http://www.dfo-mpo.gc.ca/csas-sccs/Publications/ResDocs-DocRech/2019/2019_011-eng.pdfThirteen alien freshwater fish species have established populations within the Fraser River
drainage and there is always the concern that a new species may become established that
impacts native salmonids. Brown trout (Salmo trutta), a predator of juvenile salmon, were
introduced to the Cowichan River more than 80 years ago. The majority of the species currently
occupying habitats within the lower mainland appear to pose little to no risk to migrating
salmonids. However, three spiny rayed fish: Largemouth Bass (Micropterus salmoides),
Smallmouth Bass (M. dolomieu), and Yellow Perch (Perca flavescens), are considered a threat
to Fraser River Chinook Salmon. A risk assessment completed in 2009 indicated the risk that
these invasive fin fish represented to native species was high (DFO 2010b). Their British
Columbia distribution was described by Runciman and Leaf (2009).
Largemouth Bass is a voracious piscivore that will consume salmonid juveniles (Brown et al.
2009b). To date they have not become established in the interior Fraser basin, but they now
inhabit the mouths of tributary streams, backwaters, and sloughs throughout the lower Fraser
River. A fish-wheel operating in the main Fraser River above Misson B.C. in 2009-10 caught 32
Largemouth Bass (G. Cronkite, DFO, Nanaimo, BC, pers. comm.), so they are known to utilize
the main river. Although the number of bass residing within the lower Fraser River is unknown,
the species is well established and appears to be thriving. Largemouth Bass have the potential
to consume large numbers of juvenile Chinook as they migrate to sea, thus impacting
productivity of interior Fraser River Chinook CUs. Largemouth Bass have also been formally
identified as a threat to native fish species (DFO 2011).
Smallmouth Bass reside in the littoral zone of lakes and slower moving rivers (Brown et al.
2009c). They are also piscivorous and can have a significant impact on native communities
through predation on small-bodied fish, and are considered to be a threat to native species
(Tovey et al. 2008; DFO 2010c). There is considerable literature that demonstrates that
Smallmouth Bass prey on juvenile Chinook although the ultimate effect on salmonid abundance
varies (Brown et al. 2009c; Counihan et al. 2012). In 2006, Smallmouth Bass were found in
Beaver Creek, a tributary of the Quesnel River (L.-M. Herborg, Province of British Columbia,
Victoria, B.C., pers. comm.). The Province of BC has initiated and maintains an active control
program since 2007 (L.-M. Herborg, Province of British Columbia, Victoria, B.C., pers. comm.);
however, it is likely Smallmouth Bass will eventually move downstream into the Quesnel River.
They will ultimately reduce Chinook productivity in the Quesnel drainage through predation and
may put at risk Fraser Chinook in that system (Tovey et al. 2008; DFO 2010c).
Yellow Perch is a highly adaptable species that can utilize a wide range of habitats (Brown et al
2009a). They are considered to be lacustrine-limnetic although in larger lakes, they utilize the
littoral zone. Perch juveniles tend to bottom-feed, and larger perch will consume fish eggs and
fish (Brown et al. 2009a). When introduced into small lakes, Yellow Perch can have severe
impacts on native fish species, largely as a result of competition for food (Bradford et al. 2008;
Brown et al. 2009a). Its impact in larger lakes may be less severe, though less information is
available. Competition and predation will occur where habitat utilization overlaps, especially lake
edge habitat. Spiny ray species (i.e. Yellow Perch) have the potential to dominate fish
assemblages, through both predation and interspecies competition (Brown et al. 2009a). Yellow
Perch were found in small lakes bordering Shuswap and Adams Lake in 1996 (Runciman and
Leaf 2009). Nine small interior lakes were rotenone treated from 2008-10 to eradicate the dense
populations of Yellow Perch that had developed (L.-M. Herborg, Province of British Columbia,
Victoria, B.C., pers. comm.). Yellow Perch were captured in Adams Lake in 2008 and spring
2009, during a spiny ray fish inventory program (Lynda Ritchie, DFO, Kamloops, B.C., pers.
comm.). The likely source of introduction was from an established population in Forest Lake
which is connected to Adams Lake via Sinmax Creek. Another population of Yellow Perch was
found in Rosemond Lake which is directly connected to Mara Lake that drains into Shuswap
Lake in January 2013 (Andrew Klassen, Province of British Columbia, Victoria, B.C., pers.
comm.). There is high risk regarding the possible spread in range and potential of these
introduced fish to impact native fish populations, including interior Chinook Salmon within the
Thompson River system (DFO 2010b). Once these invasive species redistribute and enter into
larger water bodies such as Shuswap Lake, they put all fish species at risk and are very difficult
to eliminate. Although they may not cause extinction, they will alter natural patterns of species
diversity and reduce native fish productivity
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Topic: Bass in the vedder? (Read 27960 times)