Should We Stop Stocking Non-native Trout? by Don Orth

Did we ever decide that non-native stocking was wrong?  The question is value laden.  Science can explain much about the phylogeny and competitive displacement of trout species.  However, deciding what is right or wrong involves consideration of values.  David Hume (1711-1776) articulated the “is-ought” problems or the fact-value gap. His philosophical law maintains that one cannot make statements about what ought to be based on statements about what is.  The NOFI (No-Ought-From-Is) idea that one cannot deduce an ‘ought’ from an ‘is’ means that we can make no logically valid arguments from the non-moral to the moral.   

Many thought they were doing the right thing for the world at the time of indiscriminate and inconsiderate stocking of non-native trout.  Maybe they were. But they violated Orth’s ‘no irreversible decisions’ law of fisheries management.  Stocking nonnative fishes outside their native range is passing through a door that goes in one direction --  there’s no going back.   Once introduced, the consequences are uncertain AND cannot be reversed.

We understand values of fish for fishing and food.  Trout provided for the well-being of trout anglers, were of cultural importance to settlers of the frontier, and provided direct financial gains for trout guides and private hatcheries. All of these were instrumental values, but other values of trout may be intrinsic or relational.  The more we study trout in a variety of settings, the more diverse the set of values held will be.  Conflicts over values affect decision making and the stocking of nonnatives trouts only considered a narrow set of instrumental values. Nature’s gifts (or nature’s contributions) to well-being broaden the values perspectives (Pascual et al 2017).  Is stocking non-natives right or wrong? The answer depends on the value argument.  What values are harmed with stocking?  Consider the intrinsic values of protecting unique and irreplaceable evolutionary lineages of native trout. Instrumental values arguments would focus on value of encouraging a vibrant economy based on abundant, catchable trout.  Relational values arguments would focus on unique way of life harmed by introduction of nonnatives. 

Seth Green from (1870) Trout Culture. Public Domain  Source

Suffice it to say, these values arguments were not part of the public discussions at the end of the 19^th century.   Trout populations were declining while a new scientific technology was developing that might reverse the decline.  Seth Green, is credited with being the father of fish culture.  He developed the first private fish hatchery in North America in Caledonia, New York, primarily to provide Atlantic Salmon and Brook Trout for food fish markets.  Soon Green’s hatchery was also producing American Shad, Brown Trout, Rainbow Trout for stocking.  More than any other individual, he is credited with introducing Rainbow Trout east of the Continental divide, Brook Trout to western states, and Brown Trout throughout the U.S. (Karas 2002; Halverson 2010; Newton 2013).   His comprehensive work Trout Culture (1870) was used by hatchery managers throughout the continent.  

Before scientists understood the evolutionary history of the native trouts and chars of North America, hatcheries were built, eggs were taken, and millions of fish were stocked to provide trout fishing.  Rainbow Trout are the state fish of Colorado and Utah, but get this—they are not native to these states.  Before the end of the 19^th century, Rainbow Trout were propagated and widely introduced outside their range by the Ornithological and Piscatorial Acclimatizing Society of California.  Seth Green was shipping eggs and fry across the continent (Halverson 2010, p 28).  The New York Fish Commission promoted the superiority of the Rainbow Trout for their hardiness, ease of hatching, game qualities, ease of capture, and fighting qualities (Halverson 2010, p 35).  Soon U.S. Fisheries Commissioner, Spencer Fullerton Baird, instructed Livingston Stone to build another hatchery devoted to Rainbow Trout on the McCloud River, California.  Since that time, the National Fish Strain Register has described 64 strains and even more broodstocks of Rainbow Trout (Kincaid et al. 2001). Despite lessons learned from Carp plantings as a food-fish-turned-pest species (Bartlett 2010), all reports on nonnative trouts were positive, until they weren’t.

 

Three voices from the 20^th century were critical of indiscriminate stocking when state and US governments were investing heavily in more trout hatcheries. 

Leopold's trips to the Rio Gavilan region of the northern Sierra Madre in 1936 and 1937 helped to shape his thinking about land health.  CC-BY-2.0 Pacific Southwest Region US Forest Service Source. 

Aldo Leopold, after completing a Master of Forestry at Yale University, worked at the Apache National Forest in the Arizona Territory. Carson National Forest in New Mexico, and regional headquarters in Albuqueque, New Mexico. In this region, Leopold would be familiar with the endemic Apache trout Onchorhyncus gilae apache, Gila trout Onchorhynchus gilae gilae, and Rio Grande cutthroat trout Onchorhynchus clarkia virginalis.  Based on his observations on trout in these waters, he presented a paper on “Mixing trout” (Leopold 1918; Warren 2010).  He wrote that “Nature, in stocking trout waters, sticks to one species.”  And Leopold recommended to “Restock with the best adapted species, the native species always preferred,” (Leopold, 1918, p. 102).  Furthermore, in restocking empty waters, “ordinarily native and indigenous species are preferable” (Leopold, 1915, p. 95).   It would be years later that he reconstituted these ideas in these famous words:

 “The last word in ignorance is the man who says of an animal or plant: "What good is it?" If the land mechanism as a whole is good, then every part is good, whether we understand it or not. If the biota, in the course of aeons, has built something we like but do not understand, then who but a fool would discard seemingly useless parts? To keep every cog and wheel is the first precaution of intelligent tinkering.” Leopold (1993, p 145-146)

Illustration of James A. Henshall,  author of Book of the Black Bass (1889). Public Domain.  Source

James A. Henshall, while best known for his Book on the Black Bass, was the first superintendent of the Bozeman National Fish Hatchery from 1897 until 1909.  The Bozeman hatchery produced Brook Trout and Rainbow Trout for Colorado and Montana.  Henshall described the accidental release of Brook Trout and Rainbow Trout into Bridger Creek.  His words were “if depleted waters had been stocked with native fishes, this happy and natural condition of affairs might have continued for many years to come” (Henshall, 1919, p. 167).

"Conservationists are notorious for their dissensions.... In each field one group (A) regards the land as soil. and its function as commodity-production; another group (B) regards the land as a biota, and its function as something broader." (Leopold 1947).

           

Edwin “Phil” Pister read the works of Aldo Leopold while in graduate school. He worked as fisheries biologist with California Department of Fish and Game during the height of the hatchery era. Hatchery trout and trophy fishing fueled a tourist economy in the High Sierra mountains of California.  License buyers who funded most agency programs also overwhelmingly viewed trout as a commodity, they were group A in Leopold's terms. Only one game species managed for fishing was native and that was the California Golden Trout Onchorhynchus mykiss aguabonita, which is the state freshwater fish of California. Others species that were not managed were on the verge of extinction.  In fact, one of the desert fishes, the Ash Meadows Poolfish Empetrichthys merriami went extinct before the Ash Meadows Wildlife Refuge was established.  In a visit to speak to Virginia Tech students after his retirement in 1991, Phil told the story of how in 1969 he scooped rare Owens Pupfish Cyprinodon radiosus out of a shoe-deep slough sure to dry.  That day he literally saved the last population of Owens Pupfish—moving 800 fish in 2 buckets—away from certain destruction.  Note: this was before passage of the Endangered Species Act.

Edwin "Phil" Pister.  Credit: Greg Boyer/OneHorseStudio.com

Pister worked tirelessly to establish and maintain the Desert Fishes Council. This group’s mission is to “preserve the biological integrity of desert aquatic ecosystems and their associated life forms, to hold symposia to report related research and management endeavors, and to effect rapid dissemination of information concerning activities of the Council and its members.”   His work on Golden Trout began in 1959 when it was apparent the state fish was at risk of extinction. In the 1970s, he sided with the National Park Service against his agency directive.   Park Service policy was that “Trout are not indigenous to the lakes of the High Sierra, they would no longer be planted in park waters.”  Phil Pister also worked to reduce threats to the rare and threatened subspecies of Golden Trout in high elevation streams of California.  Phil Pister likes to quote Stephen Jay Gould:  “We are trapped in the ignorance of our own generation.”

My role as a scientist is not to make a choice for all people about which trout to stock where?  However, I can demand that all people consider the potential problems that arise from our newfound scientific knowledge and capabilities.  Your value arguments about non-native trout stocking matter.   Yes, it will take time and slow down decision making, but the alternative is a public that does not engage nor trust the process of fish conservation and management.

California Golden Trout CC-BY-SA-4.0.  DaveWiz84, Source

References  

Bartlett, S.P. 1910. The future of the carp. Transactions of the American Fisheries Society 39(1):151-154.

Halverson, A. 2010. An Entirely Synthetic Fish: How Rainbow Trout Beguiled America and Overran the World.  Yale University Press, New Haven, Connecticut. pp. 32–34.

Henshall, J.A. 1919. Indiscriminate and inconsiderate planting of fish.  Transactions of the American Fisheries Society 48:166-169.

Karas, N. 2002. Brook Trout: A Thorough Look at North America's Great Native Trout – Its History, Biology, and Angling Possibilities, Revised Edition. Lyons Press, NY. p. 75.

Kincaid, H.L., M.J. Gray, L.J. Mengel, and S. Brimm. 2001. National fish strain registry — Trout species tables of reported strains and broodstocks. U.S. Fish and Wildlife Service, U. S. Geological Survey 98-032/NF https://archive.org/details/nationalfishstra02kinc/page/n1

Leopold, Aldo. 1918. Mixing trout in western waters. Transactions of the American Fisheries Society 47(3):101-102.

Leopold, A. 11993. Round River, Oxford University Press, New York

Newton, C. 2013. The Trout's Tale – The Fish That Conquered an Empire. Medlar Press, Ellesmere, Shropshire. pp. 115–116.

Pascual, U., Balvanera, P., Díaz, S., Pataki, G., Roth, E., Stenseke, M., et al. 2017. Valuing nature’s contributions to people: the IPBES approach. Current Opinion in Environmental Sustainability 2:7–16. doi: 10.1016/j.cosust.2016.12.006

Pister, E.P.  1992. A Pilgrim’s progress from group A to group B.  Pages 5-10 in G.H. Reeves, D.L. Bottom, and M.H. Brookes, technical coordinators.  Ethical questions for resource managers.  General Technical Report PNW-GTR-288. US Forest Service, Pacific Northwest Research Station. 39 pp.  DOI: https://doi.org/10.2737/PNW-GTR-288

Warren, J. L. 2010.  Weaving a wider net for conservation: Aldo Leopold’s water ethic.  Organization and Environment 23(2):220-232.

Rio Grande Cutthroat Trout: History, Imperilment, and Management, by Daniel Donahoe

Throughout western North America, 13 colorful subspecies of Cutthroat Trout Oncorhynchus clarki dot the montane landscape. One subspecies of Cutthroat Trout, the Rio Grande Cutthroat Trout Oncorhynchus clarki virginalis, is endemic to southern Colorado and New Mexico (Pritchard et al. 2009). This subspecies of Cutthroat Trout is arguably the gem of the American Southwest, and displays a wide gamut of colors that mimic the picturesque New Mexican sunset.

The shining gem of New Mexico’s streams, the Rio Grande Cutthroat Trout, is a Salmonid (Family Salmonidae) that inhabits some of the state’s coldest and cleanest waters. With most Cutthroat Trout species diverging around 1-2 million years ago, Rio Grande Cutthroat Trout diverged relatively recently. Rio Grande Cutthroat Trout diverged from the nearby Colorado River Cutthroat Trout Oncorhynchus clarki pleuriticus around 100,000 years ago (Pritchard et al. 2009).

This speciation stems from the rugged geography of the Rocky Mountains. For millions of years, the Rocky Mountains geographically isolated populations of Cutthroat Trout throughout western North America. ultimately leading to the evolution of a variety of colorful subspecies (Loxterman and Keeley 2012). Of the 13 subspecies of Cutthroat Trout located across western North America, the Rio Grande Cutthroat Trout is the most-southerly distributed species (Pritchard et al. 2009).

Historic range of the eight major species of Cutthroat Trout (Loxterman and Keeley 2012).

The first reported sighting of Rio Grande Cutthroat Trout was by Francisco Vázquez de Coronado and the Conquistadores in 1541 during their conquest through New Mexico and southwestern North America (Owen 2012). The Rio Grande Cutthroat Trout was once prevalent throughout rivers in Colorado and New Mexico, but currently occupies only 11 percent of its historic range (Shemai et al. 2007). This southerly subspecies of Cutthroat Trout currently inhabitants three river systems within Colorado and New Mexico. The Canadian River, the Pecos River, and the Rio Grande river are the only rivers that currently harbor populations of Rio Grande Cutthroat Trout (Pritchard et al. 2009). With this information, one might beg to ask: how did the Rio Grande Cutthroat Trout become one of the rarest piscine gems of the American Southwest?

One threat to Rio Grande Cutthroat Trout populations came in the form of a foreign competitor; the Brown Trout Salmo trutta. Brown Trout, originally native to cold-water streams of Germany, were introduced in Colorado and New Mexico throughout the late 1880’s with the intent of spurring the states’ angling opportunities (MacCrimmon et al. 1970). These trout are “hardier” than native Rio Grande Cutthroat Trout in that they can tolerate a wider range of temperatures and consume a diverse range of food sources. Rio Grande Cutthroat Trout found in streams where Brown Trout are prevalent often show signs of being outcompeted and exhibit physical damage from aggressive Brown Trout (Shemai et al. 2007).

To make things worse, Rio Grande Cutthroat Trout are fighting another foreign threat: Whirling disease. This disease, originating from Germany, is the work of a prolific parasite Myxobolus cerebralis. This parasite festers inside aquatic Sludge Worms Tubifex tubifex that eventually release “TAM” spores throughout the water column that attach to trout gills (Ayre et al. 2014). This parasite burrows into the gills, working its way into a trout’s spinal cord and feeding on cartilage along the way. This process causes spinal-deformities in infected trout, which leads to erratic behavior in infected trout (Ayre et al. 2014). Trout infected with whirling disease often exhibit tail-chasing swimming behaviors within the water column, making them easy prey for predators (Ayre et al. 2014). If the trout is not preyed upon, it’s dead carcass will sink to the bottom of the river where the parasite’s eggs are released and ingested by Sludge Worms, thus repeating the parasite’s life cycle. This parasite has been credited for substantial decreases in Rio Grande Cutthroat Trout stocks and other trout stocks in Colorado, Utah, Wyoming, and Montana (Ayre et al. 2014).

Aquatic Sludge Worm lifecycle by fishpathogens.net. (Source)

These threats underscore the importance of restoring and preserving intact native Rio Grande Cutthroat Trout populations. To save these populations, fisheries managers must first identify genetically-pure populations of Rio Grande Cutthroat Trout. Genetic sequencing has been conducted on multiple Rio Grande Cutthroat Trout populations from a variety of streams and drainages around New Mexico and Colorado (Pritchard et al. 2009). Even though genetic sequencing is becoming a part of normal, everyday fisheries management, researchers will find it difficult to pinpoint a genetically pure population of Rio Grande Cutthroat Trout, as these populations have developed small, but significant differences in their genomes. Populations of Rio Grande Cutthroat Trout that are separated by only a few kilometers have been found to show distinct differences in their genomes (Pritchard et al. 2009).  Historic stockings of genetically dissimilar Rio Grande Cutthroat Trout have diluted the gene pool, effectively creating mongrel Rio Grande Cutthroat Trout. This micro-geographic structuring of Rio Grande Cutthroat Trout populations across the New Mexican country-side has made managing Rio Grande Cutthroat Trout difficult. Fisheries managers must tweak their management strategies depending on the genetic composition of a single population of Rio Grande Cutthroat Trout contained within a single sub-drainage (Pritchard et al. 2009).

Rio Grande Cutthroat Trout by loeflyfishing.com. (Source)

           

Current efforts to conserve Rio Grande Cutthroat Trout are being carried out by a variety of state and federal conservation agencies. One agency, the U.S. Forest Service, has advised the construction of natural and artificial dams to impede the spread of nonnative trout species that can outcompete native Rio Grande Cutthroat Trout (Young 1995). Along with dams, electroshocking has been used to eradicate nonnative trout from pools to eliminate the chance of competition on Rio Grande Cutthroat Trout (Young 1995). Efforts to manually remove invasive trout have also been instituted by conservation agencies. Federal and state conservation agencies within Colorado and New Mexico require fishermen to dispose of nonnative trout species if they are caught while fishing in streams that also harbor Rio Grande Cutthroat Trout (Quist and Hubert 2004). Additional policies have been instituted such as creel limits and protection of Rio Grande Cutthroat Trout spawning areas. Fortunately, these policies have been mildly successful in allowing Cutthroat Trout return to its native range (Quist and Hubert 2004).

    

            The Rio Grande Cutthroat Trout has proven to be an integral part of the American Southwest. This trout, displaying a wide gamut of colors that mirror the picturesque New Mexican sunset, has received a variety of threats from foreign invaders. To counteract these threats, federal and state conservation agencies have instituted the use of dams, creel limits, and other methods to eradicate competitive nonnative trout. These efforts help conserve the Rio Grande Cutthroat Trout for future generations of Coloradans and New Mexicans to enjoy.

References

Ayre, K. K., C. A. Caldwell, J. Stinson, and W. G. Landis. 2014. Analysis of Regional Scale Risk of Whirling Disease in Populations of Colorado and Rio Grande Cutthroat Trout Using a Bayesian Belief Network  Model. Risk Analysis: An International Journal 34(9):1589–1605.

Loxterman, J. L., and E. R. Keeley. 2012. Watershed boundaries and geographic isolation: patterns of diversification in cutthroat trout from western North America. Evolutionary Biology 12:38.

MacCrimmon, H. R., T. L. Marshall, and B. L. Gots. 1970. World Distribution of Brown Trout, Salmo trutta: Further Observations. Journal of the Fisheries Research Board of Canada 27(4):811–818.

Owen, J. 2012. Trout. Reaktion Books, United Kingdom.

Pritchard, V. L., J. L. Metcalf, K. Jones, A. P. Martin, and D. E. Cowley. 2009. Population structure and genetic management of Rio Grande cutthroat trout (Oncorhynchus clarkii virginalis). Conservation Genetics 10(5):1209.

Quist, M. C., and W. A. Hubert. 2004. Bioinvasive species and the preservation of cutthroat trout in the western United States: ecological, social, and economic issues. Environmental Science &  Policy 7(4):303–313.

Shemai, B., R. Sallenave, and D. E. Cowley. 2007. Competition between Hatchery-Raised Rio Grande Cutthroat Trout and Wild Brown Trout. North American Journal of Fisheries Management 27(1):315–325.

Young, M. K. 1995. Conservation assessment for inland cutthroat trout. United States Forest Service General Technical Report RM-256.