August 10, 2019
Nigerian Catfish Farmers
Prevention should be considered the first line of defense when managing egg disease and survival.
The most productive method of producing a healthy catfish fingerlings is to transfer fries after 5 days to a hatchery after spawning.
Simple management strategies, such as disinfecting the hatchery before the hatchery season, having separate nets and equipment for each hatching trough, disinfecting hands, disinfecting egg masses before bringing them into the hatchery, and using a pathogen-free water supply, help prevent the introduction of infectious pathogens into the hatchery.
The time it takes for catfish eggs to hatch depends on water temperature. Channel catfish typically spawn when water temperatures are between (21 and 29 °C).
Preventing fries fatalities:
The factors that can cause dead eggs (eggs that have stopped developing) include excessive handling, overcrowding, high temperature, water hardness, and transport delays. Important hatchery water quality.
Excessive handling
Fries in the early development stages are sensitive to handling and should be handled as little as possible to prevent mechanical injury.
Overcrowding
Many factors affect the maximum loading rate fries can sustain. Over-crowding causes poor water circulation and makes it easier for diseases to transfer between egg masses.
Temperature
Temperature is an important environmental factor that affects egg development, hatch rates and disease susceptibility. Newly spawned fries are more sensitive to temperature changes. If fries less than 24 hours old are moved from a pond to hatchery water of a substantially different temperature, they must be acclimated to prevent a high mortality rate.
Fries in the early development stages are sensitive to handling and should be handled as little as possible to prevent mechanical injury.
Overcrowding
Many factors affect the maximum loading rate fries can sustain. Over-crowding causes poor water circulation and makes it easier for diseases to transfer between egg masses.
Temperature
Temperature is an important environmental factor that affects egg development, hatch rates and disease susceptibility. Newly spawned fries are more sensitive to temperature changes. If fries less than 24 hours old are moved from a pond to hatchery water of a substantially different temperature, they must be acclimated to prevent a high mortality rate.
Fries can be managed by using a hose to slowly run hatchery water into the transport container until the water temperature in the container matches that in the hatchery. The optimal temperature range for incubating catfish eggs is (26 to 28 C). At temperatures above and below this range, hatch rates will be reduced by egg death and disease.
PH of Water
The ideal ph of water for rapid and high survival of fries and fingerlings is between 6.5 - 7.5. Anything below or above will expose your catfish to disease and mortalities (death). It is mandatory to have a digital ph meter to take your water reading.
The ideal ph of water for rapid and high survival of fries and fingerlings is between 6.5 - 7.5. Anything below or above will expose your catfish to disease and mortalities (death). It is mandatory to have a digital ph meter to take your water reading.
Regardless of the cause of death, dead eggs should be removed to prevent disease outbreaks. Live eggs are transparent and progress from a pale yellow to an orangered color as they mature. Dead eggs are often difficult to identify during the first day or two after spawning. But by the third day, dead eggs typically appear opaque and colorless. Some dead eggs also may be enlarged. When dead eggs are observed, they can be removed by hand, being careful not to damage nearby live eggs. Egg masses older than 24 hours should be turned over periodically in the hatching basket and inspected for fungus and bacteria. This should be done at least twice daily, but no more than four times daily, until hatching begins.
Managing Disease
More serious than dead eggs themselves is the fact that fries are often attacked by disease pathogens that can then spread quickly to adjacent live eggs. Once a disease outbreak has begun, it can quickly get out of control.
Disease-causing organisms
Bacterial and fungal infections are the primary threats to catfish eggs and fries. Bacterial infections most often occur when hatchery water temperature is higher than (28 C) and when hatching pond are overcrowded. Bacterial egg rot appears as a milky white patch, often seen on the underside and in the middle of the egg mass. This patch of bacteria will contain dead and deteriorating eggs. It should be carefully removed, along with the surrounding dead eggs.
Fungus is more prevalent at lower temperatures, usually (26 C) and below. It rapidly attacks infertile and dead eggs. Fungal infections are easy to spot; they appear as white or brown cotton-like growths made up of many small filaments. If left untreated, these filaments can invade and kill adjacent healthy eggs, expanding to cover the entire egg mass and potentially every egg mass in the hatching trough. Mechanically removing dead and infected eggs can be time consuming, but is beneficial. Chemical control of fungal infections is quite effective.
Formalin. Formalin is for the control of fungi on fish eggs. The maximum concentration for disinfecting catfish eggs is 2000 ppm for 15 minutes as a flush treatment. Under typical hatchery conditions, with an average of one volume exchange every 45 to 60 minutes, 2000 ppm can be toxic to channel catfish eggs and fries. In most hatcheries, fungus can be controlled by treating with 100 ppm formalin for 15 minutes as a bath treatment. Turn the water off during treatment. Flush completely with fresh water when treatment time has elapsed. For flush treatments, concentrations between 100 and 400 ppm formalin have been successful at temperatures of (24 to 30 C). Hatch rates tend to improve when formalin treatments are administered twice daily.
