Recreational Fishing in Irrigation Reservoirs

The construction of moderate-size storage reservoirs for irrigation is a growing trend in Arkansas.  These reservoirs are often levee-style impoundments covering 20-150 surface acres and are supplied by surface or well water pumped into the reservoir.  These water bodies are primarily constructed to hold water for farm use, but they are increasingly being managed for quality fishing.

While fish management in irrigation reservoirs is similar in many ways to management of recreational farm pond fisheries, there are several key differences that make irrigation reservoir management more challenging.  These challenges primarily involve the source of the water and water-level management practices. 

Pumping surface waters from adjacent creeks, bayous, or irrigation ditches is almost always problematic.  Rough fish, such as gizzard shad, bullhead catfish, gar, and undesirable sunfish species can easily enter the reservoir with the re-lifted water.  Aquatic weeds, sediments, and fish health vectors also enter via pumped surface waters.  All of these can disrupt balanced fisheries and result in problems to sport fish production and management. 

Ideally, surface waters should be filtered before entering the reservoir.  However, this is generally not feasible given the high volumes of water that are being transferred.  Sock filters and more expensive canister filters will quickly clog with sediment and debris from surface water sources. 

The best practical solution is to maintain high predator abundance in the reservoir to keep small invasive species to a minimum.  If largemouth bass are abundant, most rough fish species should not reach problematic levels.  For example, if quality crappie and bream fishing is the management objective, harvest all largemouth bass 13 inches or larger when caught.  This will maintain an abundant small bass population that will prey heavily on small bream, crappie, and rough fish, making more resources available to remaining bream and crappie and allow for faster growth.

If trophy bass management is the objective, rough fish cannot be managed using abundant predators, as this reduces the growth of largemouth bass.  Instead, 10-15 pounds of largemouth bass less than 13 inches should be harvested annually to reduce the population size. This will make more resources available to remaining bass, allowing for faster growth.

With the exception of gar, which are competitors with largemouth bass, other rough fish species should be viewed as another prey resource for the trophy bass option.  Gizzard shad, although not recommended for ponds or irrigation reservoirs, can contribute to good bass growth if managed properly.  When large gizzard shad become overpopulated, low concentrations of fish toxicants such as rotenone can be used to selectively kill gizzard shad.  Contact your local Arkansas Game and Fish representative for assistance with rotenone application.   

The primary use of irrigation reservoirs is to provide water during hot summer periods.  Consequently, most reservoirs significantly drop in water level during the hottest months of the year.  This can have unintended consequences to fish populations.  First, the reduction in water volume concentrates fish.  This may be beneficial in that predators and prey are concentrated, allowing bass to feed on sunfish and rough fish, increasing growth rates of predators and prey.  Conversely, the concentration of fish and reduction of quality habitat increases the likelihood of water quality problems.  To help avoid water-quality issues, refill the reservoir whenever water is available, and do not reduce the reservoir to less than one-half of the original volume.

Irrigation reservoirs can provide high-quality fishing opportunities when properly managed.  Although they come with a unique set of issues, these concerns can be overcome with proper planning, design, and fish management.  Whether you prefer sharing your reservoir with your family and friends, or intend to lease fishing rights to paying customers, these systems can provide benefits beyond the use for which they were originally constructed.