Spawning fish maintains trophic synchrony across time and space beyond thermal drivers

Area of Science:

• Marine biology
• Climate change impacts
• Fish reproductive ecology

Background:

• Rising ocean temperatures accelerate physiological processes in ectotherms.
• Faster oocyte growth in fish may lead to earlier spawning.
• Potential for trophic asynchrony if spawning time decouples from offspring food resources.

Purpose of the Study:

• To investigate the impact of ocean warming on the spawning phenology of Northeast Arctic cod (Gadus morhua).
• To determine if cod spawning times are adjusting to environmental cues and local conditions.
• To assess the implications for trophic match-mismatch dynamics in a changing climate.

Main Methods:

• Analysis of biological data (>125,000 cod) including length, age, and gonad development (1980-2019).
• Integration of experimental data on fish oocyte growth rates.
• Statistical analysis to correlate spawning timing with oceanographic and environmental factors.

Main Results:

• Northeast Arctic cod exhibited a trend of spawning approximately one week earlier per decade, linked to ocean warming.
• Spawning time showed significant interannual and spatial variation (over 40 days).
• Cod spawning plasticity appears finely tuned to local phytoplankton bloom phenology.

Conclusions:

• Cod demonstrate a capacity to modulate spawning time, partly overriding thermal influences.
• This plasticity allows cod to track local environmental conditions crucial for offspring survival.
• Findings introduce a new perspective on trophic match-mismatch and are vital for climate change phenology models.