Saving the Greenback Cutthroat Trout
Introduction
The Greenback Cutthroat Trout has been an issue in the Colorado parks and wildlife division for many years coming. This fish, native originally to the Green and Colorado river basins, is currently listed as endangered with threat of extinction, and has been a concern to conservationists since the mid 1900s. The fish now maintains only 1% of its original historical range. A main cause of this was the introduction of the rainbow trout to Colorado rivers for its role as a excellent sport fish. However, overfishing, mishandling of the fish, and destruction of any of its small native habitat that is left are some of the other factors affecting the struggling trout population today. While efforts have been taken in the last few decades, some have been unsuccessful and much more can be done in the future.
History of The Fish
The greenback cutthroat became the Colorado state fish in 1994, replacing the rainbow trout, a rather ironic change after the state was experiencing a boom in both rainbow and brown trout at the time and a near-extinction situation with the cutthroat. The cutthroat trout require clean, rocky streams to thrive in. They specialize on small pockets of slow moving water called eddys, which is where most of their feeding is done. Overgrazing of cattle and sheep, dam building, mining, and large logging projects can all put too much mud or sediment in the water and kill the trout. In addition, Colorado has had fluctuation in mining booms and busts since the late 1850's, so the rivers have seen no absence of it. The chemicals used by mining companies to separate the gold and silver from the rock is toxic to the fish and has polluted lots of the trout's mountain streams and lakes. When a species like this becomes extinct, their loss affects the entire food web of the habitat or life zone. The cutthroat fills a special niche in its habitats, as they are native to the territories they occupy. In the long run, if humans can't help to save and restore the place of the animals and ecosystems we have already nearly destroyed, then the aftereffects could be much worse than just one species. The food web revolves around itself and enough of the food web may die off to seriously impact and hurt entire habitats or ecosystems. This should be of concern to people living in CO, whether you simply have an appreciation for wildlife, or live in towns such as Colorado Springs or Pueblo, who rely on the ecosystems in these rivers to provide them with a water source. The fly fishing game fishing industry has been on the rise in the last few decades, and every year, the state stocks rivers will thousands of rainbow trout and brown trout. Rainbows and browns are more sought after by anglers, growing to almost unlimited sizes given the right habitat, while native cutthroats are only known to grow up to 18 inches. The prior focus has been on growing the fishing industry and making the sport most suitable to consumers, but groups such as Trout Unlimited are now looking at taking steps to build a better balance and bring these endangered fish back into CO’s rivers. The fish was first declared extinct in 1937, thought to have been overfished and completely wiped out. But, in the late 1950’s, small populations of what was suspected to be greenback were found in tributaries of the South Platte River and efforts were made to quickly spread the numbers across the state. Fish were used as breeding stock in order to try and fix the problem and get the species back to its original niche in the river system. However, after lab work later done at CU, it was found that the state had been stocking the wrong fish for years: “Suspicion was raised in 2007, and five years later, genetic testing done at the University of Colorado, Boulder confirmed the case of mistaken identity” (Neuman 2014). The state had been breeding and stocking the close relative of the Greenback, the Colorado River Cutthroat. After this was discovered, it was believed for some time that the Greenback truly was extinct, until late 2012, when a very small population was found in a 3.5 mile stretch of Bear Creek, CO. Since the discovery of this population, preservation efforts have gotten much more attention.
Issues Currently Faced
Colorado must act quickly to resolve this problem, as the greenback is the native species to many ecosystems in which the rainbow trout has invaded and completely taken over. This is an issue for multiple reasons. First, the overpopulation of any fish species will cause an omission of competition within the habitat. The invasive species will take full control of the habitat, and for the rainbow trout this is especially easy, as they are a ‘disease resistant’ species which plants thousands of eggs at a young age. A second issue specific to rainbow trout is their ability to ‘hybridize’ and ‘cross’ with other species. This is believed to be a major cause in the original disappearance of greenbacks in the state. A third problem is their feeding habits. Rainbows introduced to rivers in colorado feed on insects primarily, but with overpopulation they will turn to species such as the leopard frog and humpback chub, which are endangered themselves. If these issues aren’t resolved, we could see an extinction of the greenback as well as a domino effect on the rivers which it used to maintain.
Objectives of Proposal
Preserve current communities of native greenback cutthroat trout
Breed healthy greenbacks in hatcheries
Transport greenbacks to new habitats to raise numbers
Minimize numbers of invasive rainbow trout
Ensure stabilization of rivers for the future
Proposal & Solutions
The first issue in keeping the greenbacks from going extinct is preserving the only native fish that are left, which are the few hundred in Bear Creek. Obviously, the first step to take is to not allow any sort of fishing or outside interaction with Bear Creek and surrounding tributaries. The area should also be surveyed regularly to look for any sort of issues that may come about such as fallen trees, blockage of the stream or danger to the breeding zones during spring. Even a small situation such as bank erosion can could be detrimental to their habitat. Trout, and the greenback especially, are very picky about their spawning conditions and water temperature. They need cold, well-oxygenated water and the young trout require a different water flow than the mature ones. The trout must also have adequate amounts of food in order to strive in the creek. They mainly feed on aquatic insects, which shall also be kept track of to make sure their are healthy populations of prey for the fish.
The next step to take is to collect sperm and DNA of the fish to ensure successful breeding in the hatcheries. This is the most important part of the process, as their is a limited supply of original greenback DNA left. The process involves giving the fish a sedative, and then either sperm or eggs are extracted from the sleeping fish. It is a simple process, but not always successful. Once fish are bred, a stable habitat must be found for them. The water temperature and streamflow must be adequate and other trout must be eliminated. Rainbow trout cannot thrive in the same habitat as young greenbacks because they are invasive with a faster spawning rate than the cutthroats.
Once a stable number of greenback communities has been established, efforts can be made to reintroduce them to larger rivers and restore original balance in Colorado and surrounding states. This would be many years down the road, as the greenbacks are nowhere near their capability today.