EGG SIZE, FECUNDITY, AND DEVELOPMENT RATE OF 2 INTRODUCED NEW-ZEALANDCHINOOK SALMON (ONCORHYNCHUS-TSHAWYTSCHA) POPULATIONS

Interpopulation differences in several adult phenotypic traits suggest that New Zealand (NZ) chinook salmon (Oncorhynchus tshawytscha) are e volving into distinct populations. To further investigate this hypothe sis, we compared egg sizes, fecundities, and early development rates o f chinook from two NZ streams. The two NZ study populations differed i n size-adjusted egg weight and gonadosomatic index, but not in size-ad justed fecundity. Egg weight, fecundity, and gonadosomatic index value s for both NZ populations were different than values for chinook from Battle Creek, California, the population regarded as the ancestral NZ stock. In contrast, there was little evidence of divergence in juvenil e development. Time to hatching did not differ between the two NZ stud y populations and heritability estimates were small with large standar d errors. Evidence of a small difference in alevin growth rate may hav e represented an effect of yolk conversion mechanics related to egg si ze. Despite the similarity in development rates under shared condition s, modeling based on temperature records suggests that emergence dates in the two NZ streams may differ by 4-6 weeks, yielding significant p henotypic differences.