Genetic and Morphometric Variation in the Pacific 



Sardine, Sardlnops sagax caerulea: Comparisons and 



Contrasts with Historical Data and with Variability in 



the Northern Anchovy, Engraulis mordax 



Dennis Hedgecock, Elmarie S. Hutchinson, Gang Li, 

 Frederic L. Sly, and Keith Nelson 



ABSTRACT: Pacific sardines from five widely 

 separated localities are found to have little genetic 

 variation both within and between populations. Of 

 the 32 allozyme-coding loci examined from a total 

 of 149 fish, the proportions that are polymorphic 

 within a population (P) range from 7% to 27% with 

 a mean of 12%. Average proportions of hetero- 

 zygous individuals per locus (Hg) range from 0.5% 

 to 1.6% with a mean of 1.0% over the five popula- 

 tions. Pacific sardine populations are virtually ge- 

 netically identical at the presumptive gene loci ex- 

 amined. For each locus that is polymorphic in more 

 than one population, the same rare variant allele is 

 shared at about the same frequency, suggesting 

 strongly that there has been gene flow throughout 

 the present range of the species. These results con- 

 trast with substantial genetic variation detected 

 within and between northern anchovy populations 

 from the California central stock (average P = 

 40%, average H^ = 7.5%) and with the significantly 

 higher levels of genetic variation reported for other 

 marine clupeoids. Despite a low level of genetic 

 variation, the Pacific sardine shows a north-south 

 cline in size-at-age that is as steep and as large as 

 that seen in historical, precollapse populations. In 

 the past, such differences were interpreted as evi- 

 dence of genetically distinct subpopulations. Our 

 results imply that rapid differentiation of growth 

 rate among geographic populations, probably to- 

 gether with differentiation of correlated life history 

 traits, is largely environmentally, and not geneti- 

 cally, determined. It appears that biological data 

 from historical populations can safely be used for 

 area-specific fisheries models of the recovering sar- 

 dine stocks in California. 



A variety of studies have suggested that, prior 

 to its collapse in abundance, the Pacific sardine. 



Dennis Hedgecock, Elmarie S. Hutchinson, Frederic L. 

 Sly, Keith Nelson: Aquaculture and Fisheries Progi-am, 

 University of California, Davis, Bodega Marine Laboratory, 

 Bodega B'ay, CA 94923. 



Li Gang, South China Sea Institute of Oceanology, Aca- 

 demia Sinica, 164 Xin Gang-Xi Road, Guangzhou, People's 

 Repubhc of China. 



Sardinops sagax caerulea, comprised two or 

 more distinct subpopulations (morphometry and 

 meristics: Hubbs 1925; Clark 1936, 1947; 

 McHugh 1950; growth: Phillips 1948; Felin 

 1954; Clark and Marr 1955; Radovich 1962, 

 1982; movements of tagged fish: Clark and 

 Janssen 1945; Clark and Marr 1955; spatio- 

 temporal distribution of spawning: Ahlstrom 

 1954, 1959; erythrocyte antigens: Sprague and 

 Vrooman 1962; Vrooman 1964; reviews by 

 Marr 1957; Radovich 1982). Population structure 

 likely played a role in the collapse of the fishery, 

 perhaps directly, by virtue of differences among 

 subpopulations in life history and resilience to 

 fishing pressure (Wisner 1961; Murphy 1966; 

 Radovich 1982) and more certainly, indirectly, 

 by contributing to overestimations of stock size 

 in the waning years of the fishery (MacCall 

 1979). With the return of substantial numbers of 

 Pacific sardines to the California Current in 

 recent years and the lifting of the fishing mora- 

 torium (Wolf et al. 1987) has come interest in 

 management cjuestions such as which sardine 

 has recovered and what life history character- 

 istics and yields can be expected (MacCall 1986). 

 We have made studies of protein and morpho- 

 logical variation in the Pacific sardine to shed 

 light on such questions. Electrophoretic separa- 

 tion of proteins followed by chemical staining to 

 reveal the locations of proteins or specific en- 

 zymes allows inferences to be made concerning 

 variation in the genes encoding these proteins. 

 This in turn provides a description, useful for 

 management, of the genetic structures of ex- 

 ploited fish populations (see Ryman and Utter 

 1987). Several clupeoids, including the northern 

 anchovy, Engraulis })iordax, which co-occurs 

 with the Pacific sardine in the California Cur- 

 rent, have been shown to harbor considerable 

 stores of electrophoretically detectable genetic 

 variability (Hedgecock and Li 1983; Table 8). In 

 this paper, we compare protein and allozyme 

 variation in samples of Pacific sardines collected 



Manuscript accepted February 1989. 

 Fishery Bulletin, U.S. 87:653^71. 



653 



