Environmental effects on growth of early life history stages of rockfishes (Sebastes) off Central California based on analysis of otolith growth patterns

Understanding the causes of recruitment variability in many marine fish populations is a long standing problem in fisheries research, and one that remains pressing due to the consequences of uncertainty in production models for effective management decisions. Recruitment often fluctuates greatly between years for species with a pelagic early life history (ELH) phase, and can appear independent of stock size. This phenomenon is believed to be a direct result of variable environmental conditions influencing the survival rates of marine fishes during ELH. Environmental influence on growth rate during early life may affect rates of survival through various mechanisms, and as such, examining environment-growth relationships may provide insight into the environmental effects on overall year class strength. In an effort to quantify the environmental influence on growth during the critical ELH stages, this study developed a daily growth rate time series from 1984-2004 for each of three species of winter-spawning rockfish using otolith micro-increment analysis techniques. After removing the effects of ontogeny on daily growth rate, I was able to explain a large amount of variability in growth patterns with an autoregressive multiple regression model which included several environmental parameters. Models included a combination of sea surface temperature as well as a measure of ecosystem productivity, such as modified upwelling or solar illumination indices. Environmental variables in best-fit models were able to account for 5 – 33% of overall variability in growth rate, a significant improvement over previous research into environment-growth dynamics. This analysis represents a step forward in understanding one of many potential mechanisms that connect environmental conditions to recruitment variability for winter-spawning rockfishes, and provides a foundation for future research into the environmental effects on growth during early life history.