The Importance of Fish Migration in the Colorado River

Fish migration is necessary for the success and prosperity of aquatic life. Before man-made dams, fish migrated only as far as natural barriers allowed. Fresh water fish migrate between their feeding and spawning regions. If fish are unable to reach the spawning area due to natural or man-made obstacles the species cannot carry on. As fish migrate, they produce necessary oxygen for the other aquatic life in the river. The creation of dams in the Colorado River restricts the native endangered Colorado Pikeminnow from reaching their spawning grounds. The use of dams in Colorado has effected the vital fish migration, causing the aquatic environment to suffer as well the Colorado ecosystem as a whole.

The dams along the Colorado River were not originally ideal for the migration of native fish. The Colorado Pikeminnow is a migratory species that depends on the Colorado River to live. The construction of the dams along the river caused distress among these already endangered fish. After the completion of the dams, the species was unable to progress up river leading to a decline in population. The Colorado Parks and Wildlife Department noticed the decrease in the endangered fish due to their ongoing analysis of the Colorado Pikeminnow. The Endangered Fish Recovery Program of the Upper Colorado River began researching how to create a way for the fish to migrate but keep the dam in place.

A decrease in any given fish population affects the entire aquatic ecosystem in one way or another, which, in turn, effects the residents of Colorado. As a native, I know how important our water supply is to everyday life. According to the Colorado Parks and Wildlife Department, the fish were not spawning in their usual habitats, allowing the euphotic zone, made generally from phytoplankton and algae, to overpopulate making it hard for other wildlife to use the river water to the best of their ability. On the other hand, fishermen noticed a decrease in fish population upstream. Knowing that fresh water fish migrate through rivers and the physical block from dams halts this migration calling for action from the state of Colorado. Without a change in the dam system, the Colorado River would suffer immensely on both the microscopic level and as an ecosystem.

The Endangered Fish Recovery Program created man-made fish passages through dams in order to aid in the reproduction for the fish in the Colorado River. The fish passages would later be known as fish ladders mainly because of their escalating structure. Research from the Colorado Parks and Wildlife Department Stream Habitat Investigations showed that the fish would need a specific way of getting around the dam, but still needed to reach their original destination. The fish passages would need to allow for fish to swim both up and down stream to spawn and return to their normal feeding grounds. The Colorado Fish Passage Project’s main concern with the Stream Habitat Investigation was to protect the native river systems to allow migrating fish the ability to live as normally as they can with the man-made dams in the Colorado River system.  Fish passages allow the ecosystem to continue even with human interference.

Before the success of fish passages was proven, many people were skeptical of fish understanding how to swim through the ladders. The National Oceanic and Atmospheric Administration defines a fish ladder as a series of rising pools that fish are able to swim against to reach the other side of the ladder. Each species has unique migration characteristics causing each ladder to accommodate every type of fish. The most effectively used fish ladder, in Colorado and Michigan, is called the Denil Fishway. Michigan’s Department of Natural Resources explains that the Denil works for almost every size dam and can handle a large range of water speeds. Fish ladders are very important to the Colorado environment because without them the Colorado River aquatic ecosystem would collapse.

Critics of fish ladders are unable to see how important they are to the river ecosystem. Some might say that the fish population does not benefit from the ladders because they are hard to make and have expensive upkeep. Although the cost of the initial construction of a fish ladder is quite expensive, in the long run, it is more important to keep endangered species alive for years to come. According to Colorado Parks and Wildlife, the Colorado Pikeminnow is not only a state threatened species but is also a Federally Endangered species showing we better take care of them now or they might disappear and never come back.  It doesn’t seem like a few fish could be missed, but that is definitely not the case. Thankfully, Colorado understands how important one species is to the entire ecosystem. The Colorado Pikeminnow is the main reason fish ladders were created in Colorado and if they had already gone extinct we would not know how important other aquatic species are to the state of Colorado.

The life in and around the Colorado River works together and when one aspect such as the fish population is disturbed the entire ecosystem is affected. The Colorado Pikeminnow is just one example of a fish that holds an ecosystem intact. Without fish ladders, the Pikeminnow would not be able to travel to spawn on the upstream side of a dam. It’s necessary for fresh water fish to migrate both up and down streams and the only way they are effectively able to do so is by using fish ladders. Although some might say that it will be too complicated for fish to figure out, ladders have high success rates, not only in Colorado, but all over the country.


leanneLeanne Dwyer was born and raised in Colorado. On most days, she drinks her body weight in coffee. Environmental issues are very important to her. She has played ice hockey for eleven years, and she’s currently pursuing her degree in Music Business. She has two pugs who cuddle up to her when she writes late at night.