Sunday, August 11, 2019

First Trout Hatcheries in Virginia, by Don Orth

By the 1870’s Virginians were aware of the great depletion of major food fisheries due to overfishing and multiple dams blocking fish runs.  The Virginia Assembly created the office of the Virginia Fish Commissioner in March 1871 to evaluate Virginia’s commercial fisheries and make recommendations for restoration.  One of the main strategies was artificial propagation.  William Ball was the first fish commissioner of Virginia and focused efforts to propagate and release shad, black bass, and trout. In 1894, the Virginia Commissioner of Fisheries wrote “the question of greatest importance to our fishermen is the appalling decline in the number of the free migratory fishes that annually visit the waters of the State.”  (Wilkins 1894). This effort was parallel to efforts in other states as well as the federal government, which established the Commission of Fisheries in 1871, to examine depletion of fisheries in the nation.  Seth Green, the father of fish culture, opened the Caledonia Hatchery in 1864 and the race to build hatcheries was on.  The first hatcheries in Virginia did not raise shad or striped bass.  First hatcheries to propagate these fishes were at Fort Washington and Fishing Battery Island (Maryland) and Albemarle Sound at Edenton, North Carolina.  
Marshall McDonald was Virginia Fish Commissioner 1875-1888 and U.S. Commissioner of Fish and Fisheries from 1888 to 1895.   Photo Source
Marshall McDonald played a key role in Virginia fisheries restoration during this time.  McDonald was a Professor at Virginia Military Institute before and after his military career during the Civil War. He was chair of Geology at Virginia Military Institute when he developed an interest in fish farming. He filed a patent for a new fishway design in 1879, which he sold to the state of Virginia in 1880. He also invented a hatching bucket for hatching eggs of pelagic fishes.  As Fish Commissioner of Virginia, Marshall McDonald began construction of the Lexington hatchery on the Town Branch spring in 1875 (The Advocate 2006). This hatchery and one managed in Blacksburg by Professor Mason G. Ellzey, Virginia Agricultural and Mechanical College, would train students in the art of pisciculture.  California salmon eggs (Oncorhynchus tshawytscha) were hatched in these hatcheries in 1876 and yielded salmon fry released in the tributaries of the James and Roanoke drainages.  The Virginia Fish Commission (1877, p. 56) reported that the two hatcheries were “doing good work” although they were compelled to buy trout eggs.  However, the California salmon released never returned and efforts to propagate salmon in Virginia ceased.  The Lexington hatchery closed in 1880 and I could find no historical records about the longevity of the Blacksburg hatchery.    
McDonald Fishway with Water Shut Off, in Great Falls of the Potomac, 1898. Public Domain.
Marshall McDonald traveled to Wytheville, Virginia in August, 1879 to select a location for a fish hatchery.  This new trout hatchery was built on 3 ½ acres of land donated by S.P. Browning (Chitwood 1989). The location 3.5 miles west of Wytheville, off Old Stage Road, was ideal with two springs that produced 1,100 gallons per minute and was directly on the Atlantic, Mississippi and Ohio Railroad line (later Norfolk & Western).  It was in operation by November and was operated by the U.S. Fish Commission in 1882 and completed in 1888. At the time there were twelve rearing ponds for trout, piping to ponds, a retaining wall on Tate’s Run, and a two-story building for rearing troughs.   The Wytheville hatchery raised the McCloud strain of Rainbow Trout from eggs shipped from the federal hatchery on the McCloud River.   
Wytheville hatchery layout circa 1886. (McDonald 1889).
Water supply and brood fish ponds at Wytheville hatchery, circa 1886. 
From annual reports of the U.S. Fish Commission we find that “In the spring of 1885 about 300 grayling were hatched from eggs collected from wild fish in the streams of Michigan by Mr. F. N. Clark and forwarded to Wytheville.  These 300 fish are being kept for breeders, and at the close of the year were in fine condition.”  (U.S. Fish Commissioner.  1887 Page ixxxii).  Further, stocking of Rainbow trout to the headwaters of the Shenandoah River in Augusta county and tributaries of Potomac in Maryland as well as ponds in Maryland, SW Virginia and Tennessee occurred in 1886 (U.S. Fish Commissioner.  1887.  Page ixxxv)  
Hatchery troughs at the Wytheville hatchery, circa 1886. (McDonald 1889).
Hatchery trout plan view for Wytheville hatchery. (McDonald 1889).
In the fiscal year ending June 30, 1887, McDonald (1889, p 4-5) reported receiving Rainbow Trout from California, Brook Trout from Michigan, Brown Trout from New York, Atlantic Salmon from Maine, Common Carp from Washington, D.C. and Rock Bass and Smallmouth Bass collected locally from New River and Reed Creek.   The Atlantic Salmon were stocked in a tributary of the Shenandoah River near Staunton and South Fork of Shenandoah River near Waynesboro. 

The first superintendent of the Wytheville Hatchery was William E. Page of Lynchburg, and he was soon succeeded by George A. Seagle, a native of Wythe County.  Seagle invented the Seagle shipping box for transporting trout fry long distances. Seagle was succeeded in 1922 by Charles B. Grater of Leadville, Colorado, who served until 1930.  In 1930, Samuel A. “Gus” Scott became the fourth hatchery manager (Chitwood 1989).  Under Scott’s management the Wytheville, hatchery produced 20,000 to 25,000 pounds of fish annually, mainly Rainbow Trout, bass, and bream.  

Satellite view of hatchery, now operated as Brakens Fish Hatchery.  photo (c) Google Maps 2019.
This historic hatchery operated until 1968, after a new facility was opened on Reed Creek.  The hatchery was donated to Wytheville Community College for use in biology classes.  In 1987, it was purchased by Dale Bracken who restored the hatchery, which now operates as Brakens Fish Hatchery for recreational fishing. 
Brook Trout. Photo by Steve Droter. CC BY-NC-2.0  Source. 
Approximately 100,000 anglers fish for stocked trout in Virginia waters and their fishing satisfaction depends on annual stocking of catchable-size trout.  Wild trout occur in over 2,300 miles of coldwater streams in the Commonwealth and native Brook Trout Salvelinus fontinalis thrive only in higher-elevation mountain streams.  Five trout hatcheries operate to produce stocked trout in Virginia.  These include stations at Marion (Smyth Co.), Montebello (Nelson Co.), Coursey Springs (Bath Co.), Paint Bank (Craig Co.), and Wytheville (Wythe Co.).  Trout hatcheries are open to the public to tour and learn more about the propagation of trout.  Teachers can connect students to local watersheds with Trout Unlimited's Trout in the Classroom program, which raises trout from egg to the fry stage for stocking.  

References
Chitwood, W.R. 1989.  The old Wytheville fish hatchery.  The Mountain Laurel the Journal of Mountain Life.  September   
U.S. Fish Commissioner.  1887. Report of the Commissioner of Fisheries to the Secretary of Commerce and Labor for 1885U.S. Bureau of Fisheries    Washington Government Printing Office 1887. 
McDonald, Marshall. United States Commission of Fish and Fisheries. 1889. Report of Operations at the Wytheville Station, Virginia, from January 1, 1885 to June 30, 1887. Washington, D.C.: United States Government Printing Office.
McHugh, J.L., and R. S. Bailey. 1957. History of Virginia’s commercial fisheries. The Virginia Journal of Sciences 8(1):42-64. 
The Advocate. 2006.  Salmon in the Maury? It wasn’t just a fish tale. The Rockbridge Advocate. December 2006.  49-54. 
Wilkins, J.T., Jr. 1894. The Fisheries of the Virginia Coast. In House Misc. Doc., 53rd. Congress, 2nd Session, Vol. 20, Bull, U.S. Fish Comm., for 1893: 355-356. Cited in McHugh and Bailey 1957.

Monday, August 5, 2019

What's New In the World of Freshwater Fishes of Virginia? by Don Orth

The Field Guide to the Freshwater Fishes of Virginia will be released by September 24th. I promise that even those familiar with our local fish fauna will learn something new.  I’ve received many questions about the forthcoming Field Guide and answer a few of them here. 


How many freshwater fish species are there in Virginia?  There are more species (226) and more families (28) of freshwater fishes than appeared in Jenkins and Burkhead (1994) treatise.  How’d that happen?  It’s a combination of discoveries of cryptic diversity, introductions, and elevation of subspecies to species status. 

Families                                  Species in Virginia
Lampreys - Petromyzontidae              5
Sturgeons - Acipenseridae                  2
Paddlefish – Polyodontidae                1
Gars – Lepisosteidae                          1
Bowfins – Amiidae                            1
Eels – Anguillidae                              1
Herrings – Clupeidae                          6
Carps and allies - Cyprinidae             1
Carps - Xenocyprididae – Carps        1
Minnows – Leuciscidae                      71
Suckers – Catostomidae                     19
Catfishes – Ictaluridae                        15
Trouts – Salmonidae                           3
Pikes – Esocidae1                                4
Mudminnows – Umbridae1                1   
Pirate Perch – Aphredoderidae           1
Cavefishes – Amblyopsidae               1
Silversides – Atherinopsidae              1
Killifishes – Fundulidae                     5
Livebearers – Poeciliidae                   1
Sticklebacks – Gasterosteidae            1
Sculpins – Cottidae                             10
Temperate Basses – Moronidae          3
Sunfishes – Centrarchidae                  20
Perches – Percidae                              48
Drums – Sciaenidae                            1
Snakeheads – Channidae                    1
1Note: some call for merger of Esocidae and Umbridae
Outline sketch of members of the Leuciscidae, formerly Leuciscinae, Cyprinidae
What the most species rich group?  The order Cypriniformes is the most diverse order of freshwater fishes in the world, numbering over 4,602 currently recognized species (Fricke et al. 2019).  This is more than 200 new Cypriniformes species since we first began working on the Field Guide. 

What major taxonomic revision has occurred recently? The former subfamily Leuciscinae was elevated to family level (Tan and Armbruster 2018). Leuciscidae has 680 species and this now includes what we used to consider the native North American Cyprinidae as well as some European and Asian minnows.  In Virginia, we find 71 species in the newly defined Leuciscidae, making this the most species-rich family in freshwaters of Virginia. Xenocyprididae encompases the introduced fish we know as Ctenopharyngodon idella – Grass Carp. Cyprinidae includes 1,722 valid species, such as the Common Carp, as well as other carps, barbs and barbels, and tor.    

What about the darters? There are 238 valid species of Percidae in the world and most of these are darters.   Virginia has 48 species of Percidae, 45 are darters in Ammocrypta, Percina, and Etheostoma. 

How come Virginia has such high number of freshwater fishes?
Virginia has a humid, temperate climate with about 43 inches of rainfall annually. In this relatively wet environment, differences in geology and topography provide diverse aquatic habitats and thermal regimes enabling a wide diversity of fish species to evolve and thrive. Historical factors, such as the lack of Pleistocene glaciers, interconnections between river systems, and species dispersal patterns, all contribute to Virginia’s rich fish fauna.  Virginia has five landforms, each with distinct geologic histories and freshwater habitats.  These are depicted on the map below -- Appalachian Plateau, Ridge and Valley, Blue Ridge, Piedmont, and Coastal Plain. Virginia’s highest peak is Mount Rogers at 5,729 feet above sea level.
Map of Virginia color coded by elevation (blue is low, red is high) and physiographic provinces. Map produced by coauthor Corbin Hilling.   If you don't know physiographic provinces, get the Field Guide.
Which drainage has the most nonnative fishes?   The New drainage has only 40 native fishes and an additional 46 species are introduced.

What species are extirpated from Virginia?
Cyprinella labrosaThicklip Chub
Moxostoma lacerumHarelip Sucker
Percopsis omiscomaycusTrout-perch Percopsidae
Percina bimaculataChesapeake Logperch

What is the rarest fish species of Virginia?
Erimystax cahni – Slender Chub

What is species is the newest introduction to Virginia? 
Channa argus – Northern Snakehead

What family has the most cryptic diversity?  Cottidae

What species still need of formal species descriptions?
Chrosomus sp. cf. saylori – Clinch Dace
Notropis sp. cf. spectrunculus – Sawfin Shiner
Moxostoma sp. cf. lachneri – Brassy Jumprock
Cottus n. sp.  Bluestone Sculpin
Cottus n. sp. Clinch Sculpin
Cottus n. sp. Holston Sculpin
Probably other Cottus
 
What colloquial fish name is unique to Virginia?   Shenandoah Tarpon is used by anglers who have caught the Fallfish Semotilus corporalis via flyfishing.
 
            Acipenser oxyrinchus Atlantic Sturgeon
            Acipenser brevirostrum Shortnose Sturgeon
            Etheostoma osburni Candy Darter
            Etheostoma percnurum Duskytail Darter
            Percina rex Roanoke Logperch

What species are Threatened?
Chrosomus cumberlandensis Blackside Dace
Erimystax cahni Slender Chub
Erimonax monachus syn: Cyprinella monacha Spotfin Chub
Noturus flavipinnis Yellowfin Madtom

What’s the most colorful fish in Virginia?  That’s a toss up between the
            Chrosomus oreas Mountain Redbelly Dace and
            Etheostoma osburni Candy Darter
You’ll have judge for yourself. Each of these colorful species was illustrated by Val Kells

Michael J. Pinder, coauthor, and Yellowfin Madtom Recovery t-shirt at the release in the North Fork Holston River.  Photos by David Crigger, Bristol Herald Courier

What rare fish has high promise for recovery?  The Yellowfin Madtom has been cultured in captivity and can be introduced into streams of its historic range. 

What is the most cultured species in Virginia?   More than 1.5 million trout are produced in Virginia's 5 trout hatcheries each year.  Most of these are Rainbow Trout Oncorhynchus mykiss. 

Most underappreciated cool fish in Virginia?   Swampfish Chologaster cornuta

What species has the smallest range?
Etheostoma percnurumDuskytail Darter occurs only in Copper Creek

Duskytail Darter Etheostoma percnurum.  Illustration by J. Sipiorski (Blanton et al. 2008)

What’s the best fish story? That would have to be the sturgeons (Acipenseridae).  These ancient bony fishes lived during the Cretaceous period during the age of dinosaurs (145.5 and 65.5 million years ago). Sturgeons are one of the largest and longest-lived anadromous fish in North America and two species occur in Virginia waters.  The Atlantic Sturgeon may reach a maximum size of 14 feet and 811 pounds based on a Canadian specimen.  The population has been depleted coast wide for a long time.  During the late 1800s, fishing for sturgeon eggs (to sell as caviar) attracted so many people, the trend was referred to as the “Black Gold Rush.” Atlantic Sturgeon were thought to be gone from Maryland waters of the Chesapeake Bay, but recent good news indicates they are still there. Also, Atlantic Sturgeon are reproducing in the James River.

Albert Spells, Virginia Fisheries coordinator for the Fish and Wildlife Service, didn’t believe Atlantic sturgeon were gone from the Chesapeake Bay watershed. Photo by USFWS

How many field guides do you plan to sell?  Based on US Census figures, there are 8.57 million people in Virginia, 78% are over 18, and 8% fish.  If all anglers in Virginia buy a Field Guide, we will sell 534,768 copies.  😉  Pre-order now and receive a 20% discount from the publisher.  

References
Blanton, R.E., and R.E. Jenkins. 2008. Three new darter species of the Etheostoma percnurum species complex (Percidae, subgenus Catonotus) from the Tennessee and Cumberland river drainages.  Zootaxa 1963:1-24.
Fricke, R., W.N. Eschmeyer, and R. van der Laan, editors.  2019.  CATALOG OF FISHES: GENERA, SPECIES, REFERENCES.  Accessed August 2, 2019 (http://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp).
Jenkins, R.E., and N.M. Burkhead. 1994.  Freshwater Fishes of Virginia.  American Fisheries Society, Bethesda, Maryland.  1080 pp.
Tan, M., and J.W. Armbruster. 2018. Phylogenetic classification of extant genera of fishes of the order Cypriniformes (Teleostei: Ostariophysi).  Zootaxa 4476(1):6-39.

Tuesday, July 30, 2019

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 19th 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 19th 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 20th 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.