Dataset for: Spawning fish maintain trophic synchrony across time and space beyond thermal drivers

Increasing ocean temperature will speed up physiological rates of ectotherms. In fish, this is suggested to cause earlier spawning, due to faster oocyte growth rates, causing spawning time to potentially become decoupled to the timing of the offspring’s food resources. A phenomenom referred to as trophic asynchrony. We used biological data, including body length, otolith information, and gonad developmental stages collected from > 125,000 individual Northeast Arctic cod (Gadus morhua) sampled between 59 and 73 °N in 1980-2019. Combined with experimental data of oocyte growth rates, our analysis shows that cod spawned progressively earlier by about a week per decade, partly due to ocean warming. It also appears that spawning times vary by more than 40 days, depending on year and spawning location. The significant plasticity in spawning time seems to be fine-tuned to the local phytoplankton spring bloom phenology. This ability to partly overcome thermal drivers could allow individuals to phenologically modulate their spawning time to maximize fitness by closely tracking local environmental conditions important for offspring survival. This finding highlights a new dimension for trophic match-mismatch and should be an important consideration in models used to predict phenology dynamics in a warmer climate.