Forecasted Shifts in Thermal Habitat for Cod Species in the Northwest Atlantic and Eastern Canadian Arctic

David Cote,Tristan Hauser,Jennica Seiden,Ben J Laurel,Cassandra A Konecny,Trond Kristiansen

doi:10.3389/fmars.2021.764072

Abstract

Climate change will alter ecosystems and impose hardships on marine resource users as fish assemblages redistribute to habitats that meet their physiological requirements. Marine gadids represent some of the most ecologically and socio-economically important species in the North Atlantic, but face an uncertain future in the wake of rising ocean temperatures. We applied CMIP5 ocean temperature projections to egg survival and juvenile growth models of three northwest Atlantic coastal species of gadids (Atlantic cod, Polar cod, and Greenland cod), each with different thermal affinities and life histories. We illustrate how physiologically based species distribution models (SDMs) can be used to predict habitat distribution shifts and compare vulnerabilities of species and life stages with changing ocean conditions. We also derived an integrated habitat suitability index from the combined surfaces of each metric to predict areas and periods where thermal conditions were suitable for both life stages. Suitable thermal habitat shifted poleward for the juvenile life stages of all three species, but the area remaining differed across species and life stages through time. Arctic specialists like Polar cod are predicted to experience reductions in suitable juvenile habitat based on metrics of egg survival and growth potential. In contrast, habitat loss in boreal and subarctic species like Atlantic cod and Greenland cod may be dampened due to increases in suitable egg survival habitats as suitable juvenile growth potential habitats decrease. These results emphasize the need for mechanistic SDMs that can account for the combined effects of changing seasonal thermal requirements under varying climate change scenarios.

Highlights

Climate change is having widespread impacts on marine species (Pörtner et al, 2014; Lemmen et al, 2016) through altered ocean temperatures, sea-ice loss, decreased surface salinity, ocean acidification, and reduced oxygen availability (Stortini et al, 2016)
Predicting how climate change may alter the abundance and distribution of marine species is an important application of species distribution models (SDMs)
This study aims to understand how ocean warming caused by climate change could alter egg survival and limit growth potential in cod species (Polar cod, Atlantic cod, and Greenland cod) found off the east coast of Canada

Summary

Introduction

Climate change is having widespread impacts on marine species (Pörtner et al, 2014; Lemmen et al, 2016) through altered ocean temperatures, sea-ice loss, decreased surface salinity, ocean acidification, and reduced oxygen availability (Stortini et al, 2016). Mechanistic SDMs provide an attractive alternative as they better capture a broader range of responses of species to future environments (e.g., nonlinear, threshold, changes in environmental variability, etc.) and allow users to examine constraints of other lifestages and habitats that are unavailable in typical time-series survey data. Such approaches have gained traction because they can be relatively simplistic once the biological rate (e.g., growth or survival potential) is parameterized across a broad range of environmental conditions. While biological information can be limiting in rare species, such approaches have been used to forecast habitat conditions for well-studied species like gadids and other commercially and ecologically important fish (e.g., Dahlke et al, 2018)

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