Larger eggs in resident brown trout living in sympatry with anadromous brown trout

Freshwater resident brown trout (Salmo trutta L.) in the stream Jorlandaan (southwestern Sweden) had larger eggs (range of actual mean egg wet weights , 65.9-108.5 mg) than both sympatric migratory trout (76.8-84.2 mg) and tro ut from five other Swedish streams with allopatric resident (23.7-80.1 mg) or migratory populations (44.5-121.9 mg), after accounting for differences in body size. In Jorlandaan, some resident females even had a larger absolu te mean egg weight than any of the migratory females found in the stream Re sident trout had low absolute fecundity, and our data suggest that resident females in Jorlandan produce large eggs at the expense of their fecundity The extremely large relative egg size in resident Jorlandaan females sugges ts that the production of large offspring enhances fitness, possibly throug h increased fry survival.