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Becker, George C. / Fishes of Wisconsin

Killifish family - cyprinodontidae,   pp. 753-765 ff. PDF (5.2 MB)

Page 764

764    Killifish Family-Cyprinodontidae 
   Wisconsin has given the starhead topminnow en- 
dangered status (Les 1979). Care must be taken that 
it is not lost from our waters, where it is at the north- 
ern limit of its distribution. The establishment of a 
topminnow sanctuary is recommended; it would be 
unique in the Midwest. The related pupfish of the 
arid Southwest have received special protection from 
the federal government. 
  The characteristic habitat of the starhead topmin- 
now is a quiet, shallow backwater having clear to 
slightly turbid waters and an abundance of sub- 
merged aquatic plants. Cahn (1927) noted that in the 
Mukwonago millpond habitat the water was dark, 
the banks mucky and the shores reedy. Below the 
dam, where the river was 15-18 m wide, this species 
occurred over gravel and rock in shallows with dense 
Spawning occurs from June to July In Illinois, ripe 
male and female starhead topminnows were taken at 
the end of May (Forbes and Richardson 1920). 
                  Range of the starhead topminnow 
                  a Specimens examined 
                  A Wisconsin Fish Distribution Study (1974-78) 
                  0 Literature and reports 
                  0 Greene (1935) 
   A gravid starhead topminnow female, 50 mm TL, 
 taken from the Wisconsin River (Iowa County) at the 
 end of June, had ovaries 16% of body weight; she 
 held 136 yellow, maturing or mature eggs, 0.7-1.8 
 mm diam, and a small number of white, immature 
 eggs, 0.3-0.6 mm diam. Five specimens from this 
 Wisconsin River collection, age II and 47-55 mm 
 long, had the following estimated lengths at the an- 
 nuli: 1-30 mm, and 2-49 mm. Maturity is reached 
 at age II. The mortality of a year class is almost com- 
 plete by the end of the third year of life; few starhead 
 topminnows reach age III. 
 A 60-mm male starhead topminnow, collected 30 
 May from a swamp (Union County Illinois), was 3 
 years old. According to Pflieger (1975), adults reach 
 a maximum of about 81 mm (3.2 in). 
 In Illinois (Forbes and Richardson 1920), about half 
 of the food ingested by starhead topminnows con- 
 sisted of insects, half of which were terrestrial insects 
 that had fallen into the water. Mollusks, crustaceans, 
 and delicate aquatic vegetation constituted the re- 
mainder of the starhead's diet. 

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