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Encounter rates tended to be higher in larger streams than in smaller streams and higher in winter– spring than in summer.

Predator encounter rates varied among streams and between seasons the best-fitting model of survival included a stream × season interaction. Thirty-six percent of the predator encounters occurred at night. Eight species of birds (including two species of owls) and mammals were documented as capturing fish. Over 14-d periods, predators captured fish at 66 of the 88 locations where fish were placed. To estimate maximum encounter rates, provide the clearest contrast among streams and seasons, and provide an empirical estimate of a key parameter in an individual-basedmodel of stream salmonids, we consistently placed fish in shallowmicrohabitats that lacked cover. clarkii to quantify predator encounter rates for fish in four streams of northwestern California during winter–spring and summer. We used photographic monitoring of tethered Rainbow Trout Oncorhynchus mykiss and Cutthroat Trout O.

Recognition that predators have indirect effects on prey populations that may exceed their direct consumptive effects highlights the need for a better understanding of spatiotemporal variation in predator–prey interactions.