Carbon dioxide is released from fish in much the same way oxygen is taken in by counter-current exchange. Blood high in carbon dioxide is channeled through the heart to the gills where it comes in close contact with water low in carbon dioxide.
By simple diffusion carbon dioxide is then released into the water. Depending on the needs of the fish, the rate of breathing may be variable. Fish that are stressed or are pursued by a predator have a greater oxygen demand than fish at rest. Similarly, if the oxygen concentration in the water is low, a fish has to breathe faster if it is to meet all of its oxygen requirements. During normal respiration only about 60 percent of the gill surface is used for gas exchange.
During increased respiratory demands, up to percent of the gill surface may be used. It is easy to see that any alteration in gill structure or function can be dangerous to catfish. Any increase in the thickness of the gill lamellae will decrease the efficiency of gas diffusion.
If the gills become swollen or puffy, oxygen and carbon dioxide transfer are decreased. Gills can become thickened following exposure to ammonia, certain vitamin deficiencies, or to long-term parasite or bacterial infestations. Any type of toxic agent which damages the gill filaments or lamellae will also affect the efficiency of gas exchange. Finally, if a fish is anemic or has brown blood disease, even though the gills are not damaged and there is adequate oxygen in the water, the blood may not be able to carry enough oxygen to ensure survival.
Wild populations of catfish may spawn as early as late February or as late as August depending on the location.
The length and dates of the spawning season vary from year to year depending on the weather and area, but peak spawning time in Mississippi usually occurs in May. Channel catfish are cavity spawners and will spawn only in secluded, semi-dark areas. In natural waters male catfish will build a nest in holes in the banks, undercut banks, hollow logs, logjams, or rocks. It is this behavior that necessitates the use of spawning containers in order to successfully spawn channel catfish in commercial ponds.
The male selects and prepares the nest by fanning out as much mud and debris as possible. He will then defend this location against any intruder until spawning is completed and the fry leave the nest. The female is attracted to the nest and spawning occurs within the nest with eggs being laid in a gelatinous mass on the bottom.
After the eggs are laid, the male takes over and cares for the eggs by constantly fanning them with his fins to provide aeration and to remove waste products given off by the developing eggs. Females spawn only once a year, producing about 3, to 4, eggs per pound of body weight, while the males may spawn more than once. In wild populations, males seldom spawn more than once a year, but in hatcheries where the eggs are removed from the spawning container soon after being laid, males may spawn 3 or 4 times; and there is a record of one male spawning nine females in one season.
Channel catfish usually become sexually mature at 3 years of age, although some may spawn when 2 years old. In wild populations they may not spawn until after the age of 5 years. After the eggs are laid they will usually hatch in 5 to 10 days depending on water temperature. Newly hatched fry have a large yolk sac which contains the nourishment they need for the next 2 to 5 days until they are fully developed and are ready to start feeding.
After the yolk sac is absorbed, the fry take on their typical dark color and will begin to swim-up looking for food. At first swim-up fry will gulp air to fill their swim bladders which helps them maintain and regulate their buoyancy.
Nine aquafeed companies from across the globe have officially joined the F3 Challenge - Carnivore Edition — which aims t…. Distribution Channel catfish were originally found only in the Gulf States and the Mississippi Valley north to the prairie provinces of Canada and Mexico, but were not found in the Atlantic coastal plain or west of the Rocky Mountains.
Physical characteristics Like all native North American catfishes, a channel catfish has a body that is cylindrical in cross-section, and lacks scales. Figure 1: External parts of the Channel Catfish. Figure 3: Schematic drawing of gill filament. Africa's emerging aquaculture leaders attend training course in Ghana 8 Nov During the day, when water temperatures rise, catfish can be found in deep holes, or underneath shelter such as logs or large rocks.
Most feeding and activity occurs at dusk or night. Adult channel catfish are primarily sedentary, choosing to stay in one area of the majority of their life span, while young catfish move around more frequently often in search of food.
Feeding occurs at any time of the day or night and consists of a diet rich in plant and animal material. Channel catfish feed on the bottom, but will feed at the surface, most often when food is being provided from an outside source, such as in an aquaculture facility. Young catfish feed mostly on aquatic insects, while adults have a more diverse diet that includes crawfish, aquatic insects, plant material, snails, green algae, seeds, small fish, and there are even records of small birds being eaten.
Channel catfish grow best in warm waters and the average size is 2 to 3 pounds. The largest catfish caught on record was 58 pounds. Catfish usually reach one pound by 2 to 4 years old, and the longest recorded living catfish was 40 years old.
Most channel catfish harvest commercially are about 2 years old. Channel catfish are cavity spawners, choosing to lay eggs in dark holes, or under logs and rocks. They usually spawn in the summer months when water temperatures are the highest. Largemouth bass tend to remain relatively small e. When stocked at the same time, channel catfish fingerlings should be larger than bass fingerlings.
When same-size catfish and bass fingerlings are stocked, channel catfish should be stocked six to eight months prior to bass. In ponds larger than one-half acre without fish, where channel catfish is not the focal species but one of several sport fish species, typically small fingerling channel catfish and bream species e. Then depending on bass goals, 40 to small fingerling largemouth bass per acre are stocked during the following spring.
When stocking channel catfish into a pond with an established largemouth bass population, advanced fingerling catfish longer than 8 inches should be stocked to avoid significant depredation of supplementally stocked catfish. Such advanced fingerling catfish generally grow to edible size after one growing season.
Channel catfish fry do not recruit well in ponds where significant numbers of adult largemouth bass exist. Catfish may spawn in such ponds, but adult bass consume most, if not all, catfish fry and fingerlings. Thus, advanced fingerling channel catfish must be periodically stocked to maintain catfish fisheries in ponds with bass. Mike Porter serves as a senior wildlife and fisheries consultant with Noble Research Institute, where he has worked since
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