FRESHWATER FISH CULTURE IN JAPAN 



HARVEY WILLOUGHBY' 



INTRODUCTION 



The following observations on Japanese Fish Cul- 

 ture 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 Prefec- 

 tural 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 sta- 

 tion 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 approxi- 

 mately 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 

 davs. Seaw ater is mixed u ith the fresh water at a rate 



' Chief, DM^ionof Fish Hatcheries. BureauofSport Fisheries 

 and WildHI'e. L .S. Department of the Interior. Washington. D.C. 

 20^40: piesent address; Bureau of Sport Fisheries and W'ildHfe. 

 L S Department of the Interior. P.O. Box l^ASb. Denver. CO 



s()::.s. 



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 com- 

 manding 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 pro- 

 gram 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 spawn- 

 ing run of chum salmon was in progress, and I was 

 able to observe the seining of these fish at an irriga- 

 tion dam which blocked their upstream movement. 

 Approximately 100 million eggs were being incu- 

 bated in the three hatcheries visited. 



The following day, October 23, I visited the head- 

 quarters of the Hokkaido Salmon Hatchery 

 Fisheries Agency in Sapporo where I met the Direc- 

 tor. .Ayahiko Hemmi. Later in the day. Toshinobu 

 Tokui and 1 travelled to Lake Shikotsu and visited 

 the kokanee salmon hatchery. 



Kokanee salmon fO. ncrkci kciiiwrliii are native to 

 only two lakes in Japan, both on the island of Hok- 

 kaido. They have, however, been widely trans- 



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