Graduate Thesis Or Dissertation

Seasonal changes in English sole distribution : an analysis of the inshore trawl fishery off Oregon

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  • 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.
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