Table 7. --Northern anchovy: mean number of vertebrae of adults, 

 young and post larvae grouped by area 



McHugh found less difference in dorsal 

 ray counts between areas . Again, the highest 

 mean counts were obtained from southern Cal- 

 ifornia . The variation within an area, however, 

 was considerably less than for mean values of 

 anal fin rays. McHugh concluded "on the basis 

 of dorsal fin ray counts, the northern anchovy 

 may therefore be divided into at least two popula - 

 tions. . . .Distinct populations inhabit the waters 

 of the Pacific Northwest and of southern Calif- 

 ornia and that these may be separated rather 

 sharply off the central California coast, possibly 

 somewhere in the vicinity of Point Conception . 

 There are also indications that a third popula- 

 tion exists off Baja California" (ibid . : 142-3) . 



The mean number of pectoral fin rays was 

 found to increase from north to south . McHugh 

 found clear-cut sexual dimorphism in the num- 

 ber of fin rays, with males averaging higher than 

 females in all fins studied. The dimorphism was 

 most marked in mean number of pectoral rays, 

 however . The counts on males exceeded those 

 on females by . 29 ray on the average . 



Female anchovies were found to consist- 

 ently exceed males in the mean number of gill 

 rakers; for both sexes it was found that gill 

 rakers increased gradually in number with in- 

 crease in size. In studying latitudinal variation 

 it was therefore necessary to compare individuals 

 of the same size and sex. It was found that the 

 mean number of gill rakers decreased from north 

 to south . 



Based on an analysis of all five meristic 

 characters, McHugh concluded that "at least 

 three populations inhabit the coast, occurring (1) 

 from off British Columbia to nordiern California, 

 (2) off southern California and northern Baja 

 California, and (3) off central and southern Baja 

 California ." 



It is necessary to check the above conclu- 

 sions with tagging experiments . Differences 

 between areas in all characters studied were so 

 small that based on these evidences alone it 

 would not be possible to show separateness of 

 "populations" especially if the concept of overlap 

 discussed by Royce were applied. 



Anchovetta, Cetengraulis mysticetus 



The anchovetta, Cetengraulis mysticetus, 

 is the principal bait fish used by American tuna 

 fishermen to catch yellowfin and skipjack tunas. 

 Decrease in abundance of this species, especially 

 in the Gulf of Nicoya, was one of the factors that 

 led to the establishment of the Inter -American 

 Tropical Tuna Commission. Howard (1954) re- 

 ported on a study of "populations" of this anchovy, 

 using meristic characters to determine whether 

 more than one major population occurs in the 

 range of the species from Mexico to Peru . 



Specimens were examined from six major 

 baiting localities covering nearly the entire range 

 of the species . The localities were the following: 

 Almejas Bay on the outer coast of Baja California 



66 



