Contrasting effects of coastal upwelling on growth and recruitment of nearshore Pacific rockfishes (genus Sebastes)

Abstract

Knowledge of processes underlying recruitment is critical for understanding marine population dynamics and their response to ocean climate. We investigated the relationship between coastal upwelling and early life history of black rockfish (Sebastes melanops), a midwater aggregating species, and CQB rockfishes (a solitary benthic species complex including Sebastes caurinus, Sebastes maliger, and Sebastes auriculatus), between two oceanographically distinct years on the west coast of Vancouver Island, Canada. We analysed otolith microstructure to determine parturition and settlement dates, pelagic durations, and pre- and postsettlement growth rates. High CQB rockfish recruitment in 2005 was associated with prolonged downwelling and warm ocean temperatures, late parturition dates, fast presettlement growth, short pelagic durations, and small size-at-settlement. In contrast, high black rockfish recruitment in 2006 was associated with strong upwelling and cool ocean temperatures, slow presettlement growth, and protracted pelagic durations. Presettlement growth of both rockfish complexes increased with high sea surface temperature, but was unrelated to chlorophyll a concentration. Our results indicate that the same oceanographic conditions give rise to fast presettlement growth and short pelagic durations for both groups, but that different factors lead to strong recruitment in each.