TN00346 FLATHEAD CATFISH PYLODICTIS OLIVARIS
Physical description: The head length is contained about 3.5 times, body depth about 5.0-5.5 times, in standard length. The barbels are moderately long, the anal fin short and concave, with its origin far behind the vent. The humeral process is short *789*. This is the second largest ictalurid, and the largest in Virginia. The adults commonly reach 400-900 mm TL. It is known to exceed 1000 mm TL and weigh over 31 kilograms. They may occasion- ally reach 45 kilograms. The largest from Virginia was 25.9 kilograms. The body is somewhat slender, sometimes bulky, and the the anterior body is depressed with the head broad and flat, the posterior body round or slightly compressed. The mouth is terminal and the eye small or moderate. The pectoral spine is nearly straight, roughened anteriorly, with numerous posterior ser- rae. The dorsal fin has 1 spine and 6 rays. Branched caudal rays number 15 and anal rays 14-17. Pelvic rays number (9)10 and the pectoral has 1 spine and 10-11 rays. The young are dark brown to black. The adult dorsum, side and fins are yellow, olive, or brown, mottled with medium to dark brown. The venter is yellow to yellow-white. The depigmented upper caudal tip is white in the young, paler than the lower lobe in juveniles and some adults *4205*. Reproduction: In Virginia, spawning likely peaks in June and July, based on timing in other states of similar latitude. The caudal embrace characteristic of some other ictalurids also occurs in flatheads *4205*. In Kansas and Iowa, they spawn in late June or July *3126,2980*. In a Texas lab study, parents made a nest depression in gravel. Under natural conditions, the preferred nest sites are shelves with overhanging ledges, hollow logs, or other well protected sites *1540*. The incubation period in the lab was 7-8 days *1540*. The clutch size may be as large as 1,000,000 *1187*. In Kansas, the fecundity of females 21-24 inches long was 6900-11300 eggs. The eggs hatch into sac larvae, yolk sac is absorbed in approximately 6 days *1540*. During incubation, the parents guard the eggs and nesting territory *2737,1187*. In Kansas and in Texas lab studies, only the male fanned and guarded the eggs *1540,2980*. The young stay tightly schooled for several days after hatching, and by mid-July they leave the nest and are found mostly on shallow riffles beneath stones or other cover, the yearlings are more scattered, some near large stones in riffles, or under woody debris in shallow water, while others occupy pools. The adults are almost exclusively in pools *2737*. In the Mississippi River, they are mature when they are 4-5 years old and 18 inches long *1537*. In Kansas, males mature at 15-18 inches long and 3-5 years, females when 18-20 inches long and 4-6 years *2980*. The average individual matures at 18 inches long and age 4 *2737*. In Iowa, sexual maturity is reached in 3-4 years *816, 1310,2737*. Behavior: This species exhibits a dietary shift similar to other catfishes. The young depend mostly on insect larvae and some microcrustaceans, while adults feed primarily on fishes, also taking crayfishes and clams *4205*. Flatheads are solitary, establishing individual territories under a single unit of cover, such as a drift pile. Each individual normally has a favorite resting spot where it will be found each day unless disturbed. It feeds on the bottom, and is active at night *789,1187*. They exhibited homing in an Oklahoma study: 67% of fish displaced 1.3 to 2.7 km from site of capture returned to the original site, 95% returned to within 494 meters of the original site *5680*. Results of an Arkansas study indicate a spring migration and temporary departure from home range. The average interval travelled between taggings was 44.3 km *5591*. Origin: This species is native to the Tennessee, Big Sandy, and New drainages and introduced elsewhere *4205*. Population parameters: The sex ratio is 1:1 *1187*. They may live 20 years *816,2737*. The young-of-year are 2.7 to 2.8 inches long in August *3126*. In Iowa, they reach 2-6 inches in their first year *2738*. In Missouri, they reach 3 inches in their first year, and average 6.1, 9.1, 11.8, 13.7, 16.6, and 17.8 inches in succeeding years *5967*. The adults are commonly 15-45 inches long, and weigh 1-45 pounds, with the state record at 94 pounds *1187*. Parasites include cestodes and nematodes *6106*. This species grows faster in shallow, turbid waters than in clear waters *4205*. Aquatic/terrestrial associations: Fifteen years after its introduction to the Cape Fear River, North Carolina, the flathead has become the dominant main- stream predator. An associated severe decline in other fish species, espec- ially catfishes, has been noted *4205*.
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References for Life History Codes
816, 789, 1310, 3126, 2980, 2737, 1540, 1187, 1537, 6106, 5680, 5967, 5591, 4205
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