Interannual Variability in Growth Rates of Early Juvenile Sablefish and the Role of Environmental Factors

Abstract

Otolith increments were examined to estimate growth rates of late larvae and early juvenile sablefish from an 8-yr time series (1993-2001), with fish collected from late March to mid-May at the same location off Oregon. The time series spanned a broad range of oceanographic conditions and included an extreme El Nino year (1997-1998) followed by an extreme La Nina (1999). Estimated growth rates overall were rapid for the small size of fish examined and the water temperatures they experienced, averaging 0.4 mm d-1 to 1.0 mm d-1 at fish sizes of 10-40 mm. Growth rates were strongly related to fish size and water temperature. After adjusting for these effects using regression residuals, interannual differences in growth corresponded to large-scale oceanographic indices of productivity and transport in the California Current ecosystem. Growth during the early neustonic stage was correlated with subsequent recruitment to the adult stock except in 1997, when conditions in late winter and early spring apparently were favorable for sablefish growth but survival of the year class was poor, potentially a consequence of reduced productivity as El Nino conditions developed in the summer. Within a year, there was minimal support for the occurrence of growth-dependent mortality, at least within the time frame of our collections. Overall, the results confirm the unusual capacity for rapid growth in small sablefish and are consistent with the general pattern of large-scale environmental controls on larval and early juvenile survival hypothesized for fishes resident in the California Current.