JPH043177B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for culturing zooplankton such as rotifers, daphnia, and Artemia. [Prior Art] Zooplankton is important as food for fish, and there is a demand for efficient cultivation of large amounts of zooplankton, especially for fish cultivation.
Conventionally, in culturing this type of zooplankton, algae are first cultured, and zooplankton are cultured using the algae as food. For example, the production of rotifers (hereinafter simply referred to as rotifers) has been carried out by batch culture, and cultured by a subculture method, a thinning method, etc. The residence time required for culturing is 7 days for culturing algae.
It takes 3 days to cultivate the rotifers that feed on this algae, for a total of 10 days. Nanochloropsis (hereinafter referred to as marine chlorella) is commonly used as algae. The concentration of marine chlorella produced is about 10 ⁷ cells/ml, and the concentration of rotifers is about 50 ~
It was 200 animals/ml. As mentioned above, in the conventional method,
The number of cultivation days is long, 10 days in total, and therefore the area required for cultivation is enormous. In addition, due to the long culture period, rotifers are easily infected with bacteria and the production of healthy rotifers is often impaired. As a means of solving this problem,
It is conceivable to culture marine chlorella and rotifers together in the same tank, but this is not practical. In other words, the rotifers completely eat up the marine chlorella, and since there are no seeds of marine chlorella and it does not multiply, the rotifers eventually run out of food and die, making stable culture impossible. The above problems are not limited to culturing rotifers that feed on marine chlorella, but are common problems when cultivating zooplankton using algae as food. [Problems to be Solved by the Invention] The purpose of the present invention is to improve the above-mentioned problems of the prior art and shorten the number of days required for culturing, thereby reducing the required site area and producing healthy zooplankton. An object of the present invention is to provide a method for culturing zooplankton. [Means for Solving the Problems] The method of the present invention involves introducing pellets in which algae have been comprehensively immobilized with an immobilization material into a culture tank, and feeding zooplankton using the algae grown freely from the pellets in the culture tank. It is characterized by being cultured. The tank for culturing zooplankton may be a separate tank from the culture tank into which the above-mentioned pellets are introduced, or may be carried out in the same tank as the culture tank into which the pellets are introduced. In the above, algae is a concept that includes diatoms, and includes, for example, marine chlorella, cenedesmus, tetraselmis, chietoceros, and the like. Further, as the immobilization material, conventionally well-known materials such as sodium alginate, carrageenan, acrylamide, polyethylene glycol diacrylate, urethane, and epoxy can be used. The size of the pellets should be 1 to 10 mm, and the true specific gravity should be 0.9 to 1.2. The shape shall be spherical, cylindrical, cubic, or other complex shape with unevenness of the same size. The amount of pellets added to the culture tank is usually 3 to 50% of the tank capacity. [Function] Algae that has grown inside the pellet leak out to the outside of the pellet. The leaked algae will further grow. The algae that have leaked or grown outside of these pellets are fed to zooplankton, and the zooplankton are cultivated. Since a high concentration of algae can be held inside the pellet, it is possible to culture it at a high concentration and supply a high concentration of algae to the outside of the pellet. Furthermore, when pellets and zooplankton are cultured in the same tank, algae leaking from the pellets is directly supplied to the zooplankton, so there is less contamination and healthy zooplankton can be cultured. [Example] Figs. 1 to 3 show the configuration of an apparatus for carrying out the present invention. FIG. 1 shows a case where an algae culture tank 1 and a rotifer culture tank 2 are placed separately. Pellets 6 in which algae are comprehensively fixed are put into the algae culture tank 1, and a culture solution 3 is continuously supplied. Air 5 is supplied to each culture tank as a source of carbon dioxide or oxygen. This air also contributes to stirring and flowing the liquid and pellets in the tank. In the algae culture tank 1, the algae grown inside the pellets 6 leak out to the outside of the pellets 6, and the leaked algae further proliferate within the tank. The algae grown on the outside of these pellets 6 are mixed with the overflow 8 and supplied to the rotifer culture tank 2 in the next stage. Note that the pellets in the algae culture tank 1 are blocked by the outflow prevention net 7 and do not transfer to the rotifer culture tank 2. In the rotifer culture tank 2, rotifers are cultured using the algae supplied from the algae culture tank 1 as bait and multiply to a high concentration. The grown rotifers are discharged out of the tank together with the overflow 4 and are provided as feed for aquaculture at a fish farm. Figure 2 shows algae culture tank 11 without pellets.
This is an example in which a rotifer culture tank 12 into which pellets 6 are charged is combined. The functions of the supply of the culture solution 3, the supply of air 5, the overflow 8, the overflow 4, and the outflow prevention net 7 are the same as those described in FIG. 1. In this embodiment, since the pellets 6 are put into the rotifer culture tank 12, the algae are cultured and multiplied in this tank as well. Therefore, when combined with the algae supplied from the algae culture tank 11 to which no pellets have been input, a high concentration of algae can be supplied to the rotifers, and the rotifers can be efficiently cultured. FIG. 3 shows an example in which algae cultivation and rotifer cultivation are carried out in a common culture tank 10. According to this embodiment, since the algae leaking from the pellet 6 is directly supplied to the rotifers, there is less contamination and healthy rotifers can be cultured. FIG. 4 shows the flow of carbon in this example. Carbon dioxide gas in the air 5 supplied by aeration turns into algae cells, and rotifers grow by eating the algae. At this time, for example, 1/10 of the algae weight becomes the individual weight of rotifers, and 9/10 becomes carbon dioxide gas or trace amounts of organic matter. The carbon dioxide released by rotifers is used again to grow algae. From the above, it is thought that the amount of carbon dioxide gas required for culturing algae in this example is theoretically 1/10 that of the separately installed type described in FIG. Further, the flow of oxygen in this example is shown in FIG. Since the rotifers use the oxygen released by the algae, the amount of oxygen needed to grow the rotifers is reduced accordingly. In addition, the organic matter excreted by rotifers can be used as a substrate for algae growth, just like carbon dioxide gas. This means that the amount of culture solution 3 to be supplied can be reduced. In this way, the one-tank system of the present embodiment, which uses pellets with immobilized algae and mixed culture of rotifers, requires only a small amount of aeration and a small amount of culture solution to be supplied because carbon dioxide, oxygen, and substrate are recycled. In addition, algae growth occurs inside the pellets, and since the algae inside the pellets are protected from rotifers, the algae will not be eaten up, making stable two-species mixed culture possible. Experimental Example 1 The apparatus shown in FIG. 1 was operated according to the specifications shown in Table 1.

[Table] The method for making pellets that are put into the algae culture tank is to centrifugally concentrate the marine chlorella culture solution and dilute it with 3.4% NaCl.
After washing twice, it was placed in a sodium alginate solution. The concentration of marine chlorella at this time is 1x
10 ⁸ cells/ml, concentration of sodium alginate is 1.5
It was %. Drop this suspension into seawater and
Spherical pellets with a diameter of 3 mm were prepared. In addition, as a culture solution to be supplied to an algae culture tank,
NaNO ₃ 150mg/, NaHPO ₄ 15mg/, Fe−
Seawater to which 10 mg of EDTA and 0.003 mg of MnCl ₂ were added was used, and the supply rate was 1.4 mg/min and was continuously supplied day and night. This amount of supply corresponds to the residence time in the algae culture tank for 2 days in the method of the present invention and 3 days in the conventional method. The same amount of overflow is fed into and discharged from the rotifer culture tank, and this amount corresponds to a residence time in the rotifer culture tank of 3 days. In the conventional method, pellets are not put into the algae culture tank;
Marine chlorella was directly added. Incidentally, rotifers were introduced into the rotifer culture tank. Table 2 shows the results when a steady state was reached during continuous operation.

【table】

[Table] As is clear from Table 2, the method of the present invention can maintain a high concentration of marine chlorella even though the retention period in the algae culture tank is shorter than that of the conventional method.
We were able to culture rotifers at high density. Experimental Example 2 The Tetraselmis culture solution was centrifugally concentrated and placed in an acrylamide aqueous solution. At this time, the concentration of tetracelmis was 4×10 ⁶ cells/ml, and the concentration of acrylamide monomer was 15%. β to this suspension
0.5% dimethylaminopropionitrile,
K ₂ S ₂ O ₈ was added to give a concentration of 0.25% and polymerization was carried out to produce spherical pellets with a diameter of 2 to 3 mm. 400 ml of this pellet was put into an algae culture tank of the same experimental apparatus as in Experimental Example 1, and rotifers were put into the rotifer culture tank. In the conventional method for comparison, tetracelmis was directly added to the algae culture tank without pellets. The experimental conditions other than those mentioned above, such as the structure of the apparatus, the properties of the culture solution, and the amount supplied, were all the same as in Experimental Example 1. Table 3 shows the results when a steady state was reached during continuous operation.

[Table] In this experiment, the method of the present invention was able to maintain a high concentration of tetraselmis and culture rotifers at a high density even though the residence time in the algae culture tank was shorter than that of the conventional method. Experimental Example 3 The apparatus shown in FIG. 2 was operated according to the specifications shown in Table 4.

[Table] To prepare the pellets that were introduced into the rotifer culture tank, the Tetraselmis culture solution was concentrated by centrifugation, and then suspended in an aqueous carrageenan solution. At this time, the concentration of tetracelmis was 2×10 ⁶ cells/ml, and the concentration of carrageenan was 1.
It was %. Drop this suspension into seawater and
Spherical pellets with a diameter of 3 mm were prepared. The same culture solution as in Experimental Example 1 was used as the culture solution supplied to the algae culture tank, and the same amount was supplied. Therefore, the retention days in this experimental example are based on the method of the present invention,
With the conventional method, 2 days in an algae culture tank and 2 days in a rotifer culture tank.
It will be 2.7 days. Tetraselmis was directly added to the algae culture tank, and in the conventional method, no pellets or algae were added to the rotifer culture tank. The fifth result is the result when the steady state is reached in continuous operation.
Shown in the table.

[Table] In this experiment, since the residence time in the algae culture tank was short, the concentration of tetracelmis in the algae culture tank was significantly lower than in the conventional method of Experimental Example 2. For this reason, the rotifer concentration in the rotifer culture tank is also particularly low in the conventional method. On the other hand, according to the method of the present invention, the rotifer concentration in the rotifer culture tank could be maintained at a relatively high density even though the concentration of tetracelmis in the overflow flowing from the algae culture tank was low. Experimental Example 4 The apparatus shown in FIG. 3 was operated according to the specifications shown in Table 6.

[Table] The pellets added to the culture tank in the method of the present invention were the same marine chlorella used in Experimental Example 1 immobilized with sodium alginate (hereinafter referred to as A pellets), and the pellets used in Experimental Example 3. This pellet is made by immobilizing Tetraselmis with carrageenan (hereinafter referred to as B pellet). The culture solution used was the same as in each of the above experimental examples,
Rotifers were placed in a culture tank and cultured continuously for 2.7 days. In addition, in the conventional method, pellets are not input, and marine chlorella is used at an initial concentration of 2×.
The cells were directly injected at a concentration of 10 ⁷ cells/ml. Table 7 shows the results when a steady state was reached during continuous operation.

〔Effect of the invention〕

According to the present invention, zooplankton can be efficiently cultured in a short culture period. For this reason, the zooplankton produced is healthy, with little chance for bacteria to grow. In addition, the area required for culturing is also small.

[Brief explanation of drawings]

Figures 1 to 3 are system diagrams of equipment for implementing the method of the present invention, Figure 4 is an explanatory diagram modeling the flow of carbon in the case of the one-tank type shown in Figure 3, and Figure 5 The figure is also an explanatory diagram modeling the flow of oxygen. 1... Algae culture tank, 2... Rotifer culture tank, 3... Culture solution, 4... Overflow (rotifer), 5... Air,
6...Pellet, 7...Outflow prevention net, 8...Overflow (algae).

Claims (1)

[Claims] 1. Pellet containing algae comprehensively immobilized with immobilization material is placed in a culture tank, and algae grown freely from the pellets in this culture tank are used as food to cultivate the pellet separately from or in the same culture tank as the one in which the pellet was placed. A method for cultivating zooplankton, which comprises culturing zooplankton in a tank.