Fisheries Management: Strategies for Stocking Triploid Grass Carp

Written by Industry Expert, Paul Dorsett, Fisheries Biologist 

At first glance, the idea of stocking triploid grass carp appears to be a win-win. Win number one is that grass carp offer a natural solution to controlling nuisance aquatic vegetation. Win number two is that they are cost effective and offer long lasting results. But, how do you keep an aquatic weed problem from becoming a grass carp problem?

Stocking triploid grass carp in your lake or pond can be a beneficial strategy as part of your overall fisheries management plan. Overstocking can be a concern, particularly when predator species such as largemouth bass are your management goal. Although they are sterile and will not reproduce, overstocked grass carp can denude the entire waterbody of vegetation and increase turbidity in the form of suspended solids or harmful algae blooms while also disrupting the balance of the fishery. If not managed properly, stocking grass carp can be worse for your aquatic ecosystem than not stocking them at all. The best way to get the most benefit from triploid grass carp, while minimizing risk, is to work with a fisheries biologist to tailor a custom stocking rate based on the needs of the waterbody.

SOLitude’s typical strategy for stocking grass carp is to stock a limited number in late winter or early spring, before weeds start growing, and to evaluate weed coverage the following summer. Then, we may add additional grass carp the following spring depending on the results. When budgeting for grass carp stocking, it is important to reserve funds for herbicide in order to spot treat problem areas during this period of finding the appropriate balance. Over time, the need to spot treat with herbicide may eventually shift to a need to harvest grass carp. This attempt for balance is like a swinging pendulum, where an excess of nuisance aquatic weeds and an excess of grass carp represent the ends of the swing. To achieve balance, the pendulum must reach its center point. This is not an easy task and our job as lake and pond managers is to keep the pendulum swing minimized—not allowing it to swing too far in either direction.

While stocking grass carp can be a balancing act, we have seen success. A client in Texas with a 1.2-acre private pond had a productive bass fishery that required annual treatment with herbicide to keep southern naiad (Najas guadalupensis) from covering over half of the pond. Following the winter of 2013, we added three triploid grass carp to the pond in an effort to control the southern naiad. The following spring, we observed little reduction in weed growth and herbicide treatment similar to previous years was required. Following the winter of 2014, we added two additional grass carp and observed a significant decline in weed coverage, which required only limited herbicide use. After finally adding two more TGC this past winter, weed coverage was reduced to less than 5% of the total pond area. There are no plans to add additional grass carp this winter, and we are encouraging the client to harvest one or two of the original fish. Having multiple cohorts of limited numbers of grass carp in this pond has provided sustainable weed management while minimizing excess herbivory.

Keep in mind that many states require permits prior to stocking fish. And in some states, triploid grass carp are not legal. A qualified fisheries biologist can advise if grass carp are a fit and, if so, how they can be utilized as part of an effective fisheries management program. When stocked judiciously, grass carp are a cost effective, long lasting tool that lake and pond managers can use to maintain weeds while protecting the health of the fishery.

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Contact the experts at 888-480-5253 for all of your lake, pond and fisheries management needs. 

Paul Dorsett is a Fisheries Biologist who is experienced in aquatic ecosystems development and restoration including fish production, aquatic plant management and water quality. Paul holds Bachelor of Science and Master of Science degrees in Wildlife and Fisheries Sciences from Texas A&M University.

SOLitude Lake Management is committed to providing full service lake and pond management services that improve water quality, preserve natural resources, and reduce our environmental footprint. Lake, pond and fisheries management services, consulting, and aquatic products are available nationwide. Learn more about SOLitude Lake Management and purchase products at www.solitudelakemanagement.com.