Maternal effects have been observed to interact with genotypic and environmental influences to structure offspring phenotypes across a wide variety of taxa. In fishes, maternal effects may be especially important due to their potential influence on development and survival during early ontogeny -a period with high potential for population regulation. While previous studies have confirmed that maternal effects on offspring phenotype are common in fishes, the consistency with which they positively affect offspring fitness throughout early ontogeny remains largely unknown. We examined maternal effects on offspring fitness by quantifying relationships between maternal (length, mass and age), egg (diameter, mass and density) and larval traits (length, yolk-sac volume and survival) in yellow perch (Perca flavescens). Consistent with several past studies, positive relationships among maternal and egg traits were evident. While egg mass was positively related to larval size at hatching, direct relationships between maternal and larval metrics were not apparent. Larval survival appeared to have two critical periods; in contrast with expectations, survival in the first 5 days posthatch was strongly negatively related to female size and age, while survival over the following 9 days was unrelated to maternal traits. Throughout the study, survival was positively related to yolk-sac volume. Our unexpected observation of a negative relationship between maternal size and age and initial larval survival indicates that maternal effects may not be consistent throughout larval ontogeny. In fact, maternal effects appear to be dynamic influences on offspring fitness, and may have complex effects on individual-and population-level reproductive success.

Intraspecific genetic variation across the distribution of MuskellungeEsox masquinongy suggests the existence of divergent stocks among major river drainages. Often, stocks differentiate in response to latitudinal variation in thermal regime. Genetic variation and thermal adaptation may drive fish to either maximize growth during brief growing seasons at higher latitudes (countergradient growth) or experience longer periods of slower growth at lower latitudes (cogradient growth). The strength and direction of these genetic effects matter for fish stocked outside of their native drainage and for populations experiencing changes to regional thermal regimes. We used a replicated pond experiment with uniform initial fish size and environmental conditions to compare the survival and growth of stocked age-0 Ohio River drainage (OH) Muskellunge with those of the more northerly upper Mississippi River drainage (MISS) stock following their first winter and a year after introduction into a common environment. Both stocks had similarly high winter survival, though the MISS stock had a slower growth rate overwinter than the OH stock. Survival during the latter spring-to-fall period was greatly reduced for the MISS stock, however, with the differences in growth rate persisting. These findings suggest that cogradient adaptation to temperatures experienced during early life stages in native environments results in a disadvantage for high-latitude stocks of Muskellunge in thermal regimes warmer than those they have historically experienced in their native drainages.

Turbidity can fluctuate rapidly during the early life of fishes, impacting foraging behaviours. For piscivores, turbidity may hinder foraging, whereas planktivores and juvenile fishes may increase foraging activity and decrease antipredator behaviours in moderate levels of turbidity. Black crappie (Pomoxis nigromaculatus) and white crappie (P. annularis) population trends are often related to changes in turbidity. Yet effects of turbidity on juvenile foraging of these species are unknown and may differ between species. To evaluate effects of three turbidity levels (0, 25 and 50 NTU) on juvenile crappie foraging, controlled experiments compared (a) consumption and size selection for a single prey and (b) selection, total consumption and energetic value of diets when offered three distinct prey options. Overall, black crappies exhibited universally greater diet biomass than white crappies. Black crappies displayed higher prey consumption and were more size selective of a single‐prey type, whereas white crappies were less size selective and maintained uniform consumption as turbidity increased. Selection patterns for three prey types were similar among species and turbidity levels, with Chaoborus preferred and Chironomus avoided. However, black crappies also avoided Daphnia, whereas white crappies consumed them neutrally. Overall, turbidity did not impair foraging of juvenile crappies. Turbidity‐driven fluctuations in prey base paired with predator interactions likely also contribute to observed growth and abundance fluctuations in natural systems.

No abstract