Proceedings of the Autumn Symposium on Aquaculture, '97

Transcription

1 Proceedings of the Autumn Symposium on Aquaculture, '97

2 1. Aquaculture in Hiroshima Prefecture Yasuyoshi MURAKAMI (Hiroshima Fisheries Experimental Station)

3 2. The Present Situation and Some Problems of Japanses Oyster Culture Satoru AKASHIGE (Hiroshima Fisheries Experimental Station)

4 3. Environmental Conditions in Northern Hiroshima Akira Bay OUCHI (Hiroshima Fisheries Experimental Station)

5 4. Released Red Sea Bream in Fishing Port and its Domestication Minoru TAKABA (Hiroshima Fisheries Experimental Station) Fig Change in the numbers of recaptured fish at four sampling stations after release in Okiura fishing port from Aug. to Dec T0, stable recapture; T1, recapture decreased slowly; T2, recapture decreased steeply; S1, Survival rate in T1 (40 to 110 days after release) ; S2, Survival rate in T2 (110 to 135 days after release).

6 S. ROTHBARD (YAFIT (R&D) Lab., Fish Breeding Center, Gan Shmuel 38810, Israel) The Israeli fish culture was initiated in the 30's in northern part of the Israeli coastal plain, in marshes south to the ancient town, Acre. It started as monoculture of the European mirror carp (Cyprinus carpio), that was introduced from Yugoslavia. At that time the carp was grown according to the extensive European methods and the yields were very low (ca MT/ha). With the addition of tilapia and gray mullets (Mugil cephalus) as an additional components to the fish population, the yields increased and the method was changed into polyculture. At present the annual average yield increased ten folds and reaches the MT ha. Although the common carp is still the dominant fish cultured in polyculture (55-60%), there is a continuos trend to increase the proportion of tilapias in polycul ture. At present, the Israeli fish culture is annually producing about 9,000 MT of carps and 5,500 MT of tilapia, beside 500-1,000 MT of gray mullets and other fresh water fish. In the north of the country, where cold water from Golan Heights is available, rainbow trout is cultured on a small scale (600 MT/year). Recently, some fish farms started to grow the hybrids between the American striped and the white bass. The latter were introduced from the US and now the reproduction and hybridisation is made in Israel. The rapid growth of fish culture can be attributed to the following steps, which significantly affected the fish culture development: (1) Integration of tilapia hybrids and gray mullets into the conventional culture of carps, thus converting it into polyculture, (2) Introduction of pelletized feed and feed formulas and feeding according to improved feeding schemes, (3) Development of genetically improved strains of common carp (the famous Israeli Dor-70 line) and Tilapia (hybrids of Oreochromis niloticus X O. aureus), (4) Establishment of commercial fish hatcheries that used methods of hormonal induction of spawning and were able to supply the fish growers any number of fry as stocking material, (5) Integration of, the so-called, Chinese carps, that have incredible growth potential and are successfully used as gbiological Filters h that improve water quality in ponds, water reservoirs and man-made lakes, (6) Integration of aeration devices into ponds which enabled intensification and improved growth rates. The fish culture in Israel is facing several constraints and limitations, these are: Shortage of water due to a very long and dry summer and short winter, with an annual average precipitation of about mm; Limited resources of natural waters (there is only one fresh water lake, the Sea of Gallilae and some very small rivers) ; Almost 60% of the country comprise desert and mountains and lot of efforts are put into conversion of arid land into agricultural area, involving long distance transportation of water via a network of canals and huge, 3m diameter pipeline (The National Water Carrier) ; the cost of water for agriculture is high as well as the cost of labor. In contrary to the mentioned above there are also some relative advantages. Israel has very soft climate, suitable for fish culture e. g. long and warm summer and short winter with moderate temperatures; The fish culture is operated by highly motivated and skillful workers, that are ready to adopt and to implement new techniques; There is close relationship with the academic research and during the years a net-work of collaboration and cooperation has been established between the scientific institutions and the fishery, for their mutual benefit; Israel is located in an optimal geographic location, close to the European continent, which is a great potential market for luxory aquaculture products (e. g. most of the nishikigoi produced in Israel is exported to Europe). In recent years governmental efforts are put to promote development of marine aquaculture and to initiatives aimed in production of aquatic organisms, that are potential for export. This is expressed in funds and grants given to projects in biotechnology and molecular biology of aquatic animals. Financial support is also offered to aquaculture projects which are planned in the desert area, and are based on geothermal waters present in the arid part of the country.