Quantifying thermal effects on contemporary growth variability to predict responses to climate change in northern rock sole (Lepidopsetta polyxystra)

Abstract

Understanding the causes of contemporary variation in growth rates can offer insights into the likely consequences of climate change for growth and recruitment of coastal marine fishes. We examined the growth dynamics of age-0 northern rock sole ( Lepidopsetta polyxystra ) over four years in three nurseries at Kodiak Island, Alaska, USA. Following the settlement period, fish were sampled monthly (July–October) with a 3 m beam trawl at fixed-position transects. Postsettlement sizes were positively related to temperatures during the spawning and larval periods, suggesting environmental control of spawning or settlement timing. Summer growth on the nursery grounds varied significantly among sites and years (mean size 32.8–63.1 mm in mid-September), with the Holiday Beach site consistently supporting the fastest growth rates. Contrary to expectations of density dependence and thermal regulation, nursery ground growth rates were not significantly correlated with fish density or water temperatures. The minor contribution of thermal variation to growth rates appears related to the conservative growth strategy and low thermal sensitivity of northern rock sole. These results suggest that climate changes influencing spawning time and larval growth may have larger impacts on first-year growth and recruitment of this species than temperature effects on the growth of nursery-resident juveniles.