How High Can Brook Trout Jump? A Laboratory Evaluation of Brook Trout Jumping Performance

—Quantitative data on how high brook trout Salvelinus fontinalis can jump are crucial for efforts by fisheries managers to exclude brook trout from streams containing native cutthroat trout Oncorhynchus clarkii subspp. and to build effective fishways for brook trout migration. We identified factors that could influence brook trout jumping ability and demonstrated how this knowledge could be applied to improve the design of barriers to brook trout migration or fishways to facilitate their migration. Our objective was to measure brook trout jumping performance under laboratory conditions to identify design features for constructing waterfall-type barriers or pool-and-weir-type fishways. We used flashboard-type and flume-type adjustable waterfall devices to measure brook trout jumping performance at various combinations of vertical or waterfall height (13.5–93.5 cm in 10-cm increments) and plunge pool depth (10–60 cm in 10-cm increments) over a 24-h interval. We tested three size-classes of brook trout: 10–15 cm total length (TL) (mean6 SD: 13.09 6 1.67 cm), 15–20 cm (19.306 1.19 cm), and 20 cm or more (26.52 6 2.13 cm). The 10–15-cm brook trout could jump a 63.5-cm-high waterfall, equivalent to 4.7 times their body length, from a 50-cm-deep plunge pool, which was 3.7 times their body length. Larger size-classes were capable of jumping 73.5-cm waterfalls, or 2.9–4.0 times their body length, provided the plunge pools were at least 40 cm deep (.1.6 times their body lengths). Shallow plunge pools (10 cm) prevented brook trout from all size-classes from jumping waterfalls 43.5 cm or more in height. Small fish were capable of jumping a greater number of body lengths over vertical obstacles than large fish. The data analyses identified vertical height, plunge pool depth, fish total length, and fish condition as factors important in predicting brook trout jumping performance. Over the past two centuries, human activities have significantly changed the form and function of lotic systems throughout North America. In some cases, humans have eliminated physical and geographic barriers that once kept many fish species separate. This has led to an increased number of ecological interactions between native and introduced fishes (Dill and Cordone 1997; Richter et al. 1997). The outcomes of these interactions vary, but in many cases, introduced fishes out-compete native fishes for food and habitat resources, leading to declines or local extinctions of the native species (Griffith 1988). Miller et al. (1989) identified habitat alterations (in 73% of all recorded extinctions) and the effects of nonnative species (in 68% of all recorded extinctions) as the top causal factors behind extinctions of North American fishes during the 20th century. In the western United States, for example, introductions of nonnative salmonids threaten native cutthroat trout Oncorhynchus clarkii subspp. The development or modification of lotic resources has also led to the installation of structures, such as dams, that serve as obstacles or barriers to bidirectional fish movements. This loss of ecological connectivity has affected a number of fish species, thereby isolating populations (Schlosser and Angermeier 1995) and in extreme cases causing local extinctions (Winston et al. 1991) as downstream populations were not able to recolonize upstream areas. Brook trout Salvelinus fontinalis is a species that has benefited from the elimination of natural and humanmade barriers, yet they have also experienced the detrimental effects of new instream barriers. In the Rocky Mountain region, brook trout were widely introduced to supplement populations of cutthroat trout subspecies that had declined from habitat alteration and overexploitation during the 1800s (Wiltzius 1985; Meehan and Bjornn 1991). Many of these introductions were successful, and self-sustaining populations of brook trout now occur in streams that once contained only cutthroat trout (MacCrimmon and Campbell 1969). In areas where sympatric populations are found, brook trout typically outcompete cutthroat trout for food and habitat resources (Griffith 1972; Fausch 1989; De Staso and Rahel 1994). Multiple studies have produced strong evidence implicating brook trout in the decline, and in some cases extinction, of native cutthroat trout populations (Griffith 1988; Behnke 1992). Cutthroat trout populations in areas free * Corresponding author: [email protected] Received November 24, 2004; accepted November 6, 2005 Published online February 15, 2006 361 Transactions of the American Fisheries Society 135:361–370, 2006 Copyright by the American Fisheries Society 2006 DOI: 10.1577/T04-210.1 [Article]