1. Killing Ciliate Protozoa
For aquaculture, farmers use zinc sulfate, which is a heavy metal salt-based insecticide. The zinc ions produced in water combine with the proteins in the ciliate protozoa cells to form protein salts, causing them to precipitate.
Additionally, zinc ions can easily bind with the thiol groups in enzymes within the protozoan cells. These thiol groups are critical for the enzyme’s function, and once bound to zinc, they lose their activity, leading to the destruction of the protozoa.
Zinc sulfate is used to prevent and control diseases caused by sessile ciliates in species like river crabs and shrimp in aquaculture.
Moreover, zinc sulfate contains various mineral elements that can effectively regulate the osmotic pressure inside and outside the cells of shrimp and crabs in water.
It helps reduce the stress response in shrimp and crabs when there is a significant drop in water salinity. It also has a skin-constricting effect, making the shrimp and crabs’ bodies clearer and improving the marketability of shrimp and crabs.
2. Algae Control (Blue-Green Algae)
The principle of action is similar to that of copper sulfate (CuSO4), a widely used and cost-effective algaecide.
Aquaculture professionals commonly use copper sulfate to eliminate excessive algae in ponds. As an algaecide, copper sulfate is highly effective at inhibiting algae growth and reproduction.
The advantages of copper sulfate include high efficiency, low cost, and long-lasting effects.
However, a major drawback is that copper ions cannot be removed from the water and tend to accumulate in the water and even in aquatic organisms, which can be harmful.
Copper sulfate works by using the toxicity of copper ions to interfere with the algae’s photosynthetic system, preventing normal photosynthesis, and gradually killing the algae.
When using copper sulfate as an algaecide, it is recommended to operate aerators to provide enough oxygen. This is because, without photosynthesis, algae cannot release oxygen and may consume a large amount of oxygen, leading to oxygen deficiency for fish and shrimp.
In alkaline water, copper ions easily form copper hydroxide precipitates, which lose effectiveness over time.
Therefore, copper sulfate is more effective in acidic waters than alkaline ones. To achieve the same effectiveness, a larger quantity is needed in alkaline waters than in acidic waters.
Copper ions are also easily absorbed by organic matter and calcium carbonate-containing substances. Hence, controlling the effective concentration of copper ions in pond water can be challenging.
The best approach is to monitor copper ion concentrations to ensure the drug’s efficacy remains within safe limits.
3. Some Information About Anchor Worms
The life cycle of the anchor worm involves five nauplius stages and five copepodid stages. The fifth copepodid stage mates only once in its lifetime.
After mating, the female anchor worm seeks a host with weakened immunity (i.e., a susceptible aquatic organism) to parasitize.
The anchor worm progresses through the juvenile, mature, and old worm stages, with a lifespan varying with temperature, typically lasting 20 to 30 days.
When parasitizing a fish, the anchor worm’s head burrows into the fish, while the body remains outside. In the juvenile stage, the worm is hair-like, white, and without an egg sac, with blood spots at the attachment site.
In the mature stage, the worm’s body is transparent, with visible dark brown intestinal movements, and the ovaries are visible on both sides of the intestine. There is often a pair of green egg sacs hanging behind.
In the old worm stage, the worm’s body becomes opaque and soft, often covered with algae and sessile protozoa, which is known as “dirty hanging.”
In the mature stage, the anchor worm’s head is deeply embedded in the fish, with the head horns protruding like an anchor. Only the body segments are visible outside.
Even when using insecticide dips at high concentrations (typically 10 times that of the spraying concentration), which can make the fish uncomfortable, the anchor worms may not necessarily be killed.
After the spring season, as water temperature increases and the food chain in reservoirs becomes richer, fish nutrition improves, and their immunity strengthens.
Zooplankton (such as copepods and cladocerans) can feed on the anchor worm’s eggs and juvenile stages, thus acting as natural predators of the anchor worms.
The presence of zooplankton significantly reduces anchor worm populations, which is more economical, eco-friendly, and effective than using insecticides. Therefore, based on the above two aspects, anchor worm infestations can be greatly alleviated.
Post time: Mar-07-2025
