Difference between revisions of "Brown Trout"

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 10 from 10:00 am to 12:00 pm MST (aka, Arizona) or 9:00 am to 11:00 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: (Thu) Nov. 10, 2016 10:00 am (MST), 9AM (PACIFIC) Event number: 998 220 707 Event password: FjDTH223 Panelist password: The Event has no Panelist Password

Go to: https://ucbor-events.webex.com/ucbor-events/onstage/g.php?MTID=ed77e412902cdae81eda7a821e2d2961f

Audio conference information Phone #: 1-650-479-3207 Access code: 998 220 707

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 could, however, pose a problem for both the rainbow trout fishery in Glen Canyon 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.

• Lees Ferry Rainbow Trout Fishery Page
• The HFE Page
• The Temperature Page
• The NPS Bright Angel Creek Trout Reduction Project

• Why are brown trout increasing in the Lees Ferry reach?
• Has the 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 decreased egg predation by rainbow trout?
• 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?
• Do fall HFEs increase the upstream migration of brown trout 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
• What should we do about the increasing brown trout population in the Lees Ferry reach?

2016

• File:Whiting et al. 2016 GCtroutDiets.pdf Whiting et al. 2014. Macroinvertebrate prey availability and food web dynamics of nonnative trout in a Colorado River tributary, Grand Canyon. Freshwater Science.
• 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

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.

• 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]