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Becker, George C. / Fishes of Wisconsin

Sucker family - catostomidae,   pp. 607-691 ff. PDF (39.5 MB)

Page 684

684   Sucker Family-Catostomidae 
Comparison of the pelvic fins in the sexes of the white sucker 
(Spoor 1935) 
usually takes place at night, starting at dusk; its 
greatest intensity is reached between 2200 and 2300 
hr (Schneberger 1972c). 
  Male white suckers are more numerous than fe- 
males on the spawning areas, and they arrive 2-3 days 
before the females. No nests are prepared, and no 
territories are defended. Spawning occurs in swift 
water or rapids, over a bottom of gravel; however, 
the white sucker occasionally spawns in lakes, if 
conditions are suitable (Breder and Rosen 1966). 
  The spawning behavior of the white sucker has 
been described by Reighard (1920). While the males 
are numerous on the rapids, the females locate in 
deeper water above or below the rapids. When a fe- 
male moves into the rapids and comes to rest quietly 
on the bottom, she is approached by from one to ten 
males. A male coming within a few centimeters of 
the waiting female may stop, spread his pectorals, 
erect his dorsal fin, protrude his jaw, and for a second 
vibrate his head rapidly from side to side. "Head 
trembling" also occurs when one male approaches 
another on the spawning grounds. 
   The spawning act frequently occurs between a 
 single female and two males with one male on each 
 side of her. The males spread their adjacent pectorals 
 beneath the female, and press their caudal fins 
 against hers. The backs of the males are arched, and 
 their dorsal fin rays spread like the ribs of an ex- 
 tended fan. When the fish have come into position, 
 all three fish vibrate rapidly. If they are in shallow 
 water their backs may be exposed. The powerful 
 movement of their tails stirs up the gravel, releasing 
 a cloud of sand, which is washed downstream. The 
 spawning act lasts about 1.5 seconds. 
 Although additional white sucker males may be 
 present during the spawning act and may attempt to 
 interfere, they take no part in the normal spawning. 
 There is no combat between the males that crowd 
 about the female to gain a place at her side; when not 
 at the side of the female, males seem to pay no atten- 
 tion to one another. 
 After spawning, the female white sucker moves 
 on, usually upstream, where she soon pairs with 
 other males on another part of the spawning grounds. 
 The eggs from one female are scattered in small lots 
 over a considerable area-probably over more than 
 one rapids. 
 In a Canadian study (Geen et al. 1966), the esti- 
 mated spawning mortalities of adults for two succes- 
 sive years were 16% and 20%, although the percent- 
 ages are probably high. 
 In northern Wisconsin, female white suckers 406- 
 533 mm (16-21 in) TL produced 20-50 thousand eggs 
 (Spoor 1935). An age-VI, 406-mm female from Pleas- 
 ant Lake (Walworth County), with ovaries 16% of the 
 body weight, held more than 35,600 eggs (K. Lan- 
 dauer, pers. comm.). In Minnesota (Vessel and Eddy 
 1941), 483-508-mm (19-20-in) white suckers con- 
 tained 93-139 thousand eggs. 
 The eggs are demersal and adhesive when laid. 
They stick to, and are partially covered by bottom 
materials. Fertilized eggs are 2.0-3.0 mm diam. No 
care is given to the eggs. 
  According to Dobie et al. (1956), water temper- 
atures from 13.9 to 20'C (57 to 68°F) are best for 
hatching white sucker eggs. In this temperature 
range, the incubation period is 5-7 days. A thorough 
description of the development from fertilization to 
the exhaustion of the yolk supply has been prepared 
by Long and Ballard (1976). Information on the de- 
velopment of later stages has been supplied by Man- 
sueti and Hardy (1967), who have reported that scale 
formation is first evident at about 22.0 mm and is 

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