Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations Grass Carp, Does this make any sense ?

I have around 7 Grass Carp in a 1 acre pond. Stocked them about 2 years ago at 12", now they are huge. I was thinking of removing them via bow and restocking another round of 12 inchers. Why ? I've heard the younger GC will eat more, plus these huge submarines are just taking up space; repeat process in several years. The only issue, some of my bass could snarf a 12" fish with ease.

It is true, smaller GC do eat more per body weight % wise. Are you still experiencing aquatic vegetation issues? What is the biggest bass in your pond now? It is amazing just how big a GC a bass can eat compared to their size. Cigar shaped and lacking spines = easy meal...

Yes still have weed trouble, so far it's been mainly DW, FA and Primrose but who knows what it will be this summer. Not sure on lengths of bass but they range from 3lbs up to 10 Lbs. I've got apprx 100 CC in the 5 Lbs+ range, planning on getting those down to 50 or so this season.

DW, FA and primrose are low to not gonna get eaten period by GC, even if they are starving... You may have to go the chemical route or stock tilapia if they're legal in your state at a very high rate... But even with a heavy stocking, all those big LMB will make it tough for the tilapia to do their job.

Yup, those nasty plants are not even on the grass carp's menu. In fact, those carp could be helping those plants by eating other not as bad plants that compete for the same nutrients. And Tilipia would help only with dw if the bass and cc did not eat them first. Each plant is going to need to be dealt with seperately. I don't think biological control with fish is going to work for you here.

Tilapia and GC are my preferred biological control for FA and water primmrose - don't know anything about DW.
GC on a flyrod is a blast and you can catch them on pellet flies when you want to remove them.

GC will will eat water primrose if that's all they have to eat, and if trained will continue to eat it after more tasty stuff comes along.

Goats are the answer to water primrose however - as ewest says, "they will wrap their lips around the stuff and pull it out of the pond". They love the stuff.
Works for me.

The question becomes, if they aren't eating FA, DW or Primrose what are they eating ? They are eating something to get that huge. Yes, they eat my pellets but I feed very modestly..several scoops thrown out one or two times/day.

Everything else. What you have is grass carp leftover syndrome. The stuff they turn thier noses up at. The smaller ones eat more per body weight than the grown out ones, but those big ones found a favorite food and just inhale it. I could guess, but that is all it would be. I have a feeling if you took them out, you would know soon.

The tilipia would inhale the dw if they had a chance. I hand pull like a goat the primrose, I actually plant that stuff for forage. The carp normally go for algae, but found something they like better. Normally carp have a preference menu, and they eat what they like at the top of the list first. They just are not getting to the bottom. If they are not working, I would not take big ones out and reload them.

One more slight issue. I don't know what type of algae you have, but grass carp are rated low as far as effective control on most surface stuff, even if they eat it. DW fits that bill. And they really have a low preference and are rated low on primrose. So even if they are eating the dw, they don't control it well. I think what you have is an experimental result of what grass carp control well, and what they don't.

Everything I have read says you can leave your GC in your pond up to 5 to 7 years before they become pretty much non procutive. And you said it's only been 2 years so unless you just want to get rid of them because of how big they are you should still have a few good years left in the ones you have!

I found this article is anyone is interested. The list of preferred plants and stocking rates I found of interest

http://www.asiancarp.org/Documents/UsingGrassCarp.pdf

This pretty much pinpoints where you are at with your plants, and I would guess you have filamentous algae.

http://msucares.com/pubs/infosheets/is1556.htm

I don't think it is the age of your fish, they just are not that effective on your remaining plants. Like I said, you are stuck with grass carp leftovers.

I think duckweed reproduces itself so quickly that I doubt any fish can control it.

They have worldwide experiments with tilipia/duckweed farms. Mainly in undeveloped countries. They eat so much you have to have it farmed somewhere else and bring more in. Many universities are experimenting with it for numerous applications, sewage treatment, poultry food and tilipia farms. All are meeting with very high success rates. Not going to cure world hunger, but help out. Tilipia will finish off a complete pond of duckweed with proper stocking ratios. Grass carp won't. They just are not great surface feeders.

For fun, throw a head of lettuce into a tank with 100 adult tilapia. It'll be gone in 10 minutes.

Hmmm... A new garbage disposal! I like it...