The Biogeography of  the California Golden Trout
 

by Joseph Carpenter (Joey the mover), student in Geography 316  Spring 2005

Thank you for visiting our site. This web pages was written by a student in Geography 316: Biogeography and edited by the instructor, Barbara Holzman, PhD.  All photos and maps are posted with specific copyright permission for the express use of education on these web pages. The students have tried to be as accurate as possible with the information provided and sources and references are cited at the end of each page.

Species Name: Oncorhynchus mykiss aguabonita

Kingdom: Animalia Phylum:Chordata Class: Actinopterygli Order: Salmoniformes Family: Salmonidae Genus: Oncorhynchus Species: Oncorhynchus mykiss Subspecies: Oncorhynchus mykiss aguabonita
	photo by: Justin Tellian

Description:

 The golden trout was recognized as a variant species of trout because of its uniquely vibrant markings.  The waters at the elevation where the trout are found are very cold and very clear with a high reflective rate.  The Golden Trout in particular has adapted very well to this environment in terms of appearance.  This trout adapted a yellow gold to olive green tint on its sides and belly.  The fish also developed two very brilliant red stripes; one on its belly which runs from the last lower fin to the front of the gill,  the other stripe is on the lateral line that typically begins at the seventh lateral spot which also runs to the gill.  These colors were adapted for both passive and aggressive reasons.  The gold and red, when viewed from out of the water, make the trout virtually invisible in the shallow creeks of the high Sierras.  Having this advantage makes it difficult for predators and prey alike to locate it.  Golden Trout are an average length of five to seven inches.  Golden Trout of ten inches have been recorded, but they are rare.  Its body’s depth is 3.5 inches with noticeably small scales (CDF and G 1995).  The fins have small, black spots with a black border with white tips.  Golden Trout have more spots on their back and tail than your average Rainbow or Brown Trout.  Native trout of all species typically have seven to ten large black circles along their lateral. The rule is the more predominant the “spots,” the closer to native blood the individual trout is.  Typically, the purest Golden Trout have the largest lateral spots and the brightest colors.  Knowing this helps the observer decipher between a native and nursery or hybridized trout.  Due to the sensitivity and susceptibility of this particular species of trout the number and brilliance of spots and colors depend greatly on its environmental factors (CDF and G 1995).

Natural History:

The California Golden Trout are native specifically to the Kern Plateau in the southern area of the Sierra Nevada Mountain range in California.  At an elevation of 8,000-12,000 feet, the plateau is considered coniferous forest, tundra. The trees in this tundra consist of Ponderosa pine, Lodgepole pine, and Western Spruce, all of which very greatly in size and spacing (Stefferud 1993).  There are sporadic riparian communities as well, which is where the majority of trout’s food comes from. These riparian communities are in the form of mountain meadows (see Figure 2).  The meadows are strung about the shallow streams the trout inhabit.  Bunch grasses and wild flowers are the typical vegetation of these meadows (Stefferud 1993).

Figure 2:  Title: "Susan in the Meadow." Horseshoe Meadow near cottonwood pass in the Golden Trout Wilderness.  picture courtesy of Mountainmaster 2003

The insects that come from these meadows; mayflies, gnats, mosquitoes, stoneflies, ants, beetles, spiders, dobsonflies, worms and larvae, are among the prey of the adult trout (Stefferud 1993).  Although insects are the great majority of trout sustenance, they are not the only source. Vegetable detritus, Plankton, trout eggs, and other small fish are also sources of nutrients (Stefferud 1993).  As the temperature increases with the changing seasons, the portion of plankton and vegetable detritus in the trout’s diet increases as well.  It is these types of foods that have the greatest impact on the growth of the trout.  Golden Trout are the least productive of the trout family (Gall 1982). Long winters and high elevation are the reason for this low productivity and lack of availability of food.  Stream production, riparian production, and trout growth all come to a halt with the onset of fall.   

Evolution:

The class Actinopterygli means Rayfinned fish.  This means the fins are aligned in a ray shape by bones, whereas, lobe finned fish have a single main bone when in skeletal form (Berg 1987).  Rayfinned fish are the latter of the two in the evolutionary time scale.  The Salmoniform order of boney fish evolved a special niche for spawning in freshwater and living out their adult lives in the oceans.  The niche supports the trouts growth in the oceans after maturity and protection in the rivers before maturity.  Today, Steelhead rainbow trout are sea-run migrates and Rainbow Trout live out their lives in the river systems. Through allopatric speciation, California Golden Trout parallel six other sub-species of the ancient sea-run Coastal  Rainbow Trout.  The Coastal Rainbow invaded deep into the waters of California and south into Mexico 25,000 to 20,000 years ago during a population boom (Walters 1997).  Subsequently, barriers had also formed through geomorphic disturbances around the same period. The last glaciations of the Pleistocene killed off most of the habitat throughout the Sierra Nevada.  Only certain pockets by sheer chance of location were not severely disrupted by these events. Through isolation the rainbow trout had been disrupted within adaptations range and were able to divergently evolve into a subspecies with a separate genotype all together (Gall, Bannon, 1982).  The bright colors and small size are the noticeable evolutionary strategies for survival.  Though highly susceptible to hybridization and degeneration to the rainbow trout, the Golden Trout traits are a product of heritable variation.

Distribution::  

The Golden Trout is an endemic organism to the Kern Plateau, Tulare County, California.  It is a long lost relative to another California native, the Sea Run Coastal Rainbow Trout.  This particular species had a wide geographic range, from Alaska to Mexico which gave way to many high density population pockets deep into the Sierra Nevada mountain range (Storer 1964).  The pockets were well developed due to the connectivity of the California watershed and the Pacific Ocean.  Coincidently, tectonic movement combined with glaciations and volcanoes the Kern Plateau in the southern region of the Sierra Nevada mountain range had formed.  These geomorphic disturbances created a barrier for the trout around 20,000 years ago.  High outlet falls, hanging valleys and volcanic lava cut off created this high elevation plateau for the trout (Curtis 1934).  Isolated, and no longer able to be a migrating sea run fish like it’s soon to be ancestors, the Rainbow trout quickly began to adapt to its permanent high elevation habitat (see figure 2)

Figure 2: The distribution of three golden trout sub-species in the Kern Plateau

Freezing crystal clear waters, short production seasons, very shallow streams, and scarce food are among the new obstacles for the species survival. Trout are a eurytropic species.  Though not quite a cosmopolitan distribution, the trout species have disjunct and continuous distributions (dependent on subspecies) in most of the world’s biomes.  These distributions are in the mid to high latitudes of the Northern and Southern hemispheres.  This particular sub-species of trout found in mid- latitude Southern California has become one of the world’s most coveted neoendemic species (Gold, 1976). This is because of the vibrant colors it has adapted in isolation. The trout distribution has the highest natural concentrations on the Pacific Coast because of the origin of the species.

Other interesting issues:
In1947 the Golden Trout was designated as California’s State Fish.  A 300,000 acre section of the Kern Plateau was set aside by the U.S.  Department of Forestry and named the Golden Trout Wilderness in 1978 (USDF 2002).  Also, in 1991 the Golden Trout had been added as a candidate under the  endangered species list as a Category 2 Endangered Species.  The most recent change, though, has been the addition of the Golden Trout to the Forest Services Sensitive Species List. Many Golden Trout in the late 1800’s where transplanted throughout the Sierra Nevada drainage system so their beauty could be shared by anglers all over the state and parts of Arizona.  This was also true for the Rainbow and German Brown trout being planted in the high waters of the Golden Trout habitat (Walters, 2004).  The Golden Trout, having extreme susceptibility to hybridization because of there close ancestral ties with these invasive trout, were quickly losing their blood line.  In addition to hybridization, habitat loss throughout the community was a growing concern . Golden Trout were being out competed at the population level for food and space with the invasive trout as well. The other form of habitat loss was through overgrazing of sheep and cattle (Pister, 1978).  The thousands of livestock trampled many ledges of the shallow creeks which the trout uses as a food source.  Furthermore, the excess of nitrates from the livestock waste pollute the waters which causes a liver disease Golden trout in particular are very susceptible to (Pister, 1978).  The degradation of the species and its habitat began to catch the eye of environmental groups and lobbyists in the mid 1900’s. The California Golden Trout is still under the threat of extinction, even though it is now legal to fish in the Golden Trout Wilderness.  Legal fishing is often representative of a strong and flourishing population.  There are, however, factors which are still threatening the sustainability of the Golden Trout population.  Habitat degradation and hybridization are among the top threats as the battle between private land owners and the National Park Service continues. A watchful eye must be kept by Californians as new boundaries are drawn and legislation continues to change in order to preserve this one of a kind neo-endemic species. 

Bibliography
Department of the Interior, Fish and Wildlife Service Fish and Wildlife Service, Interior September 20, 2002 (Volume 67, Number 85).

Fish Species of Special Concern in California, Volcano Creek Golden Trout. California Department of Fish and Game pp.2.

Gall, G., Bannon, M.,  Smith, R. C., Bentley, B. 1982. “Progress Report: California Native Trout of the Rainbow Series.” Univ. of Ca, Dept. of Animal Science, Davis. 9 pp.

Gold. M. F., Gold. J. R.  1976. Golden trout in trouble. Natural History 85: 74- 83.

Pister. E. P. 1978 Wild trout concepts and management of threatened fishes. Pages 49 – 59 in K. Hashagan. Ed. A National symposium on wild trout management. California Trout Inc. San Francisco

Stefferud, J. A. 1993. Spawning Season and Microhabitat Use by California Golden Trout (Onchorhynchus Mykiss Aguabonita) in the Southern Sierra Nevada. California Fish and Game 79(4): 133-144.

Storer, T., Usinger, R. L.  1964. Sierra Nevada Natural History: An Illustrated Handbook. University of Ca. Press.

Walters, M. J. 2004. “Invaders at the Gate – Survival of the Little Kern Golden Trout.” Gale Articles: 1-2.

send comments to bholzman@sfsu.edu
 

Geog 316 homepage        Back to Geography home page           Back to SFSU homepage