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Becker, George C. / Fishes of Wisconsin

Minnow and carp family - cyprinidae,   pp. 415-605 ff. PDF (93.4 MB)

Page 604

604    Minnow and Carp Family-Cyprinidae 
summer of life (age I), and some individuals probably 
do not mature until their third summer (age II). Age- 
III fish rarely appear in collections (Carlson 1967, 
Held and Peterka 1974, Chadwick 1976). 
  The largest fatheads observed, 90-101 mm TL, 
were reported from Smithys Lake (Nebraska) (Mc- 
Carraher and Thomas 1968). 
  The fathead minnow is an opportunistic feeder. In 
northern Wisconsin ponds, the stomach contents of 
fatheads consisted of algae, fragments of higher 
plants, and mud (Williamson 1939). In southeastern 
Wisconsin (Cahn 1927), the fathead was observed to 
be a bottom feeder, grubbing in the soft bottom for 
insect larvae, which formed over 90% of its diet. 
  In a Missouri pond (Divine 1968), fathead min- 
nows less than 35 mm long ate a variety of foods, 
including higher plant materials, filamentous algae, 
and colonial algae. In another pond, the dominant 
food item changed each month: filamentous algae 
(Spirogyra, Mougeotia) in June, copepods in July, Cla- 
docera in August, and insects in September. All 
larger fish consumed a greater variety of organisms, 
including-in addition to those mentioned above- 
protozoans, rotifers, and insects; insects constituted 
more than 85% of the diet in August. 
  The upper limit of the fathead minnow's temper- 
ature tolerance (permitting 50% survival) is 33°C 
(91.4°F); the lower limit is 2°C (35.6°F) (Bardach et al. 
1966). Temperature preference, determined experi- 
mentally, was 22.6°C (72.7°F) (Jones and Irwin 1962). 
Brungs (1971) evaluated the chronic effects of con- 
stant elevated temperatures on this species: the num- 
ber of eggs produced per female, the number of eggs 
per spawning, and the number of spawnings per fe- 
male were gradually reduced at successively in- 
creased temperatures above 23.5°C (74.3°F). No 
spawning or mortality occurred at 32°C (89.6°F). 
  The fathead minnow probably exhibits the great- 
est ecological diversity of all cyprinids occurring in 
North America. Cross (1967) referred to it as a 
"pioneer" (p. 151): 
... It is one of the first species to invade intermittent drain- 
age channels after rains, and it commonly progresses up- 
stream into farm ponds via their spillways. It is one of the 
last species to disappear from small, muddy, isolated pools 
that remain in stream channels during droughts. This spe- 
cies has other attributes of hardiness that enable it to flour- 
ish where few other fish survive. It seems unusually toler- 
ant of pollution, in streams having little oxygen as a 
consequence of sewage influx or barnlot drainage, and in 
other streams that are saline owing to effluents discharged 
by the petroleum industry. 
  The fathead is often found in lakes where most 
other species succumb to winterkill; it may survive in 
muskrat burrows at such times (Carlander 1969). It is 
tolerant of both clear and turbid waters, and of a 
wide range of pH. 
  In Little Hemlock Creek (Wood County), 190 fat- 
head minnows were collected with these species: 
white sucker (75), blacknose dace (28), creek chub 
(75), pearl dace (6), northern redbelly dace (32), 
bluntnose minnow (13), common shiner (178), black- 
nose shiner (12), bigmouth shiner (6), brassy min- 
now (3), black bullhead (1), central mudminnow (13), 
blackside darter (1), johnny darter (13), pumpkin- 
seed (3), and brook stickleback (6). 
The fathead minnow is an ideal forage fish, since it is 
widely distributed, small, and highly prolific, and 
has a prolonged spawning period, assuring the avail- 
ability of recently hatched or small fatheads to preda- 
tors throughout the summer months. All fish-eating 
birds and fishes associated with it must at one time 
or another use this minnow as food. Isaak (1961) 
noted that large leeches and painted turtles prey on 
the eggs of fathead minnows and destroy many fat- 
head nests. The male's attempts to ward off these 
predators are futile. 
  The fathead minnow is unable to maintain itself in 
streams or lakes which have a heavy population of 
predacious fish. In Wisconsin, the fathead is least 
common in streams which support numerous other 
kinds of fish; where the fathead does occur in such 
waters, it is generally found to be at depressed popu- 
lation levels. It becomes abundant in streams "pecu- 
liar in having emergent vegetation in pools, and a 
scarcity of other minnows" (Starrett 1950a). 
  In Wisconsin, the fathead minnow is a major bait 
fish, available at most bait stations. It is ideal bait for 
crappies, perch, white and yellow bass, and rock 
bass; the largest adults are suitable for walleyes, 
bass, and larger game fish. The fathead is one of the 
hardiest of fishes, and, if hooked through the lips or 
the tail, or under the dorsal fin, it will stay alive for a 
number of hours. 
  The fathead minnow has been used extensively as 
a testing animal, and culture units of fathead min- 
nows for this purpose are maintained at research 
laboratories (Benoit and Carlson 1977). Numerous 
studies of the effects of toxic substances on the fat- 
head minnow's body tissues, eggs, and fry are re- 
ported in the literature. 

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