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Becker, George C. / Fishes of Wisconsin

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

Page 772

772    Silverside Family-Atherinidae 
tracods, Mysis relicta, plant remains, and arachnids. 
Accompanying the change in environment, there 
was a change from the micro-organism diet to a pre- 
dominantly insectivorous diet. 
  In Lake Mendota (Pearse 1921a), brook silversides 
had eaten insect pupae and adults and cladocerans. 
In an earlier study (Pearse 1918), brook silversides in 
the Madison area had eaten insect eggs, larvae, 
pupae and adults, as well as spiders, mites, ostra- 
cods, copepods, cladocerans, rotifers, protozoans, and 
  In Illinois (Forbes 1883), spiders and terrestrial in- 
sects, accidentally washed or fallen into the water, 
amounted to 12% of the brook silverside's food. Mul- 
lan et al. (1968) reported that terrestrial organisms 
were of major seasonal importance to this species. In 
an Indiana stream, dance flies (Empedidae), which 
frequently hover above waters in large swarms, con- 
stituted 21% of the food items consumed by these 
fish (Zimmerman 1970). Fish remains have been re- 
ported from several brook silverside stomachs, and 
Labidesthes fry and centrarchid fry were taken from 
the stomachs of silversides collected from an Indiana 
lake (Nelson 1968b). 
  Keast (1965) noted that the brook silverside is spe- 
cialized for catching flying insects in the air. Its long, 
closely set gill rakers with their numerous denticles 
suit it admirably for straining micro-organisms from 
the water. In Ohio, this species often stopped feeding 
in the daytime when the water became turbid, and 
lay listlessly at the surface as it does at night (Traut- 
man 1957). 
  In a southeastern Michigan winterkill lake, with 
oxygen levels of 0.8-0.5 ppm in the upper 0.3-1.2 m 
of water, there was good survival of brook silver- 
sides. Cahn (1927) determined that it tolerates pH 
levels of 7.5-8.3, with the optimum pH tolerance at 
  The brook silverside is positively phototropic. At 
night Cahn was able to lead a small school of these 
fish 1.4 km across Oconomowoc Lake with the beam 
of his flashlight. In Lake Mendota, Tibbles (1956: 185) 
reported that, when spotlights and Coleman lan- 
terns were directed onto the water, brook silversides 
began to appear and remained in the areas of high- 
est illumination, whereas yellow perch, which were 
also attracted, stayed on the periphery of the illumi- 
nated arc, or in the shadow of the boat: 
  When a spotlight was moved to change the field of light 
intensity-the skipjacks "en masse" would rapidly follow 
to keep within the illuminated area. Any unfortunate skip- 
jack that was unable to adjust rapidly enough and follow 
the beam of light was immediately taken by the perch 
which remained in the darker zones. 
  Moonlight can also precipitate activity among 
brook silversides. If the night is dark and calm, with 
no moon or only part of a moon, the fish lie sus- 
pended and motionless in the water. When the moon 
is almost full or full, the shallows become the scene 
of one of the most startling scenes in the fish world 
(Cahn 1927:81): 
... The silversides seem to go crazy, as if they were moon- 
struck. They dart about at a most startling speed, dashing 
here and there, leaping out of the water again and again, 
bumping into each other, splashing, circling, behaving in a 
most exaggerated manner ... and the gentle splashing of 
the "breaks" is the characteristic night sound of the lake. 
Such activity goes on during the entire night if the light 
  The brook silverside's habit of leaping out of the 
water and through the air in a low, graceful arch, at 
times for distances at least 10 times its own length, is 
a source of wonder, even to the casual observer. 
Hubbs (1921) observed that occasionally such a leap 
was repeated from one to four times before the fish 
finally dove out of sight. He noted that the fishes 
seemed to be at play, although they could have been 
avoiding a predator, securing insect food, or skipping 
prior to spawning. 
  The brook silverside is the most characteristic of 
our surface fishes-more than any other Wisconsin 
fish, it locates at the surface of the water. Immature 
individuals can scarcely be driven more than a few 
centimeters below the surface, and even the adults 
spend most of their time within 10-12 cm of the sur- 
face and seldom venture below the upper meter of 
  During the winter the brook silverside generally 
remains inshore over water up to 2 m deep. Its move- 
ments are slow and sluggish. Its food habits revert 
back to those of the immature fish, but it apparently 
lives on a maintenance ration only since there is no 
visible growth during the winter. 
When young brook silversides are over deep water, 
they are preyed upon by the black tern, common 
tern, longnose gar, cisco, smallmouth bass, and 
largemouth bass. In shallow water they have been 
taken from smallmouth bass, largemouth bass, bow- 
fin, northern pike, rock bass, green sunfish, bluegill, 
pumpkinseed, white bass, yellow perch, grass pick- 
erel, cisco, American bittern, least bittern, belted 

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