Lingering legacies: Past growth and parental experience influence somatic growth in a fish population

Body size and growth rate can influence individual and population success
by mediating fitness. Understanding the factors that influence growth can
be difficult to disentangle, however, because growth can be shaped by
environmental conditions recently experienced, as well as legacy effects
from conditions experienced earlier in life and by parents (via parental
effects). To improve understanding of growth among annual cohorts
(1982-2015) of Lake Erie Walleye (Sander vitreus), a species with life
history and growth characteristics similar to many other long-lived,
iteroparous fishes, we determined the role of the following hypothesized
factors: H1) recent environmental conditions; H2) traits and experiences
of the cohort, including growth, in the previous year; H3) early-life
cohort density; H4) early-life body size; and H5) parental composition and
environment. We evaluated the relative importance of these hypothesized
factors using piecewise structural equation modeling in an
information-theoretic framework. Our results indicated that
cohort-specific growth of Lake Erie Walleye was most strongly influenced
by traits (growth) and experiences of the cohort during the previous year
(H2) and parental composition and environment (H5). The observed negative
relationship with growth during the previous year may indicate that
Walleye exhibits compensatory growth. The relationships with parental
sizes and environments may mean that parental contributions to offspring
affect cohorts into adulthood, with serious implications for the effects
of climate change. Warm winters appear to negatively influence offspring
growth performance for many years. Legacy effects had a stronger influence
on cohort growth than recent environmental conditions, providing a new
understanding of how somatic growth is regulated in Lake Erie’s Walleye
population. Specifically, the parental composition and environment appear
important via epigenetic and/or egg-provisioning legacies, with carryover
effects modifying growth over the years. Ultimately, our findings
demonstrate that understanding recent growth in animal populations similar
to Lake Erie Walleye may require knowledge of past conditions, including
those experienced by parents.