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Brown ; and their Impacts as an Invasive 1

Invasive Species of the

Brown Trout; and their Ecological Impacts as an

By Austin Burrill 423 Fall Quarter 12/5/14

Figure 1. I caught during the summer of 2014 in a small (Ruby ) to the Beaverhead River in Southwestern by means of .

Figure 2. Sea run Brown Trout, or , which is actually the same species. They are genetically homogenous, and many populations reserve the option to be migrate out to sea.

Introduction

Brown trout ( trutta) have long been a population are highly migratory, they are not favorite sport-fish among anglers, and have limited to one river system. This allows the been transported primarily on the basis of species to propagate far beyond their initial recreational . They belong to the introduction locale. During their spawning Salmoniformes, and are classed with migrations, they have been observed to the . This species is a move an average of over 100 meters per day close relative of the Atlantic (Salmo (Saraniemi 2008). As Brown trout share salar), and both originate from , but characteristics with endemic trout species, Brown trout have a native range that also they have been documented to disrupt includes North Africa and Western Asia. natural interactions, and in severe Now Brown Trout exhibit a worldwide cases cause . This species has distribution, as they have been introduced been shown to displace native species, far outside of their native range(s) compete for food, or directly predate on (Klemetsen 2003). Though they are not species of concern (Townsend 1996). They commonly thought of as invasive species by are also known for hybridizing with native the non-scientific community, they have ( fontinalis) resulting been observed to migrate far beyond their in sterile offspring. Here we will investigate initial introduction location(s). Interestingly, general information about the invasive some populations or subsets of populations Brown trout, and look at how they currently exhibit anadromy, at which point they are impact the Pacific Northwest. called Sea Trout. Since some brown trout

Figure 3. Brown Trout photo credit http://www.nps.gov/media/photo/

Brown Trout; and their Impacts as an Invasive Species 3

Figure 4. Generic trout body plan and basic anatomy.

Diagnostic information difficult to identify because their characteristics are not yet pronounced. Mature Brown trout are characterized by an Order: Salmoniformes overall brown body color, with large pronounced black spots, which are more concentrated dorsally. These spots are often Family: Salmonidae said to have a maroon “halo” around them, but these trout have fair genetic plasticity : Salmo and are often observed to vary phenotypically even within the same stream

network. Interestingly, Sea trout have long Species: trutta been considered a different species. It has been said that populations of sea-run Brown trout are difficult to distinguish from Common names: Brown trout, German , as Sea Trout have a vastly Brown, Sea Trout, Trout different life cycle that involves an anadromous form. Sea run Brown Trout Identification spend anywhere from 1-3 years at Sea before making an upstream migration Identification of brown trout has not towards their respective spawning grounds. been a cause of concern, which is unlike the Brown trout are commonly observed in the other trout, salmon, and char species. 12-20 inch range, and sexually mature males Though juveniles remain particularly often have exaggerated jaws, or “.” become more carnivorous and tend to target larger prey items such as other (including ), mice, small birds, , etc. This feeding behavior results in between brown trout and other species og interest, given their Life-history and basic ecology: predatory nature. Most Brown trout become sexually mature between ages 1 and 3, Life cycle though some Brown trout have been observed living 10 years or more. Brown trout are iteroparous, but the stress resulting Feeding habits: juvenile brown trout from often results in mortality. feed primarily on insect larvae and small . As brown trout age, they

Figure 4. Basic Trout lifecycle, starting as eggs and ending as sexually mature spawners.

Reproductive strategies:

Brown trout tend to in the , tend to spawn in early Spring fall, before the high water season, and they which subjects the juveniles to low water often use temperature, water levels, and conditions which brings with it a litany of changes in sunlight as indicators of problems involving temperatures that fall spawning time. This ensures that when the outside of the fish’s optima/tolerance, eggs hatch, in approximately (100 days), decreased dissolved , and low water that there will be sufficient water. conditions resultant of either drought or Conversely, Steelhead, which are native to irrigation. As such Brown trout share Brown Trout; and their Impacts as an Invasive Species 5 spawning times with Pacific salmon species (Salvelinus alpinus). Ideal incubation in the Northwest as well as temperatures are between 8-10 C for Brown and endemic char here in Washington. This trout. It has been observed that adult brown ensures that the fish will emerge from the trout perform better than other trout species gravel closer to peak flow as opposed to the at higher temperatures. This higher minimum flows as experienced in Pacific temperature tolerance is a great advantage to Northwest summers. Brown trout follow suit the species given that trout survival are very among other trout, salmon, and char species, sensitive to temperature shifts that are as they are highly fecund, and they exhibit outside of their optimal range. Considering an egg burying strategy (Often less than 10 climate change, temperature may greatly inches deep). As the trout sexually mature, influence brown trout distribution in the near they will develop what is known as kype, or future. Optimal incubation temperatures for exaggerated jaws. There is inherent sexual Brown trout reside between 2 and 13 C. dimorphism here, and larger kype is Their incubation tolerance range is between hypothesized to increase male fitness. 0 and 13 C. As far as free living, or post Larger males tend to be preferred over their juvenile forms of the species go, the ideal smaller counterparts, but this doesn’t stop water temperature is in the range of 7 to 15 younger sexually mature males from C and their tolerance resides between 0.4-4 participating. It has often been observed that and 19-26 C (Elliot et al 2010). Oxygen smaller males will rush in and fertilize a levels between 5 to 9 ppm dissolved give an females nest (or redd), despite there being a optimal range, at temperatures between 5 larger male at the ready. and 15 C the optimal dissolved oxygen level is subject to fluctuation though, and is Environmental optima and highly variable as such. Brown trout tolerances: perform well under a pH that ranges from 5 to 9.5 (USGS 1986). Brown trout, especially Brown trout have been observed to in smaller to mid sized streams polarize have higher temperature tolerances than towards cover, given the opportunity. Cover other species of trout. Atlantic salmon are is one of many environmental variables that most resistant to higher temperatures, can serve to enhance recruitment in brown followed by Brown trout, then Char trout streams (Eklov 1998).

Figure 5 lists the lower and upper temperature (Degrees Celsius) tolerance bounds for Brown Trout, Atlantic salmon, as well as Arctic charr. Used from: Temperature requirements of Atlantic salmon Salmo salar, brown trout Salmo trutta and Arctic charr Salvelinus alpinus: predicting the effects of climate change (Elliot et al 2010). During the pre-spawning period, in early spawning they moved an average of 160 summer, brown trout were found to travel an meters, and lastly during winter they were average of 348 meters a day. During observed to move only 23 meters a day (Saraniemi 2008). Female Brown trout other naïve trout species. Once the parasite (hens) deposit eggs into redds in the same found its way into stocking programs that way as Pacific salmon species, and have a harbored , the disease spread preference for substrate between 4 and 40 rampantly as preventative protocols were cm (USGS 1986). The female digs the red essentially nonexistent at this time. The only with her caudal fin, and she releases the signs of whirling disease occur after the eggs into the red just before fertilization the entire brood has been subjected to male (buck). The incubation periods are the pathogen. Living in the same highly variable across the species’ native environment has served as a huge advantage and invaded ranges. to brown trout, as they have been under extensive selection to evolve immunity to Biotic associations M. cerebralis. For example I look to the , where Whirling disease all Whirling disease (Myxobolus but decimated the river’s historically healthy cerebralis) is a pathogen that produces a rainbow trout population. This opened up potent neurotoxin, and is found in the same significant niche opportunities to Brown European streams as Brown Trout. This Trout, which soon flourished. Though parasite infects Tubifex worms, which are rainbow trout populations have been ingested by trout and allow the parasites to observed to develop immunity to this jump hosts. Trout infected by the disease pathogen, the cumulative effects of the commonly exhibit “whirling” behavior, as a disease are still largely detrimental. Brown result of spinal degeneration, this will trout have myriad biotic associations, but typically result in death. As Brown Trout co- this particular case exemplifies a commensal evolved with this pathogen, they evolved an pathogen that Brown trout can carry, and immunity that was not commonly shared by transmit to vulnerable species. Current geographic distribution and distribution in the PNW and the

Brown Trout; and their Impacts as an Invasive Species 7

Figure 6 is a map of brown trout that have been found in coastal to the . Two brown trout were found well outside of their original stocking programs. http://www.fs.fed.us/pnw/lwm/aem/docs/bisson/1986_bisson_occurrence_of_anadromous_brown_trout.pdf

Figure 7 Is a map of Brown trout occurrences in the United States via: http://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=931 One study found two brown trout in populations of brown trout, and occurrences are tributaries to the lower Columbia river, one in thought to be resultant of stray hatchery fish Washington and one in (Bisson 1986). The closed circles indicate the location of the History of invasiveness brown trout (Figure 7). These introductions were predicted to be the result of stocking Brown trout have been stocked programs, as no coastal populations have been extensively on behalf of the angling community. found in the Pacific Northwest to date. Seeing Brown trout provide extensive economic value, that brown trout are appearing far outside of and their introductions have been largely their stocked range has made this discovery encouraged in the past. Brown trout are often significant. It is likely that Washington will see referred to as German browns, as most strains of an influx of established brown trout populations brown trout in the United states originated from in the near future. It is evident that brown trout German stocking programs. Many stocks are inhabit an extensive range of the United States. naturally reproducing, and brown trout have Yet maps such as these only indicate the current established populations in a majority of states in locations where known brown trout populations the US. Brown trout have a nearly worldwide reside. If this were a map of self sustaining distribution, and this value is only increasing as brown trout populations the distribution would a result of their popularity. They demonstrate be a lot smaller, especially in Washington state. their ability to establish populations time and Washington isn’t currently home to sustainable time again.

Invasion process maturation allows for earlier exploitation of resources, which allows for increased liklihood Pathways, Vectors, and Routes of Introduction: of establishment. Brown trout are known to migrate across large distances independently, Brown trout have been traditionally but anglers have been reported to transport introduced via stocking programs. As such, the brown trout for the purpose of primary pathway for Brown trout introduction is enhancement. that of stocking for sport . Bucket biologists have also been known to further Potential ecological and/or economic impacts propagate invasions, but state run as well as private stocking programs have been chiefly Predicted increases in temperature responsible for the influx of brown trout in the (caused by climate change) in the Pacific United states. Many of these programs have no Northwest are predicted to further hinder regard for endemic species that will have to Steelhead, as well as other Pacific salmon compete for the same resources. Recreational species’ reproductive successes (Wade 2013). benefits continue to be a key driver in the As global temperatures increase, new niche propagation of brown trout, as such there is no oppurtunities will present themselves to Brown significant effort to impede the march of the trout, and it is predicted that their range will be Brown trout. shifted northerly. Considering how vulnerable trout are to heat stress during early Establishment and Spread: development, environments that may be well within the trout species’ current optimal range For trout species to establish, a number will likely see a polarization towards of criteria must be met. The water must be warmwater species. Washington may become a suitable to the species, ie it doesn’t exceed host to self-sustaining Brown trout populations (citation needed). Whereas spread is determined as temperature regimes shift. In Yellowstone primarily based on stream connectivity. If the National Park, predictions have been made that fish are stocked above an impasse, the as temperatures increase, Yellowstone cutthroat likelihood of their spread is greatly diminished. populations will decrease, and that invasive Conversely if the stream is connected to others, species will fill in the unoccupied niche (Al- it is more likely that the fish will occupy a range Chokhachy 2013). The lower Yellowstone that is much greater than their initial River is already host to a significant spawning introduction location. Another key component brown trout population as well. in invasion biology, are the characteristics of the invader. Host have been shown to Another interesting study looked at how greatly influence the success or failure of Brown trout influenced the growth of other establishment. Brown trout with genetics that species. It was found that in with are more similar to wild populations have been brown trout, char grew more slowly (Forseth demonstrated to have increased invasion 2003). This is a very direct impact, and is reason success. Host characteristics such as for concern in watersheds that have endemic environmental tolerances, and rate of juvenile char. Washington State has both development have been associated with the (Salvelinus confluentus) as well as closely successful invasion of , where Atlantic related Dolly Varden (Salvelinus malma). Then salmon were ill-adapted (Valiente 2010). again, in a Norwegian stream it was found that Juvenile Brown trout develop at a greater rate, when the endemic Alpine Bullhead (Cottus than salmon species in the first year. This earlier poecilopus) was present that brown trout fed in Brown Trout; and their Impacts as an Invasive Species 9 areas that put them at heightened risks of effort (ie. bucket biologists or a secondary . As such, characteristics of the stocking program). Brown trout are very invader, members of the recipient indigenous or successful at establishing new populations, as established population, as well as the has been observed throughout their native environment, all factor into the outcome. The European range. An interesting and well-known outcome is either successful or failed example of a brown trout invasion occurred in establishment, and important to the idea of . Brown trout were introduced to establishment is propagule pressure, which is New Zealand over 100 years ago, and the number of discreet introduction events, populations have since flourished. Brown trout which may or may not result in the have displaced and even been associated with establishment of the species. The stocking the extinction of species endemic to New industry often serves to increase propagule Zealand (Townsend 1996). As such, they have pressure, as many stocking programs plant trout been the focus of extensive study. It has been annually to ensure good catches. said that the effects of brown trout are in fact reversible (Townsend 1996), and that normal It is generally assumed that introducing biotic interactions could return given the a non-native species to an environment with removal of the invader. numerous endemic species would be deleterious to the recipient ecosystem. Yet in several Invasive species have been likened to a shallow New Zealand , it was found that smoking gun in popular media (citation), but in the addition of non-native Brown and rainbow reality the demise of most species is in fact trout didn’t alter the lakes original resultant of interactions with the invader, but composition on any appreciable level, which also due to degradation, exploitation, was found to directly contradict findings in and climate change, which alters previously North American and European lakes. The lakes suitable habitat. The term “invasive” has come studied in America and Europe had dramatic to carry negative connotations, and the potential invertebrate composition shifts after the beneficial ecosystem services provided by introduction of trout (Wissinger 2006). These invasive species are not well known. One study lakes exemplify that environmental found that most anglers believed that their local characteristics determine whether the invasive weren’t in need of extensive stocking species serve as a detriment or not. programs, and that the population was self- Characteristics of the invader are of limited sustaining. The reality of the issue was that importance, as the results of an invasion depend extensive stocking programs were in place to on more than invader characteristics. ensure good catches (Baer 2010). Since sport fisheries are an integral part of numerous local Most studies that have determined economies, it is worth noting that Brown trout brown trout to be harmful involve conspecifics. provide great economic benefits despite serving Findings indicate that brown trout harm as potential threat to native biotic interactions. populations of native salmonids through direct This complicates the issue, as stopping Brown competition for food or space, and more directly trout stocking programs will not only have in cases of Brown trout preying on endemics economic repercussions, but will also have (McHugh 2006). So the introduction of Brown social impacts. Brown trout have characteristics trout to has certainly caused that make them an ideal invader, and their damage, but the extent of the impact is largely proximity to the Pacific Northwest has certainly unknown. Though brown trout can be made them a concern for Washington streams. introduced without any observable damage, Seeing stray brown trout appear along the each successfully established population can Columbia river is reason for increased concern serve as invasion hub. This can allow the for Native Washington salmonids. Management species to further migrate into naïve strategies and control methods: either independently or as a result of human So far, there is no major effort to extirpate infeasible goal in cases where the invader is so brown trout from the Pacific Northwest, or other widespread, and many such eradication efforts locations for that matter. Stocking programs for have failed miserably. brown trout still exist, and brown trout are a highly valued sport fish among anglers and they have cultural significance among fishing communities. Eradication is often seen as an

1 Brown Trout; and their Impacts as an Invasive Species 1

Literature Cited

Klemetsen, A., Amundsen, P.-A., Dempson, equally invasive: genetic origin and J. B., Jonsson, B., Jonsson, N., life-history in Atlantic salmon and O'Connell, M. F., & Mortensen, E. brown trout acclimated to the Southern (March 01, 2003). Atlantic salmon Hemisphere. Biological Salmo salar L., brown trout Salmo Invasions,12, 10, 3485-3495. trutta L. and Arctic charr Salvelinus Brown, R. S., Power, G., & Beltaoa, S. alpinus (L.): a review of aspects of their (November 01, 2001). Winter life histories. Ecology of Freshwater movements and habitat use of Fish, 12, 1, 1-59. riverine brown trout, white sucker and common in relation to MacCrimmon, H. R., & Marshall, T. L. flooding and ice break-up. Journal (December 01, 1968). World of Fish Biology, 59, 5, 1126-1141. Distribution of Brown Trout,Salmo trutta. Journal of the Fisheries Research Board of , 25, 12, Wade, A. A., Beechie, T. J., Fleishman, E., 2527-2548. Mantua, N. J., Wu, H., Kimball, J. S., Stoms, D. M., ... Stanford, J. A. SCHLAEPFER, M. A. R. T. I. N. A., SAX, (January 01, 2013). Steelhead D. O. V. F., & OLDEN, J. U. L. I. A. vulnerability to climate change in the N. D. (June 01, 2011). The Potential Pacific Northwest. Journal of Applied Conservation Value of Non-Native Ecology Oxford-, 50, 5, 1093-1104. Species. Conservation Biology, 25, 3, 428-437. BAER, J., & BRINKER, A. (April 01, 2010). The response of a brown trout Thomson, D. J. (January 01, 1997). stocks and perception of anglers to Dependence of global temperatures on cessation of brown trout atmospheric CO2 and solar stocking. and irradiance. Proceedings of the National Ecology, 17, 2, 157-164. Academy of Sciences of the United States of America, 94, 16, 8370-7. Elliott, J. M., & Elliott, J. A. (January 01, 2010). Temperature requirements of Forseth, T., Ugedal, O., Jonsson, B., & Atlantic salmon Salmo salar, brown Fleming, I. A. (June 01, 2003). trout Salmo trutta and Arctic charr Selection on Arctic charr generated by Salvelinus alpinus: predicting the competition from brown effects of climate change. Journal of trout. Oikos, 101, 3, 467-478. Fish Biology, 77, 8.)

Valiente, A. G., Ayllon, F., Nuänez, P., Valiente, A. G., Ayllon, F., Nuänez, P., Juanes, F., & Garcia-Vazquez, E. Juanes, F., & Garcia-Vazquez, E. (January 01, 2010). Not all lineages are (January 01, 2010). Not all lineages are equally invasive: genetic origin and life-history in Atlantic salmon and brown trout acclimated to the Southern McHugh, P., & Budy, P. (November 01, Hemisphere. Biological 2006). Experimental Effects of Invasions,12, 10, 3485-3495. Nonnative Brown Trout on the Individual- and Population-Level WISSINGER, S. C. O. T. T. A., Performance of Native Bonneville MCINTOSH, A. N. G. U. S. R., & Cutthroat Trout. Transactions of the GREIG, H. A. M. I. S. H. S. American Fisheries Society, 135, 6, (November 01, 2006). Impacts of 1441-1455. introduced brown and rainbow trout on benthic invertebrate communities in shallow New Zealand Saraniemi, M., Huusko, A., & Tahkola, H. lakes. Freshwater Biology, 51, 11, (January 01, 2008). Spawning 2009-2028. migration and habitat use of adfluvial brown trout, Salmo trutta, in a strongly Al-Chokhachy, R., Alder, J., Hostetler, S., seasonal boreal river. Boreal Gresswell, R., & Shepard, B. (October Environment Research, 13, 2, 121- 01, 2013). Thermal controls of Yellowstone cutthroat trout and Townsend, C. R. (January 01, 1996). invasive fishes under climate Invasion biology and ecological change. Global Change impacts of brown trout Salmo trutta in Biology, 19, 10, 3069-3081. New Zealand. Biological Conservation, 78, 13.

Other Resources http://www.nwrc.usgs.gov/wdb/pub/hsi/hsi- 124.pdf http://www.nps.gov/media/photo/gallery.ht m?id=25CC9DD6-155D-451F- Expert contact information in PNW 67BF88D17DEDB375 Julian Olden http://tweedfoundation.org.uk/tweedstart/ht Associate Professor, Aquatic & Fishery ml/fishes.html (figure 2) Sciences [email protected], 206-616-3112 http://whiterivertroutdiva.net/uploads/20 13/10/trout-fish-anatomy.jpg (figure 3.) Thomas P. Quinn Professor, Aquatic & Fishery Sciences http://www.nps.gov/media/photo/ (figure 1) [email protected] 206-543-9042 http://www.nps.gov/media/photo/ Fish and Wildlife Commission http://nas.er.usgs.gov/queries/factsheet.aspx Miranda Wecker, Naselle ?SpeciesID=931 (Western Washington position, Pacific County) Occupation: Director of the Marine Program, UW Olympic Natural Resources 1 Brown Trout; and their Impacts as an Invasive Species 3

Center County) Current Term: 07/08/2013 - 12/31/18 Occupation: Dean Emeritus, Huxley College of the Environment, Western Washington Bradley Smith, Ph.D., Vice Chair, University Bellingham Current Term: 06/18/2009 - 12/31/2014 (Western Washington position, Whatcom

Current research and management efforts:

Brown trout are still stocked as part of the sport fishing industry, despite further potential invasions. Comprehensive research as to the cumulative impacts that invasive brown trout have on endemics is limited, as it’s impossible to know the extent of their damage. Brown trout will likely continue to be stocked as part of the sport fishing industry, though efforts have been made to avoid introducing brown trout into new environments. In many streams and lakes, the prospects of extirpating brown trout are poor.