When establishing spawning territories in the Susquehanna River male spotfin shiners, Notropis spilopterus, sometimes grabbed the ventral fins of their opponents to drag them from the spawning site. Attacks were preceded by an erected-fin display. Courting males made “display passes” in which they swam slowly, sometimes undulating, along crevices in the rocky substrate where eggs were to be deposited. If a female did not approach the crevice the male would swim to a group of females, which was usually waiting nearby, and try to “crowd” or “drive” one of them to the crevice. As they approached the crevice the male usually orbited the female. Two or more females sometimes accompanied a male on prespawning and spawning passes. Almost all eggs were deposited in the crevice; most of those that missed or flushed out were eaten by one or both spawners. Crevices 2 cm long were spawned in occasionally but longer ones were preferred.
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