Data from: Artificial selection on reproductive timing in hatchery salmon drives a phenological shift and potential maladaptation to climate change

The timing of breeding migration and reproduction links generations and
substantially influences individual fitness. In salmonid fishes, such
phenological events (seasonal return to fresh water and spawning) vary
among populations but are consistent among years, indicating local
adaptation in these traits to prevailing environmental conditions.
Changing reproductive phenology has been observed in many populations of
salmonids, and is sometimes attributed to adaptive responses to climate
change. The sockeye salmon spawning in the Cedar River near Seattle,
Washington have displayed dramatic changes in spawning timing over the
past 50 years, trending later through the early 1990s, and becoming
earlier since then. We explored the patterns and drivers of these changes
using generalized linear models and mathematical simulations to identify
possible environmental correlates of the changes, and test the alternative
hypothesis that hatchery propagation caused inadvertent selection on
timing. The trend toward later spawning prior to 1993 was partially
explained by environmental changes, but the advance in spawning since was
not. Instead, since its initiation in 1991 the hatchery has, on average,
selected for earlier spawning, and, depending on trait heritability, could
have advanced spawning by 1-3 weeks over this period. We estimated
heritability of spawning date to be high (h2 ~ 0.8; 95% CI: 0.5-1.1), so
the upper end of this range is not improbable, though at lower
heritabilities a smaller effect would be expected. The lower reproductive
success of early spawners and relatively low survival of early emerging
juveniles observed in recent years suggest that artificial and natural
selection are acting in opposite directions. The fitness costs of early
spawning may be exacerbated by future warming, thus artificially advanced
phenology could reduce the population’s productivity. Such artificial
selection is known in many salmon hatcheries, so there are broad
consequences for the productivity of wild populations comingled with
hatchery produced fish.