FRESHWATER FISH CULTURE IN JAPAN

HARVEY WILLOUGHBY1

INTRODUCTION

The following observations on Japanese Fish Culture were made during field travel in Japan in the period October 20-27, 1971.

SALTWATER TROUT CULTURE

My only observation of trout culture in seawater was at Ogatsu Bay in Miyagi Prefecture. John Glude and I travelled to Ogatsu Bay in the afternoon of October 20, with Akimitsu Koganezawa, Chief of Shellfish and Fish Research for the Migayi Prefectural Station.

The principal trout culture installation was a new commercial hatchery just getting into production at Karakuwa. This is a commercial venture operated by a Fishermen's Cooperative Association. The station consists of a small hatchery building and six large circular rearing ponds. Each pond has a supply line for fresh water and one for seawater.

Each pond also is equipped with its own built-in recirculating system and filter. Since the rearing facilities were completed too late to rear fish for the current year's stocking of the rearing pens in Ogatsu Bay, the fish were to be shipped in from another location and acclimated to seawater at Karakuwa before being transferred to the seawater rearing pens. Koganezawa explained the procedure to be used as follows:

The trout are hatched in fresh water and reared in the conventional manner until they are approximately 150 g each. At this time they are separated as to sex and the females are acclimated to seawater.

The acclimatization process requires from 12-20 days. Seawater is mixed with the fresh water at a rate that increases the salinity level in the rearing pond by approximately 10% per day. At a couple of points during the acclimatization period, salinities are held static for one or more days to let the fish become adjusted to the change. Average survival is 70%. Growth in seawater is very rapid. Average size at harvest after 10-12 mo in seawater is 1.5-2.0 kg. This is approximately double the growth rate in fresh water, and the price is approximately double that of freshwater-reared fish. Sea-reared trout were commanding 600-800 yen/kg compared with the market price of 300 yen/kg for farm raised rainbow trout.

SALMON CULTURE

From October 21 to 23, I visited the Island of Hokkaido to view salmon management operations.

The organization of the Hokkaido salmon program is impressive. Overall program direction and principal research activities are conducted from the central headquarters in Sapporo. Regional field supervisors at six locations direct the field work carried on at 41 hatcheries and a number of fish collection stations.

On October 22, I visited several chum salmon (Oncorhynchus keta) hatcheries on the Tokachi River in the vicinity of Obihiro. The annual spawning run of chum salmon was in progress, and I was able to observe the seining of these fish at an irrigation dam which blocked their upstream movement. Approximately 100 million eggs were being incubated in the three hatcheries visited.

The following day, October 23, I visited the headquarters of the Hokkaido Salmon Hatchery Fisheries Agency in Sapporo where I met the Director, Ayahiko Hemmi. Later in the day, Toshinobu Tokui and I travelled to Lake Shikotsu and visited the kokanee salmon hatchery.

Kokanee salmon (O. nerka kennerlii) are native to only two lakes in Japan, both on the island of Hokkaido. They have, however, been widely transplanted and now occur in about 20 lakes. Lake Shikotsu, a large natural lake on Hokkaido, contains a population of kokanee salmon and is the site of a hatchery devoted to the propagation of the species. Because of the low mineral content and consequent low productivity, it is difficult to maintain a satisfactory commercial harvest of kokanee salmon in Lake Shikotsu without depleting the spawning population. Officials of the Hokkaido Salmon Hatchery are searching for sources of kokanee salmon eggs with which to supplement their own supply. They have requested eggs from the State of Montana, but to date have not been able to get any.

I concluded my visit to Hokkaido by touring the Chitose Hatchery where an extensive expansion project is underway. I believe this is the oldest hatchery in Hokkaido. It rears chum salmon and rainbow trout (Salmo gairdneri). The capacity of the expanded hatchery will be about 13 million eggs.

In summary, I was impressed by the sheer volume of salmon released from the hatcheries in Hokkaido. These hatcheries incubate over 500 million eggs per year. The breakdown by species is approximately 85% chum, 10% pink (Oncorhynchus gorbuscha), and about 5% masu (O. masou). The chum salmon are fed for 70-90 days and released in early spring. The return after 2 or 3 yr at sea is consistently between 1 and 2%, an excellent return figure by standards achieved at Pacific salmon hatcheries in America.

On Sunday afternoon of October 24, I visited the Tansui Fish Research Laboratory in Tokyo. Yamakawa and his staff showed me the laboratory and explained their research projects.

This is a national laboratory devoted to the problems of freshwater fish culture. Their principal work is on the diseases and nutritional problems of eels, ayu, carp, and trout. The principal investigators present during my visit were: Takeshi Nose who was working on the nutritional requirements of eels, Hiroshi Kawatsu on disease and microbiology of freshwater fishes, Shimadju on ayu culture, and Inui on hepatic diseases of eels.

I visited the Nikko Branch of the Freshwater Fish Research Laboratory, which is located on Lake Chuzenji in Nikko National Park. The Chief of this laboratory was Yoshikazu Shiraishi, who passed away during his official travel to South America in 1972.

Lake Chuzenji is one of the few publicly owned bodies of fresh water in Japan where public sport fishing is permitted. This cold-water lake contains populations of the native Japanese salmon, Oncorhynchus masou, or cherry salmon, and various exotic salmonids such as rainbow and brook trout. Scientists at the Nikko Branch of the Freshwater Fish Research Laboratory, are investigating the population dynamics, the fish movements within the lake, the characteristics of various species of salmonids, including hybrids, and the management of trout in populations in streams. The interests of Yoshikazu Shiraishi and his staff parallel those of management biologists everywhere who are charged with maximizing sport fishing yield in fresh waters.

COMMERCIAL TROUT FARMS

Accompanied by Soichiro Shirahata, biologist with the Nikko Branch of the Freshwater Fisheries Research Laboratory, I visited trout farms and fish processing plants in and around Fujinoyama City, Shizuoka Prefecture, on October 25.

The Shizuoka Prefectural hatchery and laboratory produces 30 million rainbow trout eggs annually. They make extensive use of light to control time of spawning. This management technique makes it possible to provide eggs for their customers over a period of several months. The manager, Matsuura, reported that in one instance they were able to get three spawns in 2 yr from a pond of fish by regulating the photoperiods.

Matsuura and his staffare faced with a formidable labor problem of removing dead and infertile eggs by manual means. They were quite interested in slides I showed them of a mechanical egg picker in use at the Dworshak National Fish Hatchery in Idaho.

A thriving sport fishing business is operated by the Shizuoka Prefectural Hatchery. Some 10,000 fishermen per year participate in fee fishing in a stream running through the hatchery grounds. As I understand it, the provision of sport fishing facilities is a condition of granting a commercial hatchery license in some, if not all, prefectures in Japan.

Trout farms in Shizuoka Prefecture, and I assume they are typical of Japanese trout farms in general, are as modern and effcient as any I have seen. The fish are reared in raceway-type ponds with a high rate of water exchange. The food is pelleted dry food, commercially manufactured. The chemical analysis is very close to that used in the United States and a 1.4 conversion ratio of food into fish flesh also approximates that achieved at successful hatcheries in the United States.

The Fuji Rainbow Trout Breeders Association operates a processing plant in Fujinomiya City. The association president, Watanabe, and the plant manager, S. Aoki, conducted me on a tour of the modern facility that processes 1,000 tons of rainbow trout for export each year. During my visit, trout were being packed in 5-lb packages for export to the United States.

My impression of the Japanese trout farming business is that it operates on a very low margin of profit and is successful only by virtue of its operating effciency at all levels. For example, the retail price for farm raised trout is approximately 300 yen/kg. This can be compared to the price of salmon which ranges from 550 yen/kg upward and tuna which sells at 600 yen/kg and upward.

Watanabe and his associates are quite concerned over the restrictions of our salmonid import regulations. These require certification that all salmonid fishes entering the United States from foreign countries are free of the virus causing viral hemorrhagic septicemia and Myxosoma cerebralis, the causative organism of whirling disease. I discussed these regulations with Watanabe, S. Aoki, and T. Sano, virologist at the Tokyo University of Fisheries, who serves as advisor to the Cooperative on Fish Diseases. These gentlemen feel that since neither of the two diseases in question have ever been found in Japan, our regulations requiring that certification as to disease status be based upon specified sampling and analytical procedures, places an unnecessary hardship on exporters. After reviewing their problem and discussing it with our own experts in the United States, it appears that Sano and the disease technicians at the prefectural laboratory had misinterpreted our instructions and were indeed performing more laborious inspections than required. I have attempted to clarify these points by letter since my return to the United States.

EEL CULTURE

Eels, Anguilla japonica, are an important species in Japanese freshwater fish culture. They command premium prices at all times. For example, in 1969, when the production in Shizuoka Prefecture was 15,000 tons, the price ranged from 774-1,400 yen/kg. In 1970, a year of low production, the price range was 1,037- 1,718 yen/kg.

The culture of eels in Japan goes back 150 yr, and despite great effort by scientists, culture methods have not changed much. Since the eel is catadromous, spawning occurs at sea and the young migrate to fresh water where they grow to adulthood. The Japanese eel culture industry is based on the capture of young eel as they migrate to fresh water during the months of December to March. Size at time of capture is about 3 inches in length. Introduced into ponds, and fed a diet of either chopped fish or chopped fish and pelleted feeds, they reach a market size of 18-24 inches in 12-18 mo.

The principal restriction on the volume of eel culture in Japan is availability of fry. Scientists are attempting to overcome this problem by breeding eels in captivity, but so far little or no success has been achieved.

The Tokyo University of Fisheries operates an eel culture research station on Lake Hamana in Shizuoka Prefecture near the City of Hamamatsu. This well-equipped and well-staffed laboratory is conducting basic research on the problems associated with the culture of eels, mullet, carp, and various other species, including largemouth bass.

The shortage of native eels for culturing purposes is compounded by other problems connected with culture of the species. Principal among these is disease. In 1970, disease took an unusually heavy toll of eels in Shizuoka Prefecture. That year the industry was hit by an epidemic of a new disease, named branchionephritis by S. Egusa, Tokyo University of Fisheries. This epidemic took 2,600 tons of fingerling and yearling eels during the first half of the year.

Supplemental stocks of A. japonica are purchased from Taiwan and New Zealand, but these and other foreign sources cannot fulfill the need, and the Japanese are turning more and more to Europe for the Atlantic eel, A. anguilla. In 1971, 34,000 kg of glass eels from Europe were imported. So far, the results with A. anguilla have been less than satisfactory, because of disease and nutritional problems.

I concluded my trip to Lake Hamana by dining on smoked eel at the Prefectural hotel and dormitory. I was so impressed by this product that I purchased cans of smoked eel to take home with me.

1 Chief, Division of Fish Hatcheries. Bureau of Sport Fisheries and Wildlife, U.S. Department of the Interior. Washington. D.C. 20240: present address: Bureau of Sport Fisheries and Wildlife. U.S. Department of the Interior. P.O. Box 25486. Denver, CO 80225.


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