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Becker, George C. / Fishes of Wisconsin

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

Page 971

Mottled Sculpin   971 
toms of the nests were usually composed of small 
gravel, although rock, sand, silt, and mixtures of 
these were sometimes present. 
  Each nest was occupied by a single, mature male 
mottled sculpin in nuptial coloration. Ludwig and 
Norden occasionally observed gravid and spent fe- 
males and immature sculpins in the nest with the 
adult male, but in no nest was more than one mature 
male found. The mature males were in their nests 
from the onset of spawning until the fry left at the 
end of May. Females remained in the nests only dur- 
ing spawning. 
  Each nest was guarded by the attending male. 
Koster (1936) reported a behavioral pattern resem- 
bling the movements of the barking dog, which he 
called "barking"-a characteristic warning to all other 
mottled sculpins from the nesting male. Koster ob- 
served an encounter in which a resident male bit an 
intruding male, who returned the bite. 
  Courtship commences when the male mottled 
sculpin first sights a female. Savage (1963) noted a 
ritualistic display of the head by the male, which 
consisted of one or more of the following elements: 
shaking, nodding, or gill-cover elevation. Undula- 
tions of the body also occurred, either alone or ac- 
companying the head display. Shaking is a move- 
ment of the head in the horizontal plane, and nodding 
is a movement in the vertical plane. The rate of 
movement of the head was too rapid for accurate re- 
cording. Gill-cover elevation is a forward movement 
of the gill covers, which results in the visual enlarge- 
ment of the head when viewed from the front. The 
movements which appeared most frequently were 
head shaking and gill-cover elevation. 
  In a laboratory study, the actual contact of the male 
with the female outside the nest was also observed 
by Savage (1963:320): 
  Biting by the male was observed on 10 occasions and was 
of two types: (1) biting of the female's cheek, side, pectoral 
fin, or tail and (2) taking of the female's head into the 
mouth. A female was never observed to bite during en- 
A ripe female always entered the nest when bitten 
on the head or pectoral fin. In each instance, the fe- 
male turned upside down while inside the nesting 
cavity. Savage recorded the mottled sculpin's court- 
ship and spawning behavior (p. 321): 
* . . Male A, positioned at the entrance [of the nest], shook 
and nodded vigorously and bit at the female, who turned 
away at first but soon turned back toward the shelter. Then 
the male took the female's head into his mouth, shook her, 
released and bit at the female's cheek twice. Each bite was 
followed by shaking. The male continued to shake and un- 
dulate as the female moved past him and into the shelter, 
turned upside down and remained there. The male turned 
partly upside down and his venter came into contact with 
the female's dorsum. His head and all his fins, except his 
pelvics, became jet black and his body became very pale. 
The male soon righted himself and placed himself across 
the entrance. The female remained in the nest for several 
days and was often seen in the upside-down position. Fre- 
quently the male also was seen to be upside down, pressed 
against the female. 
  Savage (1963) noted that, when the region of the 
urogenital pore became swollen, it was only a matter 
of a few hours before the female spawned. If she was 
isolated and unable to spawn with a male, the eggs 
were usually released; less often, the female became 
eggbound and died. 
  At spawning the gonadal products are released 
against the roof of the nesting cavity while both 
adults are in inverted positions. The majority of the 
eggs of the mottled sculpin were laid in an initial 
burst, followed by the apparent slow release of more 
eggs. Within several minutes after their release, the 
eggs had firmly adhered to the roof of the nest and 
had hardened; this was indicated by the fact that the 
activities of the two fish no longer moved the egg 
mass along the surface of the roof. The female had 
left the nest by the next morning. 
  The eggs were attached to the roof of the nest in 
clusters, which formed a fairly round, flattened mass 
that had 6-10 layers of eggs in the center. A mass 
contained an average of 1,205 eggs. Clusters were 
distinguishable from one another by color variations, 
which indicated that more than one female had 
spawned in each nest. There was an average of 3.3 
color clusters per egg mass in 18 nests observed 
(Ludwig and Norden 1969). 
  According to Savage, the fanning of the eggs has 
been incorporated into the behavior of the male mot- 
tled sculpin during encounters with females, and 
does not appear to be necessary for the proper devel- 
opment of the eggs. 
  Eggs in preserved mottled sculpin females from 
Mt. Vernon Creek averaged 1.88 (1.50-2.06) mm 
diam. They were uniform in size and light orange- 
yellow in color. The average number of eggs in 39 
females, 41-71 mm SL, was 328 (111-635). 
  In Mt. Vernon Creek, mottled sculpin prolarvae be- 
gan to appear in the nests on 17 May. In the labora- 
tory, eggs at 11.1-12.8°C (52-55°F) developed eye 
spots in 9 days, and hatched in 17 days. Larvae were 
5.9 mm TL at hatching. At 14 days, when they had 
lost their yolk-sacs and were 6.7 mm long, they left 

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