UW Aquatic & Fishery Sciences Quantitative Seminar
Effects of climate variability on the abundance and distribution of demersal fishes in the California Current Ecosystem
Climate and ocean conditions affect the distribution and abundance of marine species, and shifts in fish distribution associated with ocean warming have been documented in marine ecosystems worldwide. These changes in the spatial structure of fish populations can have cascading effects on the dynamics of marine communities and fisheries. This study examined the biological responses of 24 groundfish species to environmental conditions to better understand how they might respond to future climate variability and long-term climate change in the California Current system. I used generalized linear mixed effects models to evaluate the relative importance of local environmental variables and longer-periodicity climate processes in dictating variation in groundfish catch per unit effort in NOAA trawl surveys from 2003 to 2009. I hypothesized that biological responses to climate-ocean conditions would be related to species' life history and behavioral characteristics. Local environmental variables (e.g., sea surface temperature, SST; chlorophyll concentration, chl-a) were important predictors of occurrence for all species. Species showing positive relationships with SST and chl-a had significantly shallower distributions, smaller maximum size, and were more sedentary than those whose occurrence varied inversely with temperature and chlorophyll. The importance of interannual climate variability was related to age, with earlier maturing and shorter-lived species showing more sensitivity to upwelling and El Nino Southern Oscillation anomalies. Resolving the mechanistic linkages between climate-ocean conditions and distribution of adult fishes remains a major challenge, however, this study provides insight into the potential vulnerability of different life history types to future climate change.