• t FISMUJES•4P.,t.i.204 ;01, OF CAMA ' f ic76,4 !;/.:iftl:.\0, B. C.

FISHbRIES RESEARCh BOARD OF CANADA Translation Se.ries ',M). 1064

ti Biological study on hybrids of the salmonid fishes. A note. of F1 hybrids between chum (Oncorhynchus keta) and pink salmon (Onconlynchus gorbusha)

By Toyohiko Hikita and Yosajiro Yokohira

From: Sake Masu Fukajo Kenkyu Hokoku. Scientific Reports of the Hokkaido Fish Hatchery. No. 18, pp. 57-65, 1964.

Translated by the Translation Bureau (MI) Foreign Languages Division Department of the SeCretary of Stat:-; of Canada

Fisheries Research Board of Canada Biological Station, Nanaimo, B. C.

1968

29 typescript • - J\ /L

-1-

Biological Study on Hybrids of the r» r. Salmon,id Fishes. (57)

A Note of F1 Hybrids between Chum

; :.; !,) (Oncorhynchus keta) and Pink Salmon H 1 • .• ••• *. (Oncorhynchus gorbuscha) • ) ci C•1 I. Toyohiko Rikata and Ybsajiro YOkohira - ....1 Scientific Reports of the Hokkaido Fish CI r'. Hatchery No. 18 pp. 57/—, 65 (1964 )

The hybridization between ehum and pink saimon was carried out du ring 1961 to 1963, and the hybrid • fry obtained were released from the Horonal river, Nitami Province, in spring of 1962 mid also 1963. The observations On te feature of the hyl;rid fry donc before release are 'summarized ;is follows. The • fertilization and development in reciprocal cros>,-breedings proveeded normally, the cleavage having been ahnost the same ,s those of ordinal eggs and embryos developed >bowed no abnormality-. ln such f hybridization. the survival of 0. /zeta (feinale)x 0. goelmscha (m(tle) was higher than that of 0. gothascha Uvinale)x--0. beta (male) throughout three years, having been 93.3 to 94.5 per cent in the former and in the latter 8.1.8 to 91.5 per cent, respectively. The hybrids grew with a goo.(1 rate, especially in male - ping x female chum case. When observed externally the ground coloraticin of the hybrids of 0. hela • (female)x 0. gorbuscha (male), is obviously divided into two types; namely about a half of the fry is pretty greenish blue or durk .green while the other hand is light•dark brown, and in all of ;the hybrid of 0. . gorbuscha (fernale)x 0. keta (male) is darltisli brown as seen in the normal fry of parent species. Furth- . ermore: in the former the 'parr mark along the body side tvhich are a characteristic to the chunisalmon show much variations, in some being absent as pink fry while in the other present distintly. However, in the latter all have the pztrr marks as chunl fry. Such parr eharactet; seems to vary according to the

' male parent used. The approximate number of hybrid fry released intô the . river wcru 176.600 in the first year and in the following year 149.186 were released after rearing with various foods for several . months. We except the fry released to come back successfully as abult sa:mon in several ytutrs. _ - - - -

Publication No. 178, Hokkaido Sake, Masu HatcherY4 • , -2- Translator's Note. It appears that the accurate translation of common ! • or of academic names is impossible unless it is done by a!, specialist with the actual sample in hand. The major difficulty is that, while the common name, masu", "sake", and "iwana" may be translated to English names trout, salmon, and char, respectively, these common) • names also refer to fish belonging to other species, genu's, [ 1 and family when they are used together with prefix or suffix or with adjectives composing compound namea. C •"` ••••

1.• ' • : ; The translator also noticed that the common names ■ ;•:".") • r ••••1 clearly vary depending on locality. For example, a kind of

117i masu" called "boni masu" (beni..pink) in Honshu of Japan r, ‘-•-■ _ ) is usually translated to pink trout. However, the translator r.•-, '-`1 ■ P.- 0 e.-..) does not know the identity of "beni masu" and "Karafuto ' (1.) (Saghalien) masu". After the translator referred to two authentic dictionaries, a) Japanese-English Scientific Tenms, Zoology, compliled by the Ministry of Education of Japan, published by Dainippon Tosho Publishing Co., Inc., 1956, Revised Ed. 1965, and h) Kenkyusha's New Japanese-English Dictionary, S. Katsumata, Editor in General, Kenkyusha Ltd., Tokyo 1954, the following translation waS applied. They are listed in' the order of appearance, and the translated words are the ones which appeared in the translated .article: • -3-

page Japanese Names Appeared Translated Naines 57 Sake-ka salmon family • salmonoid fishes Sake chum (Oncorhynchus keta) Karafuto masu pink salmon (Saghalien trout) (Oncorhynchus gorbuscha) Sake-rui chum class Masu-rui salmon class Iwana-rui char class Iwana-zoku char genus 58 Kawamasù river trout Sake-zoku salmon genus Yamabe see Sakura masu Biwamasu biwa trout _ Himemasu hime trout Sakura masu - sakura trout e:Yamabe (Oncorhynchus masou) . _ 59 Ginmasu silver trout (Oncorhynchus kisutch) Amemasu • rai trout (Salvelinus leu omaemts) Ito (Hucho perryi) Chika (Hypomesus japonius) Kawa yatsume . river yatsume (Lampetra japonica) Sunayatsume sand yatsume (Lanpetra reissneri) Sayori (Heniramphus sajori) Page Japanese Names Appeared Translated Names 59 Menada (Liza hematocheila) Ugui (TribolOdon hakonensis) FUkudojo (Barbatula toni) Itoyo (Gasterosteus aculeatus) Hanakajika (Cottus nozawae) Ukigori (Chaenogobius urotania) YOshinobori (Rhinogobius brun neus) Kawagarei river karei (Platichthys stellatus)

62 Hokke lockington Tara-rui cod Tara cod Madara ma cod (true cod) Suketodara Suketo cod'. -5- ,

It is very well known that even the higher ver- tebrates can produce a hybrid between different species of the same genus. The fishes which belong to the genealogi \P ally lower class in the animal kingdom produce a hybrid not only between different species but also between different genei-a. The fish hybrids can be produced with most of teleosts but rarely with selachians. The fish hybrids are produced by experimental crossine but they have also been found in nature

è--, by a number of research workers. It has been known that he

c chum and salmon class, both of which are classified to the c_ o ;1 their • • lower class fish by genealogists because of certain

—• 7 primitive physical structures and of their capabilities of • E- surviving in both fresh and salt water by quickly adapting! t:, 1-. their ecological fitness to the changing environment, have

r.:.; some other characteristically close, inter-species, intert •....-■ genera relationship. Therefore, the hybrids between the two species belonging to these classes can be obtained muCh easier than between other different species. Of the salmon

family fishes, Winge and Ditlevsen (1948) and Alm (1955) have euccessfully produced experimental hybrids of Atlantic chum,

salmon and char classes, and Inaba (1953) of river trout of char genus, and Yamabe and biwa trout of salmon genus. • Of the Pacific salmon, Fujita (1926) and Foerster (1935)

discussed morphogenesis of hybrids between various species. Hikita (1962) concluded that the hybrids between chum and ;

hime trout and between chum and pink salmon, which are closely related morphologically and ecologically, should have ex- 1 collent probability of survival. Recently Terao and Hayashinaka (1961) prepared a hybrid of hime trout of Shikotsu Lake and salmon'of Chitose River and reported that the hybrid showed excellent growth. They are feeding the in a freshwater pond and have released some to hybrid fry continuously studying their growth and lakes and ponds and ; eging, with the purpOse of improvement of the breeds by ' crossing. The crossing of pink salmon and chum has been known

to be experimentally feasible, but there SOOM to be sonie in practice as well as acedemic problems to be difficulty solved. Recently Karinine Hatchery (previously Taranhaku Hatchery Of Japan) at the west coast saghalien of U.S.S.R. is experimenting the crossing of these two species. Although we do not have detailed data of the results, the prime purpose of the study has been described by the chief of Karinin Hatchery as "This hatchery started its operation in 1954, and somehow in that year, we found only female fish of chum coming up the stream to the spawning area. We were convinced that the natural source of chum in Karinin area would be extinct if the situation was left without correction. There was only one thing that could be done to save the extinction of the fish. It was to fecundate the eggs of chum

It In Hokkaido Translator's Note. tat Transliterated (T.N.) : • s • -7-

with the spermatozoa of salmon. The work was risky but we decided to take a chance." * I • We do not have a record of releasing this particular hybrid fry to rivers. Therefore, we have experimented on crossing of chum and pink salmon that come up the Horonai River which runs into Okhotsk Sea, fed the fry for a certain period, and released.to Horonai River. We.also made detailed observations of the fry in order to accumulate the fundamental knowledge on the possible fixation of the hybrid thus produced. This report is a summary of the works carried out by us in the last three years. The authors thank Mr. Takeo Mihara, Chief of Hokkaido Salmon Trout Hatchery, Mr. Fumihiko Hayami, Assistant Chief of same, Mr. Seizo Sano, Chief of Investigation Section of sanie, and Mr. Shigehide Takeda, Chief of the Kitami Branch Station of same, for their various, useful suggestions. The authors are indebted to Mr. Toshio Sakaguchi of Atsuki Branch of Hokkaio Hatchery (previously of Horonai Branch of same), Mr. Norio Urushizaki of Fisheries Section of the Government of Soya (previously of Kitami Branch of Hokkaido Hatchery) and the members of the Capturing Group of Horonai Hatchery for their assistance in obtaining the references, catching the fish, feeding the fry, and sampling, and to the members of Otake Fisheries Association for the storage of the feed and other technical assistances.

e Naigai Fisheries News 1959 (Published November 24) Outline of Horonai River Horonai River is situated in the north-west of , Otake, Monbetsu Province, Hokkaido, and has relatively clean water running into Okhotsk Sea. The total river length is 35 km and the river has Osa river, Pankeoropirikai river, Penkeoropirikai river, Ikitaraironie river, Shyakin river; Orowen Horonai river, Nisekoomanai swamp, Ottotsu swamp and others as its branch. streams running into the main stream. Near the bank of the lower stream of the river, there are farms and pastures, and the upper stream turns gradually to a ravine, which is covered by thick, virgin shrubbery. The

- right bank of the mouth of the river is a tableland, where the villages of Horonai district are located. This plateau also oVerlooks the estuary. Since the estuary is covered by sand, the sandy beach is constantly subjected under the severe 'effàct of wind and waves, and also the direction of the river water running4nto the sea changes almost always. As there is only.% small difference of the height above the sea level even at a distance of about one km. along the river from the sea, the sea water back-flows at the full tide. There is a dam for a generating station at about :6.5 km. from the estuary and, thereforb, chum and salmon cannot reach up-stream beyond this dam. Also ; there is Horonai branch station of Hokkaido Fish

It Table .of the Rivers in Hokkaido. Documents of Hokkaido Salmon-Trout Hatchery 101, 1955. -9-

• t•

Figure 1 Map'of Horonai River.

Hatchery at about -,3 km. from the river mouth, and at 2.35km. A up-stream at the branch station , a fish capturing station that belongs to the Horonai branch station is located. The Horonai branch station is engaged in artifical hatching of three kinds of fishes of salmon genus each year.

11 or from the esturary (T.N.) -10- Thus, only the lower stream of this river is pre- sently being used for the fisheries industry. The quality of the river water is shown by the results of quantitative analysis in Table 1. Turbidity of the 'river due to à small-scale, starch powder manufacturing factory and relatively large-scale digging of pebbles is the only and the slight unfavorable effect for the fisheries in this river. Since Horonai river has relatively large numbers of chum and pink salmon coming up-stream every year, a part of the river;, down-stream at the dam, was designated as a protected area, where salmon fishes are protected for their natural breeding in 1963. Since 1962, a group of research workers have been studying the various problems related to natural breeding and spawning in this saine protected water of the river. -

Table 1

MI 6.6 • COD 6.5 ppm 151(1 15.0 * • P.Ot 0.068* U 113 * So, 8.2 * Ca 14.0 * . N1 11- N 0.02 * htte; D. * 'Matter Analysis by Mr. Hiroshi Eguchi

The fish that inhabit in or come up-stream to (59)

this river from the sea are chum (Oncorhynchus keta), - sakura trout yamabe (Oncorhynchus masou), pink salmon (Oncorhynchus gorbuscha), silver trout (Oncorhynchus kisutch), rain trout (Salvelinus leucomaenis), ito (Hucho perryi), chika (Hypomesus japonicus), river yatsume (Lampetra japonica) sand yatsume (Lampetra reissneri), sayori (Hemiramphus sajori), manacle_ (Liza hematocheila), ugui (Tribolodon hakonensis) fukudojo (Barbatula tohi), itoyo (Gasterosteus aculeatus), hanakajika (Cottus nozawae), ukigori (Chaenogobius urctania), yoshinobori (Rhinogobius brun nous), river karei (Platichthys stellatus) and others. The numbers of the captured chum and pink salmon in the Horonai river within the last twenty-six years are taken from the Hatchery Report and shown in Figure 2. Figure 2 shows that the number of captured chum is relatively large in the seven year period between 1942 (Showa 17) and 1948 (Showa 23), and became gradually smaller and it is presently somewhat stabilized. The number of captured pink salmon repeats approxi- mately in two year cycles of large and small capture, although we miss the number for 1946, and it was particularly large for the eight year period between 1951,(Showa 26) and 1958 (Showa 33), and later it.became considerably small.

-12-

. . 40117 . (.i ee• / h• ill Q o (1.r•r1)..1.. Ido i 11.14 g (r I 11.113 1 • . 0— — ,Do i'? 7 eiè.:11.,,F.tt.te î 1 \ 0 S.CIA il Ef j 4 , I 1.II 11 I '‘ I g 1 1 i 1 • g 7.t3 11 ? I g 1 1 1 , 1, ; eft • 1 1 IA i 1 • . I I 1 1 1 1 \ i .. 1.0» Ig II I I 1 -81 88 I il I I I I I 1 8 I I 1 1 s 1 . I • 1 / 1 u I 1 I 1 8 7I 18 ' I . I 4 1 / I ' / I 1 I 1 1 I !1• 1.e0 I11 l 8 n 1 1 I 1 84 I I 4 I a 1 ' f is la 1 I fa a 1 I s I li 1 4 0 i 4. e) s: I. 111 1/ 2 '1 i 18 1 • 11 % r.en t II t 1,1 05

L---1 1 117 43 a 43 41 IS 07 47 37 SIUUMUU YEARS

Figure 2

The number of Chum and Pink Salmon caught in the Horonai River in the last 26 Years.

t i -13-

Material and Method. The eggs and spermatozoa used for this study were obtained from the two species of parent fishes, which were caught in the Horonai river. Particular attention was paid in selecting the parent fish and only the eggs in full maturity were chosen from the good parent fish. Extraction of thé eggs and the fertilization were conducted by the dry introduction method which had been used in this hatchery. The fertilized, hybridized eggs were treated in the same way as the normal eggs , without uSing specially controlled hatching tanks, since the comparison of hybridized eggs ee and normal eggs could be done more conventiently when they were compared in the same hatching room. The conditions of controlling fry varied slightly from a year to another, during the three year period of experiment. In order to compare the observation results of growth of the hybridized eggs, pink salmon ( ) x chum ( ) and chum ( e ) x pink salmon' ( ), were completely isolated and handled separately. Each year, 100,000 eggs of one combination, and thus total 200,000 hybridized eggs were prepared. In the first year, the breeding of hybridized fry was conducted as a preliminary test, and the hatching and the feeding of the fry

11 Normal Egg - Fertilized egg from the 'parents of the same species. «elt Hybridized Egg - Fertilized egg from the parents of the different species. -14- were carried out under the saine conditions as those for the normal eggs, but in the second year, the fry were released after feeding under the experimental conditions. In 1961 at Kitami branch station, we conducted a set of the same experiments as were done at Horonai branch station, using four parent fish, to determine the limit (60) of possible pure water breeding of fry and to observe the morphogenetic change during their growing period.

• 'Results of Observation. The size of parent fishes used for the hybridization and their eggs. Male and female parent fish used for the hybridization were checked carefully and their size was determined. As an example, the parent fishes (male and female) used in 1962 had the size shown in table 2. The size was almost the same in 1961 and 1963. . The age distribution of the fish listed in table 2 was as follows: the four year old individuals had the largest distribution, 60.7%, the five year old 29.4%, and the three year old 19.9% in case of chum. Almost all of the pink salmon were two years old and only three of them were suspected to be three years old. The weight distribution was not investigated, but chum weighed between 2.5e,-J3.6 kg. and pink salmon 1.3, ■ 2.6 kg. -15- The size of eggs usually vary in their diameter depending on the river where they were spaWned, and also depending on the size of the parent fish that reach up-stream of the same river to spawn. These findings had already been confirmed by chum (Watanabe, 1955). The average egg diameter of chum is about 7.8 mm and that of pink salmon is around 6.0,./6.5 mm.

Table 2 Aver Total Fork age Sample . SIDecies Length Length Fork Number chum pink 53. 5-78. 0" 52. 0-76. 5" 68. 5" 51 . -klead 52. 5-67. 5 50 0-64 7 56 7 134 salmon _ i_ • . - '-----

Fertilization and hatching of the hybridized egg. (61) Since we suspected that the hybridized eggs might be weaker and more delicate than the normal, artificially fertilized eggs from the male and female of the same species, - we have paid particular caution in extraction of eggs and fertilization. The eggs after fertilization were treatecqin the same manner at storage, sterilization and other steps as for the normal eggs. were done We did not find any difference in the proceedings of the hatching between the hybridized eggs and normal eggs, às far as they were observed with naked eyes. However,

- 16 -

Kobayashi (1963) has published, in a separate article, his microscopical observation of the process of fertilization and hatching of hybridized eggs. The ratings of hatching of reciprocal, hybridized eggs are shown in table 3.

Table 3

F.A en O G) I I •

0 Pi al Ç- G) ai

n 0 0 ai CD

H >> b0 fry. te. io O 0 0 fry.

t b.0 bf) .1-1 4-4 d a d b.0 cI-1 b0 Pi 0 ra G) CD O 0 ase › O • he h

bin ;-• Q C) rd 4-.) rcl G) •,--1 tc tc ce O IUD ai g • > 1:10 le G) O 40 O 0 0 O G) 0 to Com Ha ›-■ C4 CO A '0 Ha Re g.:12.17Kx() 1961 4;1-lead sa]xmon 100, 000e1: 9, 660e. 7,00O ' 16. 66%; lee, i33. 3 1962 .100,000 6,810 1,680 • 8.49 ' 91,510 91.51 :• • ( ) 1963 100,000 9,187 8,821 18.01 81,592 81.",9 nOt C1'11.1111" ' completed .4)- chum (•) 1961 100,000 4, 990 1, 750 . 6. 74 93, 260 93.2'3 1962 100,000 3, 180 2, 290 5. 47 94, 53.) L'53 • pinrk not 6) 1963 100, 000 3,844 1, 881 5.72 1 . 91, 275 94. 28 • ..._.1_111_171tar_• :- completed

The comparison of the records of the both hybridizations

in table 3 shows that pink salmon ( e ) x chum ( t) has inférior . rating throughout the three year period than chum (g) x pink salmon ( de). The hatching record of the normal eggs, on the other hand, shows the slightly higher rating for pink ; salmon than chum, as seen in table 4. -17-

« Table 4

0 rcj 0:1 0 -g-I › cr3 0 0 rct 0 00 0) • 0 0 0 ttO cd .12b -1-D -P r-1 4-, tIO o WW o cd ›-1 - — C4 PG

1961 I 4, 950, 000 :!•' 379, 000 churn 1962 2, 420, 000 129, 500 I 2.290, 500 J 94.6 2, 270, CC:', 1963 2, 473, 000 124.200 . . . 1961 1, 400 I I , 000 111,300 i 1,368, 7. 00 1 92.5 I 1,360, ■.4.,0 . 99. ..t .-- 75 ....„ H 1962 i 1, 110,000 50, 300 1 1, 059, 700 95.5 : 1, 050. CV.) . ... • 1963 in I 1, 142, 500 82,900 I 1, 059, 600 .. 92.7

However, by the normal eggs, there is not much difference of hatching rate between the two species. Therefore, the poor rating of the eggs of pink salmon ) x chum (e) may be explained best and only by the observation, as already reported and discussed by Kobayashi (1963) in the separate

article, that the eggs of pink salmon (e. ) x chum ( ) need •••• much longer time than the reverse hybridized eggs, after fertilization until the first fission. We did not find any recognizable difference in the total hatching days between

the hybridized eggs and normal eggs. -18-

The treatmebt of the hybridized eggs after hatching was carried out in the following manner. Namely, in the first

year, as we have forcused our efforts in the production of hybrid fry, the fry were left in a breeding-pond immediately after hatching, and after absorption of their navel-sacks were completed, they were released to a river, in the saine way as the artificially fertilized eggs have been 'treated at the hatcheries in the past years. The release rates based on

the numbers of hatched fry are 99.4% for . pink salmon and 99.5%

for chum in 1961 at Horonai branch station, 'as shown in

table 4. Therefore, we assume that the same release rates held for the hybridized eggs. Calculation based on the afore- described release rates show that the numbers of the released

. fry in the first year are; the number of hatched fry 83,340

multiplied by 0.994 is equal to 82,840 for pink salmon (.?..)

x chum (s), and 93,260 x 0.995 is equal to 92,790 for chum (..c.?. ) x pink salmon (1). In the second year (1962), the two kinds of hybrid fry after hatching were moved separately

in two outdoor troughs (Figure 3) with the size of

360 cm x 160 cm x 120 cm. -The troughs were placed in a

• spring pond up-stream of the breeding pond which is currently - still being used.' During the feeding in the troughs, the comparison of the rate of growth, and external» morphological

change of the two hybrid fry was conducted. -19-

-

.e •,_ , . .

• .• .

/'

f.

• .• • Fig. 3 Outdoor trough for rearing hybrid fry in the spring pond. (Photo by Yoneka%;/a)

As the feed of fry, the liver of chum, meat of cod and lockington,codroe (eggs of ma cod and suketo cod), and vegetables were used. At the beginning, only the liver wâs used and later as the fry grew, the afore-described feed stuff was mixed and knead at a proper ratio, and used as a feed.. The feed was placed in a wire-basket suspended in the middle of each trough, and feeding was done twice a day, in the morning and in the (pirening. The seek-after-feed behavior of the fry was typically timid at first, but later as they became acquainted with their feed, they were positively after the feed. It was found that the hybrid fry of chum (g) x pink salmon (0 ) were more . active in seeking after the feed throughout the three year ' experiment than the reverse hybrid fry, and they also absorbed the navel-sack faster. The absorption of the navel-sack by -20-

both hybrid fry in 1964 is compared in table 5.

Table 5

Jan. Feb. Mar. ' 10 4 3 chum (.1- ) x pink salmon (e) ,„,,, 100,, Pink salmon ( q ) x chum ( e ) m 80

Once * the wire net of a trough which held the fry of pink salmon (1-) x chum (e) was broken, and 33,250 fry, died, and some more escaped to the spring pond. They were on April 10th, and on the same day 58,250 fry of ' caught pink salmon (..?) x chum (g) and 90,934 fry of chum (..e ) x pink salmon (i ) were released at the joint of Horonai river and a branch river Osa, which is the down stream of the breeding pond. In the third year, 1963, 81,992 fry of pink salmon (e- ) x chum ( ) and 94,275 fry of chum ) x pink salmon (e ) were hatched and they are being reared in the same feeding trough. These mayipe:releaà- ed at theend of Ma.rch, 1964, after marking each hybrid species separately so that • the ratio of completion'at maturity could be obtained. • 1n table 6, the growth of the fry which were released in 1962 • is shown.

A which year is not described, but it must be 1962 from the number of the released fry. (T.N.) -21-

Table 6

Chum (.?- ) x pink salmon ( t) Pink Salmon (e) x chum rg),

;S1 . 4) 4-) bO g 40" ef-1 0 bn 0 0 0 0 0G) c4-ig 4 W CIO 0 4 b0 b0 4 M g-4 0.-1 aS 14 0 g-t H H4 0.) H 4-1 F-1 gl) H G)

3. 3 3.46-4.20(3.76) 3.02--3.58(3.19) 12 2.84 32(5. 07) 2.38-2.75(2.56) 10 3.22 8.55-4.14(3.80) 3.06 --3.44(3.24) 10 2. 97--3. 33(3. 12) 2.35--3.05(2.62) 11 _ 4.10 3.92--4.95(4.35 3.34-4.23(3.70) 13 3.02-3. 74(3. 39) .2.50-3.10(2.85) IX Appears to be due to the limited numb ers of sampling from the trough.

The data shows that, although there is considerably (63) a large difference . in the size of individual samples measured, the fry of chum ) x pink salmon (1 ) grew as large as 1.9 times of the size on the starting day of the measuring after a 136 day period, but the reverse hybrid grew only 1.5 times in the same period. The mortaility of the hybrid fry of pink salmon (g) x chum ) was also a little higher, throughout the three year - period, than that of the reverse hybrid fry. • "*. -22-

Difference of the External, Inherited Characters of the Hybrid Fry. • The sizes of both fry are different, and that of pink salmon (4?) x chum is smaller than the other, corresponding to the smaller size of the egg of pink salmon. After the fertilization, while the deutoplasm is absorbed gradually and pigments appear, the differences of the extecnal characters of the hybrid fry become evident. First, the comparison of normal fry of chum and pink saimon reveals certain distinct differences of the species. Namely, the chUm fry have the characteristic pearl-mark of the family on the body side, but pink salmon fry do not have it, but both fry show the same ground color of brown or dark brown on the posterior body. The most remarkable differences of the hybrid fry and normal fry can be found by comparison of the body color and the pearl mark. Particularly the body color.of the fry, chum (e).x pink salmon ( 1à), show two distinctively different sets of color. One is indigo blue,— dark green.,..-green from the head to the tail, and the other, of the total hybrid fry, is 4 which is the color of the half light brown ,,,dark brown and resembles the color of the nànnal fry. On the other hand, all of the fry,.pink salmon x chum _( 6 ), have light brown—Jdark brown color. The develop- ment of the pearl-mark varies considerably by the fry,

chum (+)0 x pink salmon (C), and some fry do not developl the mark at all while other. fry show the characteristic park of chum fry, and still others develop only smaller numberà of -23- the mark or obscUre marks. In general, however, the green colored fry showed the tendency of showing no mark at all. On the other hand, all of the fry, pink salmon (e) x chum ( e), showed the pearl-mark and the mark was relatively much clearer than that of the reverse hybrid fry. Their small, black dots on the back werè also similar to those of the ' normal chum fry (Figure 4).

/

.\

0 • C.,.

4 Remarkable ft.attireA of both hybrid fry : . Ahoy, _ i nk (F P on;( 1.4 x Chtun 1..`. 1 Iklow - Chum (Female) x Pink tNt ,1 -24-

The green colored fry seemed to have a better chance of survival as the green color functions effectively as a protective color when they hide by the hydrophites in the spring pond, or later when they are released to the river. Finally, we want to reflect the reason the reason for choosing the hybrids of chum and pink salmon, the later release of the fry and the related complicated circumstances. First we chose the particular species as we intended to breed and release the fry that could live in the'ocean at a later period.. In order to . satisfy the purposes, 1) the artificially hybridized fry had to be produced from two species that have the same area of circular trip in the ocean and that come to breed to the same river, and 2) these two species must have totally or partially overlapped period of swimming up-stream in the river, or have their periods of coming up-stream close enough so that the first arrival could be saved . under co trol to meet the second for the possible hybridization. The particular advantages of choosing pink salmon and chum for hybrid formation are based on their clearly dis- tinguishable«morphological characteristics. Naffiely 1) their eggs are different in size; 2) their fry are different In size immediately after hatching, and 5) pink salmon does not have the pearl-mark which is characteristic to the family of I chum, but chum has that mark. Further, since the adult ish î of both species are distinctively different, it was expected that the adult hybrid fish from the two species might still show some different characteristic appearances in future when -25- they return to the river. We have already known that the adult fish of the two pure species have the following different characteristics when they return to the river to breed. They are: a) the posterior projection which is a secondary sexual characteristic, h) appearance of puberty color, e) ground color and spot formation, d) pigment distribution at the palate, e) the number of gills and their shapè. Besides, pink salmon attains full growth usually in two years but chum in years, and mostly in four years. The degree of the growth of their scales are also different. (64) After considering .all .the factors listed above, thé two species were chosen. The authors, at the beginning of this àtudy, expected the return of the. adult hybrids in three years to the saine river. In the autuMn of 1963, we could catch (à) two year old hybrid(s) which was strongly suspected to be the hybrid fry released in the previous year, and, therefore, the expected.probability of the return of the three year old hybrid has become better. The authors plan to pilblish the results of morphological observation of the hybrid later. Summary We report the progress of a three year study between 1961 and 1963 on the artificial reciprocal hybridization of male and female of pink salmon and chum.

1. Hatching rate of the hybrid eggs of pink

salmon ( .e. ) x c1i ) was 81.--191% which is inferior to that of normal eggs, but that of the hybrid eggs of chum (4a) x pink salmon (e ) was higher than 93%, which is almost the same of . that of normal eggs. 2. Growth of the body and the disappearance of the navel sack of the fry were . faster by the

hybrid of chum (i. ) x pink salmon ( e) than by the reverse hybrid. 3. The most distinctive chromatic .characteristic of the hybrids was that about half of the

hybrid fry of chum (41) x pink salmon ( e) had green or dark green colr which is entirely different from the color of normal fry. The pearl-mark of the hybrid fry varied considerably and it ranged from non-existant to as clear as the normal fry.. On the other hand, the hybrid 4 fry of pink salmon (-r) x chum (o ) had the same color as that of normal fry, i;_nd they also had pearl marks similar to those of chum. 4. The fry were releas6d in 1961 without feeding, but in the second and third year, they were fed 4. (Continued) in a special trough. .The fry of 1962 were kept in the trough for several months and then released at a confluence of the main- and a branch river. The 1963 fry are still under feeding, and they will receive a . different identification mark for each hybrid species and then will be released. -28-

REFERENCES

Alm, G. 1955 Artificial hybridization between different species • • of the Salmon family. Ann. Rep. Drottuningholm, 36: pp. 13-56. Disler, N.N. 1957. Development of the "Osenniaia" salmon of the Amur River. Oncorhyncus keta (Walb.). Proc. Inst. A Morf. Acad. Sel. U.S.S.R., 20: 1-70. Foerster, R.S. 1953. Interspecific cross-breeding of pacifie salmon. Trans. Roy. Soc. Canada, See y. pp. 21-33. Fujita, K. (or T) 1926. On the characteristics observed in hybrids (F1 ) of salmon and trout. Dobutsu-gaku-zasshi 38(44): 38-51 (Journal of Zoology, Japan). Hubbs, O. and K. Strewn 1957. Relative variability of hybrids between the darters, Ethcostoma spectabile and Periena caprodes. Evolution, 11 (1): pp. 1-10. 1959 Artificial production of an intergeneric Atherinid fish hybrid. Copeia, 1: pp. 80-81.

and G.E. Drawry . 1962 Artificial hybridization of Crenichthys baileyi with related Cyprinodont fishes.

s. Texas Jour. Soi. 14 (1): pp. 107-110. Kobayashi, H. 1962. Morphological and genetical observations in hybrids of some teleost fishes. I. Jour. Hokkaido Gakugei Univ., 13: pp. 1-112.

1963. Some cytological observations on hybridization in the Loach (Female)-Funa (Male) cross. Jap. Jour. Cen., 38 (2): pp. 113-122.

A This translated by Dr. N. Rumin, McGill University, Montreal, Que. -29-

1963 Morphological and genetical observations in hybrids of some telecost fishes II. Jour. Hokkaido Cakgei Univ., 14 (1): pp. 1-24. Stizuki, R. 1963. Hybridization experiments in Cyprinid fishes. Reciprocal cross between Gnathopogon clongatus elongatus and G. japonicus. Jap. Jour. Ichthy. . 10 (2-6): pp. 39-42. Terao, T. and Hayashinaka, N. 1961 Hybridization experiments of salmon and trout. Hokusui-fu-ken-ho 16: 51-65. (Scientific Reports of Hokkaio Hatchery). Watanabe, M. 1955. Some observations on salmon eggs spawn in Hokkaido. Special reference to the phyietic line based on the size of eggs. Fu-shi-ho 10 (1, 2): 7-20. (Sciehtific Reports of Hatchery). Winge, 0. and E. Ditlevsen 1948. A study on artificial hybrids between salmon (Salmo'salar) and brown trout (Salmo trutta). Comp.-rend. Lab. Ber. Physiol., 24(23): pp. 317-339.