264 



Fishery Bulletin 90(2). 1992 



Table 2 



Environmental and stock biomass covariates of Pacific whiting Merluccius prodiictiis growth, assessed using the growth-increment 

 regression model. Mean summer (April-August) sea-surface temperature (°C) is an average over lat. 40-50°N, and from the coast, 

 west to long. 125°W. The Bakun upwelling indices are mean summer coastal upwelling (April-August) from lat. 42-48°N. Stock biomass 

 is measured in millions of tons of age-2 and older fish in the coastal whiting population. Anomalies of temperature, upwelling index, 

 and biomass are calculated as the annual value minus the mean over 1978-87. 



'J.G. Norton, Pac. Fish. Environ. Group, P.O. Box 831, Monterey, CA 93942, pers. commun., 

 ''Mason and Bakun (1986). 

 "Dorn and Methot (1990). 



Aug. 1989. 



age are not point estimates in time, but averages over 

 2 or 3 months. As a result, relating the growth incre- 

 ment to the environment over a short time-period 



would tend to blur environmentally -determined growth 

 differences. 



The environmental variables and stock abundance 

 measures examined in the analysis were intentionally 

 limited to a few variables which would characterize the 

 environment of the population on the largest scale 

 possible. The environmental variables are summer 

 averages over the geographic range of the mature 

 stock. Mean summer (April- August) sea-surface tem- 

 perature (°C), provided by J.G. Norton (Pac. Fish. En- 

 viron. Group, Monterey, CA 93942, pers. commun., 

 Aug. 1989), represents the mean value obtained from 

 ships of opportunity between lat. 40°N and 50°N, and 

 from the North American coast west to long. 125°W 

 (Table 2). The Bakun upwelling indices are a mean of 

 the monthly coastal upwelling indices during April- 

 August from lat. 42-48°N and are in units of metric 

 tons of water transported through the Ekman layer per 

 second per 100 m of coastline (Mason and Bakun 1986). 

 Stock biomass is measured in millions of tons of age-2 

 and older fish in the coastal whiting population, and 

 is estimated using the stock synthesis model (Dom and 

 Methot 1990). The estimates of year-class strength in 

 Table 3 come from the same source. 



Results 



Length analysis of variance 



Annual length-at-age estimates by sex for 1978-88 

 were obtained using the procedures described in the 



