In these situations, stocking grass carp at a high rate such as fish per acre will often eradicate the vegetation and leave even higher nutrient loads, making the pond prone to dense algae blooms. If this is the case, you may need to consider applying algaecides to control the undesired algae and also implement management strategies that help to lower the nutrient level.
Ponds in areas with runoff can minimize this risk through flushing with fresher water. Prior to stocking grass carp you should first be able to answer the following questions properly: Are they legal in your state? Do you have sufficient cover to help your predator-to-prey ratio stay in balance once your submersed vegetation is eradicated?
Is your undesired vegetation a species that grass carp will eat? If you are using fish feeders and grass carp start eating the fish feed, will you take the necessary action to remove the grass carp? Or, will you change your feeding strategy? Do you plan to install beneficial emergent vegetation in the future?
Answers to these questions set the stage for wise decisions. One important factor when stocking grass carp is to stock the correct size. Far too often I see and hear of people stocking 8-inch fish. An 8-inch grass carp is a snack to most adult bass and catfish. To improve odds of success it is important to stock grass carp that are a minimum of 10 inches in length, but preferably 12 inches. These larger fish are hardier and can avoid predation more easily. Additionally, they have the ability to eat more aggressively and reach larger sizes more quickly, which will help reduce predation while also reducing their ability to escape through the outflow.
A inch grass carp is about 2 pounds and will be better suited to avoid predation from larger bass. The key to knowing when to stock grass carp depends on how easy the carp can escape the pond as well as the timing of fresh, succulent growth of your plants.
If the outflow is set up so grass carp cannot fit through the openings, then you can get away with stocking them nearly any time of year. If the pond has the tendency to go over the emergency spillway regularly, or it is difficult to limit escapement through the outflow, then it will become much more important to stock in the spring right before the plants germinate. Additionally, scientific literature estimates the mortality rate on grass carp at approximately 20 to 30 percent the first couple years after you stock them.
So, if you are stocking carp in the fall, keep in mind that your rate will need to be slightly higher since the grass carp population will likely diminish some prior to plants germinating in the spring. When it comes to stocking rates, you can take two approaches. The first is to stock a low-moderate rate of grass carp to help reduce some vegetation, but not likely eradicate it. The reality is that this low-moderate stocking rate does not seem to work very quickly, especially when dealing with invasive species.
In many cases of low stocking rates the vegetation tends to maintain its dominant status for 18 months or longer. This is likely the reason why many people experience failures with grass carp, they simply do not have enough fish present to do the job. The second approach and, in my experience, the most successful strategy for controlling nuisance or invasive submersed vegetation is to stock what it will take to eradicate the plants.
This can be as simple as placing a mesh screen across the spillway. Grass carp should never be stocked as a preventive measure. Introducing grass carp into a new impoundment before aquatic flora is established can lead to an impoundment denuded of all vegetation, a problem equally as severe as vegetation overgrowth. Grass carp will not control filamentous algae moss growth, except at stocking rates far beyond those suggested, which leads to other complications.
Learn about methods for reducing algae on the algae control page. There are no guidelines for grass carp stocking density rates that will fit all situations. Each pond or lake has its own combination of fertility, water clarity, shallow water, and chemical makeup.
Each of these variables affect the number of grass carp required to achieve the level of plant control desired. In addition, different pond owners often desire different amounts of weed control. The table below suggests an approximate number of grass carp to stock per acre, based upon percentage of weed coverage.
These numbers may be modified based upon the variables mentioned above. If in doubt, contact your local fisheries personnel for stocking information specific to your pond or lake.
Percent of plant coverage in lake. Number of carp per acre of water. The standard recommended size of stocked grass carp is 8—12 inches. Fish at this size are large enough to escape being eaten by bass. Grass carp may be obtained from commercial fish producers throughout the state. For the names of nearby grass carp sources, you may contact either your local MDC office or download the Missouri Fish Producers list. Keep in mind that aquatic weed control with grass carp takes time.
Monitor progress by making a simple map of the vegetation when the grass carp are stocked. After three growing seasons, refer to the map.
If the desired results have not been achieved, you may want to increase the number of grass carp in the pond, but do not exceed the next highest rate shown in the "How Much To Stock" section above. There are generally two circumstances that lead to harvesting grass carp from a pond. Observations of plant growth and reference to your vegetation map will help determine when restocking is necessary.
Before restocking, it is very important that a similar number of fish be removed from the pond. There are several methods of attempting this. Grass carp can be very difficult to catch with a pole and line. They are a very cautious and reclusive fish, preferring to feed unobserved. Their capture makes the effort gratifying due to grass carp being spectacular fighters on a line and very difficult to land. I have a , gallon swim pond. It has a bio-filter that does a pretty good job and a UV light that takes care of much of the algae.
My biggest problem is with pond weed growing in this natural bottom. I am going to rake it out, but was also thinking of planting a few fish to help keep them from growing. In the Summer months I use a dye to help, but since much of my pond is shallow and the water us crystal clear it still grows. Water temp in the Summer is as high as 84 and it drops to about 60 in the winter. The pond is also well aerated with 3 diffusers in it as well as a small waterfall.
Would you recommend grass carp for my situation and if so how many? Thanks, Tony. Hello Tony. Yes, I would recommend using the grass carp. I have checked with the Division of Natural Resources here in Salt Lake City, UT and they do not have a problem with me doing this as long as I purchase them from a certified supplier.
The only 2 suggestions they had were in Arkansas and both were unable to ship to Utah. Any suggestions would be greatly appreciated. Thank you. Hello Gary, unfortunately I do not have any sources to obtain these grass carp, they are very difficult to procure! Can anyone please advise how sensitive are grass carp to the quality of water in a pond i. Also, is it necessary to aerate a pond or would the combination of water inflow and a fountain be enough to maintain oxygen levels?
Hello Paul, I think grass carp can are pretty tolerant fish, however, I am not too sure they can go into a pond that has very high organic waste.
Be careful!! Hi Mike great article! I am going to put some grass carp in my 1acre farm pond 12 feet deep in central illinois. Is there such a thing as over stocking with these fish?
Hi Scott, it would be hard to overstock because they are a regulated species and you will need a permit to keep them. Two triploid gc in one third to one half acre pond cleaned up all visible plants.
Actively swimming surface. Should we feed them and with what? Hi, glad to hear they did their job! If you want to feed them try using a game fish chow like trout chow. Cattails are growing rapidly. Will carp help to keep the growth from becoming too dense? Also the water lilies are growing exponentially. We have purchased chemicals but do not like using them with the coi and other fish. Your comments appreciated. Hello Crystal, thanks for reaching out! I do not think you will get much help from Grass Carp for those types of plant growth.
Sometimes it really takes manual removal to get them under control. Hello I am from nepal and I have two artificial ponds of about 13m length, 4m breadth and 2m depth.
I am planning to put grass carp on them, can they survive in steady water? And should water be changed at regular interval of time? Please I am so confused, thank you. Hello Anish, I would not suggest using grass carp in such a small pond, they can get to be quite large.
They will not do well in steady water either since oxygen levels would likely be too low. Good luck. I have a one acre pond 7 to 8 feet deep how many grass carp would i need to help keep down the coontail and duckweed in my pond. Hi Michael. How long do grass carp live, or how often should they be restocked? I have heard that the older they are the less they eat, any truth in that. Hello Eldon. Grass carp can live a couple decades under the right circumstances.
They are better at eating aquatic algae and vegetation during their younger years so if you depend on them for algae and weed control I would rotate in some new stock every 5 years or so. Can you suggest a research that I can submit to my proffessor? I am interested in grass carp.
Hello Michael. Grass carp can help with aquatic weeds but may not help that much with aggressive water lily growth. Google that shit! So I need to buy more. Hello Sir, I want to keep grass carp in l drums and feed them with aquatic weeds for my research purpose. Will they survive in this small place?
Is their any possibility that grass carp become diseased due to macrophytes? It sounds like you are doing research. I am not sure that the grass carp would do well in the containers you describe for any long period of time, however I am not fully confident in that.
Good luck!! I have a small lake here in Northern France which I have created for fly fishing for rainbow trout. It is about 1. I have only finished the lake in November last year but I now have a problem with filamentous algae and a virtual blanket covering with starwort. Would grass grass carp help me get rid of these weeds? I have invested in an ultrasonic system for control of the algae but it is too soon to see if this system is effective.
I would be grateful for your views. Bought tilapia last summer that did absolutely nothing and of course, died off at the first sign of cold weather. I released ten grass carp in the pond in late March and have yet to see any activity. We have at least 3 huge fish swimming around the surface of our pond. If so… they must weigh at least pounds. Is there someone we can call to try to identify what kind of fish they are.
Contact your local Division of Fish and Wildlife and ask for someone to come and identify them. Hope they are NOT sharks!!!
Hello Pat. You need the type of carp this article talks about. I would guess grass carp would do the trick! I planted Grass carp in my 2 ac. The lake was heavily infected with char algae.
The algae was to much for the grass carp to handle so I poisoned the algae. I have about 11 grass carp left and the neighbor put in two asian, colored carp. They appear to be healthy and look to be about 15 lbs in size. My problem know is Algae plume, the lake is olive green in color. Did the Grass carp have any thing to do with it.
How is the best way to clear the water up. Hello Bruce. The cause for the green condition of the lake is not likely due to the fish, but rather local environmental conditions. Are you taking any steps to actively clear the water? If not then take the most basic step and add aeration to the pond. Can they run out of a food source? Hello Tom. I have never heard of grass carp running out of food, but worst case scenario is giving some food to them from time to time.
Hello Mike, Our 8th pond on the golf course here in Telford England is about 50 yards by 40 yards and is about 3 to 5 feet deep. I have put 4 off 8 inch grass carp in to help weed control. The pond has a big fountain to look good and aerate the water. Will the fish be OK in this shallower water? Kind regards from Ralph ….
Hello Ralph. Although deeper is preferred, the carp should do just fine in that depth of water. Thanks for reaching out! I have a 6 acre pond that I was told that carp per acre should be enough.
The pond is ft around the banks, and gets to about ft in the middle and by the dam. I have a spill way in the pond and is fed by spring and creeks. I was told by one person that grass carp would be the way to go to control the weeds etc. I was told by another that it would not be due to the spill way and depth of pond. I was told that the carp would first manage to escape from the spill way, and I would be wasting my money.
Then he told me that the carp most likely would not come out of the deep portions of my pond to feed in the shallow ends due to cooler temps in the deeper end. Can you advise please. Hey Joe. I think they will still come out to feed along the shoreline regardless of how deep your pond is.
Dear Mike We have built a 0.
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