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Efforts to Control Aquatic Invasive Species in the Lower Columbia River, Robson Reach -2017 Update. Invasive Species in Robson Reach, Controlling Invasive Aquatic Weeds, Assessing Northern Pike Habitat Use

  • Indigo River Consulting
Efforts to Control Aquatic Invasive Species
in the Lower Columbia River, Robson Reach
Bronwen Lewis, B.Sc., RP BIO and Evan Smith, B.Sc.
3535 Old Okanagan Hwy., Westbank, BC (Columbia Region Team based in Castlegar, BC)
Whats in the Columbia River
Invasive Species in LCR
Controlling Invasive Aquatic Weeds
Assessing Northern Pike Habitat Use
Figure 3. One young-of-the-year NP was
located along southern shoreline of
Robson Reach on July 27, 2016.
Bronwen Lewis / Evan Smith
Okanagan Nation Alliance Columbia Region
Phone: 250-777-2724
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The Columbia River near Castlegar,
BC (Robson Reach) has become the
receiving environment for a growing
number of invasive aquatic species in
the last 20 years. As well, invasive
Eurasian Watermilfoil (EVM) has been
observed to increase coverage
annually along the margins of the
Columbia River downstream from
Hugh L. Keenleyside Dam
(HLK) since the late 1990’s. The first
invasive Northern Pike (NP), a
voracious predator, was captured from
the Robson Reach in 2009, and now
this species extensively uses the EVM
beds as ambush cover habitat. NP are
considered the top piscivorus threat to
native fish species, adult fish having
been observed to feed mainly on
Mountain Whitefish and Rainbow
Trout. In 2017, we started a limited
pilot program using two suppression
methods to target the removal the
invasive weeds, both as an invasive
depletion method and as high quality
NP habitat.
Timing of NP spawning activity that occurs in the Canadian
Columbia River is thought to peak during May, but spawning
may occur in the period from April to June. Generally NP eggs
are released onto the substrate and hatch in 12-14 days.
Larvae rise to attach themselves to aquatic vegetation using a
head sucker for 9-14 days.
To determine if NP were successful in spawning and hatching
larvae in the Robson Reach, quatrefoil light traps, lighted
minnow traps, backpack electrofishing, beach seining, plankton
tows, and dip netting techniques were variously deployed in
2015 at approximately 2 week intervals after a spent female NP
was removed from the river. Larval pike were not located at that
The Invasive Aquatic Weed Program (EVM and recently
identified Curly Pond Weed) will involve a combination of
geotextile barriers and scuba diver hand removal at
selected sites of heavy weed infestation. The geotextile
barriers will lay on the river bottom for 8 to 16 weeks to
block sunlight and potentially kill the milfoil root system. We
will be monitoring the success of EWM depletion (and thus
NP habitat removal) between the hand removal sites
versus the geotextile barrier during the fall of 2017.
This program is funded by the Environmental Damages Fund,
Environment and Climate Change Canada
The lower Columbia River has been monitored for key fish
species by BC Hydro annually since 2001 by conducting boat
electroshocking surveys from HLK to the Canada-US border.
A number of introduced (non-native) and invasive (potentially
harmful non-native) species have been detected.
Table 1. List of non-native fish species in the lower Columbia River
between Hugh L. Keenleyside Dam and the Can/US border.
Smallmouth Bass
Largemouth Bass
Northern Pike
Photos by staff of ONA, Golder Associates Ltd., and Dynamic Diving
Thanks to Amy Duncan and Michael Zimmer of ONA; Dr. Dana Schmidt
and Chris King of Golder Associates Ltd.; Rick Allen and Emily Neilson
of CBT; Central Kootenay Invasive Species Society; and Cindy Blaison of
Environment and Climate Change Canada .
In 2016, an intensive shoreline fyke net program was
implemented for age 1+ NP with supplemental beach seining
sites. One young-of-the-year NP was captured in a fyke net on
July 27 associated with a school of Redside Shiners. Juvenile
NP have the potential to be preying on blue-listed Shorthead
Sculpin and Umatilla Dace which are similar in size to Redside
Water temperatures in the Columbia River were highest in 2016
than in the last 15 years. Higher temperatures starting at the
end of April were thought to be supportive of successful NP
Non-native Fish Species in LCR
Brook Trout (Salvelinus fontinalis) Northern Pike (Esox lucius)
Brown Trout (Salmo trutta)Tiger Muskie (confirmed upstream;
Esox masquinongy X Esox lucius)
Common Carp (Cyprinus carpio)Tench (Tinca tinca)
Lake Trout (Salvelinus namaycush)Walleye (Sander vitreus)
Bass (Micropterus
Bass (Micropterus
Curly Pond
Figure 1. Deployed fyke net along
shoreline habitat. Figure 2. Beach seining along shoreline
Figure 4. 2016 Columbia river water
temperature (black line) at Birchbank gauge.
NP spawning period
between April and
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