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Charlyn Partridge


Understanding the reproductive biology of invasive species is an important step in managing populations. Yet little is known about the reproductive strategies of invasive round goby (Neogobius melanostomus) in Lake Michigan. Fertilization in round goby occurs externally in nests guarded by “paternal” males. However, some males pursue alternative reproductive tactics (ARTs), where males sneak into a larger male’s nest and fertilize a portion of the eggs. We investigated how the proportion of round goby ARTs varies between sites. We caught 264 fish from 4 drowned-river lakes along Lake Michigan. We measured their color, morphology, and gonad traits to determine reproductive type. Our results suggest ARTs represent at least 20% of reproductive round goby males. As predicted, sneaker males had larger testes relative to body mass, and paternal males had larger accessory glands relative to mass. Our next step is to model how the proportion of ARTs in these populations may be impacting them.

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