Although once broadly distributed in the region, the blacknose shiner, Notropis heterolepis, has declined or has already been extirpated throughout much of the Midwest and little is known about its life history. We describe characteristics of reproductive biology and food habits for a lake population of N. heterolepis in northern Illinois to provide information for conservation and management. Gonado-somatic index scores and ovarian stage of female individuals indicated that multiple clutches of ova were produced over a prolonged period lasting from spring until mid-summer. The number of ova present in a clutch was positively related to standard length. However, this relationship weakened and less ova were present in clutches of larger individuals as the reproductive season progressed. Female individuals ≥34 mm SL were mature and the presence of tubercles on male pectoral fins suggested a similar size at maturity for males. Individuals consumed the greatest number of prey items during morning and night -time periods and consumption was less in summer and fall compared to spring. Cladocerans (Chydoridae and Bosminidae) and ostracods were principal diet contributors. Chydorid cladocerans, which are known to associate with aquatic vegetation, were increasingly selected for when ambient densities of all three principal diet contributors were relatively low. Our results indicate that N. heterolepis utilizes a reproductive strategy that should allow resilience to short term, minor disturbances, but they are likely vulnerable to chronic disturbances. In particular, chronic disturbances that reduce or eliminate aquatic vegetation, an important foraging habitat and nursery habitat, will likely have negative impacts on remaining populations.
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Vol. 155 • No. 1