AGE, LENGTH, AND BODY WEIGHT OF SALMON CAUGHT BY JAPANESE HIGH SEAS FLEETS IN NORTH PACIFIC Marine Biological Laboratory LIBRARY n ;■■"- 2 7 1958 WOODS HOLE, MASS. SPECIAL SCIENTIFIC REPORT- FISHERIES No. 259 UNITED STATES DEPARTMENT OF THE INTERIOR FISH AND WILDLIFE SERVICE EXPLANATORY NOTE The series embodies results of investigations, usually of restiicted scope, intended to aid or direct management or utilization practices and as guides for administrative or legislative action. It is issued in limited fiuantities for official use of Federal, State or cooperating agencies and in processed form for economy and to avoid delay in pu Jiication . United States Department of the Interior, Fred A. Seaton, Secretary Fish and Wildlife Service, Amie J. Suomela, Commissioner AGE, LENGTH, AND BODY WEIGHT OF SALMON CAUGHT BY JAPANESE HIGH-SEAS FLEETS IN NORTH PACIFIC A PRELIMINARY REPORT by George Taxionaka Contribution No. 3 to research conducted with the approval of the United States Section of the International- North Pacific Fisheries Commission. The Commission, es- tablished in 1953 ^y "the International Convention for the High Seas Fisheries of the North Pacific Ocean, coordinates the research of the member nations: Japan, Canada, and the United States. The resulting investigations provide data to the Commission for use in carrying out its duties in connection with fishery conservation problems in the North Pacific Ocean- Publication of this scientific report has been approved by the United States Section of the Commission. Special Scientific Report- -Fisheries No. 259 Pacific Salmon Investigations U.S. Fish and Wildlife Service, Seattle, Washington February, 1957- ABSTRACT Data on the age composition of red salmon caught by the Japanese high-seas salmon fleets indicates the dominance of 2-year-in-ocean reds in the even years and 3-year- in-ocean reds in the odd years. The majority of the 3-year-in-ocean reds are sexually mature. Some of the 2-year-in-ocean red salmon are mature fish but the proportion of mature and immature cannot be assigned at this time. More than 75 percent of the 1957 catch of red salmon were mature fish. The majority of the 5 -year-old chum sal mon are sexually mature, while the U-year-olds represent both immature and mature fish. In 1955 the majority of the chum salmon taken by this fishery were k years old; a significant number were Immature. In 1956 the majority of the chum salmon were 5 years old and mostly mature. The pink salmon available to the f ishe ry were all mature fish. CONTENTS Page Introduction 1 Source of data 1 The data Red salmon 1 Chum salmon 2 Pink salmon 2 Conclusions 2 INTRODUCTION This report is an outline of the age composition, lengths, and weights of the Japanese high-seas catch and an in- terpretation of these data as they relate to the possible proportion of mature and immature fish contributing to their fishery. SOURCE OF DATA The age composition data for 1955, 1956, and 1957, the fork length data for 1955 and 1956, and the body weight data for 1955 were taken from the Interim Reports on Research by the Japanese Fishery Agency for 1955, 1956, and 1957- Age data for 195^ were obtained from information gathered by a U. S. Fish and Wildlife Service biologist aboard one of the Japanese motherships. Body weights for 1956 were taken from data compiled from Japanese high- seas samples sent to the Seattle laboratory of the Pacific Salmon Investigations, U.S. Fish and Wildlife Service. THE DATA Red Salmon Records to date indicate that red salmon spend a maximum of 4 years in the ocean before returning to spawn. These U-year-in-ocean reds are absent in many river systems and where they occur, their incidence is less than 1 percent of the total run or catch. As the percentage of these it-year-in-ocean reds returning to spawn is very small, and as the major spawners are 3-ysar-in-ocean reds (and even 2-year-in-oceaji reds in some areas), we must regard all k- and nearly all 3- year-in-ocean reds as mature fish, i.e., fish destined to spawn in the year caught. In some systems such as the Fraser River, normally the majority of spawners are red salmon which have spent 2 years in the ocean. The Kvichak River (Bristol Bay) had a dominance of 2-year-in-ocean reds returning to spawn in 1956. Data on the age composition of maturing reds in the river systems of the Asian continent are not available at the present time. Examination of the age composition of red salmon caught by the Japanese high- seas fleet in figure 1 (195^-57) indicates the dominance of 2-year-in-ocean reds in even years and of 3-year-in-ocean reds for odd years. The majority of the 3-year-in- ocean reds caught by the Japanese fleet in both even and odd years were undoubtedly sexually mature fish. Not all of the 2-year-in-oceaJi reds caught in the high-seas can be classified as mature fish, because some will probably remain in the ocean for another year to become the 3-ysar-in-oce£in reds. Neither can all these 2-year-in-ocean reds be classified as being immature fish because, as previously stated, in some systems the majority of spawners are fish which have spent only 2 years in the ocean (e.g., Fraser River and Kvichak River, 1956)- In table 1 the eige composition of the 1957 red salmon sampled aboard the motherships is expressed in percentages. By applying these percentages to the total red -salmon catch the catch of each age group was calculated. We may assvmie that most of the 3-year-in-ocean reds (15,100,000 fish) were mature. Twenty-four percent (i+, 700,000 2-year-in-ocean reds) represents the catch of mixed immature and mature fish in the 1957 high -seas catch. The actual percentage of immature red salmon was probably somewhat less than 2U percent. The number of 1-year-in-ocean reds taken by the Japanese in any year is insignificant. The average fork lengths (fig. 3) and average body weights (fig. ^) of red salmon sampled aboard 10 Japanese mother- ships in 1955 shows the decline in average length and average body weight during the month of August, even with a greater per- centage of 3-year-ln-ocean reds making up the total catch. The fishing area in August of 1955 is along the eastern coast of Kamchatka, and consequently until com- plete and accurate data can be obtained on the red salmon populations in the river systems of the Asian continent, no expla- nation can be given of the catch of small 3-year-in-ocean reds during August. The average fork lengths and average body weights of red salmon caught in 1956 are shown in figures 5 and 7- Chum Salmon Analagous to the 3-year-in-oceaxi reds, most of the 5 -year-old chums may be classi- fied as sexually mature fish. The 6-year- old chums returning to spawn in any given year form a small percentage of the run. The i+'year-old chums fall into the same category as the 2-year-in-oce€in reds. Depending on the system and locality, U- year-old chums do return to spawn along with 5-ysar-olds and in instances may be the dominant age group of a run. Some 3-year-old chums are sexually mature es- pecially in systems along the more southern area of the North American continent. Information on the age composition of chums in systems of the Asian continent is lacking at present. Examination of the age composition of chiun salmon caught by the Japanese high- seas fleet in 1955 and 1956 (fig. 2) indi- cates that the h- and 5 -year-old chums dominate the total chum catch. In 1955 the fishery caught a predominance of k- year-old chums, but in 1956 5 -year-old chums were dominant. Since the dominant 5 -year-old chums of 1956 were of the same brood year as the dominant U -year-old chums of the previous year, we may assiMie that most of the 5 -year-old chums caught were sexually mature fish. However, not all the U-year-old ch'jms can be classified as immature, because, depending on area of origin, many return to spawn in their fourth year. They also cannot all be mature fish; some would have to remain in the ocean for another ye?.r to becone 5- /'esr-cld fish, as in the instance above where nany U-year-old chums of 1955 remained a year in the ocean to be caught as the dominant 5 -year-old chums of 1956. Finally, not all 3-year-old chums caught in the high- seas can be classified as immature fish, although the probability that they are is great. The average fork lengths (fig. 3) and average body weights (fig. k) of chums caught in August of 1955 show a decline in both length and weight similar to that of the red salmon. Not even a tentative ex- planation of this condition is warranted at present nor of the similar decline of both chums and reds in length and weight during the period from late June to early July. The average fork lengths and weights of chum salmon caught in 1956 by the Japanese salmon fleet are shown in figures 6 and 7 • Pink Salmon All pink salmon in any system or locality return to spawn in their second year, and consequently all pink salmon taken by the fishery are mature fish. Figures 3 and k show the average fork lengths and average body weights of pink salmon caught by the Japanese in 1955- These figures show the general decrease in both length and weight of pinks from May to mid- June, and the general increase from late June to August. This decrease and increase in average fork lengths and average body weights indicates that this fishery is exploiting different populations of mature fish in its fishing movement from the eastern to the western North Pacific. The mean body weights of pink salmon caught by the Japanese in 1956 are shown in figure 7. CONCLUSIONS The majority of 3-year-in-ocean reds caught by the Japanese high-seas fishery in siny year are sexually mature fish. Tr.e 2-year- in -ocean red salmon include both immature and matui^ fish and the proportion of each cannot be assigned at this time. However, more than 75 percent of the 1957 catch of red salmon were mature fish. As the 5 -year-old chum is comparable in maturity to the 3-year-in-ocean red, and the U-year-old chum to the 2-year-in- ocean red, findings cited above also apply to the chum salmon. The data on hand do not permit ascertaining the proportion of 4-year-old chums attaining sexual maturity in the year of capture . In 1955 the majority of the chum salmon were 4-year-in-ocean type and probably contained a significant number of immature fish. In 1956 the majority of the chum salmon were 5-year-in-ocean type and mostly mature. The pink salmon which are available to the fishery are all mature fish. Table l.--Age composition of samples sind calculated age composition of Pacific red salmon catch, 1957. Samples l/ High-seas catch 2/ Caught Total number 2-year Nbr. f 3 -year Nbr. ^■ Total number Number of 2 -year Number of 3 -year May June July 3221 2969 kid 1082 99i* 13.0 25.0 33-5 2803 32i+8 1975 87.0 75.0 66.5 5,874,765 10,322,415 3,604,711 763,719 2,580,604 1,207,578 5,111,046 7,741,811 2,397A33 Total 10520 2U9U 23.7 8026 76.3 19,801,891 4,693,048 15,108,843 1/ Samples taken aboard motherships by the Japanese Fishery Agency. Data taken from INPFC Document No. II8, "Interim Report on Salmon Investigations in the North Pacific in 1957 under the Research Program of the International North Pacific Fisheries Commission." September, 1957- 2/ Japanese high-seas fishery catch data on red salmon taken from INPFC Dociiment No. 124, "I957 Salmon Catch by Japanese Mothership Fishery in Aleutian Waters, in Numbers of Fish." 150 100 50 500 250 JUNE X ^ i500r u. 1000 u. O 750 Ul I 500 ^ 250 1000 750 500 250 200r I 50 100 50 JULY I50r 100 50 AUGUST 150 100 50 MAY 1500 1000 500 2500 2000 MAY ,500 1000 JUNE 2500r 2000 1500 1000 500 500 JULY 1500 1000 500 JUNE 3ooor 2500 2000 1500 1000 JULY m 1000 AUGUST 500 AUGUST 500 2000 1500 1000 500 MAY JUNE JULY 2 3 954 2 3 2 3 OCEAN AGE 1955 1956 2 3 1957 Figure 1. — Ocean age con^^osition by months of red salmon sampled aboard Japanese motherships from 1951i to 19^7. I50r 100 50 50 X 100 50 CD I50r 2 100 50 50 100 50 MAY JUNE JULY AUGUST 3 4 5 6 AGE 1955 2000 • 1500 - MA 1000 - 500 - 2500r 2000 1500 1000 500 h 1500 1000 500 500 JUNE JULY AUGUST 3 4 5 6 1956 Figure 2. --Age composition by months of chum salmon sampled aboard Japanese motherships in 1955 and 1956. 57.6 56 55 54 53 52 51 ■ 10 I 1-20 21-31 MAY l-IO 11-20 21-30 1-10 11-20 21-31 JUNE JULY 10 11-20 21-30 AUGUST Fi gure 3. --Average fork lengths, by ten-day periods of red, chum and pink salmon sampled aboard ten Japanese motherships in 1955. 6 RED 5.0 4.0 3.0 2.0 .0 ■ 0 5.0 to i 4.0 z> o a. 3.0 z X 2.0 UJ 5: 1.0 I 0 QD 5.0 4.0 3.0 2.0 1.0 0 Average 4.5 4.6 4.7 4.5 4.4 4,2 4.3 5.0 5.2 5.0 4.2 3.8 MALES FEMALES CHUM Average 3.8 4.0 4.0 4.3 4.4 4.2 5.0 4.9 4.9 4.6 4.6 PINK Average 2.9 2.7 3.0 3.0 2.9 3.2 3.2 3.4 3.7 4.3 4.4 -t- i l-IO 11-20 21-31 1-10 11-20 21-30 J-tO 11-20 21-3! |-10 11-20 21-31 MAY JUNE JULY AUGUST Figure U. --Average body weights per ten-day periods of red, chum and pink salmon sampled aboard ten Japanese motherships in 1955. 54 r 53 51.3 2 OCEAN AGE 52.1 50.5 51.4 Average oc. UJ I- UJ I- z UJ o 52 51 50 3 OCEAN AGE 58 ^ 57 o ^ 56 g 55 54 53 52 51 ^ 55.6 57. MALES FEMALES 56.9 55.9 Average 50 MAY JUNE JULY 1 AUGUST Figure 5. — Average fork lengths by months of red salmon sampled aboard Japanese motherships, 1956. 56 54- 52 - 50 48 50.8 49.2 3 YEAR OLDS 50. 51.4 Average 56 to 54 q: III H 52 LU 2 h- 50 2 UJ o 48 z ■JC 58 H O 2 56 UJ _J 54 i«: K O 52 u. 50 58 56 54 52 50 4 YEAR OLDS 53.8 53.4 53.6 54.5 Average 5 YEAR OLDS 55.2 55.5 55.5 54.9 Averoge 6 YEAR OLDS 57.0 ^^ .Mf 57.6 58.3 Average MALES FEMALES MAY JUNE JULY AUGUST Figure 6. --Average fork lengths by months of chum salmon sampled aboard Japanese motherships in 1956. RED 5.0 4.0 3.0 2.0 4.4 4.8 5.0 4.4 4.2 5.0 4.5 1.0 0 to 5.0 Q z: o 4.0h CHUM i h 3,0 I- X CD 201- 5J 4.6 4.5 4.6 4.0 4.0 4.4 5.0 >- o o m i.ol- 0 4.0- 3.0 2.0 I ,0 i 1 h PINKS 2.7 3.3 i f- 3.3 0 i- -I- ■t- ■t- ■t- -I- ■+- ■t- i- i- -J l-IO 11-20 21-31 l-IO 11-20 21-30 1-I0 11-20 21-31 |-I0 11-20 21-30 MAY JUNE JULY AUGUST Figure 7. --Average body weights per ten-day periods of red, chum and pink salmon samples from two Japanese motherships in 1956. 10 INT.-DUP. SEC, WASH., D.C. M ." ' 0 C ■iiiii lliflii Y ,.ri. , D.c. K ; ■'oe