Global warming can alter early life histories of fish through shifts in phenology and growth rates but disentangling age and growth processes can be challenging. During recent marine heatwaves in the North Pacific Ocean, fewer juvenile Pacific Cod (Gadus macrocephalus) were observed after settlement near Kodiak Island, Alaska, but those present were larger than previous years. To determine the degree to which earlier spawning and faster growth contributed to larger juveniles in those years, we examined daily otolith increments of age-0 juveniles collected in years before (2007, 2009, 2010, 2012, 2013), during (2014-2016, 2019), and between (2017, 2018) marine heatwaves.

Preliminary Results:

Thus far, our results indicate that warming contributed to larger age-0 juvenile Pacific Cod through both earlier spawning and faster apparent growth. Our results will advance understanding of how heatwaves alter growth and performance of Pacific Cod, which helps explain and anticipate changes in size-structure and recruitment potential in near-future climates.