On 30 July 1994, lake trout (Salvelinus namaycush) were discovered in Yellowstone Lake in Yellowstone National Park, Wyoming, the core of the remaining undisturbed natural habitat for native Yellowstone cutthroat trout (Oncorhynchus clarki bouvieri). Data from this and other lake trout subsequently caught by anglers and the U.S. Fish and Wildlife Service suggest lake trout have reproduced in Yellowstone Lake since at least 1989 and now number in the thousands, perhaps tens of thousands. A highly piscivorous, nonnative species, lake trout will probably thrive in Yellowstone Lake and reduce the lake's cutthroat trout stocks substantially unless preventive management actions are taken. A team of scientists that convened in February 1995 to discuss the lake trout problem concluded that there is little chance lake trout can be eliminated from Yellowstone Lake. The team projected a decline of 90% or more in cutthroat trout numbers in 20 years–100 years if the lake trout population is not controlled. The team considered mechanical removal methods, either gillnetting or some combination of gillnetting and trapping, to be the management actions most likely to control lake trout.

Remote‐site incubators (RSIs) adjacent to five streams were evaluated as part of a program to reestablish spawning stocks of Arctic grayling Thymallus arcticus in Upper Red Rock Lake in southwest Montana. From 2000 to 2002, wild adult Arctic grayling were caught from the only study stream that currently supports natural spawning. Adults were artificially spawned, and the fertilized eggs were immediately placed into 12 RSIs in 2000, 8 in 2001, and 10 in 2002. Apart from daily removal of dead eggs and dead fry, no prophylaxis was administered. Median numbers of accumulated degree‐days (and calendar days) to first observation of eye‐up, hatch, and swim‐up were 106.1 (10.5), 139.2 (14.0), and 169.2 (17.5), respectively. Mean (±95% confidence interval) percent emergence was greater in 2000 (73.4 ± 15.1%) than in 2001 and 2002 (pooled mean, 26.5 ± 11.9%). Mean percent emergence at a warm (∼13°C) site (East Elk Springs Creek; 69.8 ± 22.0%) was higher than the pooled mean for the other four sites (35.3 ± 15.0%). In 2002, Arctic grayling were observed spawning in the main‐stem Elk Springs Creek downstream from two RSI sites on tributaries; the species was last reported in this creek in the late 1960s. We believe that the fish observed spawning in 2002 emerged from the RSIs during 2000. Remote‐site incubators are useful, cost‐effective tools that could help reestablish Arctic grayling spawning stocks.

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