Clutch size of anadromous and freshwater threespine sticklebacks: a reassessment
There is conflicting evidence in the literature regarding the size-specific fecundity of anadromous and freshwater threespine sticklebacks (Gasterosteus aculeatus L.). To examine this question, I reared offspring of threespine sticklebacks collected from an inland location along the Navarro River, Mendocino County, California, and compared their initial clutch size and egg size with data obtained earlier for two other stickleback populations (an anadromous and a coastal freshwater population) from the same drainage. Size-specific clutch size was lower and eggs were larger in the inland population compared with the two populations studied previously. When wild-caught threespine sticklebacks are compared, fecundity of anadromous forms should usually be higher due to their higher size-specific fecundity as well as their larger average size at maturity. The eggs of anadromous sticklebacks may also be smaller than those of typical freshwater sticklebacks, since there is evidence of negative phenotypic correlations between egg size and clutch size in these fish.