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Life History of the Least Darter Etheostoma microperca at the Northwestern Limits of Its Range
James D. Johnson and Jay T. Hatch
The American Midland Naturalist
Vol. 125, No. 1 (Jan., 1991), pp. 87-103
Published by: The University of Notre Dame
Stable URL: http://www.jstor.org/stable/2426372
Page Count: 17
You can always find the topics here!Topics: Female animals, Oocytes, Growing seasons, Freshwater fishes, Larvae, Fecundity, Ecological life histories, Ova, Larval development, Vegetation
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From May 1984 to October 1985, we studied the life history of the least darter in a small low-gradient stream at the northwestern limit of the species' range. During the spawning and growing seasons, least darters occupied shallow, heavily weeded water in and immediately downstream of pools. In late autumn, they moved to the deep water of pools where they overwintered. Adults spawned between late May and late July on the leaves of Vallisneria, Potamogeton and Carex located at stream margins near pools. Larvae hatched in June and July, at 3.5-3.8 mm total length, absorbed the yolk at 4.0-4.5 mm and completed fin ray development at ca. 10 mm. Males and females grew to similar lengths in the 1st 2 yr (29 mm and 34 mm total length, respectively), but females attained greater total body mass (0.22 g vs. 0.20 g the 1st yr and 0.38 g vs. 0.33 g the 2nd yr). On average, females lived longer than males and reached a longer ultimate total length (38 mm vs. 35 mm). Of the 432 fish aged, 78.0% were young-of-the-year and 1-year-olds, 21.1% were 3-year-olds and 0.9% were 3-year-olds (3 females, 1 male). Both sexes reached maturity at age 1. Spawning potential in females was associated with gonadosomatic indices of 10-35%, but a similar association could not be determined for males. We believe that females developed a minimum of three egg clutches during the spawning season, with an average of 88 eggs for each of the first two clutches. Total fecundity averaged at least 226-264 eggs per female and increased as a function of body size. The diet of adult least darters consisted primarily of copepods and cladocerans in May (94%) and October (63%), and midge larvae in June (73%) and July (62%). When compared to a centrally located population, our population exhibited a slower growth rate, smaller size at maturity, and greater longevity, which translated into repeated reproduction. These life history differences may represent an adaptive response to reproductive uncertainty as predicted by bet-hedging theory.
The American Midland Naturalist © 1991 The University of Notre Dame