The blue catfish ( Ictalurus furcatus) is the largest freshwater sportfish in Texas and the largest North American catfish species, making it an extremely popular sport fish. Tales of blue catfish reaching enormous sizes have captured the imagination of anglers for generations. American author Mark Twain even recounted seeing blue catfish on the Mississippi River that were close to 6 feet long and weighed nearly 250 pounds.
Classification and Distribution
Belonging to the Ictaluridae family, which includes channel catfish, white catfish, bullheads, and flathead catfish, the blue catfish was first described by Achille Valenciennes in 1840. Native to the southern reaches of the Mississippi, Missouri, Ohio, and Rio Grande river basins, its original range extended from southern Pennsylvania west to South Dakota, south through southwestern Nebraska, and southward to the Gulf of Mexico, including coastal Texas, New Mexico, and parts of Mexico and northern Guatemala along the Gulf Coast.
However, due to its popularity as a sportfish, a fierce predator, and its use in commercial stocking, the blue catfish has expanded well beyond its native range. Within Virginia, blue catfish are only native to the upper reaches of the Tennessee River Basin. Established populations also exist within Virginia’s Chesapeake Bay tributaries (e.g., the James River) as well as tributaries to North Carolina’s Albermarle Sound (e.g., the Nottoway River). They are most commonly found in large rivers, such as the Mississippi, Ohio, and Wabash Rivers.
Physical Characteristics
Like other catfish species, the blue catfish has smooth scaleless skin and soft barbels around the mouth, which are harmless sense organs used primarily for locating food. The four barbels above the mouth are dark, while those below are lighter in color, ranging from white to gray. The mouth is slightly subterminal, large for its body size, and contains hundreds of small cardiform teeth.
The head is round with small eyes positioned more forward compared to channel catfish. Some blue catfish exhibit a slight body hump behind the head where the dorsal fin sits. The dorsal and pectoral spines have well-developed serrations that become dull with age. Behind the dorsal fin is an adipose fin, which is rounded and flexible at the tip. The caudal fin, or tail fin, is deeply forked. A notable difference between blue and channel catfish is the anal fin: blue catfish have a straight-edged anal fin, while channel catfish have a rounded one. The anal fin of the blue catfish is also longer, with more rays.
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Body coloration is generally bluish to gray on the back and head, lightening to a white to gray belly region. The fins are light-colored with dark margins. Unlike young channel catfish, blue catfish typically lack black spots on the body, except for the Rio Grande population, which may have dark spots on the back and sides.
Spawning and Life Cycle
Blue catfish spawn once per year, in late spring and early summer. The spawning season begins in early summer when water temperatures range from 70°F to 77°F, with peak activity occurring between 75°F and 82°F. They are primarily cavity nest spawners. The male selects a cavity, often under rocks, in undercut banks, under root wads, in a barrel, or under fallen trees, and prepares it by sweeping the area with his tail to remove debris and expose the hard bottom.
Courtship involves cues such as the male's body darkening, specific swimming patterns around the female, mild biting, and rubbing his belly and barbels on her face. Females typically select one male per season and lay 2,000 to 4,000 eggs per pound of body weight. The translucent and adhesive eggs stick to the nest substrate, darkening and turning yellow over one to two weeks.
Hatching time depends on water temperature and flow, with the male pushing water over the eggs periodically. At 77°F, eggs hatch in about 10 days, but this can be reduced to 6 days at 80°F. Upon hatching, the fry are without pigment and non-mobile.
Blue catfish grow and mature more slowly than channel catfish. They grow an average of 3 to 6 inches in length in their first year, continuing at a rate of 2 to 4 inches per year, speeding up as they exceed 12 inches. Males typically mature in at least 4 years, while females take 5 years.
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After the spawning process, fertilized blue catfish eggs usually hatch in six to ten days depending on water temperature. Optimal temperatures for egg growth range between 25 to 27 degrees Celsius, while temperatures below 21 degrees tend to damage eggs and promote fungal growth, resulting in weak fry. Once hatched, blue catfish remain in the fry stage until they completely absorb their yolk sacs, a process that is also dependent on water temperature and usually takes between 3 to 6 days.
Blue catfish become sexually mature between the ages of 4 to 7 years; at this time, they are generally 35 to 66 cm (14 to 26 in) long and weigh 2.3 kg. During the first few years of development, blue catfish grow slowly; however, this rate typically increases with their size as they age. Growth rates vary from river to river depending on the population density and available food. Both male and female blue catfish are necessary in order for reproduction to take place. Blue catfish spawn monogamously, mating with only one partner per yearly reproductive cycle.
Habitat and Behavior
Adult blue catfish thrive in rivers with quick currents or deep lakes with large amounts of open water. They prefer secluded areas and are often found in deep channels or pools where they can ambush prey. They can also be found around gravel or sandy areas in lakes where hard substrate is limited. Temperature influences their location, with blue catfish moving to warmer waters during colder periods and cooler waters in summer months.
Blue catfish commonly rest during the day near the bottom of deep, restrictive waters. During the night, they swim to swifter, faster flowing waters, to find food. Blue catfish also exhibit migratory behaviors and adjust to temperature changes within their habitats by swimming to warmer waters during the winter and cooler waters during the summer. They often travel upstream during the reproductive seasons and tend to move back downstream towards estuaries after the mating season.
Feeding activity peaks in the early morning or late evening, depending on the size of the fish. Smaller to medium-sized blue catfish can be caught on shallow flats, while larger fish feed in deeper areas where the current delivers food. They sometimes school up and feed in groups throughout the water column.
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Blue catfish have a well-developed system for communication based on the release of chemical pheromones and sensory organs. Their communication systems are developed enough that social systems such as pecking orders have been observed. Hormonal pheromones also play a key role in reproduction and mating systems between blue catfish.
Diet and Feeding Habits
Blue Catfish are an omnivorous, or trophic generalist species of fish. Because of this, their diet varies by waterbody and the availability of prey items, but studies indicate that their diet most often consists of small fish, crayfish, mollusks, and plant matter.
Blue catfish are opportunistic feeders, using taste receptors on their barbels and throughout their body to locate food from great distances, even in low-visibility conditions. They primarily feed at the bottom of the water column but occasionally venture to the surface, though their mouth orientation can make surface feeding challenging.
Juvenile blue catfish consume aquatic insects, zooplankton, and detritus. As they grow beyond 4 inches, they begin to consume various invertebrates and mollusks, including crayfish, crabs, and freshwater mussels. Once they reach 10 inches, fish become a significant part of their diet, leading to increased growth rates. Blue catfish consume their prey whole, with mouth size being the primary limiting factor in what they can eat.
A recent study estimated food consumption rates for blue catfish in four tidal tributaries of the Chesapeake Bay: the James River, the Mattaponi River, the Pamunkey River, and the Rappahannock River. The research found that, on average, a blue catfish eats roughly 2-5 percent of its body weight in food per day during peak feeding season. When given unlimited food (blue crab or gizzard shad) in a laboratory setting, they could consume 8-9 percent of their body weight in a day. Medium-sized blue catfish consumed more food than the largest blue catfish in the laboratory tanks.
Conservation and Management
Blue catfish have an expanded range and a stable population within their home range. The introduction of large reservoirs with deep water and current-controlling dams has provided refuge for adult catfish. However, due to their lack of scales, they are susceptible to parasites and bacterial infections.
The species' introduction into new ecosystems has had unintended consequences. In Virginia, blue catfish were initially introduced by The Virginia Department of Wildlife Resources (DWR) into the James and Rappahannock Rivers in 1974. Additional stockings took place within the York River watershed in 1985. Once established, the Blue Catfish population grew rapidly in Virginia through the 1990s. One unintended consequence of establishing this new fishery was the range expansion of Blue Catfish into adjacent river systems. When Blue Catfish were initially stocked in 1974, it was a common belief that the species would be confined to the rivers in which they were stocked.
Blue Catfish now inhabit the same waters as several of Virginia’s iconic wildlife species. Many of these, such as Atlantic Sturgeon, American Shad, Blue Crab, and River Herring are invaluable from a cultural, commercial, ecological, and recreational standpoint
The overabundance of Blue Catfish in Virginia’s tidal rivers gives beginner anglers great opportunities at success when fishing with such setups.
The increased population growth and dominance of blue catfish has triggered declines in other aquatic organisms. Declines in the populations of white catfish, shads, and herrings were most notable upon the introduction of blue catfish in states like Maryland, Ohio, and Virginia.
Blue catfish populations generate important economic benefits in both recreational and commercial fishing. In the many of the nation’s major rivers, blue catfish can grow to large sizes, so recreational fishers often travel to locations in hopes of catching them. This popularity has led to a profitable business in guided fishing tours. Their abundance and firm tasty flesh make them a source of profit for several inland fisheries. Blue catfish account for one third of the total recreational fishing efforts in some areas, offering a market gain for environmental agencies and fisheries alike.