Age and Growth Study of Tillamook Bag Chum Salmon

Age and Growth Study of Tillamook Bag Chum Salmon (Oncorhynchus keta) KENNETH A. HENRY FISH COMMISSION OF OREGON Portland, Oregon Contribution No. 19 March, 1954

GEORGE Y. HARRY, JR., Editor Fish Commission Research Laboratory Route I, Box 31A CLACKAMAS, OREGON

Age and Growth Study of Tillamook Bag Chum Salmon (Oncorhynchus keta) KENNETH A. HENRY FISH COMMISSION OF OREGON Portland, Oregon Contribution No. 19 March, 1954

TABLE OF CONTENTS INTRODUCTION 5 Page BIOLOGICAL ASPECTS OF TILLAMOOK BAY CHUM SALMON 5 Methods of Collecting Data 5 Age Composition 6 Methods of analysis 6 Results 7 Sex Ratio 10 Growth as Determined by Scale Analysis 12 Methods used for growth studies 12 Growth in length 13 Growth in weight 18 Length-weight relationship 19 Comparison with Other Areas 21 SUMMARY 26 ACKNOWLEDGMENTS 26 LITERATURE CITED 27 2

LIST OF FIGURES Figure 1. Length-frequency distribution of Tillamook Bay chum salmon sampled from the landings of the c o m m e r c i a l fishery in 1949 8 Figure 2. Length-frequency distribution, by age and sex, for Tillamook Bay chum salmon sampled from the landings of the commercial fishery in 1949 9 Figure 3. Relationship between scale radius and fish length, by age and sex, for Tillamook Bay chum salmon sampled from the landings of the commercial fishery in 1949 15 Figure 4. Growth curves and annual growth increments for Tillamook Bay chum salmon sampled from the landings of the commercial fishery in 1949 (after the first year the lower points are the annual increments) 16 Figure 5. Average growth in length (L) and weight (W) upper portion of the curves and average increments of growth in length (I L) and weight (4) lower portion of the curves for Tillamook Bay chum salmon sampled from the landings of the commercial fishery in 1949; weight solid line and length dotted line 20 Figure 6. Length-weight relationship for male chum salmon from Tillamook Bay, Oregon, based on 376 fish ranging in size from 25.0 to 38.5 inches 22 Figure 7. Length-weight relationship for female chum salmon from Tillamook Bay, Oregon, based on 311 fish ranging in size from 21.5 to 32.0 inches 22 Page 3

LIST OF TABLES Table 1. Average lengths and weights for 65 chum salmon, grouped by sex and age, sampled from the landings of the commercial fishery on Tillamook Bay in 1947 (lengths in inches; weights in pounds) 7 Table 2. Average lengths and weights for 287 chum salmon, grouped by sex and age, sampled from the landings of the commercial fishery on Tillamook Bay in 1949 (lengths in inches; weights in pounds) 8 Table 3. Changes in the percentage of each year class for samples of Tillamook Bay chum salmon 10 Table 4. Sex ratio for samples of Tillamook Bay chum salmon from the landings of the commercial fishery in 1947 10 Table 5. Sex ratio for samples of Tillamook Bay chum salmon from the landings of the commercial fishery in 1949 11 Table 6. Changes in sex ratio of Tillamook Bay chum salmon sampled from the landings of the commercial fishery 11 Table 7. Calculated growth histories for Tillamook Bay chum salmon [means of scale radii (R) in arbitrary units, fork lengths of fish (L) in inches, weights of fish (W) in pounds, and yearly increments (IL) in inches and (ITV) in pounds; numbers in parentheses represent the number of fish in each category; year of capture-1949] 14 Table 8. Mean increments of calculated length (in inches) for various year-classes of Tillamook Bay chum salmon caught in 1949 17 Table 9. Variation in standard deviation of the length within ageclasses [mean lengths (L), standard deviations in length (S)] at successive annuli of 273 chum salmon sampled from commercial gill-net landings on Tillamook Bay in 1949 18 Table 10. Mean increments of calculated weight in pounds for various year-classes of Tillamook Bay chum salmon caught in 1949 20 Table 11. Comparison of lengths of age classes of commercially caught Tillamook Bay chum salmon with fish from other localities (N is the number of fish, M is mean length in inches, SD is standard deviation, Ma are males, and F are females) 23 Table 12. Percentage of age classes in samples of chum salmon from different localities 25 4 Page

Age and Growth Study of Tillamook Bay Chum Salmon (Oncorhynchus keta) KENNETH A. HENRY INTRODUCTION The biological aspects of churn salmon (Oncorhynchus iceta) have not been studied along the North American coast to as great an extent as have the biological aspects of the other species of Pacific salmon, although some work has been done in Alaska, on Puget Sound in Washington, and particularly in British Columbia. A few studies have been conducted on the chum salmon of the Columbia River, particularly a rather comprehensive report by Marr (1944) ; however, no extensive studies have been conducted on this species south of the Columbia River. A previous report on Tillamook Bay chum salmon (Henry, 1953) dealt principally with the factors affecting production and a method for predicting the size of future runs of these fish as well as a description of the commercial fishery. This present study deals with some of the biological characteristics of Tillamook Bay chum salmon. BIOLOGICAL ASPECTS OF TILLAMOOK BAY CHUM SALMON METHO OF COLLECTING DATA During the 1947 fishing season the first extensive attempt was made by biologists of the Fish Commission of Oregon to collect biological data on chum salmon in Tillamook Bay. Only a limited amount of data was gathered at that time, however, and during the 1948 fishing season the sampling of chum salmon was almost completely neglected because of expansion into other investigations and lack of personnel. During the 1949 fishing season an attempt was made to collect as much data as possible on this species, and it is primarily these 1949 data that are the basis for this study. Data from the other years have been included for a comparison wherever they have been extensive enough to do so. All these data to be discussed were collected by taking random samples of the commercial landings throughout the fishing season. These samples consisted of scale samples, length and weight measurements, and sex determinations. The data included in this study have been taken in a consistent manner in all the samples. The length was measured to the nearest half inch, from the tip of the snout to the distal end of the middle caudal ray (commonly known as fork length), by laying the fish on a measuring board with a built-in ruler. The scales were taken from the mid-lateral portion of the fish, approximately midway between the dorsal fin and the lateral line. C) Based upon portions of a thesis accepted by the Graduate School, Iowa State College, in partial fulfillment of the requirements for the degree of Master of Science. 5

Weight was measured on a spring scale to the nearest half pound. Sex was determined by inspection of the gonads during the early part of the run and by examination of external characteristics during the latter part of the run. These fish were butchered only during the early part of the run; later on they were shipped "in the round" and it was impossible to obtain absolute verification of their sex. However, during the early stages of the run the sex of many of the fish was guessed prior to butchering to gain experience, and this method proved to be very accurate. Furthermore, the sex ratios of samples of fish whose sex was guessed were compared, by means of chi-square, with the sex ratios of samples of fish that were butchered during the same period and no significant differences were found to exist. Finally, inasmuch as it was not necessary to guess the sexes of these fish until the later part of the run when the secondary sexual characteristics were much more pronounced, it is felt that this method was extremely accurate. Incidentally, this species is very pronounced in its secondary sexual characteristics, making identification of sexes reasonably simple. Methods of Analysis AGE COMPOSITION Scales have been established quite generally as a means of determining the ages of salmon, although the only known verification of this method for chum salmon in particular was some experiments conducted in British Columbia (Dr. Ferris Neave, private communication), and the scale method has been utilized in this study. Lee (1920) and Graham (1929) present quite extensive reviews of the literature on the use of scales for age determination. Sixty-five scales from fish caught in 1947 and 287 scales from fish caught in 1949 were read. These scales were prepared for analysis as dry mounts. At least two readings were made of every scale. All the readings were made without reference to length, weight, or sex of the fish. The first reading was made with a stereoscopic widefield microscope (40X). All the scales were then read a second time, without reference to the first reading, by means of a micro-projector. This projector was so arranged that the scale image produced was about 10 inches in diameter. In case of a disagreement between the two readings, which occurred in 5.1 per cent of the total scales read, the disputed scales were read a third time before reaching any decision. Scales could be arranged for analysis much faster with the microscope, and that was why it was used for the first reading. However, it was felt that the micro-projector gave a clearer picture of the scale, and it was therefore used in making any additional readings. Later an enclosed cabinet, about 4 feet high with a sheet of ground glass at the top upon which the scale image could be projected, was obtained, and the disputed scales were again analyzed, using this device. It is interesting to note that the two annuli on the scales of 3-year-old fish were quite easy to distinguish. Most of those of the 4-year-old fish were also relatively distinct, but there was one group of about 30 scales which definitely did not follow the usual pattern. These disputed scales had four very definite checks and, offhand, would appear to be from 5-year-old fish. However, the distance between the supposed second and the third annuli was unusually short; and when the distances between the circuli were graphed, they presented a rather unusual pattern for the checks. 6

These aberrant scales caused considerable annoyance, and were observed numerous times without reaching any definite conclusion. Finally, Dr. Ferris Neave and Mr. Percy Wickett of the Fisheries Research Board of Canada, who have both had considerable experience in the reading of chum scales, were kind enough to examine some of these scales. They were both of the opinion that the one check in the second year represented a "false" check and, therefore, these would be 4-year-old fish. Their personal observations were further substantiated by the fact that they have encountered similar conditions in marked chums of a known age. Designating a fish as a 4-year-old means the egg was spawned in the fall of 1945, for example, hatched in the spring of 1946, and the fish matured in the fall of 1949. Since young chum salmon migrate to salt water at a very early age, most of their growth takes place while they are in the ocean. Therefore, the growth of the fish, as calculated from an analysis of their scales, would primarily be ocean growth. Scales from 3-, 4-, and 5-year-old fish were observed. No 2-year-old fish were encountered. Length-frequency distributions were prepared for each respective category determined by a single age, sex, and date of collection. Then, in order to detect whether there were any differences in the lengths of the fish sampled at different periods during the run i.e., whether the smaller fish arrived during the early part of the run and the larger fish during the latter part of the run, or vice versa the various samples for each sex-age group were analyzed separately. An analysis of variance table with a single classification (Snedecor, 1948) and consisting of the samples of lengths collected on the different dates was then constructed for each of the sex-age groups. Next, assuming that these samples of lengths, collected on the different days for the same sex-age group, were all random samples from a normal population, the null hypothesis was proposed that they were all samples from the same normal population; and this hypothesis was tested by means of an F-test. The F-values obtained and the probabilities of obtaining such values entirely by chance were as follows: 3-year-old males, F 0.99 (P.999) ; 4-year-old males, F 0.74 (P.999) ; 4-year-old females, F 0.65 (P.999). In view of these results the null hypothesis was not rejected in any case, and the samples were condensed into one lengthfrequency distribution for each sex-age group. Results Table 1 summarizes the average length and weight data for the 1947 sampling grouped by age and sex without regard to the date of capture. Table 1. Average lengths and weights for 65 chum salmon, grouped by sex and age, sampled from the landings of the commercial fishery on Tillamook Bay in 1947 (lengths in inches; weights in pounds). Average Length Standard Deviation Average Wt Number 3-year-old 4-year-old 5-year-old Males Females Males Females Males Females 29.60 1.56 10.6 5 27.44 1.60 8.5 16 31.39 1.67 12.4 23 28.80 1.52 10.5 20 Percentage of Total 32.3 66.2 1.5 7 30.00 1

Table 2 contains the same information for the 1949 sampling. Table 2. Average lengths and weights for 287 chum salmon, grouped by sex and age, sampled from the landings of the commercial fishery on Tillamook Bay in 1949 (lengths in inches; weights in pounds). 3-year-old 4-year-old 5-year-old Males Females Males Females Males Females Average Length 27.88 25.50 30.29 27.92 28.00 Standard Deviation 1.61 0.82 1.74 0.96 Average Wt. 10.4 7.8 12.9 10.3 10.0 Number 12 3 134 137 1 Percentage of Total 5.2 94.4 0.4 Older fish were generally longer than the younger fish, and males were longer than the females of the same age. Figure 1 depicts the lengthfrequency distribution, by sex, of all churns sampled during the 1949 fishing season on Tillamook Bay. Figure 2 shows the length-frequency as a percentage of the total number of fish sampled, by age and sex, for the 1949 data. It is quite obvious from these figures that there is considerable overlapping of the lengths between the various year classes. 20-257 MALES 199 FEMALES 15 H LU (.) I 0 LU a_ 5-23 24 LENGTH IN INCHE S Figure I. Length-frequency distribution of Tillamook Bay chum salmon sampled from the landings of the commercial fishery in 1949. 8

60 3-YEAR-OLD SI=3 FEMALES 30 Z 12 0 6 A 3-YEAR-OLD N.12 MALES Li 18 12 4-YEAR- OLD N =137 FEMALES 6 12 4-YEAR-OLD N =134 MALES 6 24 25 26 27 28 29 30 31 32 33 34 35 LENGTH IN INCHES Figure 2. Length-frequency distribution, by age and sex, for Tillamook Bay chum salmon sampled from the landings of the commercial fishery in 1949. The majority (66.2 per cent) of the fish sampled in 1947 were 4-yearold fish; 32.3 per cent of the total were 3-year-old fish; and 1.5 per cent of the total were 5-year-old fish (Table 1). Assuming that the ages were actually samples from a multinomial population and using large sample theory, an approximate 95 per cent confidence interval was calculated for the true percentage for the 4-year-old fish. This interval was from 54.7 to 77.7, which indicates that one would be approximately 95 per cent confident that the true percentage of 4-year-old fish lies between these extremes. In 1949 an even greater majority of the fish sampled were 4-year-old fish; that year 94.4 per cent of the total were 4-year-old fish, 5.2 per cent of the total were 3-year-old fish, and 0.4 per cent of the total were 5-year-old fish (Table 2). An approximate 95 per cent confidence interval for the true percentage of the 4-year-old fish was from 91.7 to 97.1. A preliminary analysis of approximately one thousand scales taken from fish sampled during the 1950 run has shown that well over 90 per cent of the fish sampled that year were 4-year-old fish. Table 3 lists the changes in the percentage of each year class during the. course of the run for the 1947 and 1949 samples. The data have been grouped into 2-week periods to give a more uniform distribution. There was not a large enough sample. obtained in 1947 to show much of a definite trend, although the results obtained are statistically significant when tested by means of chi-square. It appears that the older fish appeared later in the run. Again for the 1949 data there is a tendency for the percentage of the 9

older fish to increase later on in the run, although the results are not statistically significant. This does not quite agree with Marr's work (1944, p. 171) in that he believed that the reason there was a predominance of males early in the run was because the older fish, the majority of which were males, appeared earlier in the season. However, Marr's result was for the Columbia River which may not be exactly comparable to the coastal streams in the Tillamook Bay area. Table 3. Changes in the percentage of each year class for samples of Tillamook Bay chum salmon. 3-year Number of Fish Thtal Percentage 4-year 1947 Nov. 27-Dec. 9 20 32 Dec. 10-23 1 11 1949 Oct. 16-29 4 40 Oct. 30-Nov. 12 2 47 Nov. 13-26 9 184 5-year Number 3-year 4-year 5-year 52 38.5 61.5 1 13 7.7 84.6 7.7 1 45 8.9 88.9 2.2 49 4.1 95.9 193 4.7 95.3 SEX RATIO Table 4 lists the sex ratio during a portion of the 1947 run, and Table 5 lists the same information for the 1949 run. The 1947 data are quite limited as to range of time, being restricted to the last few days of the fishing season, and therefore do not give a picture for the entire run. For the 1949 data (Table 5) a more extensive coverage was obtained. In Table 5 there is a continual decrease in the value of the ratio of males to females throughout the run, indicating that the samples contained a greater percentage of females as the run progressed. This ratio was 1.04 males for every female for the combined samples. The null hypothesis that there were equal numbers of males and females in the combined samples was tested by means of chi-square. Chi-square and P values were 0.055 and 0.8122 respectively, so the null hypothesis was not rejected. Table 4. Sex ratio for samples of Tillamook Bay chum salmon from the landings of the commercial fishery in 1947. 3-year-old 4-year-old 5-year-old Sums of All Ages Males Females Males Females Males Females Males Females Totals MillFP Dec. 1 3 5 4 4 7 9 16 0.77 Dec. 2 1 8 10 7 11 15 26 0.73 Dec. 3 1 2 4 3 5 5 10 1.00 Dec. 10 1 5 6 1 5 8 13 0.63 Totals 5 16 23 20 1 28 37 65 0.76 Percent of Grand Total 7.7 24.6 35.4 30.8 1.5 AIMFF 0.31 1.15 10

Table 5. Sex ratio for samples of Tillamook Bay chum salmon from the landings of the commercial fishery in 1949. 3-year-old 4-year-old 5-year-old Sums of All Ages Males Females Males Females Males Females Males Females Totals MMF? Oct. 20 4 4... 4 Oct. 26 2 9 4 11 4 15 2.75 Oct. 27 2 17 6 1 19 7 26 2.71 Nov. 1 2 29 18 31 18 49 1.72 Nov. 13 2 1 50 66 52 67 119 0.78 Nov. 25 4 2 25 43 29 45 74 0.64 Totals 12 3 134 137 1 146 141 287 1.04 Percent of Grand Total 4.2 1.0 46.7 47.8 0.3 M-MFF 4.00 0.98 Although the sex ratio for the entire sample did not depart significantly from the hypothetical ratio of 1:1, there were significant differences at various times throughout the course of the run. Table 6 lists the changes in the sex ratio for the 1947, 1948, and 1949 data. The data have again been grouped into 2-week periods. It will be noted that for all 3 years there was a tendency for the ratio of males to females to decrease as the run progressed, and also that each year the trend of the ratios was quite similar. The latest sample was obtained in December of 1947; this sample also had the lowest ratio of males to females. Table 6. Changes in sex ratio of Tillamook Bay chum salmon sampled from the landings of the commercial fishery. Males Females N Per cent Females MMFF Adjusted Chi-square 1947 Nov. 27-Dec. 9 30 40 70 57.1 0.75 1.152 0.282 Dec. 10-23 5 8 13 61.5 0.63 0.308 0.579 1948 Oct. 16-29 14 2 16 12.5 7.00 7.825 0.006 Oct. 30-Nov. 12 40 22 62 35.5 1.82 4.661 0.031 Nov. 27-Dec. 9 43 57 100 57.0 0.75 1.690 0.194 1949 Oct. 16-29 47 19 66 28.8 2.47 11.046 0.001 Oct. 30-Nov. 12 31 18 49 36.7 1.72 2.939 0.086 Nov. 13-26 179 162 341 47.5 1.10 0.751 0.386 These various ratios were then tested, by means of an adjusted chisquare, against a hypothetical ratio of 1:1 (Table 6). It is apparent that during the latter part of October there were significantly more males than females in the catch. During November the percentage of females in the catch tended to increase, and the ratio of males to females no longer differed significantly from the hypothetical 1:1. Finally, during the early part of December, which was the latest any sampling was done, although the ratio of males to females still did not depart significantly from the 1:1 hypothesis, the percentage of females comprising the catch had continued to increase. It may well be that if later December samples were available, they would indicate significantly more females than males. 11

GROWTH AS DETERMINED BY SCALE ANALYSIS Methods Used for Growth Studies In addition to obtaining age determinations from the scale samples, it was possible to use the scales to obtain data for the determination of the growth rates of the Tillamook Bay chum salmon. The approximate position of the center of the projected scale was marked on a piece of paper and then the distance from the center to the outer edge of each year's growth was measured, using the same degree of magnification for all the scales. The units of measurement were actually millimeters, although they may be considered as arbitrary units for this particular study. The measurements were made as consistently as possible along a line slightly to the right of a perpendicular to the axis formed by the juncture of the exposed and unexposed portions of the scale. This same region was used in all the scales to eliminate any variation that might arise from measuring the radii without regard to a particular region of the scales. It would perhaps have been better to have measured the scales along the exact anterior-posterior, line, but for many of the scales examined it was not possible to distinguish exact location of the annuli in that particular region. This difficulty was not encountered in the area of the scale selected. All the scales used were taken from the same general area of the body. In 14 of the 287 scales examined the edges were so badly damaged as to make their exact measurement doubtful, so these scales were eliminated from this phase of this study. Also, particular attention was paid to the possibility of any absorption of the scales. If this did occur and was not noted, erroneous results would be obtained. There appeared to be some absorption, but only to a very slight degree; and where this occurred, it appeared to consist primarily of the obliteration of a few of the terminal circuli, the outer edge of the scale itself remaining intact. These data were utilized to calculate the length of the fish at the end of any given year by the assumption that scale growth is proportional to fish growth throughout life, a method originated by Dahl (1911). That is, R t : L t Lx, where R t = the total radius of the scale, L t = the tot al length of the fish at capture, and R a, and L, the radius of the scale and the length of the fish, respectively, at the end of any given year's growth. If this relationship holds true, it is apparent that the length of the fish at the end of any given year can be calculated from the other three known measurements. Since this relationship was first established, numerous fishery biologists have demonstrated for many different species of fish that for practical purposes this simple relationship may be utilized to determine the length at the end of any given year. The assumption that scale growth is proportional to fish growth includes the assumption that the scales start to grow as soon as the fish is formed. However, the scales do not appear until after the fish has obtained some length. Furthermore, in the early life of the fish the scales tend to grow slightly faster in relation to the length of the fish than later on. This has been demonstrated for sockeye salmon (0. nerka) by Dunlop (1924), for rock bass (Ambloplites rupestris) by Hile (1941), for rainbow trout (Salmo gairdnerii) by Mottley (1942), for herring 12

(Clupea sp.) by Meek (1916), for yellow perch (Perca flavescens) by Hile and Jobes (1941), and for many other fishes by other investigators. Numerous investigators have made various corrections to the above simple relationship to allow for this factor of the scales being formed after the fish has started to grow. Fraser (1916) determined that the simple formula tended to underestimate the length at the earlier ages because the scales were not formed until after hatching. Therefore, he modified the above formula to R t: Lt Ls= Lx L s, where Ls the length of the fish at the time the scale was formed. However, Dunlop (1924, p. 7) found for sockeye salmon that this modification tended to over-correct because of the initial more rapid growth of the scale. Marr (1944, p. 165), working with chum salmon, after analyzing the results obtained by using various correction factors, determined that for practical purposes the simple uncorrected ratio gave satisfactory results. If a very thorough growth study is to be made by this method, the exact relationship should be determined for whatever species is being investigated, as was done for the rock bass by Hue (1941). However, such extensive investigations usually have their greatest value in the study of more sedentary fish populations, particularly those of fresh water fishes. Furthermore, all that was desired in this study was to obtain a general idea of the relative growth of these fish during their life in the ocean, and any slight deviations from the simple ratio would not materially affect the general results desired and would not warrant the added computations involved in using correction factors. In view of the above facts it was felt that the simple ratio formula would give sufficiently satisfactory results for this particular study; therefore, the ratio R t : L t = R x: Lx has been used throughout this paper. It must be realized that the, growth obtained for the earlier years applies only to those fish sampled. It may be that there was some selectivity; e.g., faster growing fish maturing at an earlier age, and therefore the growth obtained here would not be representative for the entire year class. A comparison between the growth of the 3-year-old fish taken in 1947, the 4-yearold fish taken in 1948, and the 5-year-fish taken in 1949 would tend to clarify this problem, but data are not available for the 1948 fish. Growth in Length The amount the scale grew each year was determined for each individual fish. Then, using the ratio mentioned above, where the length of the fish was assumed to increase in direct proportion to the growth of the scale, the length of the fish at the end of each year's growth was calculated. The mean of the scale radius measurements to each annulus and the mean of the calculated fish lengths for each year of life were calculated for each sex-age group, and these results are listed in Table 7. For example, the 129 fouryear-old females at the end of the third year of their life had scales with an average radius of 27.9 units, the fish averaged 23.2 inches in length, and the increment of length for the third year was 4.0 inches. 13

Table 7. Calculated growth histories for Tillamook Bay chum salmon [means of scale radii (R) in arbitrary units, fork lengths of fish (L) in inches, weights of fish (W) in pounds, and yearly increments (IL) in inches and ( w) in pounds; numbers in parentheses represent the number of fish in each category; year of capture-1949]. Year Class ' Age Females Males R - L IL W Iw R L IL W Iw (1) 1 11.1 9.3 9.3 0.4 0.4 I 2 20.6 17.2 7.9 2.2 1.8 9 3 25.8 21.6 4.4 4.5 2.3 4 4 30.1 25.2 3.6 7.0 2.5 4 5 33.5 28.0 2.8 9.9 2.9 (129) (128) 1 1 13.9 11.7 11.7 0.7 0.7 13.7 11.9 11.9 0.6 0.6 9 2 22.9 19.2 7.5 3.2 2.5 22.7 19.6 7.7 3.2 2.6 4 3 27.9 23.2 4.0 5.7 2.5 28.1 24.4 4.8 6.4 3.2 5 4 33.3 27.9 4.7 10.2 4.5 34.9 30.3 5.9 13.0 6.6 1 (3) (12) 9 1 13.3 11.8 11.8 0.7 0.7 14.2 12.2 12.2 0.7 0.7 4 2 21.7 19.3 7.5 3.3 2.6 23.8 20.5 8.3 3.7 3.0 6 3 28.8 25.5 6.2 7.8 4.5 32.4 27.9 7.4 10.4 6.7 The relationship between the mean of the scale radius measurements to each annulus and the length of the fish are depicted in Figure 3. The 4- year-old fish were the only ones present in sufficient numbers to lend any credence to the results. Notice that the values of this relationship are higher for the 4-year-old females than for the 4-year-old males. In order to determine the significance of this difference, the ratio RL (total scale radiustotal fish length) was determined for each fish, and RL frequency distributions were computed for the 4-year-old males and females. The mean and standard deviation for these RL distributions were for 4-year-old males 115.59 and 10.42, and for the 4-year-old females 120.96 and 10.13. These values were also computed for the other sex-age groups, but the numbers of fish involved were so small in each case that the statistics obtained should be treated with considerable caution. Nevertheless. the mean and the standard deviation were for the 3-year-old males 116.42 and 14.04, and for the 3-year-old females 113.00 and 12.49. The RL distributions for the 4-year-old fish closely approximated normal curves, so normal theory was used in analyzing them. Assuming that these ratio values represented random samples from a normal population and that the variances were equal, the null hypothesis was proposed that there was no difference between the means of the RL distributions for the 4-year-old males and for the 4-year-old females. This hypothesis was tested by means of a t-test. The value obtained was t - 4.25 (P<.01). This indicated that a significant difference existed between the two distributions. On this basis, the null hypothesis was rejected and the various sex-age categories were retained separately. The fact that the ratio of RL is significantly higher for the females than for the males (at least for the 4-year-old fish) may be interpreted as an 14

35- (f) z 30 -FIRST YEAR -SECOND YE AR Ø-THIRD YEAR a-fourth YE AR c.-fifth YEAR U CZ I-- 25- cf) et f, z U) 20 w -------3- YEAR-OLD --3 -YEAR -OLD 4-YEAR-OLD 4-YEAR-OLD AR -- OLD MALES FE M ALES MALES FEMALES FE MALE 15- I 0 12 14 16 18 20 22 24 26 28 30 LENGTH IN INCHES Figure 3. Relationship between scale radius and fish length, by age and sex, for Tillamook Bay chum salmon sampled from the landings of the commercial fishery in 1949. indication of the greater modification of the sexually mature males. The male chum salmon is distinguished by its elongate snout and canine teeth, probably more so than any of the other species of salmon. Pentegoff, Mentoff, and Kurnaid (1928), who studied the chum salmon spawning migration in the Amur River of Siberia, state: "Length of head in males increased a maximum of 1.26 times; at death it was 1.11 times (average) longer than at the beginning of the migration. Length of head of females increased 1.15 times (maximum) ; at death it was 1.07 times longer than at the beginning of the migration." The length of the migration of the chum salmon in the Amur River is considerably longer than it is for Tillamook Bay, so the two migrations 15

are not directly comparable. However, the basic tendencies are probably the same in both places. Relatively more elongation in the snout and jaws of males would produce greater length measurements for these fish, thereby lowering the ratio of scale radius to fish length. As stated above, the 4- year-old fish were the only ones which were present in sufficient numbers so that definite conclusions could be derived. In. Figure 4 are depicted the growth curves, in length, for the sex-age groups in 1949. Table 8 lists the annual mean increments of growth in length by year for each year class of chum salmon sampled in 1949. The diagonal lines combine increments of growth for the same year of life for the different year classes. The 1944 year class would be the progeny of those fish which spawned in the fall of 1944, and naturally 1945 would be their first season of growth. Likewise, the 1945 year class would be the progeny of those fish which spawned in the fall of 1945, and 1946 would be 25- ----- 3-YEAR-OLD -- 3-YEAR-OLD 4-YEAR-OLD 4-Y EAR - OLD 5-YEAR OLD MALES F E M ALES MALES FEMALES FEMALE AGE IN YEARS Figure 4. Growth curves and annual growth increments for Tillamook Bay chum salmon sampled from the landings of the commercial fishery in 1949 (after the first year the lower points are the annual increments). 16

their first season of growth. Therefore, the first two diagonal lines enclose the increments of growth attained by the different year classes in the first year of their life. From Table 8 it is readily evident that the fish sampled Table 8. Mean increments of calculated length (in inches) for various year-classes of Tillamook Bay chum salmon caught in 1949. Year Season Year of Class 1945 1945 1947 1948 1949 Life 1944 1945 1946 Percales Males Year Class 1945 1946 Year of Life 4th 3rd 2nd 1st apparently had their greatest increment of growth in length, based on an analysis of scale growth, during their first growing season. Then, with only two exceptions, the mean increment decreased throughout the life of the fish. An indication of growth compensation was also apparent, at least for the fish that were sampled. Under the assumption that the length at the end of the first year's growth and the lengths at the end of the second year's growth, for each sex-age group, are random samples from a normal bivariate population, an estimate of the population correlation P was computed by means of the statistic r. For the 12 three-year-old males the value of r was 0.583, which has a probability of less than 5 per cent of occurring by chance alone under the null hypothesis that P = 0. For 128 four-year-old males the value of r was 0.237 (P<.01) for 129 four-year-old females r was 0.394 (P.01). These results indicate that those fish which grew faster in the first year tended to grow slower in the second. Another phase of growth which is of interest is the variation in length within the different age classes. Table 9 lists the mean lengths and standard deviations at the end of each year's growth for the different sex-age groups. Thus, the 3-year-old females averaged 11.8 inches at the end of their first year of growth with a standard deviation of 0.72. Consideration of the variation in length within individual sex-age groups represented in this sample should give a rough idea of the variation to be expected with this species. 17

The standard deviations tend to increase with length for both the males and females, and for all age classes in most instances. The standard deviation also appears to increase with length proportionately faster with the males than it does with the females. Table 9. Variation in standard deviation of the length within age-classes [mean lengths (L), standard deviations in length (S) 1 at successive annuli of 273 chum salmon sampled from commercial gill-net landings on Tillamook Bay in 1949. Age Number Mean length 3 3 25.5 Females 4 129 27.9 5 1 28.0 3 12 27.9 Males 4 128 30.3 Annulus 1St L 11.8 11.7 9.3 12.2 11.9 S 0.72 0.85 1.13 0.88 2nd L 19.3 19.2 17.2 20.5 19.6 S 0.70 0.95 1.18 1.38 3rd L 25.5 23.2 21.6 27.9 24.4 S 0.87 1,06 1.62 1.77 4th L 27.9 25.2 30.3 S 0.95 1.72 5th L 28.0 S The standard deviations listed in Table 9 would not be reliable estimates of the true variation occurring in the population if they were computed from a sample which was not representative of the population. Note that the standard deviations of the 3-year-old fish are generally less than those of the 4-year-old fish when compared at the same annulus (for example, when 2 years old, the standard deviation was 0.70 for the females maturing as 3-year-olds, and 0.95 for those maturing as 4-year-olds). This indicates that the range in size is not as great for the 3-year-old fish as it is for the 4-year-old fish. Incomplete sampling of the 3-year-old fish could cause such a phenomenon, particularly if only the larger 3-year-old fish were sampled as may be the case because of the selective nature of the gill-net gear. This also could occur if only the larger, or smaller, of the chum salmon matured as 3-year-old fish. There appears to be some indication for the 4-year-old fish that the standard deviations in length for the mature fish are actually smaller than those calculated for the same fish when they were 1 year younger. This may be caused by either the size range narrowing because of a diminished growth rate of the faster growing fish, or the selective fishing gear catching only certain sizes. Apparently the 3-year-old fish do not experience these phenomena, although the evidence is by no means conclusive because of the small number of fish involved. The variance of S 2 is 2c 4 (f = degrees of freedom for S2). Growth in Weight There is another phase of growth, growth in weight, which is also of interest and is probably more important than growth in length. The weight of an individual fish is subject to variation because of reproductive and nutritional conditions, so that an accurate analysis of growth in weight 18

is difficult to attain. However, growth in weight is certainly a more fundamental measure of the growth of a fish than is growth in length. Growth in weight for the earlier ages of these fish may also be studied as a consequence of an analysis of their scale growth. The growth in length at the earlier ages was determined by assuming that growth in fish length was in direct proportion to scale growth. After the lengths of the fish at the end of each year's growth had been calculated by the ratio method, the weight of the fish at each calculated length was computed by means of the appropriate length-weight equation (page 21). The fish were then grouped by half-inch intervals, and an average weight was calculated for each group. Weights were calculated to the nearest 0.1 of a pound. The computed weights were substituted in place of the computed lengths at the end of each year's growth. The mean of these weights and the annual increments in growth are shown in Table 7. The final values listed in this table for the mean of the length and weight, respectively, are averages of the actual values obtained at the time of sampling. On streams where fish have long distances to migrate after passing the fishery, such as the Yukon River, they might undergo more change in length because of the longer time available for the secondary sexual characteristics (such as elongation of snout) to develop, and also they might lose more weight because of cessation of feeding. However, the Tillamook Bay fish are almost on the spawning grounds at the time of capture, and they should have completed most changes in length and weight which may take place prior to spawning. In Table 10 are listed the annual increments of growth in weight by year class. The diagonal lines group together increments of growth for the same year of life in a manner similar to that explained for Table 8. In this table it will be seen that the greatest absolute increase in weight occurred in the last year of life; the greatest absolute increase in length took place in the first year of life. Figure 5 depicts the average growth curves, in length and weight, for the different sex-age groups along with the annual increments. These results are based on three 3-year-old females, 12 three-year-old males, 129 four-year-old females, 128 four-year-old males, and one 5-year-old female. One possible source of error in this particular phase of the study is the fact that the length-weight equations (page 21) were calculated for a certain size range of fish for both sexes. Consequently, in order to determine weights for fish of sizes smaller than those which were sampled, it was necessary to extrapolate beyond the sample range. However, there is no evidence that the length-weight relationship for the smaller fish differs to any great extent from that for the larger fish, and it is not believed that any important error has been introduced by this extrapolation. Length-Weight Relationship In the computations for the length-weight relationship, the usual formula W = al" -vas used. In this formula W is the weight of the fish in pounds, a is a constant to be determined, L is the length of the fish in inches, and b is a number to be determined. By using a logarithmic transformation (a linear relationship resulted when data were plotted on logarithmic paper) 19

Table 10. Mean increments of calculated weight in pounds for various year-classes of Tillamook Bay chum salmon caught in 1949. Females Year Class 1944 0.4 1.8 2.3 1945 1946 Season 1945 1946 1947 1948 1949 0.7 2.5 2.5 2.9 2.5 4 5 2.6 4.5 Year of Life 5th 4th 3rd 2nd 1st Year Class Males Season 1946 1947 1948 1949 Year of Life 1945 06 2.6 3:2 6.6 1946 0.7 3.0 6:7 4th 3rd 2nd 1st 30 (f) w M20 z z w _J 0 3-YEAR-OLD FEMALES I - 1_, < \-.IL e e e e -I... 3-YEAR-OLD MALES <. \ e ( 4-YEAR-OLD FEMALES. I e ee e e i - 4-YEAR-OLD MALES I i ( e \ e e \ 4. 5-YEAR-OLD FEMALE e, e 15 m -4 z 5C Cf) 2 3 I 2 3 4 3 4 I 2 3 4 5 AGE IN YEARS Figure 5. Average growth in length (L) and weight (W) upper portion of the curves and average increments of growth in length (I L ) and weight (1 w ) lower portion of the curves for Tillamook Bay chum salmon sampled from the landings of the commercial fishery in 1949; weight solid line and length dotted line. 20

this formula may be written as log W = log a + b x log L. Using the general linear model 31x ei where log W = yi, log L = X log a fib, a parameter to be determined b = 0,, a parameter to be determined = deviation of actual yield from true yield along with the assumption that the observations y are expressible as linear functions of known variables x1,, xn with residual errors which are normally and independently distributed with zero mean and constant variance, the estimates of the parameters may be obtained by the method of least squares. Although the term q in the above mathematical model does not enter into the actual computations, it is in accordance with statistical theory that the existence of such a source of error be recognized. This deviation is caused by the use of a particular experimental unit and the fact that the observations are subject to environmental and other uncontrolled causes of variation. Inasmuch as there was so much overlapping of lengths among the various age classes, they were all combined to make one distribution for each sex. Data were available for 376 males ranging in size from 25.0 to 38.5 inches, and for 311 females ranging in size from 21.5 to 32.0 inches. The regression coefficient (b) for the 376 males proved to be 3.1937 with a standard error of 0.02761; for the 311 females the regression coefficient was 3.0148 and the standard error 0.0338. Under the null hypothesis that the regression coefficient for the males equalled that for the females, the two computed values of b were compared by means of a t-test (Fisher, 1948) The t-value obtained was 5.818 (P<.01). In view of this significant result, the null hypothesis was rejected and the data for the two sexes were treated separately. The length-weight relationship for the males is shown in Figure 6. The equation of the curve is log W -3.6313 + 3.1937 log L. The same information for the females is shown in Figure 7. The equation of this curve is log W = -3.3667 ± 3.0148 log L. The curves in both these figures have been drawn through points calculated from the above equation. The points in these figures are avera ge values and they were weighted by the frequencies in computing the length-weight equations. The average length and the average weight for all the sex-age groups for the 1947 and 1949 samples are given in Tables 1 and 2 respectively. The older fish were generally longer and heavier, and the males were longer and heavier than the females for each respective age class. COMPARISON WITH OTHER AREAS In Table 11 are listed average length data by age and sex for chum salmon from various locations along the coast. These data, with the exception of the data for the Tillamook Bay chums, have been reproduced from Marr's report (1944, p. 173) on the Columbia River chums. There are several possible sources of variation among these results: (1) some of the samples covered only a small portion of the run while others covered the main portion; (2) some of the samples may have been taken from discrete populations successively passing a given location; (3) the data cover a period of 33 years and many different localities, and may reflect varying oceanographic conditions such as temperature or abundance of food; (4) the different samples were gathered at varying distances from the 21

25- v7 0 z 020 0 z H 15-10 15 20 25 30 35 40 LENGTH IN INCHES Figure 6. Length-weight relationship for male chum salmon from Tillamook Bay, Oregon, based or 376 fish ranging in size from 25.0 to 38.5 inches. 10 15 20 25 30 35 40 LENGTH IN INCHES Figure 7. Length-weight relationship for female chum salmon from Tillamook Bay, Oregon, based on. 311 fish ranging in size from 21.5 to 32.0 inches. 22

spawning grounds; and (5) the different samples were undoubtedly taken with different types of fishing gear such as purse-seine and gill-net. The fishery on Tillamook Bay is carried on entirely by gill-net, probably the most selective type of salmon gear used anywhere in that certain mesh sizes will efficiently catch only certain sizes of fish. In analyzing the data contained in Table 11 it will be seen that the tendency, as noted by Marr, for the average length of each sex-age group to decrease from south to north is further substantiated by the data from Tillamook Bay. The 3-year-old fish were not obtained in sufficient quantities to give adequate and dependable results, but those fish sampled in 1947 Table 11. Comparison of lengths of age classes of commercially caught Tillamook Bay chum salmon with fish from other localities (N is the number of fish, M is mean length in, inches, SD is standard deviation, Ma are males, and F are females).0 Source Tillamook Bay, Nov. N 13-Dec. 3, 1947 SD 2-year 3-year 4-year 11,' a Ma Ma F 5 16 23 20 29.6 27.44 31.39 28.80 1.56 1.60 1.67 1.52 5-year Ma 1 30.00 Tillamook Bay, Oct. 20- N Nov. 25, 1949 SD Marr (1944), Columbia N B., Oct. 13-Nov. 20, M 1914 SD ilbert (1913), Bel- N 1 lingham, Aug. 2-3, M 21 1910 SD Rounsefell & K el e z (1938), Admirality N Inlet, Oct. 10-Nov. M 11, 1935 SD Fraser (1921), Che- N mainus 1917 SD Fraser (1921), Nanai- N mo, 1917 SD raser (1921), Quali- N 1 cum, 1917 21.00 SD raser (1920), Quali- N 1 cum & Nanaimo, M Sept. 5-Oct. 7, 1916 SD 12 3 134 137 1 27.88 25.50 30.29 27.92 28.00 1.61 0.82 1.74 0.96 186 179 81 68 29.86 27.57 31.73 29.47 1.60 1.21 2.17 1.53 21 10 17 9 27.10 25.00 29.94 27.67 2.17 2.86 334 463 78 65 61 24.99 24.31 1.23 0.87 116 150 59 53 1 26.58 25.89 29.10 27.92 31.00 1.10 1.03 0.91 0.71 94 93 232 83 3 26.6 25.9 29.12 27.96 30.83 1.03 0.80 395 379 767 436 22 25.98 25.31 28.53 27.04 1.13 0.96 1.31 1.15 Gilbert (1922), Yukon N 8 7 164 141 86 42 Eiver, June 15-July M 24.00 23.00 26.42 24.43 28.24 25.66 31, 1920 SD 1.19 1.02 1.36 1.08 () This table, other than Tillamook Bay data, reproduced from Marr (1944, p. 173). 23

follow this south to north tendency. The 4-year-old fish, which were much more abundant, also follow this tendency. In the analysis of the age composition of the catch, however, Tillamook Bay departs quite markedly from the results expected on the basis of the data from the other locations. Two-year-old chums are quite rare in any of the commercial fisheries, and none have been observed from Tillamook Bay. Marr (1944, p. 176) states: "... that there is a generalized south to north trend in the relative abundance of the different age classes; the southern localities tend to have a larger percentage of younger fishes, and the northern localities to have a larger percentage of the older fishes". Pritchard (1943, p. 11) also had noted this result in his British Columbia material. However, data from a few localities along the coast are listed in Table 12, and from these it will be noted that the Tillamook Bay samples do not follow this pattern. To fit this hypothesis the Tillamook Bay run should consist primarily of 3-year-old fish with possibly some 2-year-olds. In other areas these smaller fish could be captured by traps andor purse-seines, but because of the selectivity of the gill-net gear of the Tillamook Bay fishery these smaller fish would probably not be caught even if they happened to be present. However, if these smaller fish were actually most abundant, the fishermen would undoubtedly adapt their gear to catch them. There is a possibility that the samples from Tillamook Bay listed herein represent abnormal years, although there is no actual evidence of this. It appears most likely that such a trend should be considered as being of a very general nature with rather wide allowances for variation. It has been noted in other areas that the percentage composition of the age classes may vary from year to year, and this problem has been previously discussed (Henry, 1953). The extent of such variations for Tillamook Bay chum salmon will be discovered only through extensive sampling of the run for several successive years. 24

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