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Winter flounder Pseudopleuronectes americanus in Narragansett Bay, Rhode Island reached peak abundance in 1968 and then went into an 8 yr decline, dropping to 1/7 of its former population size, as estimated form weekly tows by otter trawl. Meanwhile a succession of species increased offshore: red hake Urophycis chuss became the commercial dominant in 1973, the ocean pout Macrozoarces americanus and silver hake Merluccius bilinearis in 1974, but among these coastal migrants only scup Stenotomus chrysops entered the bay in substantial numbers. By 1976 scup had increased 25 times in the bay, numerically overshadowing the flounder’s 8 yr decline. A year later, flounder began to recover; and after 3 yr (1979) it had achieved its former abundance, only to decrease 58% over the next 3 yr (1982). Throughout the entire sampling period, migrants and residents bore close inverse relations in bay and sound. Thus, when the bay’s flounder population dropped to 1/3 of its 1968 maximum, migrants dominated the sound’s fishes, possibly having been attracted to the immediate area by foods not utilized by the dwindling flounder population during its spring-fall migration from estuarine to coastal waters. These patterns appeared to be initiated by warming and cooling trends so subtle that the effect may have been mediated by predation on larvae at metamorphosis, a process eventually influencing the entire complex of benthic fishes in the Narragansett Bay area.