Culture technology of Gracilaria lemaneiformis

2021-03-27 4

1、 Cultivation mode

1. Raft culture of Gracilaria lemaneiformis. This is the main form of cultivation, most of which are cultivated in autumn, winter and spring for three consecutive stubbles, and a few of which are cultivated for four consecutive stubbles without rafting all year round.

2. Raft rotation of Gracilaria lemaneiformis and kelp. Gracilaria lemaneiformis was cultivated from September to December, kelp was cultivated from December to next April, Gracilaria lemaneiformis was cultivated from April to July, and Gracilaria lemaneiformis was also cultivated from July to September.

3. Raft rotation of Gracilaria lemaneiformis and oyster. In summer, autumn and winter, Crassostrea plicata was raised by hanging, and in winter and spring, Gracilaria lemaneiformis was cultivated for one or two times.

2、 Cultivation techniques of Gracilaria lemaneiformis

1. Sea area selection. ① Sediment: except for the uneven reef sediment. ② In winter, the water depth below the dry tide line is 2.0m. ③ Wind wave and current: at present, due to the strong equipment and strong resistance to wind and wave, it can be cultivated in the sea area with high tide, and the sea area with low wind and wave requires smooth current. ④ Water quality: the water quality of southern sea area is generally fertile, as long as the proportion of sea water is above 1.018 in breeding season and there is no serious pollution of industrial wastewater.

2. Sea area layout. It is required to be arranged in the shape of "pin".

3. Raft arrangement

(1) Position piling. As Gracilaria lemaneiformis production in South China should avoid typhoon period in high temperature season, the main factor to consider raft direction is tidal current, and the raft direction should be downstream as far as possible. After the position and direction of raft are determined, the raft length and the distance between piles should be determined. The length of raft is 50m-65m, and the pure length of anchor rope is 2-3 times of the water depth at full tide. The horizontal distance between the two piles of a raft is twice the length of the raft plus the length of the other side of the right triangle formed by the anchor rope and the water depth. The distance between two rafts is the distance between adjacent piles. Different breeding modes are different. Some are 2.5m-3.0m, some are 4.5m-5.5m, so the pile position can be determined.

The pile foundation material varies with the bottom material of the sea area. Pine with a diameter of about 13cm and a length of 2m should be used as piles in the sea area with sandy and muddy bottom; Phyllostachys pubescens with a diameter of about 16cm and a length of more than 3m should be used as piles in the sea area with sandy and muddy bottom; 50kg-100kg anchor should be thrown in the sea area with soft and muddy bottom. Attention should be paid to the end of Moso bamboo, which is about 1 / 3 of the total length. Except for the anchor, each pile shall be drilled at the top to tie the pile rope.

(2) Get off the raft. Before getting off the raft, the anchor rope should be well connected with the pile rope, and the buoyancy pipe rope should be tied with the lifting rope and the corresponding float every 50cm-60cm before going into the sea. The horizontal rope should be reinforced on both sides of the platform in each small area, and the buoyancy pipe rope and the horizontal rope should be well connected with the anchor rope, and then the raft with uneven tightness should be arranged to make the spacing consistent. The tightness of raft should be kept loose at the climax.

(3) Each plot (about 3 MU) of materials. In addition to the pile foundation, there are 2160 wire -- 2800 wire polyethylene floating pipe rope, horizontal rope, 180 wire polyethylene hanging rope and 2800 wire -- 3600 wire polyethylene pile rope, anchor rope and float.

4. Take, clip and hang seedlings

(1) Time. When the water temperature drops to 27 ℃, it is from late September to early October every year.

(2) Miao rope. There are three strands of three flowers and three strands of six flowers in 180 silk-360 silk polyethylene rope. The twist of seedling rope must be appropriate, too loose is easy to drop seedlings, and too tight is easy to damage seedlings. The rope should be treated a few days before seedling separation, that is, the new rope should be soaked in water for one day, and the old rope should be disinfected and washed with 200ppm bleaching powder.

(3) Take seedlings. Because the growth rate of the base of Gracilaria lemaneiformis is slower than that of the top, it is necessary to select the Gracilaria lemaneiformis with good growth, purple red color and less miscellaneous algae, and not use the base algae as the seedlings as far as possible. It is necessary to prevent the algae from drying and the temperature from exceeding 30 ℃ during seedling transportation.

(4) The seedlings are mixed. Clustering method should be used. The amount of seedlings is 50g Gracilaria lemaneiformis per meter of seedling rope. After removing miscellaneous algae (Enteromorpha prolifera, etc.), when the seedlings of Gracilaria lemaneiformis pass through the seedling rope in a small cluster of 5g or so, a cluster of seedlings should be clamped every 5cm-10cm or so, and it should be clamped in the middle of the seedling, with 5cm-6cm exposed at both ends. In order to prevent the algae from dehydrating and exceeding the upper limit of temperature, sun exposure and algae drying should be prevented.

(5) Hang seedlings. Connect the two ends of the clamped seedling rope with the hanging rope on the floating ridge.

5. Cultivation management

(1) Water layer regulation. In fact, the regulation of cultivation water layer is to regulate the light reception of Gracilaria lemaneiformis. Gracilaria lemaneiformis is a photogenic seaweed, which grows slowly under too weak light, but too strong light can inhibit the growth, and even the pigment will fade and turn yellow due to the decomposition of sunlight. If it is not adjusted in time, it will become white and fall off.

(2) Adjust the raft. In addition to increasing or decreasing the buoyancy properly, the broken rope should be mended in time; attention should be paid to the firmness of the raft frame, and the tightness of each raft should be consistent, and the requirements should be uniform, so as to ensure the safety of production and the uniform light of Gracilaria lemaneiformis.

(3) Fertilization. The water quality in the southern sea area is fertile and fertilization is generally not needed, but in some seasons, when nutrients are insufficient in some sea areas, bagging fertilization should be considered.

6. Harvesting and drying

After two to three months of growth, Gracilaria lemaneiformis weight gain up to 100 times, when the algae is thick, purple and black color, when the seedling rope reaches 3kg per meter, it can be harvested. It is not suitable to harvest Gracilaria lemaneiformis too early, because the gum content of Gracilaria lemaneiformis is low. The harvesting should be carried out with the seedling rope, and the cutting method should not be adopted to keep the base. Choose a sunny morning to ensure that Gracilaria lemaneiformis can be exposed in time without deterioration. If it is not dried on the first day, it must be dried the next day and stored in bags.

3、 Existing problems and suggestions

1. Serious insect damage. From 2000 to 2001, when Gracilaria lemaneiformis was produced on a small scale, there was almost no serious shedding of algae caused by insect pests. Since the spring of 2002, the insect pests first occurred in neiwanli District, and gradually developed to other districts, even in the open sea. When the insect attack occurs, the algal body has an insect wound, causing serious shedding or even failure. The main pest is Daphnia undulata, which has a rapid reproduction rate and an amazing number. In winter 2002, it even threatened the normal production of kelp. The reason for the pest is that the cultivation of Gracilaria lemaneiformis provides a good habitat for pests. Especially in summer, Gracilaria lemaneiformis breeding rafts and even Gracilaria lemaneiformis are still kept on the sea, causing waves. Water fleas have a suitable habitat and palatable food organisms all year round. Therefore, in order to reduce the influence of water fleas and other pests on the growth of Gracilaria lemaneiformis, it is necessary to consider the fallow method of forbidding the cultivation of seaweeds in high temperature period (also typhoon period).

2. Local disease. In the spring of 2002, the rot phenomenon of Gracilaria lemaneiformis began to be found in some areas. The base and branches of the rot algae were mostly white spots, hollow or light yellow dots. Some algae were yellow green, the color of the diseased algae was not bright, and the detached algae were easy to rot. There are many reasons for disease rot, but the main factors are: 1. Gracilaria lemaneiformis is a kind of asexual propagation seaweed. After multiple cultivation (especially high temperature in summer) in the southern sea area, its physiological metabolism is affected, and its stress resistance is reduced. Once the environment is not suitable, it is easy to cause disease and rot. ② Light changes. During the transition period from winter to spring, the light intensity often changes abruptly. If the water layer is not adjusted in time, it will cause physiological diseases. ③ The density is too high. Due to the good growth benefit of Gracilaria lemaneiformis in the first few crops, the adverse conditions such as excessive culture density, poor water flow and insufficient local nutrients affected the normal growth of Gracilaria lemaneiformis and reduced the disease resistance. ④ It's unscientific. At present, most farmers believe that increasing the number of seedlings can increase the unit yield. The number of seedlings used in the rope of sea rice seedlings is several times of that in the technical regulations, resulting in too dense clusters of seedlings. Some farmers even clamp the seedlings in successive clusters instead of single cluster, resulting in too large difference of light inside and outside each cluster of Gracilaria lemaneiformis, which is easy to rot.

In order to reduce the occurrence of disease rot of Gracilaria lemaneiformis, we must do: 1. Every year, Gracilaria lemaneiformis is introduced from the north to establish an expansion base. In the second crop production, Gracilaria lemaneiformis without passing through the summer in the South should be used to maintain the original germplasm of Gracilaria lemaneiformis. At the same time, the original species of Gracilaria lemaneiformis should be selected manually every few years. ② Reasonable layout. In Xinghua Bay, where the culture layout is reasonable, the disease and rotten condition is light, and the insect damage is less. ③ Scientific management. In particular, when the weather changes suddenly, Gracilaria lemaneiformis would rather grow more slowly away from the water surface than be exposed to strong light for a long time. At the same time, when the nutrients are insufficient in some sea areas, ammonium fertilizer can be applied, and ammonium fertilizer has a certain repellent effect on pests.