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Becker, George C. / Fishes of Wisconsin
(1983)

Bullhead catfish family - ictaluridae,   pp. 693-732 PDF (19.6 MB)


Page 731

 
Flathead Catfish  731 
the upper lobe of the caudal fin may indicate sexual 
maturity. 
  Large flathead catfish are reported yearly from 
Wisconsin. In the Lake Michigan basin, individuals 
weighing 9.1-18.1 kg (20-40 lb) are common. A 27.7- 
kg (61-1b) fish was caught from the Fox River at Eu- 
reka (Winnebago County) in 1966. In the Mississippi 
River, commercial fishermen have reported speci- 
mens as large as 1.5 m (5 ft) and 45.4 kg (100 lb) 
(Harlan and Speaker 1956). In 1911, two flathead cat- 
fish weighing 53.5 and 56.7 kg (118 and 125 lb) were 
reported caught on setlines (Bachay 1944). 
  In Wisconsin, a 419-mm (16.5-in) channel catfish 
was taken from the stomach of an 18.1-kg (40-1b) flat- 
head from the Pecatonica River, and a 457-mm (18- 
in) northern pike was taken from the stomach of a 
7.26-kg (16-1b) flathead from Lake Puckaway. Unlike 
the channel catfish, the flathead is not a scavenger; it 
rarely eats dead or decaying matter. Stomachs usu- 
ally contain small quantities of debris consisting of 
mud, sand, gravel, pieces of wood, and leaves. Bull- 
head and channel catfish spines have been found 
imbedded in the stomach wall or mesenteries of flat- 
head catfish. 
  In flathead catfish measuring more than 250 mm 
(10 in) from the Big Blue River, Kansas (Minckley and 
Deacon 1959), fishes occurred in 90% of the stom- 
achs that contained food and comprised 79% vol- 
ume. The ingested fishes identified from Kansas col- 
lections were suckers, minnows, channel catfish, 
madtoms, darters, sunfish, and freshwater drums. In 
the Neosho River, crayfish constituted a large part of 
the diet of larger flatheads. 
  Flathead catfish feed most actively in May and early 
June, and from July to September; they feed less dur- 
ing the winter months and in late June and early July, 
when spawning occurs. The flathead is often a pas- 
sive predator that lies in wait for its victim (Minckley 
and Deacon 1959:347): 
We twice observed the feeding behavior of a 14-inch speci- 
men in an aquarium. The fish lay motionless, except for 
slight movements of the eyes and opercles, and allowed 
the food-fish (Notropis lutrensis) to draw near, on one occa- 
sion touching the barbels. Then, with a short lunge by the 
catfish, the minnow was eaten. 
Trautman (1957) has observed flathead catfish feed- 
ing at night on riffles so shallow that their dorsal fins 
stuck out of the water; he has also seen them lying 
on the bottom, usually beside a log or other object, 
with their mouths wide open. Ohio River fishermen 
have reported that they have seen frightened fish dart 
into the open mouths of flatheads, to be swallowed 
immediately. The large numbers of such hiding spe- 
cies as rock bass, spotted black bass, and small cat- 
fishes found in the stomachs of large flatheads lend 
credence to these statements. 
  In the Wabash River, Indiana, the optimum tem- 
perature range for the flathead catfish was 31.5-33.5°C 
(89-92°F) (Gammon 1973). Gammon noted that the 
flathead catfish is sedentary, and that tagging studies 
suggest that it does not move about enough to en- 
counter the other thermal possibilities. In 1971, elec- 
trofishing catches of flathead catfish were uniformly 
low among nearly all of the zones studied. In the same 
year the Cayuga power plant began releasing heated 
effluents into the river which, according to Gam- 
mon, was responsible for a "dramatic . . . increase 
... in the density of flathead catfish in the heated 
zones alone." He reported that in 1972 "the major in- 
crease came from large numbers of 100 to 200 mm 
long fish, presumably the result of a highly success- 
ful 1971 year class, the first year class to follow the 
introduction of heated effluents into the river." 
  According to Minckley and Deacon (1959), young- 
of-year flatheads move or are carried from the place 
of hatching to swift, rubble-bottomed riffles where 
they remain until they are 51-102 mm (2-4 in) TL. At 
that size, the young fish become more evenly distrib- 
uted in the stream; some remain on the original rif- 
fles, but more move into pools, deeper riffles, and 
into almost all other habitats. This random distribu- 
tion seems to be the rule among fish ranging from 
102 mm (4 in) to approximately 305 mm (12 in) long. 
Large individuals, more than 406 mm (16 in) long, 
are found near the more massive logs and drift piles, 
and usually in or near deep holes in the stream bed. 
A drift pile usually yields only one, or at most two 
or three adults. Each individual has a favorite resting 
place where it can be counted on to be each day un- 
less disturbed (Pflieger 1975). In the Mississippi River 
during the winter, the flatheads go into a "pseudo- 
hibernation state, embedding themselves in muddy 
holes in forty to sixty feet of water" (Bachay 1944). 
  Two out of three flathead catfish, implanted with 
ultrasonic transmitters and displaced a distance of 1.3- 
2.7 km (0.8-1.7 mi) from their site of capture, showed 
a strong tendency to return to the point of release 
(Hart 1974). Funk (1957) classified the flathead cat- 
fish as a semimobile species. He reported that 48.9% 
of tagged flathead catfish which were recaptured were 
found less than 1.6 km (1 mi) from the point of tag- 
ging; 72.1% were found less than 8.1 km (5 mi) from 
the point of tagging. No fish was recovered more than 
80.7 km (50 mi) from the point of release. 
  Fighting between members of this species appears 
to be common. When a female flathead was returned 
to the tank with a male with which she had spawned 


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