( = 200 p), the amount of one 

 sample which might belong to another specified 

 sample, the value is 93 percent. Hence, mix- 

 ture between the two areas could be as high as 

 93 percent. 



Yellowfin tuna, Neothunnus macropterus 



It is difficult to investigate the subpopula- 

 tions of tunas when even the number and 



distribution of the species is a matter of contro- 

 versy. The exceedingly widespread distribution 

 of these pelagic fishes, together with their large 

 size, have contributed to the complexity of the 

 problem. Because of their size, tunas are poorly 

 represented in museum collections and, as a 

 consequence, series of specimens have not been 

 available for comparative studies until quite 

 recently . 



Kishinouye (1923) laid an excellent founda- 

 tion for the morphological study of scombroid 

 fishes . He not only used external characters 

 such as meristic counts and proportionate mea- 

 surements, but detailed anatomical studies of 

 internal organs, circulatory system, and skeletal 

 structures. His methods have been continued in 

 detailed studies of various tunas by Frade (1931), 

 Godsil and Byers (1944), Godsil and Holmberg 

 (1950), and other workers. Although this approach 

 has aided in clarifying the taxonomy of tunas, the 

 studies to date have not been comprehensive 

 enough to settle the species problem . It is still 

 a matter of controversy whether there is a single 

 yellowfin tuna species of widespread distribution 

 or a number of related species of yellowfin tunas 

 with more localized distributions . Similarly, the 

 taxonomy of bluefin tunas and of albacores is un- 

 settled. 



The population studies have been more de- 

 tailed than similar studies attempted on other 

 groups of fish. There are several reasons why 

 this was necessary. Meristic characters, with 

 the possible exception of gill raker counts, are 

 not particularly useful in defining subpopulations 

 of tunas which (except skipjack) almost invariably 

 have 39 vertebra. Fin counts are more variable, 

 but little more useful . The proportionate length 

 of fins changes with size, as do a number of body 

 dimensions . Furthermore, different body parts 

 grow at different rates . To define the relation of 

 each character to size it is necessary to examine 

 fish in the entire size range available at any one 

 locality. This permits the various body propor- 

 tions to be expressed as the regression of one 

 dimension on another or on total (fork) length. 



Marr and Schaefer (1949) define the body 

 dimensions used in describing tunas including no 

 fewer than 27 meristic and morphometric char- 

 acters. Even this represented a selected list of 

 characters, chosen (1) because of prior use, 



58 



