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• 1. [Article] Analysis of factors affecting the production of chum salmon (Oncorhynchus keta) in Tillamook Bay

  Tillamook Bay chum salmon are caught commercially by gill-nets, both set and drift, and from 1928 through 1949 the landings have averaged 819,689 pounds per season. More chum salmon are caught on Tillamook ...

  Citation × Citation Citation Abstract Copy Title: Analysis of factors affecting the production of chum salmon (Oncorhynchus keta) in Tillamook Bay Author: Oregon. Fish Commission, Henry, Kenneth A. Tillamook Bay chum salmon are caught commercially by gill-nets, both set and drift, and from 1928 through 1949 the landings have averaged 819,689 pounds per season. More chum salmon are caught on Tillamook Bay than on the rest of the Oregon coastal rivers combined. These fish enter the ocean only a few weeks after hatching and return to their native streams to spawn, apparently in the third, fourth, or fifth year of their life. There are numerous factors such as predation, fishing intensity, success of spawning, which may have some effect on the production of Tillamook Bay chum salmon. There was no apparent relationship between total chum landings and lumber production 4 and 8 years previous. It is possible that a relationship between these two factors may exist for some period other than 4 or 8 years previous, but this was not investigated further at this time. Numerous factors, mainly various combinations of stream flow data, were correlated with the size of the commercial landings of chum salmon in an attempt to determine a "predictor" of future abundance. An apparent good relationship, with b = 2.05944 (P = 01), between total chum landings and the minimum stream flow occurring between January 15 and March 20 three years previous was discovered. The regression equation obtained is y = -493.6355 + 2.05944x. The regression of the size of the commercial landings of chum salmon on three variables was computed. These three variables were: (1) minimum stream flow occurring between January 15 and March 20 three years previous; (2) highest air temperature occurring during January or February 3 years previous; and (3) the maximum stream flow occurring between November 1-10 four years previous. The regression equation obtained is y = 346.4554 + 97.3148x[subscript 1] + 66.1037x[subscript 2] — 77.8188x[subscript 3]. The probabilities attached to the results of all the regression functions which were computed are biased because of the manner in which the data were selected to obtain the best relationship. Furthermore, although an apparent good relationship was determined between minimum flows and the size of the commercial landings, it must be realized that these results have some very definite limitations to their actual values. In addition to the biased nature of the probabilities, is the fact that these results have been derived from a very limited amount of data. Also, these analyses have been based on some very important assumptions which, if not true, would almost completely invalidate the results obtained. These assumptions are: (1) catch = a constant X abundance; (2) all the fish mature at 4 years of age; (3) these data can be fitted to a linear model along with the other general assumptions about regression data; (4) fishing intensity has remained relatively constant (implied in 1); and (5) methods of recording flow data have remained consistent from year to year. Title: Analysis of factors affecting the production of chum salmon (Oncorhynchus keta) in Tillamook Bay Author: Oregon. Fish Commission, Henry, Kenneth A. Tillamook Bay chum salmon are caught commercially by gill-nets, both set and drift, and from 1928 through 1949 the landings have averaged 819,689 pounds per season. More chum salmon are caught on Tillamook Bay than on the rest of the Oregon coastal rivers combined. These fish enter the ocean only a few weeks after hatching and return to their native streams to spawn, apparently in the third, fourth, or fifth year of their life. There are numerous factors such as predation, fishing intensity, success of spawning, which may have some effect on the production of Tillamook Bay chum salmon. There was no apparent relationship between total chum landings and lumber production 4 and 8 years previous. It is possible that a relationship between these two factors may exist for some period other than 4 or 8 years previous, but this was not investigated further at this time. Numerous factors, mainly various combinations of stream flow data, were correlated with the size of the commercial landings of chum salmon in an attempt to determine a "predictor" of future abundance. An apparent good relationship, with b = 2.05944 (P = 01), between total chum landings and the minimum stream flow occurring between January 15 and March 20 three years previous was discovered. The regression equation obtained is y = -493.6355 + 2.05944x. The regression of the size of the commercial landings of chum salmon on three variables was computed. These three variables were: (1) minimum stream flow occurring between January 15 and March 20 three years previous; (2) highest air temperature occurring during January or February 3 years previous; and (3) the maximum stream flow occurring between November 1-10 four years previous. The regression equation obtained is y = 346.4554 + 97.3148x[subscript 1] + 66.1037x[subscript 2] — 77.8188x[subscript 3]. The probabilities attached to the results of all the regression functions which were computed are biased because of the manner in which the data were selected to obtain the best relationship. Furthermore, although an apparent good relationship was determined between minimum flows and the size of the commercial landings, it must be realized that these results have some very definite limitations to their actual values. In addition to the biased nature of the probabilities, is the fact that these results have been derived from a very limited amount of data. Also, these analyses have been based on some very important assumptions which, if not true, would almost completely invalidate the results obtained. These assumptions are: (1) catch = a constant X abundance; (2) all the fish mature at 4 years of age; (3) these data can be fitted to a linear model along with the other general assumptions about regression data; (4) fishing intensity has remained relatively constant (implied in 1); and (5) methods of recording flow data have remained consistent from year to year. Close

• 2. [Article] Age and growth study of Tillamook Bay chum salmon (Oncorhynchus keta)

  Ages were determined for 65 fish from the 1947 run and for 287 fish from the 1949 run. In 1947 the percentage composition by age was as follows: 32.3 percent 3-year-old fish, 66.2 percent 4-year-old fish, ...

  Citation × Citation Citation Abstract Copy Title: Age and growth study of Tillamook Bay chum salmon (Oncorhynchus keta) Author: Henry, Kenneth A., Oregon. Fish Commission Ages were determined for 65 fish from the 1947 run and for 287 fish from the 1949 run. In 1947 the percentage composition by age was as follows: 32.3 percent 3-year-old fish, 66.2 percent 4-year-old fish, and 1.5 percent 5-year-old fish. An approximate 95 percent confidence interval for the true proportion of 4-year-old fish was 54.7 to 77.7 percent. In 1949 the percentage composition by age was as follows: 5.2 percent 3-year-old fish, 94.4 percent 4-year-old fish, and 0.4 percent 5-year-old fish. An approximate 95 percent confidence interval for the true proportion of 4-year-old fish in 1949 was 91.7 to 97.1 percent. Sex ratios during the course of the run were computed. It appeared that during the latter part of October there were significantly more males than females in the catch. During November the number of males and females tended to be nearly equal. Finally, during the first part of December there were more females than males in the catch. Growth for the earlier ages was determined by analyzing the growth of the scales and then assuming that scale growth was proportionate to fish growth throughout life. It appeared that the greatest absolute increase in length occurred in the first year of life, and that the greatest absolute increase in weight occurred during the last year of life. Length-weight equations were computed for both the males and the females. When tested by means of a t-test, these equations proved to be significantly different. These equations are: for the males W = 0.000234 [superscript L3.19370]; for the females W = 0.000430 [superscript L 3.01479]. In comparing Tillamook Bay chum salmon with chum salmon from other localities, it was observed that chums of like age decrease in average length from south to north. Tillamook Bay chums do not follow the tendency for the percentage of younger fish to decrease from south to north. Finally, there are limitations to some of the results determined in the study because of the assumptions upon which these results are based. The principal limitation is the small amount of data available. Furthermore, the following assumptions were made, and if they were not true, they could invalidate the results obtained: (1) fish length increases in direct proportion to scale growth; (2) the samples used in this study do not represent an abnormal year and do represent the populations sampled; (3) ages of these fish can be determined from their scales; and (4) that the sexes can be determined by their external characteristics. Title: Age and growth study of Tillamook Bay chum salmon (Oncorhynchus keta) Author: Henry, Kenneth A., Oregon. Fish Commission Ages were determined for 65 fish from the 1947 run and for 287 fish from the 1949 run. In 1947 the percentage composition by age was as follows: 32.3 percent 3-year-old fish, 66.2 percent 4-year-old fish, and 1.5 percent 5-year-old fish. An approximate 95 percent confidence interval for the true proportion of 4-year-old fish was 54.7 to 77.7 percent. In 1949 the percentage composition by age was as follows: 5.2 percent 3-year-old fish, 94.4 percent 4-year-old fish, and 0.4 percent 5-year-old fish. An approximate 95 percent confidence interval for the true proportion of 4-year-old fish in 1949 was 91.7 to 97.1 percent. Sex ratios during the course of the run were computed. It appeared that during the latter part of October there were significantly more males than females in the catch. During November the number of males and females tended to be nearly equal. Finally, during the first part of December there were more females than males in the catch. Growth for the earlier ages was determined by analyzing the growth of the scales and then assuming that scale growth was proportionate to fish growth throughout life. It appeared that the greatest absolute increase in length occurred in the first year of life, and that the greatest absolute increase in weight occurred during the last year of life. Length-weight equations were computed for both the males and the females. When tested by means of a t-test, these equations proved to be significantly different. These equations are: for the males W = 0.000234 [superscript L3.19370]; for the females W = 0.000430 [superscript L 3.01479]. In comparing Tillamook Bay chum salmon with chum salmon from other localities, it was observed that chums of like age decrease in average length from south to north. Tillamook Bay chums do not follow the tendency for the percentage of younger fish to decrease from south to north. Finally, there are limitations to some of the results determined in the study because of the assumptions upon which these results are based. The principal limitation is the small amount of data available. Furthermore, the following assumptions were made, and if they were not true, they could invalidate the results obtained: (1) fish length increases in direct proportion to scale growth; (2) the samples used in this study do not represent an abnormal year and do represent the populations sampled; (3) ages of these fish can be determined from their scales; and (4) that the sexes can be determined by their external characteristics. Close