Brown Trout

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Brown trout caught at the LCR during the 2013 summer Natal Origins trip

Brown Trout Brown trout are native to Europe and were introduced to tributaries in the Grand Canyon in the 1920s. They are capable of withstanding slightly higher temperature than rainbow trout. Unlike most other trout species, brown trout spawn in the late fall. Their spawning behavior, however, is similar to other trout species. Like rainbow trout, young brown trout feed on aquatic and terrestrial insects and invertebrates but brown trout are more apt to switch to eating other fish as they get bigger. The rainbow trout found in Grand Canyon are more likely to continue to eat mostly insects and invertebrates even as adults. [1] (2) Studies have shown that rainbow trout and native fish like humpback chub often have a difficult time persisting in the presence of a large population of brown trout. [2] [3] [4] Desired Future Condition for the Lees Ferry Trout Fishery A high quality trout fishery in GCNRA, as further described in the Recreation DFC that does not adversely affect the native aquatic community in GCNP. • Minimize emigration of non-native fish from the Lees Ferry reach in Glen Canyon National Recreation Area to downstream locations. • Minimize emigration of non-native warm water fish to the mainstem Colorado River.

File:RainbowTrout1.jpg* Rainbow Trout	File:BrownTrout1.jpg* Brown Trout

Updates This webinar has been postponed until sometime later in November 2016 Hi TWG, As many of you all know by now, recent field work in Glen Canyon resulted in an higher number of brown trout captures compared to last year. I have received numerous inquiries from TWG members who want to learn more about the status of brown trout downstream from Glen Canyon Dam, therefore, please call in for an informational webinar on November XX from XX am to XX pm MST (aka, Arizona) or XX am to XX am Pacific to learn more. Dave Rogowski will present AZGFD data first followed by Josh Korman and Mike Yard who will present data from the natal origins project. After the presentations, we can discuss potential underlying causes of these recent increases. Thanks, Seth WebEx/Conference Call Information Topic: Brown Trout Discussion Date and Time: (XX) Nov. XX, 2016 XX:XX am (MST), XX AM (PACIFIC) Event number: XX Event password: XX Panelist password: The Event has no Panelist Password Go to: XX Audio conference information Phone #: XX Access code: XX [5] [6] [7] [8] Brown trout are much more likely to eat other fish (piscivory) but since there are many more rainbow trout in the Colorado River between Glen and Marble Canyons, rainbow trout probably eat more fish numerically than brown trout.[9] An increasing brown trout population in Glen Canyon could pose a problem for both the Lees Ferry rainbow trout fishery and native fish in Grand Canyon because brown trout eat both rainbow trout and native fish alike. Above is a photo of a brown trout collected during 2016 trout monitoring below Flaming Gorge dam that had just eaten a 10" stocked rainbow trout.

Information and Links Lees Ferry Rainbow Trout Fishery Page The HFE Page The Temperature Page The NPS Bright Angel Creek Trout Reduction Project Questions Why are brown trout increasing in the Lees Ferry reach? Has the recent (winter 2014-15) decrease in the rainbow trout population allowed for increased brown trout spawning in the Lees Ferry reach because of decreased competition for spawning area and/or decreased egg predation by rainbow trout? If so, what caused the decrease in the rainbow trout population and what can be done in the future to avoid this from happening? Are increased numbers of brown trout in Lees Ferry a product of higher release temperatures? Do fall HFEs clean spawning substrate in the Lees Ferry reach leading to increased the spawning success of brown trout during their fall spawning season? Do fall HFEs increase the upstream migration of brown trout from other parts of the canyon resulting in more brown trout spawning in the Lees Ferry reach? Could delaying a fall HFE to late November be effective in disrupting the brown trout spawn? When do brown trout spawn in Lees Ferry? Ans: Nov-Dec Irregardless of the cause, what should we do about the increasing brown trout population currently found in the Lees Ferry reach? Presentations and Papers 2016 Grand Canyon Monitoring and Research Center Science Updates (BO Compliance, Trout Updates, Green Sunfish, Fisheries PEP, Partners in Science) Brown Trout Update Lees Ferry Bright Angel Creek Non-Native Trout Reduction, Grand Canyon National Park 2014 Whiting et al. 2014. Macroinvertebrate prey availability and food web dynamics of nonnative trout in a Colorado River tributary, Grand Canyon. Freshwater Science. 2013 Diets of trout in Bright Angel Creek Nonnative fish control in GCNP tributaries 2011 Yard et al. 2011. Trout piscivory in the Colorado River, Grand Canyon: Effects of turbidity, temperature, and fish prey availability. Transactions of the American Fisheries Society. Other Stuff Hasegawa, K., N. Ishiyama, H. Kawai. 2014. Replacement of nonnative rainbow trout by nonnative brown trout in the Chitose River system, Hokkaido, northern Japan. Aquatic Invasions. Vol. 9 Issue 2, p221-226. 6p. S.D. George, B.P. Baldigo, A.J. Smith, and G.R. Robinson. 2016. Effects of extreme floods on trout populations and fish communities in a Catskill Mountain river. Freshwater Biology. "The divergent responses of brown trout and rainbow trout populations to the summer flood could be explained by competitive interactions. Brown trout are autumn spawners, whereas rainbow trout are spring spawners, and thus, YOY brown trout emerge earlier, are larger and may outcompete YOY rainbow trout (Gatz, Sale & Loar, 1987; Strange et al., 1992 ). Conversely , the autumn spawning of brown trout increases the risk of egg loss if autumn or winter floods occur. Several investigations showed that YOY brown trout or brook trout were generally more numerous than YOY rainbow trout except during years when floods scoured the eggs of the autumn spawners (Seegrist & Gard, 1972; Strange et al., 1992; Warren et al., 2009 ). " [10]