Regions native to blue catfish include the Mississippi, Missouri, and Ohio river basins and the Gulf of Mexico drainages that stretch north from Pennsylvania to South Dakota, and south to the Gulf Coast. Between 1974 and 1985 the United States Fish Commission and the Virginia Division of Inland Fish and Game stocked blue catfish in the James, Rappahannock, and York Rivers. Since then, they have quickly expanded to major tributaries in Maryland and Virginia, and the surrounding Chesapeake Bay areas. Smaller introductions of blue catfish have taken place in the rivers of more than 5 other states such as Alabama, Florida, and California, as well as Mexico. Today, their habitat includes most rivers in California, Louisiana, and the Atlantic slope regions including the Rio Grande, James, Rappahannock, Mattaponi, York, Potomac, Patuxent, and Nanticoke Rivers. There have also been reports of blue catfish in the Burke and Brittle Lakes and far north in the Chesapeake Bay tributaries such as the Susquehanna River. ("Blue catfish - Chesapeake Bay", 2014; "Invasive catfish", 2013; "Ictalurus furcatus", 2013; Schloesser, et al., 2011; "Ictalurus furcatus", 2014)
Blue catfish prefer to live on the sandy bottoms of medium to large freshwater channels and pools that possess swift and well-flowing currents in depths greater than 6 meters. They enjoy living near or in complex structures and rock piles that offer both cover and a place to rest without currents. During spring, they may enter areas with little to no currents such as backwaters, sloughs, and reservoirs for nesting and reproduction. During these times, they seek protected, slightly isolated, and covered areas such as in logs and under rocks. Blue catfish have a more migratory nature than other catfish and often travel long distances in pursuit of these locations. This species adjusts to water temperature changes and swims to warmer waters during the winter and cooler waters during the summer. Although blue catfish prefer freshwater, in rare situations they can occur in brackish estuaries with salinities below 12%, and can tolerate salinities up to 22 ppt (parts per thousand). This tolerance has allowed blue catfish to pass through brackish waters that were thought to serve as barriers. They have now spread beyond the rivers and tributaries stocked by the USFC. ("Blue catfish - Chesapeake Bay", 2014; "Blue catfish", 2012; Jenkins and Burkhead, 1994; "Maryland fish facts", 2014; Murdy, et al., 1997; "Invasive catfish", 2013; "Ictalurus furcatus", 2013)
Blue catfish are included in family Ictaluridae, or bullhead catfishes, and have many characteristics shared by members of this family. These characteristics include lack of scales, a single dorsal fin followed by an adipose fin just before the caudal fin, and a flat anal fin. The anal fin is long, possesses a straight distal margin, and contains between 27 to 38 rays, although the typical range is 30 to 36. The tail fin, or caudal fin, is deeply forked and contains 16 branched rays with 6 soft rays. Their dorsal fin and posterior fins contain spines, which are strongly serrated for defense. Blue catfish have eight barbels (whiskers) positioned around their faces. Two barbels arise dorsally, from the nose, two extend from both corners of the mouth (one for each corner), and four protrude from the chin. Their jaws contain small teeth in villiform bands. Recognized for their large bodies that can weigh up to 100 pounds (45kg), blue catfish can reach two to five feet in length (600 to 1500mm). Their bodies appear bluish-silver and grey dorsally, silvery-white on their sides, and white ventrally. They have similar characteristics as channel catfish; however, unlike channel catfish, blue catfish have no dark blue spots, possess a straight edged adipose fin, and usually have more than 29 rays in their anal fin. No sexual dimorphisms have been observed in blue catfish. ("Blue catfish", 2012; Jenkins and Burkhead, 1994; "Maryland fish facts", 2014; Murdy, et al., 1997)
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. Although the exact habits of blue catfish hatchlings are unknown in the wild, in hatcheries the fry have been observed swimming in schools for several weeks before dispersing; however, this may occur for a shorter time in the wild. 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. In the James River, they can grow up to 3 pounds in the first 8 years, while in 11 years, they can reach 20 pounds. ("Blue catfish - Chesapeake Bay", 2014; Greenlee, 2011; Jenkins and Burkhead, 1994; "Freshwater catfish in Texas", 2012; Wyatt, et al., 2006)
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. Mating includes many chemical interactions between males and females. Males build nests and attract females using species-specific pheromones before they swim together in various patterns. (Holtan, 1998; Jenkins and Burkhead, 1994; "Ictalurus furcatus", 2014)
Spawning and breeding season occurs once a year, between April and June in freshwater reservoirs and backwaters depending on geographic location. Their general behavior and semantics of reproduction share similarities with the entire Bullhead family, especially with channel catfish. Reproduction begins with the foundation and creation of a nest in a suitable place by a male. They use a vigorous sweeping motion with their tails to clear debris and use their jaws to remove larger objects; their nests can range from 6 to 14 inches in diameter. Attraction between male and female catfish occurs with the use of pheromonal cues. Catfish often perform various courtship swimming patterns and even mild biting in the nest before fertilization. Patterns include rubbing their belly and barbels on the female’s face. Reproduction proceeds from courtship behavior to female catfish depositing roughly 40 eggs at a time that adhere to the nest. For every kilogram of body weight, females lay 4,000 to 8,000 eggs, a gradual process that may take several hours. During egg dispersal, male catfish fertilize the eggs with their sperm, which is dispersed in the form of milt upon and near the eggs. Upon completing egg fertilization, male catfish chase the female away and guard, organize, and periodically ventilate eggs with their tails. Once the young blue catfish hatch, they are believed to form schools before becoming independent. Until then, fry remain in close proximity to their nest, which is guarded by the male. (Holtan, 1998; Jenkins and Burkhead, 1994; "Invasive catfish", 2013; "Freshwater catfish in Texas", 2012)
Although the male is the primary caretaker, both male and female blue catfish care for their fry. They seek low current areas with protective structures to better secure their eggs and rear their fry. In addition, they seek sturdy and stable surfaces to which their sticky eggs can properly adhere. Once eggs are fertilized, male catfish force females away from the nest to organize and protect the eggs. Males remain within the nest after eggs hatch to guard and direct the fry, leaving only when the fry completely absorb their yolk sacs. ("Blue catfish - Chesapeake Bay", 2014; Holtan, 1998; "Freshwater catfish in Texas", 2012)
Blue catfish have an average life expectancy of 9 to 10 years, but can live to ages upward of twenty years. Their life expectancy does not exceed 25 years, a record set in Virginia in the Rappahannock River. Life expectancies can range from river to river, with rivers in Virginia being better suited at producing older and larger catfish. In Maryland, electrofishing surveys produced blue catfish between the ages of 3 to 14 years; however, the majority were between 5 to 7 years old. High parental investment from male blue catfish in the early stages of development increases the longevity of the young by making it difficult for predators to prey on the species at an early age. During their early life, when they are smaller in size, they are hunted by other predatory fish such as flathead catfish and even their own species. However, as they age, they become larger than other predatory fish, resulting in less predation. ("Blue catfish", 2012; Greenlee, 2011; Murdy, et al., 1997; "Ictalurus furcatus", 2014)
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. The feeding nature of blue catfish is very opportunistic and can result in cannibalism. Catfish employ pecking orders to communicate fitness levels with other members of the same species. These behaviors include biting, slamming into each other, and highly energetic swimming. ("Blue catfish - Chesapeake Bay", 2014; "Blue catfish", 2012; Greenlee, 2011; Holtan, 1998; Jenkins and Burkhead, 1994; "Ictalurus furcatus", 2013)
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. In the wild, hybrids between channel catfish, a similar species, and blue catfish are very rare. This is most likely because each catfish species releases species-specific pheromones. Blue catfish have the ability to taste their surroundings with sensory tissues on their barbels and certain areas on their skin; they utilize these sensory devices to search for food. Instead of relying heavily on their eyesight, they use their barbels and olfactory senses to identify their surroundings. (Broach and Phelps, 2011; "Maryland fish facts", 2014)
The diet of a blue catfish periodically changes throughout its development, expanding from small invertebrates to a larger variety of fish, worms, clams, small crustaceans, mussels, crabs, insects and even frogs, as they age. Blue catfish are opportunistic feeders that search for food primarily with the use of sensory tissues on their barbels and skin. These taste buds enable blue catfish to taste the surrounding environment before they actually eat anything. Fry are very small and are easily preyed upon by other fish, so they feed nocturnally at low depths and near cover on zooplankton and aquatic insects. As they grow in size and age, their diet expands to include a variety of smaller fish, even their own species. Mollusks have also been found in catfish stomachs, including Asiatic clams. ("Blue catfish - Chesapeake Bay", 2014; Greenlee, 2011; Jenkins and Burkhead, 1994)
Sea and shorebirds, such as double-crested cormorants, willets, brown pelicans, and osprey, hunt small fish, including blue catfish. Catfish are actually preferred by bald eagles over other fish species. To avoid predation, blue catfish defend themselves with a serrated spinal barb located on both their dorsal and pectoral fins. The spines have glands positioned at their base that can expel toxins; they make their way into predators’ wounds and cause sharp pain. ("Blue catfish - Chesapeake Bay", 2014; "Blue catfish", 2012; Jenkins and Burkhead, 1994)
Blue catfish serve as predators and prey, providing food and selective pressure for the organisms that share their habitat. They also feed on many other fish, creating pressure and limiting the growth of these species. Blue catfish are an excellent food source for avian predators of the Chesapeake region and are also food sources for otters, and predatory fish like flathead catfish. As adults, blue catfish serve as a food source for humans and birds. Many blue catfish grow to tremendous sizes; this in combination with their feeding style has lead to the belief that they exhibit adverse effects on other fish communities. Their vast diet enables them to eat endangered fish like shads and herrings, causing these species to suffer a decrease in population size. Introduced in several rivers, blue catfish have overcome the salinity barrier that was originally thought to prevent them from expanding in other rivers. The abundance of blue catfish has caused competition with and reduced populations of white catfish in Virginia and Maryland. Bacteria including Aeromonas hydrophila, Flavobacterium columnare, and Edwardsiella ictaluri also impact catfish health. If a catfish is infected by Aeromonas hydrophila, they develop ulcers and their fins redden and begin to fray. Flavobacterium columnare causes catfish to develop infected white spots around their mouths, fins, and scales, and degenerates their fins. Edwardsiella ictaluri causes white lesions on their backs and sides to form, and external hemorrhages under their bodies and around their mouths. (Bonvechio, et al., 2012; Jenkins and Burkhead, 1994; Schloesser, et al., 2011; "Ictalurus furcatus", 2014; Wyatt, et al., 2006)
Blue catfish populations generate important economic benefits in both recreational and commercial fishing. In the James River, blue catfish can grow to large sizes, so recreational fishers often travel to Virginia and the surrounding commonwealths in hopes of catching them. This popularity has lead 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 Virginia, offering a market gain for environmental agencies and fisheries alike. In Virginia, commercial catches of blue catfish have made a dramatic increase from approximately 25,000 pounds in the early 2000s, to well over 1.5 million pounds in 2011. Not only are blue catfish used as sport fishes, they are also an important food source for more than sixteen states. They provide adequate economic success and good sport fishing for many people. ("Blue catfish - Chesapeake Bay", 2014; Greenlee, 2011; Schloesser, et al., 2011)
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. Due to the rapid decline of these organisms, blue catfish have gained recognition as a detriment to their own ecosystem. (Schloesser, et al., 2011)
Major threats for blue catfish come from impoundments like Bull Shoals and Table Rock reservoirs, which have resulted in population losses in the White River in Missouri. However, blue catfish are healthy members of family Ictaluridae, with populations that are considered to be of least concern overall. Birth, death, and growth rates remain stable for blue catfish. They are neither threatened nor endangered according to the IUCN, United States Federal List, CITES, or the State of Michigan List. ("Ictalurus furcatus", 2013)
Yama Barekzi (author), Bridgewater College, Maria Hawkins (author), Bridgewater College, Jacob Sheets (author), Bridgewater College, Tamara Johnstone-Yellin (editor), Bridgewater College, Leila Siciliano Martina (editor), Animal Diversity Web Staff.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
uses sound to communicate
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
areas with salty water, usually in coastal marshes and estuaries.
an animal that mainly eats meat
uses smells or other chemicals to communicate
ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates
humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
fertilization takes place outside the female's body
union of egg and spermatozoan
A substance that provides both nutrients and energy to a living thing.
mainly lives in water that is not salty.
Animals with indeterminate growth continue to grow throughout their lives.
An animal that eats mainly insects or spiders.
parental care is carried out by males
makes seasonal movements between breeding and wintering grounds
eats mollusks, members of Phylum Mollusca
Having one mate at a time.
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
chemicals released into air or water that are detected by and responded to by other animals of the same species
an animal that mainly eats fish
an animal that mainly eats plankton
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
movements of a hard surface that are produced by animals as signals to others
uses sight to communicate
animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)
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Chesapeake Bay Program. 2012. "Blue catfish" (On-line). Chesapeake Bay Program. Accessed April 20, 2014 at http://www.chesapeakebay.net/fieldguide/critter/blue_catfish.
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Murdy, E., R. Birdsong, J. Musick. 1997. Fishes of the Chesapeake Bay. Washington, D.C: Smithsonian Institution Press.
Schloesser, R., M. Fabrizio, R. Latour, G. Garman, B. Greenlee, M. Groves, J. Gartland. 2011. Ecological Role of Blue Catﬁsh in Chesapeake Bay Communities and Implications for Management. American Fisheries Society Symposium, 77: 369–382.
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