Study Finds Climate Change Accelerates Hybridization Between Native, Invasive Trout
MISSOULA – A new article by researchers from the University of Montana, the U.S. Geological Survey and Montana Fish, Wildlife & Parks asserts that climate warming is increasing the hybridization of trout – interbreeding between native and non-native species – in the interior western United States.
Clint Muhlfeld, a research assistant professor in the UM Division of Biological Sciences’ Flathead Lake Biological Station and research ecologist with the USGS Northern Rocky Mountain Science Center in Glacier National Park, is the lead author of the article, titled “Invasive hybridization in a threatened species is accelerated by climate change,” which was published in the latest issue of Nature Climate Change. Co-authors are Ryan Kovach, a postdoctoral scholar at UM’s Flathead Lake Biological Station, and Leslie Jones, a UM doctoral student who works with Muhlfeld and USGS.
Specifically, rapid increases in stream temperature and decreases in spring flow over the past several decades contributed to the spread of hybridization between native westslope cutthroat trout and the introduced rainbow trout – the world’s most widely introduced invasive fish – across the Flathead River system in Montana and British Columbia, Canada.
Experts have hypothesized that climate change could decrease worldwide biodiversity through cross-breeding between invasive and native species, but this study is the first to directly and scientifically support this prediction. The study was based on 30 years of research by scientists with UM, USGS and Montana FWP.
Hybridization has contributed to the decline and extinction of many native fishes worldwide, including all subspecies of cutthroat trout in western North America, which have enormous ecological and socioeconomic value. The researchers used long-term genetic monitoring data coupled with high-resolution climate and stream temperature predictions to measure whether climate warming enhances interactions between native and non-native species through hybridization.
“Climatic changes are threatening highly prized native trout as introduced rainbow trout continue to expand their range and hybridize with native populations through climate-induced ‘windows of opportunity,’ putting many populations and species at greater risk than previously thought,” Muhlfeld said.
“The study illustrates that protecting genetic integrity and diversity of native species will be incredibly challenging when species are threatened with climate-induced invasive hybridization,” he said.
Westslope cutthroat trout and rainbow trout both spawn in the spring and can produce fertile offspring when they interbreed. Over time, a mating population of native and non-native fish will result in only hybrid individuals with substantially reduced fitness because their genomes have been altered by non-native genes that are maladapted to the local environment. Protecting and maintaining the genetic integrity of native species is important for a species’ ability to be resilient and better adapt to a rapidly changing climate.
Historical genetic samples revealed that hybridization between the two species was largely confined to one downstream Flathead River population. However, the study noted, during the past 30 years, hybridization rapidly spread upstream, irreversibly reducing the genetic integrity of native westslope cutthroat trout populations. Genetically pure populations of westslope cutthroat trout are known to occupy less than 10 percent of their historical range.
The rapid increase in hybridization was associated with climatic changes in the region. From 1978 to 2008, the rate of warming nearly tripled in the Flathead basin, resulting in earlier spring runoff, lower spring flooding and flows, and warming summer stream temperatures. Those locations with the greatest changes in stream flow and temperature experienced the greatest increases in hybridization.
Relative to cutthroat trout, rainbow trout prefer these climate-induced changes and tolerate greater environmental disturbance. These conditions likely have enhanced rainbow trout spawning and population numbers, leading to massive expansion of hybridization with westslope cutthroat trout.
“The evolutionary consequences of climate change are one of our greatest areas of uncertainty because empirical data addressing this issue are extraordinarily rare,” Kovach said. “This study is a tremendous step forward in our understanding of how climate change can influence evolutionary process and ultimately species biodiversity.”
Overall, aquatic ecosystems in western North America are predicted to experience earlier snowmelt in the spring, reduced late spring and summer flows, warmer and drier summers, and increased water temperatures – all of which indicate increased hybridization between these species.
Additional UM-affiliated authors are UM Wildlife Biology Program Director Winsor Lowe, UM Associate Professor of Conservation Ecology Gordon Luikart and Regents Professor Emeritus Fred Allendorf. Authors not affiliated with UM are Robert Al-Chokhachy with the USGS Northern Rocky Mountain Science Center, Matthew Boyer with Montana FWP in Kalispell and Robb Leary with Montana FWP in Missoula.
The study was supported by the Great Northern Landscape Conservation Cooperative, the U.S. Department of the Interior’s Northwest Climate Science Center, the National Climate Change and Wildlife Science Center, the National Science Foundation and Bonneville Power Administration.
The article can be viewed online at http://dx.doi.org/10.1038/nclimate2252. For more information call Muhlfeld at 406-600-9686 or email cmuhlfeld@usgs.gov.
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* The Warm List – seen here: http://www.numberwatch.co.uk/warmlist.htm
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I once scared the holly sh** outa my previous boyfriend when I said I had ordered wedding rings and they finally came in the mail.
@Pamela Gray – you were using the wrong bait. 😉
Pamela, try using a bare red Gamakatu Octopus hook as a droper tied snell a couple inches below your fly. For those that don’t know, we are talking the fly on the end of the line, not on your pants. I tried this and it worked. Fish went for the bare red hook. Must imitate a red San Juan worm. The fly was the attractant while the red hook was the bait. Worked for cutts, bows, and browns.
As to the study, can’t read it because it’s behind a paywall. During this explosion of hybrids, there were severe forest fires on the westside of the divide. There could have been ash buildup in the streams affecting both the fish and their food sources. The loss of shade would also warm the streams. Fish just went looking for better water.
There are a number of landlocked mountain lakes in the Flathead Basin and nearly all of them were stocked in years past with Rainbows. These hybridized readily with the native cutthroat producing “cutbows” that grow to large size. I don’t know if they are sterile or require the two original species (though the State stopped the stocking effort years ago) but I do know that they are fun to catch and delicious to eat. Those lakes are extremely cold. Global warming doesn’t seem necessary for this hybridization. I would think, rather, that there is a close genetic match between the two and that leads to the cross (Brook Trout and Bull Trout, both occurring in these same streams, and both being arctic char, are remnants of the last ice age and will readily interbreed as well). A fish biologist friend told me once that Rainbows (and other large species like Brown Trout) occupy the stronger currents in the middle of streams and the smaller fish like Cutthroats occupy the edges where the currents are slowed by friction with the banks and bottoms. One would think, therefore, that another place to look (other than global warming) for the origin of the crossing phenomena might be increased streamflow (ie. from the many large fires recently – the North Fork of the Flathead is nearly totally transformed by large fires over the past 10 to 15 years-, increased precipitation, etc. I suspect there wouldn’t be as much money available without the magic words “global warming” however.
I’ve been reading the responses to this post and thought a lot about the different interpretations of species being bandied about and discovered I was having a difficult time, even with a solid background in biology, in arguing for or against any particular idea presented. So, I did some research and discovered that what is a species has been argued since ancient times and that there is still no uniform definition. And, depending on your particular field of study, the whole concept of species may be quite counter to that used by someone in another field. Since, what is a species is often central to AGW alarmism and is many times used in studies to ‘prove’ it is worse than we thought, this linked book may help illuminate the current state of understanding regarding the many definitions being used to define species:
http://www.macroevolution.net/support-files/forms_of_life.pdf
Species is covered in chapter 1 beginning on page 6.
I also thought the first quote apropos to us skeptics:
“By doubting we come to questioning, and by questioning we perceive the truth.” – Pierre Abelard
I have never understood who decides what is a native species and what isn’t, most species migrated from somewhere and then evolved. I’ll never understand why some people think that no species should ever be allowed to go extinct , surely if no species went extinct it would prevent some other species from evolving.
Hey, I resemble that remark!
Wardens tend to be interesting people. They can be very lenient in some cases. Finding bait, i.e. flesh of vertebrates or invertebrates, on your line will be deemed illegal by those funny guys.
If you’ve tied the grasshopper, mammal hair, Aves feathers, foam or rug will be accepted as a lure. Method is a presentation is just not dry fly fishing.
If you’ve dipped the fly in scent mix, keep your mouth shut and don’t confuse the poor official. In Bass or saltwater fishing fully accepts scent attractor addition as lures; fly fishing purists are not always so open minded. Though fly fishers who use saliva when soaking their fly for better sink are not considered as adding scent, though they do and many fishermen attest to a person’s saliva increasing success.
Brookies are well known for eating anything that floats by. It is one way they learn what is not edible; it is also how brookies survive so well in freestone waters where food is scarce as some of the things they eat may not be normal fish food till it was eaten by the fish.
If you like to tease the brook trout, tie a fly with the web part of Velcro. It catches the hooked teach of the trout and can hold them till they wiggle off at your feet.
Rainbows will chase things too, until they learn better. Ending up on your plate is a sure evolution lesson leaving less adventurous rainbows watching the currents.
Try anything and any terminal arrangement you think of. Often those folks who are not catching fish are only fishing one basic method. As you did with the trout in eddies under banks, figure out where the trout would likely hold and fish to them.
I was raised by parents who were raised during the depression years. A great deal of what they learned has been ingrained in myself and siblings.
I’m happy to spend time fly fishing catch and release, but my nervous system does start to feel like I will bring nothing back for the family because of my efforts.
So I am quite happy fishing the classic way where the fisherman tosses his line into the right water at around the right time (dawn or dusk) and settling down to practice native American patience waiting for the line to twitch.
I could blame the years I lived in New Orleans amongst the Cajuns for my attitude that most things that grow, fly, swim, walk or run are potential food. Only my Father taught me early in my life to not discard/disdain gifts. When someone would offer us their ‘trash’ fish we’d only turn down the fish that were less than fresh. When they waved their stringers at us we saw fried, grilled or broiled fish for the night. Given my Mother’s lack of ability to cook and that my Father could cook fish very well might’ve helped.
Yes, this attitude hangs on through adult years. When I was trying to find land fishing access around New Orleans, (a definite waste of time, buy a boat any boat), dressed in old fishing gear while trying waters down a bayou from a marina; a commercial captain stopped his boat and showed me a basket of sheepshead fish and offered them to me. Sheepshead are notorious bait stealers with flesh often mistaken for crab meat. A very good eating fish. A little wading and I made a very large quantity of sheepshead fish dip then took it to a dinner party; I gave up trying to tell people that it wasn’t crabmeat (lacks the sweet crab aroma and light sweet flavor). In my fishing clothes, I am not a picture of a wealthy serenely tailored fly fisherman.
Absolutely. No I didn’t read the whole paper at the end of your link, but the ‘species’ chapter is interesting.
Consider it this way; order – family – species are theoretical application concepts developed by man to place life into an orderly system.
Even with DNA, exactly determining placement of an organism into position requires several things, including someone’s determination of organic detail, acceptance within their branch of ‘ology along with an organism to describe.
None of those components ‘make’ family or species relationship true or absolutely correct. What they do is make someone’s opinion a current favorite.
You want fun? Try and exactly determine which species of mushrooms you’ve picked. Get into the microscopic spore measurement and color determination. Or grow some unusual species of orchids where you’re counting lip keels, pollinia orientation, size and number. Add to that recent attempts to utilize DNA analysis in deciding species relationships which is roiling some fields.
Careful! Getting into species minutia is a sure step towards a type of madness. Just when is “close enough for government work” good enough? When eating mushrooms, perhaps accurate species determination, even as currently known, is best.
Well foreign fish were put in the river some time ago, there are more hybrids now than in the past, Aucun de merde Hercule.. The current temperature is higher now than then. Aren’t these things going to both correlate with time even if independent.
The supplementary info shows only 1sample from each test point,with the sample period extending over 5 years. i.e no year on year comparison for any site. No one year data for all sites. 58% of the sample sites found no hybrids.
The key diagram seems to show model outputs not data.
Have I missed something or am I right to regard this as a bit fishy?
The colder water theory is a “red herring” (no pun intended). Until the government spent a lot of money to reduce lake trout populations in Yellowstone Lake, the lake trout were displacing cutthroat trout there. Lake trout require colder temperatures than cutthroat trout.
I read the first few comments and saw nothing but smart ass crap. Automatic rejection based on the post not fitting people’s set belief system – i.e. anything related to global warming has to be a load of crap.
There are impacts from a changing climate, mostly based on competition. The same applies to changes in other environmental factors. Clear cut a forest and what replaces it will be different. Change the average temperature or flows in salmon and trout bearing streams and you will see impacts. Change in environment can provide one species with a new found competative advantage. Oregon forests are home to both salamanders and newts. The newts are out competing the salamanders for the same habitat. Some of it is due to how they each lay eggs. Some is due to the red skinned newts having developed a means of deterrence to their predators (namely garter snakes and owls). By secreting a poison from their back skin, they are not as palatible – meaning they have a better chance to be passed up, while the salamander gets to star as dinner. And some of it is their changing environment. They are proving more adaptable. The result is that the newts are well on their way to replacing salamanders. That is nature at work. Do humans have an impact? Most likely. Is it the dominate impact? I don’t know. Do we care if the salamanders disappear from Oregon forests? That probably depends on who you ask. I personally think there are bigger issues to be concerned about. One being the health of fish runs, both wild and hatchery. Salmon are very temperature sensitive. Additionally they depend on stream flow being sufficient to entrain enough oxygen and keep sedimentation to a minimum. Oregon streams are seeing increases in temperature at the same time as flows in some areas are diminishing. There is nothing in the story above that I see as bogus or poor science. Those making fun of it should be ashamed.
FYI – I will admit to a bit of bias here, as I did a 6 month internship with USGS while in grad school. There I learned they are one of, if not the best science organization operating under the auspices of the federal government, respected by acadamia, the market place and other government organizations.
timg56 says:
May 28, 2014 at 1:37 pm
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and in your internship you learned nothing about what defines a species, introduced non-natives, cross breeding, and hybrid vigor
Hummm, wonder if David Suzuki would agree that there is no such thing as “hybrid vigor” in cross-bred trout. Last i heard, the climate hasn’t changed in Montana. So, could it be that Cutthroat and Rainbow are simply opportunists when it comes to propagation and that cross breading has nothing to do with being hot and bothered?
Really? You must have missed this part:
“Over time, a mating population of native and non-native fish will result in only hybrid individuals with substantially reduced fitness because their genomes have been altered by non-native genes that are maladapted to the local environment.”
Tell me, Mr USGS former intern, how it is that the less fit out-compete the more fit? Where but in the field of agenda driven climate science would a biologist make the dumbass statement that population A is replacing population B because population A is maladapted to the local environment?
Smarmy warmists whine and moan and gnash their teeth to equate skeptics with creationists, meanwhile putative evolutionists are out there arguing survival of the unfittest to support “climate science.”
The ones to be ashamed are those propagating false stories of global warming and nonsense stories about trout cross-breeding because it’s getting warm in Montana. Well when mangos start multiplying in Montana then that will be global warming, climate change or climate disruption or whatever buzz words the regime uses to scare monger. Until then, global warming exists . . . in the minds of men paid to lie!
All this talk about trout has made me get out my gear, go shopping for some lures, and setting my alarm clock for 0-dark:30. Goin fishin.
[With or without your wide? 8<) .mod]
Only read the first few comments? Made your mind up, based on a few comments. Did you really read them? Did you bother to actually read the abstract and article? Did you bother to read JJ’s comment above? I’m a bit skeptical.
So the forest is clear cut, and you are convinced that what replaces it will be different… Different from what? Forests have been eaten, died out, burned out or frozen out for eons. Maybe they are different when regrown, but that is because competition decided the successful replacement, something that has also been happening for eons.
Of course. Now explain where this paper demonstrates water temperature changes due to global warming or whatever you want to call it. In fact, demonstrate any global warming in the study area that are enough to change water temperatures.
And man caused all this competition advantage to the newts. Who knew the power of man?
Do tell! We didn’t notice your personal opinions before, so it’s nice that you help us by pointing them out.
All caused by global warming? Or perhaps you are afflicting the climate with man draining rivers, streams and aquifers to water plants, food crops and lawns. Got a lawn? Like to eat? Or would you prefer others to suffer?
All well covered by JJ. Even Latitude noticed your comment and responded nicely.
A bit of a bias? One of the better laughs in this thread.
USGS may be on of the best science organizations, especially in the trenches; but if they’re going to keep producing similar science as above, they’re only direction is not better science. Shake the USGS dust from your eyes and read papers looking for the science, not the wild claims.
Trout breed in cold weather, don’t ask me why? But our trout season ceases in June and reopens in October.
Lattitude,
I worked on water quality stuff. I construct and manager communications sites now.
JJ & ATheoK,
Nice doggies. Here, go play with this bone.
I am afraid a day will come everything will be half-done because of climate change. There should be allocation if reasonable amount of funds to learn the exact reasons of half breed trout and how to combat this menace both.