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The ocean salmon troll fishery of Oregon

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  • Reprinted from Bulletin 2 of the Pacific Marine Fisheries Commission (1951).
  • 1. The Oregon troll salmon fishery developed rapidly prior to World War I to reach a peak of between one and three thousand boats fishing off the mouth of the Columbia River during 1919. The fishery later expanded to the other coastal areas. There has been a decrease in the number of boats fishing, but a great increase in their efficiency. The development of the tuna fishery resulted in the larger trollers fishing for tuna during the late summer and concentrating on salmon during the spring and early summer. There are about 500 trollers which make Oregon ports their base of operations at the present time. Since 1940 the Oregon troll fishery has landed about 3,000,000 pounds of chinook and silver salmon per year. The troll fishery was practically unregulated until 1948, at which time, preliminary regulations were imposed. 2. Preliminary troll regulations which were imposed since 1948 and altered somewhat in 1949 include a 26 inch minimum size limit and a closed season from November 1 to March 15 on chinook salmon. A closed season for silver salmon extends from November 1 to June 15 to prevent the landing of small silvers during the late spring. 3. This report covers in part the tagging and biological data gathered by the staff of the Oregon Fish Commission during 1946, 1947, 1948 and 1949. 4. There were 506 silvers tagged off Oregon in 1948 and 1949, and 29 (5.7 percent) were recovered. By far the greater percentage were recovered north of their tagging location, indicating a northward migration of silvers in their third and last year to their spawning streams. 5. The recovery of marked silver salmon in the ocean, confirms the findings of the tagging in that early in the season (June) the marked fish were found south of their home streams, and as the season advanced they moved north until during September they were grouped around the mouths of the rivers. 6. The length-weight relationship of troll-caught silver salmon was found to be an exponential type of relationship, and the equation for 1947 is W = 0.23215 x 1.0535 [superscript L]; that for 1948 is W = 0.27952 x 1.04949 [superscript L]. 7. The commercial catch of silver salmon is composed largely of individuals in their third year. There seems to be a considerable difference between the growth rates of different years, but the silvers show an average increase in mean weight from about 4.5 pounds on June first to about eight pounds by November first, dressed weight. They showed an increase in modal length in 1948 from 25.2 inches (total length) in June to 30.4 inches (total length) in November. 8. There were 221 chinook salmon tagged in 1948 and 1949 and eleven recoveries were made. No consistent migration pattern is apparent, but it is apparent that the chinook move both north and south of their natal streams and probably migrate farther than do the silver salmon. 9. The length-weight relationship of the chinook salmon was found to conform to the usual parabolic relationship, W = AL [superscript b]. The equation for 1947 was W = 0.000013126 [superscript L 3.17008] and for 1948, W = 0.000009256 [superscript L 3.24142]. 10. The age and growth of the troll caught chinook salmon was studied. The 2+ group was the dominant year class in the catch of 1919, 1946, and probably 1948, but in 1947 there was slightly more of the 3+ group. The 3+ group was next in abundance in 1919 and 1946, with the 1+ group age class comprising a relatively small part of the catch. There is a considerable variation in the sizes and ages of chinooks found in the different areas at different times, and also between years. 11. During April and May, trolling is concentrated off the mouth of the Columbia River. Usually there is a slight peaking in average weight in the spring, followed by a decline and a subsequent rise to a peak in August. In all cases average weight dropped appreciably after August. 12. The ocean sport fishery operates mainly out of Depoe Bay and Newport, with smaller fleets out of nearly every port on the Oregon Coast. The estimated ocean sport catch in 1949 was 700 chinooks (9,000 pounds) and 9,000 silvers (70,000 pounds).
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