Oregon English sole catch data from 0 to 80 fathoms between Coos Bay and Cape Lookout were examined for the years 1973, 1975, and 1976. English sole is a major target species of this inshore trawl fishery. Comparison of depths of maximal values of catch per unit effort, effort, and total English sole landings for each month was used to determine when effort in this mixed-species fishery was directed on English sole. Petrale sole, normally a deeper water species, move inshore during late spring and summer months and may be a primary target during this season. Dover sole appeared to be a target species during certain spring months but rarely overshadowed either English or petrale sole catches. External factors such as weather conditions and market variability affected total monthly effort levels and were included in an interpretation of seasonal abundance and migration trends of English sole. Longshore movements were largely obscured by the month-to-month fluctuations of effort from Newport and Coos Bay, the two major fishing ports within the defined landing area. The Newport fleet is somewhat larger, but variable weather conditions may result in greater effort on the part of the Coos Bay fleet during certain months. Seasonal inshore-off shore movements of English sole, however, were consistently evident for the three years. Average depths of capture and catch per effort increased during fall and early winter months suggesting movement into deep water. Examination of ovary condition of English sole caught in the vicinity of Heceta and Stonewall Banks off the central Oregon coast linked this concentration and offshore movement to spawning. Inshore movement and decreased landings in the spring suggested a post-spawning dispersal. / Graduation date: 1980

Demographic characteristics of juvenile Dover sole (Microstomus pacificus) were examined in relation to physical and biotic factors to develop a hypothesis explaining annual variations in recruitment. Surveys were conducted along the Oregon continental shelf at depths between 50-400 m bimonthly during 1989 and annually (in March) between 1990 and 1993. To determine settlement timing, growth, and mortality, daily growth increments were validated, as was position of the first post-settlement annulus. A method of estimating precision of otolith elemental composition with the electron microprobe was developed; otolith microstructure and microchemistry were used to identify a landmark associated with settlement. Mean density of 0-group settlers varied annually, with 1989 and 1990 high, 1991 and 1992 low, and 1993 intermediate. 0-group abundance was correlated with fall offshore divergence one year before settlement and with southward geostrophic velocity during the summer before settlement. These conditions may be related to production of prey available to pelagic larvae. Density of 0-group Dover sole was highest between 100-119 m, but deeper areas were also utilized in years of highest abundance. Density was not correlated with spawning stock biomass or density of older juveniles. It was correlated with rex sole (Glyptocephalus [Errex] zachirus) density. Growth rate was positively correlated with mean April-October upwelling and was not related to density or mortality of Dover sole. First-year mortality was positively correlated with early settlement of 0-group larvae, possibly due to an advantage of settling and migrating to the primary nursery area well in advance of the spring transition. A multiple regression model predicting density of 1-group Dover sole from three physical environmental factors was applied to an independent time series of Dover sole "age-5" recruitment estimates (Turnock and Methot 1992). The model was a poor predictor of annual recruitment to fisheries but a good predictor of trends based on five-year running averages. Results suggest that multi-year trends in Dover sole recruitment to fisheries can be explained by a small set of density-independent physical factors. / Graduation date: 1995