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Becker, George C. / Fishes of Wisconsin

Sculpin family - cottidae,   pp. 963-981 ff. PDF (8.9 MB)

Page 972

972   Sculpin Family-Cottidae 
the nest. In Erickson and Little John lakes (Vilas 
County), larval mottled sculpins were sporadically 
collected during May and June. Tow net data sug- 
gested that larval mottled sculpins located in open 
water areas for a short time (Faber 1967). Fish (1932) 
illustrated and described the 6.0-, 6.6-, 7.2-, 10-, and 
11-mm stages. 
  In Mt. Vernon Creek 6.5 months after hatching, 
male mottled sculpins averaged 37.5 mm SL, and fe- 
males, 33.8 mm SL (Ludwig and Norden 1969). In 
central Wisconsin, young-of-year from Lyndon Creek 
were 24-28 mm TL on 26 June; in northern Wiscon- 
sin, young from the Pine River (Florence County) 
were 18-25 mm on 22-23 July. In Lake Winnebago 
(Winnebago County), the young were 31-40 mm on 
18 August, and in Lake Michigan shallows (Door 
County), they were 27-42 mm on 19 September. 
  By examining the otoliths of mottled sculpins, 
Ludwig and Norden (1969) determined that, in col- 
lections made from Mt. Vernon Creek in May, age-I 
males averaged 37.5 mm SL, and females, 32.7 mm 
SL; age-II males, 59.2 mm, and females, 53.1 mm; and 
age-ILL males, 74.5 mm, and females, 67.9 mm. In the 
Wisconsin collections, only one fish of age-IV was 
found-a female which contained 949 eggs (Ludwig 
and Lange 1975). 
  In the lower Jordan River, Michigan, the calculated 
total lengths of mottled sculpins at annuli 1 through 
4 were 39.5 mm, 71.4 mm, 89.9 mm, and 87.8 mm; in 
the Ausable River, these lengths were 48.3 mm, 82.8 
mm, 102.9 mm, and 102.3 mm (Quick 1971). 
  Sexual maturity is reached by some mottled scul- 
pins at age II. Bailey (1952) noted that all females over 
74 mm (2.9 in) TL were sexually mature. The largest 
male, collected from an irrigation canal which origi- 
nated in the West Gallatin River, Montana, was 140 
mm (5.4 in) TL. A large Wisconsin mottled sculpin 
(UWSP 586) is a female, 137 mm (5.4 in) TL, taken 
from Elton Creek (Langlade County) on 20 July 1966. 
  In the Madison area, mottled sculpins fed mainly 
on amphipods, mayfly nymphs, and chironomid lar- 
vae, and to a lesser extent on caddisfly larvae, ostra- 
cods, copepods, cladocerans, oligochaetes, leeches, 
plant remains, and algae (Pearse 1918). Mottled scul- 
pins from the Lt. Plover River (Portage County) had 
eaten Gammarus sp., Diptera, and Trichoptera larvae; 
one stomach contained seeds (P. Brogan, pers. comm.). 
In the stomachs of mottled sculpins from southeast- 
ern Wisconsin, Cahn (1927) found stonefly larvae, 
small dragonfly and mayfly nymphs, chironomid 
and Simulium larvae, and rarely a small mollusk. A 
mottled sculpin from the Pine River (Florence County), 
104 mm TL, contained a 51-mm central mudminnow. 
  Mottled sculpins from the West Gallatin River, 
Montana, had ingested mollusks (Physa and Pisidium), 
insects (Ephemeroptera nymphs, Plecoptera nymphs, 
Coleoptera larvae and adults, Hemiptera, Trichop- 
tera larvae and pupae, Diptera larvae and pupae), 
Hydrachnidae, fish (longnose dace, mottled scul- 
pins), and the eggs of mottled sculpins. 
  A few cases have been reported of mottled sculpins 
eating the eggs of trout, but evidence indicates that 
these eggs were improperly covered with gravel by 
the spawning trout. Most studies indicated that the 
mottled sculpin feeds on invertebrates that are found 
between and underneath rocks, where they are not 
available to most other fish (Moyle 1969). Mottled 
sculpins are more or less continuous feeders. 
  In southern Ontario, mottled sculpins were taken 
at average water temperatures of 16.6°C (62°F) when 
air temperatures averaged 22.9°C (73°F) (Hallam 
1959). In Lake Monona (Dane County), Neill (1971) 
noted that this species tended to avoid the thermal 
plume of the Lake Monona steam generation plant. 
The unheated littoral zones, where this species oc- 
curred, rarely exceeded 29°C (84°F). In Lake Huron, 
the behavior of mottled sculpins was affected by a 
drop in water temperatures from 20 to 7'C (68 to 
45°F) within a few seconds; the drop was caused by 
a sudden underwater seiche (Emery 1970). The mot- 
tled sculpins ceased feeding, and, in the cold water, 
often swam erratically. A number died as a result of 
thermal stress. In Iowa streams, M. Johnson 
(1971-1972) found the mottled sculpin in waters av- 
eraging 20'C (16-22°C). 
  The large pectoral fins of the mottled sculpin are 
used in darter fashion to support the body against 
the current, with the head upstream. The move- 
ments of the mottled sculpin are also darterlike in 
their rapidity; they often resemble hopping. The 
mottled sculpin hides under rocks during the major 
part of the day; large growths of vegetation provide 
secondary hiding places. Bailey (1952) noted that 
some small mottled sculpins hide in the quiet water 
near shore by stirring up clouds of silt which settle 
and cover them. 
  During the nonbreeding season, spatial isolation 
and aggressive behavior were not observed in mot- 
tled sculpins in a laboratory experiment. McCleave 
(1964) captured as many as six sculpins at one time 
in a 0.093-M2 (1-ft2) area, and fish often were seen 
touching one another. In Lake Huron, mottled scul- 
pins occasionally reached densities of 2-5 per m2 dur- 
ing the daytime, when feeding activity was rare 
(Emery 1973). Emery found that at night this species 
was more active than during the daytime, and was 

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