By Scott Bryan, CAP Senior Biologist
Some people believe that water in the CAP canal is, or should be, just like a swimming pool – no critters, just pristine waters.
The reality is that the water quality in the canal is really good, but we have all of the same organisms that our source water supports. Aquatic vegetation, insects, invasive species, and even fish – the CAP is just an extension of the Colorado River and Lake Pleasant. It’s like a river with concrete banks and a very complex ecosystem.
Of all the organisms in the canal, probably the most interesting are the fish. You might think they have it pretty easy – plenty of food and water in the canal, water quality is good and there is no angling pressure (fishing is not allowed in the CAP).
But a fish’s life in the canal can be pretty difficult. Due to the force of our pumps and lifting action, adult fish cannot get into the canal from Lake Havasu or Lake Pleasant – they have to come in as eggs or very small larvae. If they are lucky enough to make it through the pumps, they are easy prey for the existing fish in the canal. And if the eggs and larvae somehow survive into the juvenile and adult stage, they have to constantly swim against the strong current of the CAP for their entire lives.
There are very few places to go that allows the fish to escape the current. For the most part, they have to build up incredible strength and endurance to survive the flows and avoid being sucked into the pumping plants. Because of the energy it takes to sustain swimming, most of the fish in the canal are relatively small and lean.
Spawning in the canal is not impossible, but the lack of habitat and constant current makes it very difficult. There are limited materials (gravels) for nest builders and there is virtually no vegetation on which fish can attach their eggs. As a result, very few fish in the canal are “home grown.” CAP stocks channel catfish for caddisfly control, grass carp for vegetation control and redear sunfish for quagga control, but a majority of the other fish have come in from the source water.
The U.S. Bureau of Reclamation has sampled the fish in the canal annually from 1995-2010. and Now they sample every five years – the last sample was taken in 2015. Their sampling is basically an inventory of the non-native fish present in the canal. The Bureau samples up to seven locations using gill nets, seines, minnow traps and electrofishing. Over the years, 17 different species have been found in the canal with striped bass and bluegill making up a majority of the catch.
The fish in the canal play an important role in helping to keep vegetation and insects under control, provide a food resource for predatory birds and other animals, and help to maintain good water quality by cycling nutrients. When we undertake large projects that include dewatering sections of the canal, reasonable efforts are made to relocate the fish within the system.
One important point to note: even though there are fish in the canal, fishing and swimming are not allowed in the canal due to safety and liability concerns! The sides of the canal are very steep and the water moves up to 3,500 cubic feet per second. If someone were to fall in, the current would quickly sweep them away and the slope of the canal sides is too steep to climb out. Stay safe and observe the canal from afar!