Regional warming exacerbates match/mismatch vulnerability for cod larvae in Alaska

Abstract

The match-mismatch hypothesis predicts that variability in spring primary production will increase starvation risk for marine fish populations. However, it is often unclear whether the synergic effects of temperature, phytoplankton phenology and metabolic demands of fish support these prediction within and across regions. In this study, we combine experimentally-derived rates of larval survival in relation to water temperature with satellite remote-sensing estimates of chlorophyll a and sea surface temperature to predict habitat quality of first feeding Pacific cod (Gadus macrocephalus) larvae in two adjacent large marine ecosystems; southeast Bering Sea (BS) and Gulf of Alaska (GOA). Predictions are made from 1998 to 2019, a period comprised of both warm and cool springs, followed by a series of extreme warming events (heatwaves) beginning in 2014. Model results indicate that the drivers of a mismatch between cod larvae and their food is fundamentally different between the two systems. In the GOA, larval habitat suitability is highly dependent on interannual fluctuations in sea surface temperature that regulate yolk reserves in embryos. In contrast, larval habitat suitability in the BS was more sensitive to the onset of the surface expression of Chl a production. The combined effects of changes in timing of Chl a and increased metabolic demands of larvae were captured by the model during the GOA marine heatwave (2014–16, 2019), which predicted significant loss of larval habitat across the entire region. These habitat models integrate important spatial, temporal and physiological components of match-mismatch theory that can be used to examine marine fish populations experiencing different rates of climate stress across regions.