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3~d Meeting of the I.C.E.S. Working Group on J~a~iculture, Rrest, Franae, May 10-13, 1977. Actes de Colloques du C.N.E.X.O., 4 : 111-117.

RED SEA BREAM CULTURE IN JA~AN,

by Jire KITTAKA Scheel of Fisheries Sciences, KÏtasate University, Sanriku-cho, Iwate-ken, Japan.

ABSTRACT.

The red sea bream becomes sexually mature ~hen 3 years old. The spa~ing season ex tends trom April to June. About 100-300 matured males and females are introduced in a' large tank of 100-1,000 m3 aapacity. The floating eggs are gathered and transferred into a net cage. The optimum incubation temperature ranges from 15;Oto 17~5°C, and the optimum specifia gra­ vity is higher than 1.023. The ne~ly hatched larvae are introduced into floating tanks hanged in a large conarete tank and aultured for about 10 days. The prelarvae are released into large aonarete tanks and cultured for about 20 days. O,yster eggs, rotifers (~achionus~liaatilis), eopepods eollected by net, and nauplius of Artemia salina are used for feeding i ividuals in prelarval stage. The survival rates of prelarvae are improved in tanks ~ith abunàant propaga­ tion of uni-cellular green algae. postlarvae are transferred into net cages installed at sea and reared to jry stage for about 10-40 days. Survival rate of trY from hatching to 20 mm total length is about 3 J.

RESUME.

La daurade royale atteint Za maturit4 sexueZle ~ l'âge de 3 ans. Sa saison de ponte s'4tend d'avril d juin. 100 d 300 mâles et femelles ~ maturit4 sexuelle sont plaeAs dans un grand bassin de 100 ~ 1 000 m3• Les oeufs, qui sont p4lagiques, sont coZZectds et transfdrAs dans des cages en filet. La tempArature d'inaubation optimale est de 15,0 d 17,5 0 C, avea une densit4 sup4rieure d 1,023. Les larves venant d'4clore sont placAes dans des bacs flottants suspendus dans un grand bassin en ciment, et AlevAes ainsi pendant environ 10 jours. Les ani­ maux sont ensuite libArAs dans Zes grands bassins de ciment pour une vingtaine de jours. Ils sont nourris de larve, d'huttres, de rotif~res (Brachionus Rlicatilis), de copApodes pêchAs au filet, et de nauplius d'Artemia salina. Les taux de survte pendant 1'4levage larvaire sont am4liorAs par des ensemenaements importants en algues vertes uniaellulaires. Les post-larves sont transf4r4es dan, des aages en filet, instal14es en mer, et 4levAes jusqu'au stade juvA­ nile en 10 d 40 Jours. Le taux de survie, de 1'4cZosion au JuvAnile de l'ordre de 20 mm, avoisine 3 %.

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INTRODUCTION.

The rad sea bream, ChryBophryB major, is the most valuable marine fish in Japan. A first trial to culture it has been made at a hatchery located at Seto Inland Sea coast in

1902 (KAJIYAHA, 1937). The hatchery was soon closed because of difficulty in rearin~ the lar­ vae. Since 1960, the culture of the young yellow-tail, SerioZa quinqueradiata has become po­ pular in Seto Inland Sea area. The culture of the red sea bream did not progress until 1970.

Basic research on larval production has been carried out at the universities since 1955. KASAHARA, HlRANO and OSHIMA succeeded in rearing the larval stage of black sea bream, MYlio maaroaephaluB, in 1959 (KASAHARA et al., 1960). SHlKAMA, YA~SHITA and NISHIZUKA suc­ ceeded in rearing 22 red sea bream fry from the eggs for the first time in Japan in 1962 (YAMASHITA, 1967). These successes were achieved on an experimental scale, and therefore, further experimentation was necessary before developing mass production methods.

In 1964, KITTAKA showed effectiveness in larval production with large scale outdoor concrete tanks. He developed a method for mixed cultures of larvae and suitable food or~anisms in 200 m3 tanks (HUDINAGA and KITTAKA, 1967). In 1967, NOGUCHI observed natural spawning of cultured red sea breams in a large tank at Naruto Aquarium, Tokushima, Japan+(NOGUCHI, 1968).

Based on these'successes, research has been carried out in order to find a mass rearing method for red sea bream larvae at the hatcheries belonging to Seto Inland Sea Fish Farming Association (ANONYMOUS, 1974).

SPAWNING AND HATCHlNG.

Maturation. The red sea breams used for spawning are kapt in net cages or concrete tanks (dimensions: 10-20 m x 10 m x 5 m), for about a year or two depending on their initial ages. The red sea bream becomes sexually mature when 3 years old. lts feeding activity is dependant on temperature. Breeders are cultured in the southern part of Japan during winter. The spaw­ ning season extends from April to June, with a peak in early May.

Spawning. ,Natural spawning method is more practical method than the stripping method for obtaining fertilized egsS. Spawning begins at water temperatures of 12-13° C. A large concrete tank (water volume: about 100-1,000 m3, depth : about 2-5 m) is used for spawning. About 100-300 matured red lea bream are introducedin the tank. Male and female breeders are in equal number.

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+ The late B. n1AZU!Jas the first one to obserwnatul'aZ spaz,ming of l'ed eea brea:'! at lIiyoriya'7'K1 AquariUM. - 113 -

Spawning starts just before sunset and lasts unt!l midnight. The egg is spherical and 1.0-1.1 mm in diameter. The normal eggs float at the surface, but the dead ones sink ta the bottom. Average numbers of eggs spawned per female were recorded at 4,800POOfor 6-13 years old fishes and 270,000 for 3-4 years old fishes.

Fertilization. The rate of fertilization is hereon defined as the ratio of the floating eggs ta the total eggs. Average rate of fertilized eggs was 80 % for the younger breeders and 34 % for the older ones. Although the rate of the fertilization is very poor for the aIder bree­ ders, production of fry depends mainly on the aIder group because the number of eggs spawned per female in this group is much larger th an in the younger one.

The floating eggs are gathered into a net (mesh : 0.16 cm) by draining. They are transferred into a net cage (dimensions diameter 0.7 m x depth 0.5 m). The net cages are hanged in a concrete tànk (dimensions: 2 m x 1 m x 1 m). Number of eggs per net cage is about 120,000 - 360,000 (100-300 ml of floating egge). Fresh sea water runs around the net cage at,a rate sufficient for replacing 0.2 to 2.0 times the total water volume per hour.

Hatching. Hatching begins about 58 hours after fertilization at 15.SoC. Average hatching rate of the floating eggs is 85 % for the younger group and 55 % for the older one.

The factors affecting the hatching rate are as follows

~!E~!_E~~E~!!E~!~ : The fertilized eggs cease to develop at morula stage at 10° C. The hatching rate becomes poorer and mortality increases at 25° C. The optimum incubation temperature ranges from 15.0 ta 17.5° C.

~E~=!f!=_8!!~!Eï ,The fertilized eggs float at the water surface when its specifie gravit y is higher than 1.023. They sink under the Middle layer when the specific gravit y is Iower than 1.023. The hatching rate ia 80-98 % for the former case and 20-50 % for the latter. In the latter case, the larvae become abnormai and die.

!~!~!~!Eï_~~~_E2_~g : The effect on the hatching rates of 50 ppm silt in the water is not detectable. However a decrease in hatching rates is noticeable at 100 ppm.

~!~~!~!=!!_!~2=!! 1 lt ia important to avoid mechanical shocks such as disturbance and vibration, as much a. possible, when gathering and transferring the eggs. Aeration is also unsuitable, uniess suppl y is slight.

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REARlNG THE LARVAE.

Prelarval stage. The newly hatched larvae are introduced into floating tanks (dimensions : about 2-4 m x 2-4 m x 1.5-2 m) made of synthetic fibre clotho The floating tanks are hanged in a :3 large concrete tank (water volume: 50-200 m ).

The survival rates of prelarvae are improved in tanks with abundant propagation of uni-cellular green algae. ln order to promote the propagation of uni-cellular ~reen algae, small amounts of inorganic and organic nutrients are added into the floating tank. The optimum density of uni-cellular green algae is about 300,000 cells/ml. Slight aeration is provided by about 8 vinyl hoses (diameter : 5 mm) per floating tank.

The prelarvae are released into large concrete tanks after they have been reared for about 10 days in the floating tanks. Fertilization is also necessary in most cases. However, in case of remarkably dense propagation of uni-cellular green algae, the illumination is reduced by covering the top of the tanks and water is exchanged for fresh sea water. Aera­ tion is provided by about 30 vinyl hoses per concrete tank. The daily rate of water renewal is set to 1/4 of the total volume several days before transferring the larvae to another rearing net cage. Waste accumulated on the bottom is removed by siphoning.

The newly hatched larvae live for the initial 3 days on their yolk sac. The actual feeding begins on the 4th day after hatching, when the yolk sac is resorbed and the digestive organ is formed. Oyster eggs, rotifers (BraahionuB pZiaatiZis) , copepods collected by net, and nauplius of Artemia saZina are used for feeding individuals in prelarval stage. The feeding scheme used is shawn in figure 1.

Trash shrimp and fish Zooplankton ( collected by net) Artemia salina ( nauphusr------Rotirer ( Brachionus pllcatills) Oye ter ejlj;(f! ( fertil1'l.ed) ------

o -.--.-.--.-75~~~~D~~~~~·~t·-5~·~·~·~·-2~·O~·-·~·~·-2~·S-'~~~-3~o~~~~j5

Kind oC food No. of days aCter hatching

FIGURE 1 Food uBed for rearing red Bea bream Zarvae.

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The food value of copepods and Art?mia wal compared. 5urvival rate of larvae during the period from 23rd to 34th day after hatching wal 50 % with copepods and 15 % with Artemia. Thus copepods seem ta be a better food than Artemia. However. the species and amount of cope­ pods vary depending on location and season. lt will be necessary to establish mass culture method of copepods.

Maximal initial density of prelarvae was 25.000/m3 while the density at harvest was 2.000/m3• Average survival rate at prelarval stage was 10 %

Prelarvae hatch at 2.0-2.3 mm total length. They grow to about 6 mm total length in 20 days.

Postlarval stage. Postlarvae of red sea bream (about 6 mm in total length) are transferred into net cages installed at sea. The water depth of the large concrete tanks is decreased to 1/3 (water volume : 50 m3) before gathering the larvae in order to avoid in jury due to water current. A hose (diameter : 5 cm) is connected to the drain. The water flow of the drain is regulated to about 3-5 m3 per hour. Gathering is done from the evening to midnight.

The mortality during transfer is about 10 %. lt is higher for smaller size post­ larvae. However, the postlarvae begin to swim against the water current when la mm total length, and mortality increases again at this stage. Therefore. it is recommendable to trans­ fer the postlarvae when 8 mm total length.

Four net cages (dimensions 3 m x 3 m x 2 m) are hanged per raft (dimensions : 8 m x 8 m). Mesh of the net is 0.16 cm. The nets are cleaned every 2-3 days, and replaced every 5 to la days.

Postlarvae are cultured ta fry stage (20-30 mm total length) in the net cages for about 10-40 days. Initial density of postlarvae in the net cages is about 2.000/m3• The number of fry harvested is about 400-800/m3• Survival rate during net cage stage is about 30 %. Survival rate of fry from hatching ta 20 mm total length is about 3 %.

An example of rearing result il a8 follows 1 311,000 newly hatched larvae were placed in a tank of 50 m3• After 22 days. 109.878 p08tlarvae lurvived. The lurvival rate wa8 35.3 %. They were transferred ta 3 net cages and reared for 30 days. Total number of fry harvested was 30.521. Survival rate after transfer wal 30.4 %. Survival rate from newly hatched larvae to fry WBI about la %.

Feeding with Braahionus pZicatiZis and Artemia saZina ia preferable at the early stage of the net cages. But the main feed used during the net cage stage ia trash shrimp and fish fleeh.

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LARGE SCALE PRODUCTION METIIDD.

As long as the scale and the method of producing red sea bream larvae are limited to the above mentioned level, the mass production of larvae in the true sense will be diffi­ cult to achieve.

It was considered that the larvae of red sea bream are sensitive to the change of the environmental conditions. Therefore, rearing of the larvae was carried out in indoor tanks using filtered sea water. However, many experiments have shown that the larvae can be reared successfully in outdoor tanks using regular sea water.

An interesting experiment was carried out in an outdoor pond at Tamano in'1973. Postlarvae of red sea bream of total length 6-8 mm were released into a nursery pond (area about 500 m2 , volume: 400 m3 , and depth : about 0.8 m). Prior to the release, fertilization was applied with about 100 kg chicken manure and 30 kg soy sauce waste. Zooplankton, such as, copepods, brachyura larvae, ostracoda, polychaeta larvae and gammarus were propagated into the pond. In order to avoid a temperature increase, water was exchanged at rates of 1/8 of total volume daily and 1/4 nightly. The 'initial number of postlarvae released into the pond was 25,800. After 25 days, 4,013 fry were harvested. Survival rate was 16 %. 'The average total' length of the larvae at the beginriing andat harvest were 8.5 and 44.5 mm, respectively; Although the survival rate was not so much improved. the growth rate was much better than with net cages.

At present, several thousands m2 ponds are constructed with dikes in former sait fields, and the newly hatched larvae are released directly into the ponds, whose water is fertilized. The larvae grow to a size of 20 mm total length in about 35 days. By using this method, it becomes possible to produce several hundred thousands of fry per pond per operation.

ACKNOWLEDGEMENT.

The author wishes to express his sincere thanks to Mr. T. FURUSAWA, Seto Inland Sea Fish Farmi'ng Association, for providing information used in preparing this paper.

BIBLIOGRAPHY.

AllONYMOUS, 1974. Project team on red sea bream farming : Development of the seedling techniques of red sea bream. Data on the research st Seto Inlsnd Ses Fish Farming A~so­ cistlon, 8 : 1-51.

ImDINAGA (FUJINAGA), M. and J. KITTAKA, 1967. The large scale production of the young Kuruma prawn, Penaeus Japonicus Bate. Inform. Bull. Plankto. Jspan. Commemoration Number of Dr. Y. Matsue, 35-46.

Y"'JIY~fA, r., 1937. Red .ea bream, Sugiyamll-shoten, Tokyo. .../ ... - 117 -

KASAHARA, S., R. HIRANO and Y. OSHIMA, 1960. A study on the growth and rearing methods of the fry of black porgy, MyZio macrrooephaZu8 (Rasilewsky). Rull. Japan. Soc. Sci. Fish., 26 : 239-244.

NOGUCHI, T., 1968. On the natural spawning of red sea bream in the aquarium. Yoshoku (Aquacul­ ture), 5 : 81-85.

YAMASHltA, K., 1967. In Yogyogaku Kakuron (Fish culture science, a multidisciplinary treatise) (N. Kawamoto, Ed.), ~seisha-Koseikaku, Tokyo, 515-524. POISSONS ANADROMES ET D'EAU DOUCE

ANADROMOUS AND FRESHWA TER FINFISH