In the breeding stage of fish fry, there is a disease known as the "first killer of fish fry", it can lead to the death of the whole batch of fish fry in a short time, and even let the farmer lose blood - this is bubble disease!
How exactly did it come about? Why are fry particularly vulnerable? How can it be prevented and treated? Today, we delve deeper into this "invisible killer" in aquaculture!
What is bubble disease?
Bubble disease is due to the nitrogen content or dissolved oxygen in the water body supersaturation, resulting in the formation of bubbles in the body or body surface, so that the fish body floating or swimming out of balance, serious can cause a large number of deaths, this disease mainly harm the fry.
Main symptoms:
Fry floating, abnormal swimming (such as "backstroke", spinning);
Bubbles attached to the body surface, fins and gills (small white bubbles visible to the naked eye);
Inflating the intestine (leading to intestinal blockage in severe cases);
Exophthalmia, fin congestion (secondary bacterial infection may occur later).
Second, the cause of bubble disease
1. The culture environment temperature rises suddenly, the free oxygen in the blood is saturated before the change of air pressure, the environment temperature rises suddenly, the solubility of free oxygen in the blood decreases after the change of air pressure, and the dissolved oxygen in the blood is in a state of supersaturation.
2. The mutation of external environmental factors leads to the decrease of oxygen solubility in the water body and the rapid change of oxygen partial pressure, and the free oxygen in the blood cannot quickly diffuse from the body to the environment, and finally escape to form bubbles.
3. The shallow water level of the pond in early spring leads to excessive dissolved oxygen in the water, creating conditions for the occurrence of bubble disease. In spring, severe bubble disease and acute death occurred in ponds with water depths of less than 1.5 meters.
4. Too much unfermented organic fertilizer is put in the pond, and the fertilizer continues to decompose at the bottom of the pond, causing a large amount of oxygen to decompose and release small bubbles of methane and hydrogen sulfide.
Third, the development process of bubble disease
Early stage: the fry swim abnormally, jump wildly and stir violently with the tail (easy to be ignored);
Middle stage: white granular bubbles appear in the fins, head and tail, and the fin strips are red with blood;
Later stage: The fin bars rot from the end, eventually leading to death.
High-risk fish species:
Dace, loach, California perch fry (extremely sensitive to bubble disease);
Carp, grass fry (prone to viral disease, higher mortality).
Fourth, how to prevent bubble disease?
1. Deepen water level and reduce water temperature fluctuations.
2. Avoid unfermented organic fertilizers and use "soluble organic fertilizers" and "carbon sources".
3. Rational use of aerator to improve the efficiency of aeration and balance dissolved oxygen. When dissolved oxygen is too high, aerator can be used to accelerate the overflow of dissolved oxygen.
4. Regularly test water quality indicators to maintain water stability.
5. Enhance the physique of fish fry, use animal protection products to improve anti-stress ability.
Five, how to treat bubble disease?
Immediate water change: Inject new water with low gas concentration to reduce water saturation.
Salt water after the whole pond sprinkling (10 jin/mu) : adjust the osmotic pressure, help fry to discharge bubbles.
Use of surfactants (such as benzalkonium bromide) : accelerate gas escape and inhibit algal reproduction.
And then disinfect with povidone iodine.