BIOCHEMICAL GENETICS OF PACIFIC BLUE MARLIN, MAKAIRA NIGRICANS, FROM HAWAIIAN WATERS I

An electrophoretic survey of 35 enzyme-coding gene loci in Pacific blue marlin was accomplished to determine levels of genetic variation and the feasibility of using electrophoresis to study stock structure in this species. Polymorphism (P9') in the marlin was 0.26 and the average heterozygosity (H) was O.OH. Allele frequencies at 11 variable loci were determined for a sample of 95 fish fl'om Kona, Hawaii. The observed levels of polymorphism and heterozygosity suggest that a biochemical genetic analysis of blue marlin stock structure is possible and may I'eveal stock heterogeneity. The Pacific blue marlin, Makaim nigricans, is the predominant billfish species in the central tropical Pacific. As such, it is an important com­ mercial species and the object of a considerable SPort fishery. The average annual catch of this species in the Pacific exceeds 14,000 t (metric tons) (Shomura 1980). The Pacific blue marlin is primarily distributed in equatorial areas, al­ though Japanese longliner catch records indi­ cate that its range extends from lat. 48°N to 48°S. During the Southern Hemisphere summer (December through March) a center of concen­ tration Occurs in the western and central South Pacific (between lat. 8 0 S and 26°S). In the North­ ern Hemisphere summer(May through October) a center of concentration occurs in the central :North Pacific (between lat. 2°N and 24 ON). Dur­ Ing April and November the fish appear to be concentrated equatorially between lat. lOON and 10~S (Rivas 1975). There is currently no direct ~vldence of migration of blue marlin within the acific. However, a general movement to the ~orthwestern Pacific during the Northern Hem­ ~sp~ere summer and to the southeastern Pacific UrIng the Southern Hemisphere summer has been postulated by Howard and Ueyanagi (1965)