Transgenerational effects of anadromy on juvenile growth traits in an introduced population of rainbow trout (Oncorhynchus mykiss)

Abstract

We determined whether the propensity for anadromy was related to maternal phenotype in a population of partially anadromous rainbow trout (Oncorhynchus mykiss). We identified the maternal phenotype (anadromous versus resident) of wild juveniles from two successive cohorts using stable isotope analysis (δ15N) of muscle tissue and (or) strontium to calcium ratios in the otolith core. We also tested the hypothesis that juvenile size and growth are related to maternal migratory history. For both cohorts, juvenile size at capture and growth, as determined using otolith and scale structural analyses, were strongly related to maternal migratory history. Offspring of anadromous mothers were larger and grew faster than resident offspring. Back-calculated length at age 1 of anadromous and resident adults provided support for a positive association between body size and anadromy, indicating that larger offspring are more prone to displaying anadromy. We conclude that maternal anadromy, which influences adult size and egg quality, affects the propensity of progeny to migrate, thus perpetuating the anadromous tactic across generations and influencing the establishment and persistence of anadromy.