Interplay of temperature and hypoxia in habitat quality for a juvenile demersal fish in a coastal upwelling system

Coastal hypoxia around the world has raised concerns about its sublethal effects on juvenile demersal fishes. We examined the growth rate of juvenile English sole (Parophrys vetulus) under 15 combinations of temperature and dissolved oxygen levels. We found interactive effects of temperature and hypoxia on fish growth. Fish exposed to moderate hypoxia and normoxia exhibited similar growth responses to increasing temperature; however, a threshold effect was evident under severe hypoxia, which caused a significant reduction in growth. Further, a generalized additive mixed model was applied to simulate fish growth off the Oregon coast during a climate transition from the 2009 El Nino to the 2010-2011 La Nina. Model simulations indicated that habitat quality varied significantly between estuarine (high quality) and coastal (low quality) nurseries. Coastal habitats may remain moderately suitable during El Nino years, while estuarine refuges are more preferred during La Nina years. This study contributes to the assessment of climate change and hypoxic disturbance on demersal fisheries by providing an analytical framework to evaluate synergistic temperature-hypoxia interactions on juveniles in their nursery habitats.