Cultivation Of Conchoceus

Cultivation of Porphyra begins with the culture of filamentous sporophytic phase, or Conchocelis. The culture of Con-chocelis begins at the end of February to the middle of March depending on the water temperature. During this time the water temperature (17-22°C) becomes suitable for the germination of carpospores and the growth of the conchocelis plants. The flat upper parts of oyster shells are used as substrate for the carpospores.

The attachment of carpospores to the shells is initiated by sprinkling carpospore suspension over the shells placed side by side on the bottom of small shallow tanks which are 40 x 61 x 15 cm in size, containing seawater about 10 cm deep. The suspension of carpospores is prepared by filtering the suspension of pulverized mature plants of Porphyra crushed in a grinder. After the completion of seeding carpospores on shells, the tank is placed on a woody shelf under 1000 to 1500 lux light intensity for one week to allow the carpospores to germinate on the shells. The water then is changed. The carpospores germinate into conchocelis plants and burrow into the pearl layer. The conchocelis are cultured in the tank until the end of October for seeding conchospoes on the net. During the cultivation of conchocelis, the water in the shell-tank should be changed once every two to three weeks, and the shells should be cleaned with a brush every one to two months depending on the growth of epiphytes on the shells. Once the conchocelis grow into the shell, the growing conditions of the conchocelis and epiphytes can be controlled by changing light intensity. During summer, special attention should also be paid to the temperature of the nursery room to avoid undue rise in temperature of the tank water to affect on the growth of the conchocelis. If the room temperature rises to higher than 30°C, seawater is used to lower the temperature by spraying it on the floor, at the same time, the light intensity of the room is lowered to about 400 lux or less.

Another method of growing conchocelis is seeding the conchocelis fragments on shells. Seeding conchocelis fragments on the shells starts during the middle of May through the middle of June, by grinding several conchocelis colonies which are growing in a flask and kept in the laboratory. The colonies are cut in a sterile grinder with 500-mL filtered seawater for about 30 seconds. Then conchocelis-fragments solution is diluted with about 30 times of filtered seawater and spread thinly on the shells to allow the conchocelis to grow into it.

Seeding Conchospores on Nets and Cultivation of Leafy Porphyra

Conditions for conchospore formation and liberation of these Porphyra species are still not well understood. Therefore, seeding conchospores on cultivation nets is still (at the mercy of nature) and the annual production fluctuates greatly. It usually starts in the middle of October at Penghu, or from the end of October through early November at Kinmen.

The attachment of conchospores on the net is accomplished by putting the mature conchocelis-bearing shells into troughs of bamboo which form the frames of the net rafts, or into plastic bags opened at top which are attached beneath the net. About 75 to 100 shells are needed for each net. At Penghu, the floating raft type (9) is employed in the cultivation of leafy plants. The net rafts are floated with anchor ropes fixed in the middle part of the intertidal zone. The net rafts are made of bamboo. They are rectangular in shape, about 2.0 x 9.0 m in size and with six bamboo legs of about one meter long. The cultivation nets are made of synthetic strings. They are rectangular in shape and measures 1.5 x 8.0 m (Penghu) or 2 x 20 m (Kinmen) in size. In general, used old nets are preferable to new ones, because the surface of new strings are too slippery for the conchospores to attach. Two nets which are stacked one upon another are fastened on a net raft.

About 40 days after seeding, the seedings of Porphyra plants may reach 15 to 30 cm long and can be harvested. They are cultivated until March of the next year and can then be harvested 3 or 4 times, producing about 18 to 30 kg of fresh seaweed per raft (2 nets).

In Taiwan, fishermen usually cultivate Porphyra as profitable side job during winter when they cannot go out fishing. Since Mainland China produces large quantity of very cheap dried "Tsu-tsai" the fishermen in Taiwan are gradually losing their interest to cultivate Porphyra and the area of cultivation in Taiwan is decreasing.

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