RU2802585C1 - Biological method of combating saprolegniosis of fish roe during incubation of unglued eggs - Google Patents

Abstract

FIELD: fish farming.

SUBSTANCE: invention relates to fish farming, in particular, to methods for improving the preservation of caviar and can be used for the artificial breeding of fish. During the laying of non-glued eggs in the incubation container, freshwater cherry shrimp 5–10 mm in size are placed there in the amount of 10–20 specimens per 1,000 fish eggs. After hatching of the prelarvae, which did not swim until the yolk sac is resorbed, the shrimp are removed from the incubation tank.

EFFECT: increase in the yield of fish larvae.

1 cl, 1 tbl

Description

Saprolegniosis of fish eggs (byssus) is a mycotic disease of eggs, characterized by damage to it by saprolegnia fungi during factory incubation. Widespread since the use of the artificial method of incubating eggs. Currently, it is found during the incubation of carp, sturgeon, and salmon fish, as well as during the breeding of aquarium fish.

Saprolegniosis affects the eggs of spawning fish in autumn and spring in incubation apparatus at fish factories, as well as in fish farms when incubating eggs of trout, whitefish, carp and herbivorous fish. Egg disease can be observed both at low water temperatures (up to 5-10°C) - when incubating eggs of autumn-spawning fish, and at higher temperatures (up to 18-22°C), when incubating eggs of spring-spawning fish. On the affected eggs, single dotted threads of fungal hyphae first appear. Then, growing, they envelop the egg with a continuous layer, which looks like a small ottoman or a ripe dandelion. Initially, unfertilized, injured, and physiologically inferior eggs with an insufficient supply of nutrients (yolk) are affected. With the development of the pathological process on the weakened eggs and the accumulation of the infectious principle in the incubation apparatus, the rest of the eggs are also affected. If incubation and development of eggs occur under unsatisfactory environmental conditions (unfavorable gas conditions, high oxidation), as well as at a low level of production technology (untimely removal of unfertilized or dead eggs, injury to eggs during their collection and fertilization, etc.), the disease develops very quickly. fast. Under factory incubation conditions, 10-50% of eggs die from saprolegniosis. Sometimes the entire batch of caviar dies in the machine. Therefore, much attention is paid to measures to prevent and treat saprolegnia infections. [Vasilkov G.V., Grishchenko L.I., Engashev V.G. and etc.; Edited by Osetrova V.S. Fish diseases: Handbook. - M. - Agropromizdat, 1989. - 288 p.].

Egg stickiness is a property in which the shell of fertilized eggs sticks to the substrate with the help of secreted liquid. Known among phytophilous, psammophilic and lithophilic fish [Kozlov V.I., Abramovich L.S. A short dictionary of the fish farmer. - M. - Rosselkhozizdat, - 1982. - 160 p.].

Phytophiles (from Latin Fitos - plants) are a group of fish that lay eggs on plants. These include fish from the families carp, pike, and aquarium fish - neons and angelfish.

Psammophiles (from Latin Psammos - sand) are a group of fish that lay eggs on sandy soil. These include fish of the whitefish family, and of aquarium fish, some representatives of the characin suborder.

Lithophiles (from Latin Litos - stone) are a group of fish that lay eggs on rocky and gravel soils. These include fish of the families sturgeon, salmon, and aquarium fish - cichlids and gobies. [Vlasov V.A. Fish farming. - Ed. "Lan" - St. Petersburg-Moscow-Krasnodar. - 2010. - 349 p.].

For fish with sticky eggs, two incubation methods are used. The first involves de-gluing the eggs using a milk suspension, talc and some other de-gluing preparations, and incubation is carried out in Weiss or VNIIPRKh apparatus. The second does not involve de-sticking the eggs, and incubation is carried out in a tray incubator, where the eggs are glued to the surface of the tray and water is supplied to the top tray, from which it flows onto the trays below. With both incubation methods, it is necessary to regularly, sometimes every 2 hours, remove dead eggs. Otherwise, dead eggs affected by saprolegniosis infect live eggs and the death of eggs can be 100% [Vlasov V.A. Fish farming. - Ed. "Lan" - St. Petersburg-Moscow-Krasnodar. - 2010. - 349 p.]. The second method allows you to reduce injury to eggs during degumming, but makes it difficult to remove dead eggs that are firmly attached to the substrate - the surface of the tray.

For the prevention and treatment of saprolegniosis, malachite green is used in a ratio of 1:200000 with an exposure of 60 minutes or a solution of methylene blue 1:100000 for 30 minutes. A positive result is obtained by keeping caviar for 15 minutes in a formaldehyde solution (1:500 and 1:1000). Weak solutions of copper sulfate (1:200,000 for 60 minutes) and potassium permanganate (1:100,000 for 15 minutes) are also effective. [Vasilkov G.V., Grishchenko L.I., Engashev V.G. and etc.; Edited by Osetrova V.S. Fish diseases: Handbook. - M. - Agropromizdat, 1989. - 288 p.].

There is a known method of double preventive treatment of caviar with a standard solution of the drug violet “K” (10 mg per 1 liter of water) with an exposure of 30 minutes during the period of embryonic development [Lartseva L.V. Prevention and treatment of saprolegniosis in sturgeon and whitefish caviar during artificial breeding. - Abstract of Ph.D. diss., M. - VNIIPRH. - M. - 1987. - 22 p.].

There is a known method for incubating sturgeon caviar, including preventive treatment with the drug purple “K” by maintaining a constant concentration within 0.1-0.3 mg/l of water, until the stage of embryo rotation [Mamedov Ch.A.O. RF Patent No. 2165696 - 1999].

There is a known method of increasing the resistance of fish eggs to diseases by single-time (at the stage of egg laying) or double-time (additionally at the “eye” stage) treatment of eggs with the iodine-containing preparation “Monclavit-1” [Nechaeva T.A., Kuznetsova E.V., Varyukhin A. .V., Petropavlovsky A.G. A method for increasing the resistance of caviar to diseases. RF Patent No. 2 421 987. - 2011].

All of these methods for the prevention and treatment of saprolegniosis have significant drawbacks. The first is that all these methods involve chemical reagents that in one way or another harm the normal process of embryogenesis. So, now in the EU countries and the Russian Federation all organic dyes are prohibited for use, including malachite green, brilliant green, methylene blue, violet “K” due to their carcinogenicity. The second significant drawback is the rather large labor costs. When incubating fish eggs, they are usually on duty around the clock and, as noted above, even with preventive treatment with these drugs, constant removal of dead eggs is required. Therefore, the authors were faced with the task of eliminating these shortcomings.

The purpose of this invention is to reduce losses of fish farming products by increasing the yield of fish larvae and reducing labor costs when incubating eggs with sticky eggs.

This goal is achieved by the fact that when laying unbleached eggs in a tray incubator or aquarium, cherry shrimp measuring 5-10 mm are placed there at the rate of 10-20 specimens per 1000 eggs. After hatching of the prelarvae, which did not float until the yolk sac is absorbed, the shrimp are removed from the containers for incubating the eggs.

Cherry shrimp (Cherry) - Neocaridina Davidi - a freshwater shrimp from the family Alyidae belongs to the order of decapods. Among aquarists, it is better known as the cherry shrimp, or cherry shrimp [moreryb.com/racoobraznye/neocardina-davidi]. Cherry shrimp, or cherry shrimp, is a species selectively bred in Germany, obtained through a long process of crossing wild shrimp Neocaridina Heteropoda. Cherry shrimp are waste collectors in the wild. They eat everything they find 24/7 [fanfishka.ru/news/1040-krevetka-vishnya-cherri.html].

The property of cherry shrimp to consume saprophytes (dead organic matter) gave the authors the idea of using them when incubating non-glued eggs to combat saprolegnia to destroy dead eggs. Observations have shown that shrimp, constantly fingering the eggs with their paws, find dead ones and eat them without touching live eggs.

An example of the method.

2000 fertilized carp eggs were placed in 6 aquariums with a capacity of 100 liters each. They stuck to the bottom of the aquariums. The aquariums were combined into a single closed water system with a flow rate of 2 l/min. Cherry shrimp in quantities of 20, 30 and 40 were placed in 3 aquariums. In 3 control variants there were no shrimps. The incubation temperature was 21-22°C. The average oxygen concentration in all aquariums was 6.5-8.5 mg/l. The duration of incubation was 4 days. After 4 days, after hatching of the prelarvae, which did not swim until the yolk sac was reabsorbed, the shrimp were removed from the aquariums. An additional side effect of this experiment was the growth of cherry shrimp. Their weight increased from 400 mg to 800 mg on average. When incubating carp eggs with freshwater cherry shrimp, no 24-hour watch was established. The work was carried out in 5/2 mode. One employee participated. The employee's working day lasted the usual 8 hours. To control the incubation of eggs in variants without freshwater cherry shrimp, round-the-clock duty of employees was established every three days. 4 people were involved. The results of the method are presented in the table.

As can be seen from the table, the yield of prelarvae using the proposed method turned out to be more than 2 times higher with approximately the same percentage of fertilization. Labor costs for four days amounted to 32 man-hours instead of 96 man-hours with round-the-clock duty when incubating eggs without freshwater cherry shrimp, that is, they were reduced by three times.

Claims (1)

A biological method of combating saprolegniosis of fish eggs during incubation, characterized by the fact that when laying unbleached eggs in an incubation tank, freshwater cherry shrimp 5-10 mm in size are placed there in the amount of 10-20 copies per 1000 fish eggs, after hatching the pre-larvae that have not passed float until the yolk sac is absorbed, the shrimp are removed from the incubation container.