Effects of river otters on benthic macroinvertebrate populations of the Colorado Rocky Mountains

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Effects of river otters on benthic macroinvertebrate populations of the Colorado Rocky Mountains
Tetz, Amanda
Place of Publication:
Denver, CO
Metropolitan State University of Denver
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Conference Papers ( sobekcm )


Collected for Auraria Institutional Repository by the Self-Submittal tool. Submitted by Matthew Mariner.
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Faculty mentor: Christopher Cooley
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Major: Biology

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Auraria Institutional Repository
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Auraria Library
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1 Effects of river otters on benthic macroinvertebrate populations of the Colorado Rocky Mountains Amanda J. Tetz Department of Biology Metropolitan State University of Denver Photo by Victoria Alexander on Unsplash


2 Early 19 th century : first record of otter observation in the state Found in every major watershed of the state of Colorado North American River Otter Lontra canadensis Photo by David Groves on Unsplash


3 Bad News for River Otters L . Canadensis populations declined in the 19 th & 20 th centuries Mining Agriculture Fur Trapping [Coryell Coal Mine Newcastle, Garfield County CO], Retrieved from Mines.html State Endangered in 1975


4 State of Colorado River Otter Recovery Plan Over 100 otters released at five sites across the state between 1976 1991


5 Species Reintroduction Programs Trophic effects caused by wolves in Yellowstone include : Elk Aspen & Cottonwood recruitment Beaver & Bison Wolves of Yellowstone Frank, J.W. ( n.d ). [Wolf portrait taken from a vehicle in a pullout]. Retrieved from item.htm?pg=0&id=cebbfa91 94e3 4e62 bf1d 1dca050c5d5f&gid=25C97BD8 155D 451F 675E208BE082FE26


6 Has reintroduction of L. canadensis caused similar trophic effects? Reestablishment of otter populations fish populations macroinvertebrate populations [ BugsinDish ] Retrieved from


7 Five sites selected along 29.7 km stretches of two Rocky Mountain rivers Colorado River (Between Dotsera & Glenwood Springs) Roaring Fork River (Between Basalt & Aspen) Two river bottom samples collected at each site Photo credit: Brad Samuels




9 Intact macroinvertebrates from each river sample were Colorado River Roaring Fork River x count = 132.6 SD count = 62.5 temp = 8.1 ° C Sd temp = 0.2 ° C x count = 100.2 SD count = 55.3 temp = 8.3 ° C SD temp = 0.7 ° C Factor p River 0.249 Temp 0.476 River:Temp 0.461


10 What can we learn? [ Finalist_Fryingpan River East of Basalt]. Retrieved from: ditch Photo credit: Brad Samuels Substrate Differences Diet of L. Canadensis Fly Fishing


11 Entomopathogenic Nematodes Greb , P. ( n.d ). [entomopathogenic nematode ( Heterorhabditis bacteriophora )]. Retrieved from: 1316021


12 [w 631933162 ]. Retrieved from: otters/


13 Acknowledgements MSU Denver Department of Biology Mr. Christopher Cooley My husband, Brad Samuels for all his support, assistance with sample collection, photography, and co parenting during this project! [River Otter]. Retrieved from: notes/nature notes river otters/


14 Literature Cited Adams B.J., Nguyen K.B. ( 2008 ). Nematode Parasites of Insects. In: Capinera J.L. (eds) Encyclopedia of Entomology. Springer, Dordrecht Armstrong D. M. ( 1972 ). Distribution of mammals in Colorado . (Vol. 3 ). U of KA Printing Service. Berg, J. K. ( 1999 ). Final Report of the River Otter Research Project on the Upper Colorado River Basin in and Adjacent to Rocky Mountain National Park, Colorado . Colorado Division of Wildlife. ( 2003 ). State of Colorado River Otter Recovery Plan (Issue June). 2003 Riverotterrecoveryplan.pdf Ripple, W. J., & Beschta , R. L. ( 2012 ). Trophic cascades in Yellowstone: The first 15 years after wolf reintroduction . Biological Conservation, 145 , 205 213 . Send any questions to:


Effects of river otters on benthic macroinvertebrate populations of the Colorado Rocky Mountains Acknowledgments I would like to thank MSU Denver Bio Dept . , my project mentor Christopher Cooley, and my husband for his assistance with sample collection, photography and co parenting . Amanda J. Tetz Introduction River otters, Lontra Canadensis , are endemic to nearly every major watershed in Colorado state . However, after being extirpated from the state in the 19 th and 20 th centuries, it was declared a state endangered species in 1975 . In 1976 , the State of Colorado River Otter Recovery Plan was implemented and over 100 otters were released at five sites across the state over 15 years . Reintroduction of endemic keystone predators is often tied to significant trophic effects on the ecosystems they inhabit . If the reestablishment of L . canadensis results in a decrease of fish within riparian ecosystems, it is possible that the presence of otters may coincide with an increase in benthic macroinvertebrates . Results A total of 2328 macroinvertebrates were collected from both rivers . Fig 1. Study area of Colorado & Roaring Fork River Department of Biology Fig 2. Larvae & mayfly nymph from Roaring Fork Samples Fig 3 . Boxplot comparing mean macroinvertebrate counts from the Colorado and Roaring Fork rivers Discussion Differences in water depth and flow rate and river bottom substrate may contribute to differences in number of macroinvertebrates Colorado : Deep, slower currents, sandier substrate Greater number of nematodes and worms Roaring Fork : Shallow, faster currents, rockier substrate Greater number of midge larvae, caddisfly larvae and nymph mayflies Otters occasionally feed on insects, and may consumer larger macroinvertebrates, even though the abundance of fish is lower . The Roaring Fork is popular with fly fishermen, which can act as a predator to fish in the river much like the otters do in the Colorado . Further research is necessary to determine whether the abundance of nematodes observed in the Colorado are entomopathogenic . Fig 4. Lontra canadensis (Retrieved from: otters/ ) References Colorado Division of Wildlife. (2003). State of Colorado River Otter Recovery Plan (Issue June). fConcern/RecoveryPlans/CDOW2003Riverotterrecoveryplan. pdf Berg, J . K . ( 1999 ) . Final Report of the River Otter Research Project on the Upper Colorado River Basin in and Adjacent to Rocky Mountain National Park, Colorado . Methods Two rivers were selected based on reported otter sighting data compiled by the Colorado Division of Wildlife between 1976 2017 . Otters present : Colorado River Otters absent : Roaring Fork River Two invertebrate samples and temperature data were collected from five sites along both rivers for a total of 20 water samples . Counts of intact benthos were conducted for each sample to compare mean number of macro invertebrates present in each of the two rivers . Two factor ANOVA performed using RStudio . Colorado River count = 132 . 6 SD count = 63 . 5 temp = 8 . 1 C SD temp = 0 . 2 C Roaring Fork River count = 100 . 2 SD count = 55 . 3 temp = 8 . 3 C SD temp = 0 . 7 C These data show no statistical difference between number of macroinvertebrates in each river (p = 0.249) , no difference in temperature (p = 0.476) , nor is there an interaction affect between number and temperature (p = 0.461) . There is a significant qualitative difference in the rivers when it comes to diversity of macro invertebrates observed in the samples.