Data from: Fishing-induced changes in adult length are mediated by skipped-spawning

Elucidating fishing effects on fish population dynamics is a critical step
toward sustainable fisheries management. Despite previous studies that
have suggested age or size truncation in exploited fish populations, other
aspects of fishing effects on population demography, e.g., via altering
life histories and density, have received less attention. Here, we
investigated the fishing effects altering adult demography via shifting
reproductive trade-offs in the iconic, overexploited, Pacific bluefin tuna
Thunnus orientalis. We found that, contrary to our expectation, mean
lengths of catch increased over time in longline fisheries. On the other
hand, mean catch lengths for purse seine fisheries did not show such
increasing trends. We hypothesized that the size-dependent energetic cost
of the spawning migration and elevated fishing mortality on the spawning
grounds potentially drive size-dependent skipped spawning for adult tuna,
mediating the observed changes in the catch lengths. Using eco-genetic
individual-based modeling, we demonstrated that fishing-induced evolution
of skipped spawning and size truncation interacted to shape the observed
temporal changes in mean catch lengths for tuna. Skipped spawning of the
small adults led to increased mean catch lengths for the longline
fisheries, while truncation of small adults by the purse seines could
offset such a pattern. Our results highlight the eco-evolutionary dynamics
of fishing effects on population demography and caution against using
demographic traits as a basis for fisheries management of the Pacific
bluefin tuna as well as other migratory species.