I am sure you have heard it a thousand times, bass need to eat 10 lbs of live forage to gain 1 lb of body weight. What you don't hear is that if you need 10 lbs of forage fish that means you need 100 lbs of whatever the forage fish eat, and if they eat something that eats something else then you need 1000 lbs of that something else. Therefore, competition between forage species can be just as important as competition between predators. This means you really need diverse forage population. Most lakes have a single species which is the base of the food chain. In a trophy management situation along with the base species other forage species which fill unique niches are used to consume food that is underutilized by the base species.
Phytoplankton are consumed by almost all juvenile fish, some insects, and zooplankton. Few adult fish can feed directly on phytoplankton. One that can is threadfin shad. They can grow to a maximum of 6-8 inches, mature quickly, live in open water, and spawn in communities multiple times during from spring through fall. They are somewhat temperature intolerant and will die off at water temperatures below 42 degrees. They do have a short life expectancy and likely will not live over 3 years. Their small adult size and temperature intolerance will make periodic restocking mandatory.
Detritus is another food source not utilized by bluegill. Detritus feeders include gizzard shad, crawfish, and freshwater prawns. Detritus is decaying plant and animal matter on the bottom of the pond. This food source is constantly increasing as the lake decomposes waste. Gizzard shad begin life feeding on phytoplankton. As adults they feed on zooplankton and eventually as zooplankton is depleted they feed on detritus. Unlike threadfin shad, gizzard shad have a slightly down turned mouth meaning they can feed on the bottom more easily. They grow to lengths of 18 inches, have life expectancy of 8 to 10 year, have extremely high amounts of egg production, and mature quickly. Due to their large growth and ability to out compete other forage species gizzard shad use in trophy fisheries can be considered controversial. Upon initial stocking gizzard shad add a huge benefit to a trophy lake but long term their presence will become more detrimental to the fishery.
Prawns are a relative newcomer to being used as a forage species. They do not burrow so there is little to no risk when stocking them. They typically are purchased as juveniles 1-2 inches in length. Prawns grow quickly and can reach over 12 inches in 3 to 4 months if fed correctly. It is beneficial to stock them into a nursery pond as juveniles and grow them to the desired size before stocking them as forage in the lake. Prawns will not reproduce in the lake because they need brackish water and they are slightly temperature intolerant. Due to these characteristics they will need to be restocked every spring.
Diversifying the food chain is an important principle in managing a trophy fishery. Once the base of the food chain is established the use of multiple other forage species which utilize specific food sources will greatly increase forage abundance and diversity. Increasing forage abundance and diversity will insure long term growth of bass or other predators. This is one part of managing a fishery and is no more important then improving habitat or culling fish to create low density predator population. There are several other forage species which we didn't cover because they create competition with predators, one of these is the rainbow trout. Selecting a proper forage plan may take further guidance from a professional but hopefully this article will help you began to understand the reasons forage species are recommended.
Thank you for reading and Happy Fishing!!
Steven Bardin M.S.