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Becker, George C. / Fishes of Wisconsin

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

Page 770

770    Silverside Family-Atherinidae 
spurts, and the interval of alignment decreases to 
about 5 cm. When the breeding season reaches its 
peak, the position of the fish shifts to a horizontal 
alignment with the male following the female as she 
"travels at a furious pace." 
   When the spawning activities are in full sway, a 
 school of silversides presents a wild sight (Cahn 
 p. 65): 
 *.. In and out dart the females, pursued by one or more 
 males, darting this way and that, shooting an inch or more 
 out of the water and landing again three or four inches 
 from the spot of their emergence amid a spatter of spray, 
 followed immediately by the attending male retinue. Sud- 
 denly the female slows down her pace and comes to what 
 amounts to comparative rest. The first male to reach her ap- 
 proaches from the rear and draws up along side. This ap- 
 parently is the signal for the departure of any males that 
 may be pursuing that particular female .... Other males 
 simply disperse and join in the chase of other females. The 
 paired fish now begin a downward glide, approaching the 
bottom at an angle of approximately 300. During the de- 
scent, the fish bring the edges of their abdomens into re- 
                   Range of the brook silverside 
                   0 Specimens examined 
                   A Wisconsin Fish Distribution Study (1974-75) 
                   0 Literature and reports 
                   o Greene (1935) 
 peated momentary contacts-from eight to twenty-one 
 times being the extreme numbers observed, with fourteen 
 as an average of forty-six observations. During the descent 
 the eggs are extruded from the body of the female and may 
 be seen slowly settling toward the bottom in the wake of 
 the descending pair. Fertilization takes place in the water 
 immediately after the eggs leave the female, the spermato- 
 zoa being extruded by the male coincident with the mo- 
 mentary contact with the abdomen of the female.... 
 Cahn observed that, after completion of the de- 
 scent, 26 females showed empty ovaries, and that 
 only a few females had retained some half-dozen 
 eggs. The males ascend at once to the surface where 
 they take off in pursuit of other females. 
 In the brook silverside populations I have looked 
 at, it is obvious that all eggs do not ripen at once, nor 
is the entire complement of eggs released at one 
time. On the lower Wisconsin River, spawning was 
well under way by 19 June. An 81-mm, 2.77-g fe- 
male, with ovaries 15.5% of body weight, held 785 
maturing to mature (orange) eggs, 0.6-1.0 mm diam; 

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