Most marine fish species express life-history changes across temperature gradients, such as faster growth, earlier maturation, and higher mortality at higher temperature. However, such climate-driven effects on life histories and population dynamics remain unassessed for most fishes. For 332 Indo-Pacific fishes, we show positive effects of temperature on body growth (but with decreasing asymptotic length), reproductive rates (including earlier age-atmaturation), and natural mortality for all species, with the effect strength varying among habitat-related species groups. Reef and demersal fishes are more sensitive to temperature changes than pelagic and bathydemersal fishes. Using a life table, we show that the combined changes of life histories upon increasing temperature tend to facilitate population growth for slow life-history populations, but reduce it for fast life-history ones. Within our data, lower proportions (25-30%) of slow life-history fishes but greater proportions of fast life-history fishes (42-60%) show declined population growth rates under 1°C warming. Together, these findings suggest prioritizing sustainable management for fast life-history species.

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.

Many subtropical fishes spawn multiple batches throughout a year. To understand plasticity in their reproductive output, we evaluated variation in oocyte size and batch fecundity for an exploited subtropical cutlassfish, Trichiurus japonicus, between two temperature periods (warm vs. cold) on the NE and SW coasts of Taiwan, northwestern Pacific. Given greater temperature variability on NE compared with SW coast, we hypothesized greater changes between warm and cold periods in oocyte size and fecundity for T. japonicus on the NE coast. We found opposite changes in sizes of ripe oocytes between periods (cold > warm on the NE but warm > cold on the SW coast) but consistent patterns in batch fecundity between coasts (warm > cold). Furthermore, the between‐period patterns in female length were consistent on both coasts (warm > cold). The differential between‐period patterns in oocyte size were related to potential adaptive responses to differential thermal environments between coasts, whereas the changes in fecundity mainly involved plastic processes (e.g., changes in population demography or movement). Together, our findings suggest that variability of temperature and maternal effects underlie recruitment variability of T. japonicus.