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Becker, George C. / Fishes of Wisconsin

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

Page 724

724    Bullhead Catfish Family-Ictaluridae 
the Oconomowoc River (Waukesha County), showed 
the following growth (Paruch 1979): 
Age    No. of 
Class   Fish 
Avg   Range 
Calculated TL at 
1    2      3 
I        6        76.3 74-81       69.6 
II       6        99.7  88-113     42.4 99.7 
Il1     18       111.7  96-126     37.9 71.9 111.7 
Avg (weighted)                     45.2 78.9 111.7 
Age-I and age-II fish each had condition (Ku) means 
of 1.31, and age-III fish had a condition mean of 1.22 
  The largest Wisconsin specimen seen was a 126-mm 
(5-in) slender madtom from the Oconomowoc River 
sample. The largest slender madtom known was a 
specimen retained in an aquarium at the Museum of 
Zoology, University of Michigan, for 11/2 years; it had 
attained 113 mm SL (estimated 132 mm TL) (Taylor 
  The slender madtom is insectivorous. In late May, 
the stomach contents of a fish from the Bark River 
contained mostly caddisflies, a trace of midgeflies, 
unidentifiable insects parts, filamentous algae, and 
debris. In aquariums this species will take a variety 
of foods, including earthworms, insect larvae, and 
dry rations. According to Miller and Robison (1973), 
it hides under stones and in weeds during the day, 
venturing forth after dark to feed on insect larvae and 
other small animals. 
  Several slender madtoms were studied in a large 
aquarium in the Museum of Natural History at Ste- 
vens Point, Wisconsin. In one end of the aquarium, 
a number of large stones was heaped up. Each of the 
six madtoms selected a niche for itself among the 
stones, and seldom ventured from this except when 
food was introduced into the aquarium. When one 
slender madtom followed food into another's occu- 
pied den, there was a struggle for at least a piece of 
the worm (W Paruch, pers. comm.). The fish chased 
and nipped one another when territorial rights were 
  With the lights on in the room and the aquarium 
bathed in light, there was little activity among the 
fish. Normally, each individual rested quietly in its 
crevice, and only at long intervals shifted its position. 
Sometimes a fish assumed a rigid headstand or tail- 
stand position for 15-30 min or more, using a vertical 
side of a rock as a prop. An individual fish in phys- 
iological distress would swim frantically up and 
down the side of the aquarium opposite the mound 
of rocks, and, within hours, or up to a few days later, 
such fish died. 
  With the lights extinguished in the museum and 
the aquarium in darkness, the slender madtoms 
swam from their holes and soon cleaned up food 
from the floor of the aquarium just as they entered 
open shallows to feed during the night in their native 
waters. Bunting and Irwin (1965) noted that daylight 
seining for madtoms proved ineffective because the 
fish were located on the bottom among rocks and de- 
bris at that time; but at night, when madtoms moved 
into open water, more than 600 specimens were 
  When the aquarium lights were turned on late at 
night, there was a frantic flurry of activity. Some in- 
dividuals headed directly for the mound of stones, 
but others swam violently from one side of the 
aquarium to the other, their unscaled bodies undu- 
lating from side to side like oversized tadpoles. An 
occasional individual, totally disoriented, swam the 
entire length of the 50-gallon aquarium, and at full 
speed struck the glass with such a thud that it could 
be heard the length of the museum. On several oc- 
casions, an individual knocked itself senseless for a 
few seconds. 
  According to Bunting and Irwin (1965), during a 
holding period of 20 days, a number of slender mad- 
toms died when the aeration pump stopped for 24 
hours during a power failure. When aeration was re- 
established, surviving specimens were in poor con- 
dition but recovered within a few hours. 
  When subjected to toxicity bioassay, using petro- 
leum refinery effluent as a toxicant, the slender mad- 
tom exhibited little reaction to the test solutions. 
Only when the toxic concentrations were high was 
there an initial and brief distress. 
Predation on the slender madtom by fish or wading 
birds is probably low because of its secretive daytime 
habits. It may be more vulnerable at night when it 
leaves cover. However, the slender madtom can ma- 
neuver and swim quickly for short distances, and 
probably elude most pursuers. For their size, these 
madtoms are fast swimmers and quite energetic. 
  The slender madtom is much too small to be used 
as a food fish for people, although it is occasionally 
taken with worms on small hooks. 
  Several authors agree that the slender madtom is 
an interesting, adaptable aquarium fish. "Its loach- 
like form, serpentine swimming-motions, and odd 
poses when at rest add to its interest as a novelty in 
aquaria" (Cross 1967). 

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