Gerking (1959. Biol. Rev. 34: 221–242) proposed a theory about the restricted movement of stream fishes that may be considered a paradigm in salmonid biology. The restricted movement paradigm (our term) hold that resident stream salmonids are sedentary. Numerous studies have supported the restricted movement paradigm, but nearly all have relied on the recapture of marked fish from the same areas in which they were released, an approach we believe is biased against detecting movement. We found substantial movement of trout in streams in Colorado and Wyoming using two-way weirs and radio telemetry. A review of the research on Lawrence Creek, Wisconsin, also showed that movement was important in the response of the trout population to habitat enhancement. Movement of resident stream fish has profound implications for research (e.g., measuring production and habitat models) and management (e.g., habitat enhancement, special regulations, and stocking hatchery fish). Methods capable of detecting fish movement could be incorporated into many studies to assess its importance in systems of interest. New theories and experiments are needed to understand the mechanisms that cause stream salmonids to move.

We conducted four‐pass electrofishing in seven sections of five small Colorado mountain streams to estimate the frequency that two‐ and three‐pass removal estimates underestimated trout abundance, Results for 23 four‐pass removal estimates suggest that underestimation by two‐ and three‐pass estimates occurred more than 50% of the time, and this underestimation was most often related to decreasing capture probabilities but was not related to the amount of deep or complex habitat in the streams. Monte Carlo simulations indicated that removal estimates with high capture probabilities and a greater number of capture occasions show the least bias under conditions of decreasing capture probability. When at least three passes are completed, a chi‐square test can be used to detect decreasing capture probability, but the power of this test is low below a population size of 200. We therefore recommend that biologists perform at least three passes when using the removal method.

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