Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants Grass Carp Question

Do grass carp really slow down on consumption when they get a little age on them? If so, what age would it be?

Hey Kegger welcome to the PBF!! And to answer your question yes they do slow down.

They are at there best from about 12 inches to 7 or 8 years old. After that they dont eat as much. They still eat but do not require the same amount once they get that age. By the 9 to 10 year mark I would look at removing them if you can and replace with a new youngster again!

Have a good one,

Kegger,
Here is a novice two-cents worth on your question. Until my first fishkill, I had 7 grass carp cruising around in my half-acre pond; they were each 3 feet long. Before the fishkill, there were no plants growing from the bottom beyond a foot from the shore. Also, I couldn't figure out why I should remove the grass carp even though they were huge; if they are eating any weeds or algae, that had to be good. If not much, at least they weren't contributing much waste. After they died, I went a year without grass carp. Big increase in plant growth out into the water. I intend to restock with about 5 grass carp this spring, so I can see then how much those guys trim the weeds back. Also, I will be getting some tilapia for the first time, so I am hoping my watermeal problem will be lessened.

There is a double whammy with older, larger grass carp (white amur).

As a percentage of body weight, GC do consume significantly less vegetation. GC do NOT target FA unless it is all there is to eat. the other "whammy" depending on goals is the biomass taken by large fish...One 40 pound GC theoretically takes the space that COULD be used by ten 4 pound bass or four 10 pound bass...you get the picture.

For good management of GC, stock 12"+ fish and replace 1/3 of the stockers with fresh 12"+ three years later....then continue replacing the largest 1/3 of GC with new 12"+ stock anually.

It is pretty cool though walking down to the pond for a little whale watching. I have one I stocked at 12inches 3 years ago thats over 2ft and at least 25lbs. When my pond floods up into the fresh grass he eats like a pig! I have noticed some like FA and others dont I have seen one of my GC clear a 30ft section of it in one sitting.

Rex,

Doesn't the fact the Grass carp are consuming vegetation vs. forage the bass eat, lessen the impact of the increased biomass?

Hey RC51! Thanks for the info.
I have a 5 acre pond built in 1962 to support the construction of I74 running across Indiana. About 10 years ago I started trying to turn the pond into a good fishery. When I started there were loads of BG about 3-5 inches, and a ton of bass 12 in. The water was as clear as a bell with a ton of plan growth. I stocked 20 GC, 25 catfish 4-5 lbs, 25-30 LMB in the 2-5 lbs, and 20 BG 8-10 in. I also took a lot of small BG and LMB from the pond for about 5 years straight. After 2-3 years the GC finally made a dent in the vegetation, and the BG and LMB started to show signs of growth. Over the past 2 year the vegetation has returned with a vengeance, and the BG and LMB weight ratio has dropped significantly. I stocked 12 more GC last spring- hopefully I will see their impact this summer. Moving forward I will start removing the old herd and replace at a rate of 5 12 inchers every 3 years. Do you thing that would be a good program to start with? If so, does anyone know how to catch those 3-4 ft. GC with a rod?
I have also just built a 1 acre pond this winter and can't wait to get started stocking soon!

kegger:


I think the reason why the LMB are skinny is that they can't get enough food of the right size to eat. That could be due to the excessive weed growth.

If you pellet feed, the GC will come up and eat pellets. Use a heavy line due to the weeds in the pond. If one gets off, you'll probably never catch it again - they learn quick.

The easiest way to remove them is with bowfishing equipment.

My guess is it’s not the plants that are the problem. Sounds like to many top end predators and not enough forage. You could remove some of the plants by hand (rake them out) or spray them.

Get a frog/fish gig on a long pole (6 to 7 feet) with a rope attached. When the GC comes to feed use a 22 and shoot it in or near the head. The shock should stun it then gig the fish and pull it out. That should work for 1 or 2 fish.

esshup,

I'll try the bowfishing this summer- thanks for the tip!

I agree by mid summer I get some kind of vegetation grown on the bottom that can be 4 feet high in 10 foot of water- too much cover for the bait fish.

I see you raise tilapia in Indiana- where do you get your fish each spring?

Hey Kegger my guess would be that the vegetation your talking about is called Chara! Not sure but I have the same issue. By mid June I have chare beds out as far as 5 feet! Saturday I just added 4 more GC to my pond as well. My pond is 1 acre and that will give me about 6 GC in it. I hope that helps. Good luck bud and keep us posted.

Cecil.I am sure it does and is why I said theoretically...since there is no way to get an actual biomass capacity due to the constant flux, it is close enough IMO.

RC51,
Based om the pics that I've seen on the internet it is chara. By mid June it covers 95% of the pond bottom. I'll keep you posted on the success of the GC!

Take Care

Yeah that sounds like it. I think I got about 65 percent coverage. I bought a 12 pound bag of Cutrine Plus Granuals this spring and I am going to use it to help my GC out getting started. I hope we can get it under control this year. I'll try and keep you posted as well.

Good Luck,

If you can get a bloom going, that will reduce the amount of sunlight hitting the bottom of the pond, which will inhibit the growth of the Chara.

RC51,
How did the Cutrine Plus work out last year?