Barriers Should Keep Invasive Interlopers out of Gila’s Native Habitat
Gila Trout by Debbie Kay
In a move to protect a stretch of Willow Creek along the Gila Wilderness, the US Forest Service is moving forward with construction of a fish passage barrier during the spring of 2016. These barriers are designed to keep invasive fish, often hatchery-bred rainbows, from taking over the habitat. Also protect threatened Gila trout from interbreeding them out of existence. The project, funded by a combination of state and federal grants, is one of many barriers that have been constructed throughout the American West. Also to protect unique trout species with limited range.
About Gila Trout
Gila Trout are a federally threatened species that lives in the Gila River system of Arizona and New Mexico. They are yellow with black spots, and can grow to almost a foot long. Like other trout species, Gilas like cool, clear water and feed on aquatic insects. The main reason for their decline has been low water flows and developments cutting the shady trees around their fish streams. Interbreeding with hatchery trout has been another issue, and this is the problem that the barrier hopes to address. Much of the wild trout areas are closed to fishing, however there was a hatchery Gila trout program that began in the 1970’s when the population was even lower than it is now, and there are several stocked Gila trout lakes that you can fish if you want to discover this desert gem of a fish.
How Fish Barriers Work
Fish barriers are designed to allow water to flow through without allowing fish to pass beyond a certain point. They are typically constructed to keep two distinct populations of fish away from one another. Two different forms of barrier are typically made. When the gradient allows for it, a drop barrier, or artificial waterfall, is made along a section of stream. A second electrical barrier can also be made in areas where the gradient is too flat. This works by creating a current that temporarily paralyses the fish (like a taser does). Therefore pushing it downstream in the current and not allowing it to pass through into the upstream region. The drop structure is typically the more effective of the two, because the risk of temporary power outages and the cost of maintenance to keep the electrical field running are high.
How Will it Work?
Barriers have been successful in protecting some of the rarer California trout species, like the golden trout subspecies. In some cases, there is a need to go through the stream and catch existing fish. to ensure that none of the undesirable species has already made its way into the system. For the Gila trout, this is one of many fish barriers that have been created to keep the population at sustainable levels. Anglers groups have been highly supportive of these measures. Because they increase the chance of keeping fish-able levels of rare native fish in the local stream systems.