Effects of Changing Temperature Phenology on Fish Species Distributions and Biomass

Previous studies have found that warming waters along the Northeast United States continental shelf, a robustly predicted impact of numerous climate models, drive fish assemblages towards higher latitudes and deeper waters. These studies relied on surveys with fixed seasonal timing. Meanwhile, temperatures along the shelf have shifted towards earlier warming. Seasonal migrations of fish onto the continental shelf likely follow the temperature phenology. This study seeks to determine whether apparent changes in fish biomass and distributions are linked to changing temperature phenology. Fisheries independent data from the Northeast Fisheries Science Center spring bottom trawl survey and daily sea surface temperature data from the NOAA Optimum Interpolation Sea Surface Temperature (OISST) series were used.  Temperature phenology of the shelf was assessed by calculating the day of year at which various temperature thresholds were reached. We tested the hypothesis that earlier spring warming would cause fish distributions to be more poleward, inshore, and shallow, and for observed biomasses to be greater.  We also tested the hypothesis that these relationships would be strongest for migratory fish species that are more likely to follow environmental cues like temperature.  Results suggest sampling phenology may affect observed impacts of warming in some, but not all fishes.