Life History and Reproduction

The life of a Slenderhead Darter usually begins in spring to early summer. Research indicates that mating occurs roughly between April and June, though this may occur a few weeks later due to high water. (Becker,1983)(ODNR, 2013)(Brewer, 2006) Weeks before this happens, however, male Slenderheads arrive early in their breeding habitat, which experts believe is due to a territorial element in the Slenderhead. The females arrive around 2 weeks after the males have and for a short period of time they can be distinguished by their swollen genital papilla, contrasted to the males which are smaller and triangular.(Becker,1983)(Page, 1971)

Though egg production varies with each female, 500-2,000 eggs is the average before spawning. As the egg develops, in undergoes multiple color changes. At the earliest stage the egg is white and about .5 mm in diameter. At roughly .6-1.1 mm it turns yellow, and by 1.3 mm it begins to fade into orange. (Becker,1983)  Once an egg is mature it becomes transparent, any eggs left unfertilized are reabsorbed into the mother. (Becker,1983) (Brewer, 2006) They lay these fertilized eggs into pre-dug holes then cover them in gravel or sand. After this is completed they provide no care for their young.(ODNR, 2013)

Slenderhead growth and development is rapid. By the young age of 2 weeks, they are commonly around 22.5 mm and nearly completely scaled. It is estimated that nearly half of the overall growth of this species occurs in its first 2 weeks. By late September (14 weeks) slenderheads are around 45 mm and fully mature. (Becker,1983)  There is little evidence that sex affects the size of adult slenderheads, though the largest of the species caught have been male, with a sex ratio of males to females being 1.4 to 1. (Page, 1983)  Though some Slenderheads have been found to live as long as 4 years, the average life expectancy is around 3 years or less. (Page, 1983)(Smith, 1979)


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