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Becker, George C. / Fishes of Wisconsin

Silverside family - atherinidae,   pp. 767-773 ff. PDF (2.7 MB)

Page 769

Brook Silverside  769 
Brook Silverside 
Labidesthes sicculus (Cope). Labidesthes-a pair of pin- 
     cers, for eating; sicculus-dried, found in half- 
     dry pools. 
Other common names: silverside, northern silver- 
     side, skipjack, friar, topwater. 
Adult 95 mm, Rinehart L. (Portage Co.), 13 June 1977 
Body slender and elongate, translucent, slightly 
compressed; top profile of head straight, and head 
flattened. Length 51-76 mm (2-3 in.). TL = 1.18 SL. 
Depth into SL 7-10. Head length into SL 4.6-5.2. 
Snout beaklike, with lower jaw slightly projecting. 
Mouth long, almost horizontal near tip, and strongly 
oblique posteriorly; minute, needlelike teeth on up- 
per and lower jaws. Two dorsal fins on posterior half 
of back, first dorsal with 4 spines, second with 1 spine 
and 9-11 rays. Anal fin with 1 spine and 20-26 rays; 
pelvic fin with 1 spine and 5 rays; caudal fin forked. 
Scales small, cycloid; lateral series scales 75-84; lat- 
eral line incomplete. Digestive tract short, S-shaped, 
about 0.5 TL. Pyloric caeca absent. 
  General color pale green; body translucent in life. 
Dorsal scales outlined with pigment; prominent lat- 
eral silvery stripe. Preserved fish light colored (but 
opaque), lower jaw and top of head pigmented; scales 
of back outlined with pigmented dots; prominent 
dark midlateral stripe fading out anteriorly. Fins clear 
to lightly pigmented along edges of rays; spinous 
dorsal fin pigmented near tip. 
  Breeding male with short, conical urogenital pa- 
pilla behind anus; female with a broad, round, 
fleshy-lipped genital papilla with large opening. 
Male with prominently black-tipped first dorsal fin; 
first dorsal fin in female only lightly pigmented 
(J. Yrios, pers. comm.). 
The brook silverside occurs in the Mississippi River 
and Lake Michigan drainage basins in Wisconsin. 
The northernmost report is from the St. Croix Flow- 
age in Douglas County (Sather and Johannes 1973). 
Although we have no Wisconsin record from the 
Lake Superior drainage basin, it has recently been 
collected from the Dead River at Marquette, Michi- 
gan (Berg et al. 1975). 
  The brook silverside is common in many lakes and 
rivers in Wisconsin. Because of its visible habits, 
large numbers are documented for many waters. Its 
status appears to be secure. 
  In Wisconsin the brook silverside was encountered 
most frequently at the surface in clear water, 0.1-1.5 m 
deep, over substrates of sand (39% frequency), gravel 
(22%), mud (15%), silt (9%), clay (6%), rubble (6%), 
and boulders (3%). It occurred in lakes and in lake- 
like habitats such as sloughs, reservoirs, and pools of 
large rivers. Occasionally it was taken in moderate 
currents of medium-sized rivers 12-50 m wide. It is 
frequently associated with sparse vegetation, seldom 
with dense vegetation. 
The brook silverside spawns only one season, at age 
I, and dies shortly thereafter. In Wisconsin, spawn- 
ing begins as early as May (Cahn 1927), reaches its 
height in June and July, and probably extends into 
early August. The pairing of fish begins when water 
temperatures reach 18'C (64.4°F); spawning occurs at 
20'C (68°F), and the peak of spawning is reached at 
22.7°C (72.9°F). 
  In Michigan (Hubbs 1921), each male brook silver- 
side appeared to command a rather ill-defined area 
of surface water, 2-4 m long by 1-2 m wide, in mod- 
erate current. From this area each guardian male vig- 
orously drove off invading males, then usually re- 
turned to his original position. Hubbs noted, however, 
that during the height of the breeding activities, ter- 
ritorial restrictions were lost as both males and fe- 
males "were engaged in their wild spawning." 
  Cahn (1927), who made extensive observations on 
this species in Oconomowoc Lake and adjacent lakes 
in Waukesha County, did not observe the establish- 
ment of territories. The following account, unless 
otherwise specified, is taken from Cahn. All of the 
spawning activities described took place in shallow 
water near shores. 
  The prespawning activity of the brook silverside is 
in the form of vertical pairing, during which the male 
swims on the surface of the water, and the female 
swims in perfect alignment with the male, approxi- 
mately 25-30 cm below him. The female determines 
the direction of movement. Frequently two or more 
males may be present, but generally one male drives 
the others away. Early in the season the progress of 
the fish is leisurely-30 cm is traveled in 3-4 sec- 
onds. As the water warms up, the fish travel in 

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