Pond Boss
Posted By: MrSandman What is the Life span of Grass Carp? - 01/27/09 11:48 PM
From 1987 through 1990 I stocked 180 grass carp in my 6 acre lake. I kept adding them in batches of 30 because over those first 4 years I saw hardly any weed reduction. The lake was about 1/4 covered with pond weeds and algae mats. When the weed reduction started, it really kicked in! Now there's no algae or submerged weeds in the lake.

In summer, the lake tends to become overly green with plankton, somewhat murky, and with patches of floating green slime. We have to treat it with Cutrine Plus a couple of times a summer. My hypothesis is that the planktonic algae is over abundant because there are no weeds with which it has to compete for nutrients. Stocking so many grass carp denuded the lake. My bad! I can still see them lurking in schools beneath the surface. Dozens feed on the grass at the shoreline following a good rain.

Figuring that the grass carp were about a year old when stocked, even the youngest is now 20 years old! This defies almost every estimate I've read concerning their life expectancy (ie. 15-20 years). Can someone tell me how much longer I may have to put up with these behemoths? When will they die? How can I get some of my weeds back?

Thanks!
Posted By: Theo Gallus Re: What is the Life span of Grass Carp? - 01/28/09 12:03 AM
Welcome to the Forum, Sandman.

There ARE some aquatic plants that GC usually don't like to eat. But 30 GC per acre are crowded enough that they might even chow down on those.

It's a shame for your situation that Tilapia aren't easier to obtain up here in Ohio.

GC are notoriously hard to eliminate in large numbers - onesie-twosies we can manage via shooting or archery, but they smarten up pretty fast.

Stay tuned and let's see what options, advice, and info the Forum can come up with for you.
Posted By: MrSandman Re: What is the Life span of Grass Carp? - 01/28/09 12:10 AM
Thanks Theo! I thought of planting lilly pads since I don't think grass carp like them much. However, I'm afraid they might take over major part of the lake.
Posted By: catmandoo Re: What is the Life span of Grass Carp? - 01/28/09 02:12 AM
And, another welcome to the Pond Boss forum. I'm glad you found us.

Unfortunately, experience seems to indicate that grass carp live very long lives. This question came up a conference I attended a couple of weeks ago. I can't verify the accuracy, but one of the dealers who sells them said they can live for over a hundred years.

There is a 44 acre lake near me that was stocked with about 1500 of them sometime in the 1960s or early 1970s. The DNR figures there are still 1200 to 1300 left. They can't get them out, and they are gigantic. About two years ago, a fellow pulled out a 72-inch, 51 pounder. WV Fishing Records

This one, from my pond, was about 12-13 years old when I pulled it out.



As Theo said, they can be difficult to catch. I have found that they will come up for pellets when I'm feeding my bluegill and catfish. If I take the crust off a piece of Wonderbread, and tightly pack it around a hook, there is a good chance I can hook one of the grass carp. However, if it gets loose, it won't be back for weeks, maybe months. Neither will its friends.

Good luck,
Ken
Posted By: Shawn Banks Re: What is the Life span of Grass Carp? - 01/28/09 03:43 AM
I know of a lake that has some that are now 24 years old. My mind is deteriorating, but I believe the diploid grass carp live much longer lives than the triploids. It might be reversed but I don't think so. It seems like diploids were stocked heavily in the 80's and these are the older fish. Anymore, its hard to find diploids as many states have outlawed them.

You could potentially have at least 4 more years!!! Unless you start shooting them!!
Posted By: MrSandman Re: What is the Life span of Grass Carp? - 01/28/09 03:35 PM
Cat, that's a scary prospect, 100 + years! Sounds like those Galapagos tortoises! Shawn gives me more hope, my grass carp are triploids. I hope my story at least serves as a lesson to those who would just dump these plant-eating fish in their ponds without first consulting an expert or at least doing some serious homework.

I think I'm going to invite my neighbors to come shoot them. I'll also try harder this year to catch them. The bread on the hook idea might work. I was also thinking of trying canned corn on a hook. In any event, looks like I'll have to put up with greener, murkier water for years to come with no rooted vegetation.

PS. Thanks for your welcomes! I just subscribed to Pond Boss and was so impressed that I purchased many past issues. I went years as a subscriber to another, now defunct, publication thinking that it was the only one out there on the subject of ponds. It was woefully short on the latest scientific research. Pond Boss is appropriately named.
Posted By: catmandoo Re: What is the Life span of Grass Carp? - 01/28/09 06:12 PM
Sandman,

For shooting them, you'll probably need to find a good archer. Bullets hardly penetrate water, plus they dangerously ricochet.

Arrows are more effective, but they are expensive. I had a friend helping out here, and I believe he said the arrows were about $75 each. He also had a spool/reel mounted on his bow that allowed him to reel the fish/arrow back in. Whoever is doing the shooting will need to be well above the water to get a reasonable penetration angle.

Unfortunately, these carp are quite smart. After the first arrow hits one, or near one, they stay away from humans for several of weeks.

My best success was with hook and line using the bread.

Good luck,
Ken
Posted By: george1 Re: What is the Life span of Grass Carp? - 01/28/09 07:02 PM
You'll think you hooked on to a freight train when you hook one, let alone when you try to land them.

Like Cat says they get hook shy fast, but a blast on a fly rod with Purina Nymph flies.
My PB 14.5#'s.
Posted By: MrSandman Re: What is the Life span of Grass Carp? - 01/28/09 08:26 PM
George... I know! A few times I've hooked those monsters using plastic grubs. In one case I was able to beach one. They fight for a good half hour on light tackle (8 lb. test) with the drag set just right. A couple of times they even jumped. I thought I had on a sailfish. I can't even imagine hooking 'em on a fly rod! What are Purina Nymph flies?
Posted By: CJBS2003 Re: What is the Life span of Grass Carp? - 01/28/09 08:56 PM
I bowfish and quality arrows for bowfishing run around $20. Not that expensive... They are spooky once you start shooting them, but if you done camo and are really slow, you can get within range.

I have had decent luck catching them on canned corn as well. Particularly if prebait an area for several days prior to fishing it...

Good luck! If I lived closer I'd offer to come shoot some for you! They are the best fighting freshwater fish I've shot with my bow. Only stingrays out do them bowfishing!
Posted By: george1 Re: What is the Life span of Grass Carp? - 01/28/09 09:51 PM
 Originally Posted By: MrSandman
George... What are Purina Nymph flies?

Mr. Sandman, Purina Nymph is my "politically correct" terminology for Cecil Bairds crude name "panty hose" fish food pellet ... also known as AQMX fly ....
Posted By: MrSandman Re: What is the Life span of Grass Carp? - 01/28/09 10:06 PM
CJBS, I may take up bowfishing. Wish you were closer too. Thanks for the pointers. George, give me some time to acquaint myself with the jargon. Cecil may be on to something though.
Posted By: Shorty Re: What is the Life span of Grass Carp? - 01/28/09 10:09 PM
The current NE state record grass carp that was caught a couple of years ago was estimated to be 26 years old and weighed 64 lbs.

Good luck!
Posted By: csteffen Re: What is the Life span of Grass Carp? - 01/28/09 10:34 PM
One of the fisheries biologists in Iowa told me that for Iowa they calculated that grass carp have about a 2.5% mortality rate per year for the first 20 years. It increases after that. I don't know if that was for diploid or triploid carp though.

He also told me they drained a half acre pond that had exactly 10 grass carp stocked in it 21 years prior to draining. They found 10 grass carp averaging 50lbs each. Thats 1,000 lbs grass carp per acre \:o
Posted By: Greg Grimes Re: What is the Life span of Grass Carp? - 01/28/09 11:00 PM
Guys this is totally contradictory to my experience and education. I have always been total they live no more than 10 years. Well we proofed that wrong back in 2003 with some that had to be 18 years old, but total major exception to the rule. 100 years is just insane. Maybe it is due to being triploid as required in GA maybe it is due to warmer climate thus not living as long. I have literally stocked 100’s of ponds with grass carp. The natural mortality is very high, within 3-5 years the number is always half of what was stocked. We make sure to use 10-12 inch but sure of them may be expensive bass food btu this does not explain this low of a number.

Mr. sandman yes that is a very high number but doubt you know have any were near that number in the pond. In the summer months you can pretty much catch them sunning and count all you got. Most clients majorly over estimate they assume they are only seeing a small % like with other fish but not the case. When draining lakes they are amazed at how few they have compared to what they thought. Also our experience shows the metabolism slows after a couple of years. I think with some bow efforts and yes I bought my bow fishing arrows for $18 you can reduce population so as to get a return of submersed grasses. I agree with you theory on phytoplankton bloom die to lack of nutrient absorption by macrophytes.
Posted By: Dave Willis Re: What is the Life span of Grass Carp? - 01/28/09 11:26 PM
Csteffen - that Iowa study was on diploid fish. You have a good memory. Shawn mentioned earlier that the triploids have a much shorter lifespan.
Posted By: LRunkle Re: What is the Life span of Grass Carp? - 01/29/09 12:11 AM
I can personnaly attest that grass carp like water lilies, and pickerel rush but not the yellow water iris or water willow. I have abundant irises and water willow but if I want to grow water lilies or pickerel rush I have to enclose them with chicken wire pens-and if there are small gaps in the fencing they will search them out to get inside to get to the plantings.
Have purchased a bowfishing setup to attempt to address the grass carp situation. My problem with catching them with corn or bread is that bluegills and catfish always want to steal the bait before the grass carp get to it. Also, the carp are so hook shy that you have to use a very small hook making landing them very dicey due to the small tissue bite you have for purchase during the fight.
Posted By: CJBS2003 Re: What is the Life span of Grass Carp? - 01/29/09 12:30 AM
Try this rig when fishing for carp using corn: http://www.carpecarpio.com/carptips.html

It has worked well for me for hook shy common and grass carp. I use very light monofilament line instead of the braided line on the link but none the less, it works quite well. Good luck!
Posted By: MrSandman Re: What is the Life span of Grass Carp? - 01/29/09 03:19 PM
Csteffen, you quote a 2.5% mortality rate for grass carp in the first 20 years; that means that in 20 years half of the fish die. Then, in the actual situation that follows, you show where all 10 fish survived for 21 years. What do you suppose is going on there? I hope Shawn is right that the life span for triploids is shorter.

Greg, your observations are much more optimistic, thank you! I sure hope you're right that I'm over estimating the number of carp still in my lake. I thought I saw what looked like dozens feeding on shoreline grass after heavy rains and high water levels last summer, but after further review, maybe it was just ONE dozen.

RL, aren't you concerned that the yellow water iris will spread to cover all the shallower areas of your pond? That's my concern with lilies. Then I would be back to square one with too many weeds, only this time with no biological weapons left to employ.

CJBS, thanks for the GC rigging tip. Wow, it's elaborate though!

Shorty, that's one old fat fish they caught there in NE. Ohio doesn't list a GRASS carp record. The record carp here is 50 lbs.
Posted By: csteffen Re: What is the Life span of Grass Carp? - 01/29/09 04:05 PM
The 2.5% mortality rate only applies to fish that survived the prior year. Im not very good with words, but this table should help:

To make the numbers easier lets say 1000 fish were stocked.

Year # Fish at end of year
1 975
2 951
3 927
4 904
5 881
6 859
7 838
8 817
9 796
10 776
11 757
12 738
13 720
14 702
15 684
16 667
17 650
18 634
19 618
20 603

So over 20 years you would expect just under 40% of the fish to die.

I added the situation with all the fish surviving to show an exception to the rule for a VERY unlucky pond owner . These numbers are for diploid fish though (thanks for filling in that gap Dr. Willis). You should try to find out if your grass carp are diploids or triploids to determine if these numbers even apply.



Pic of me with a grass carp electrofished from an oxbow lake in Mississippi. He was 47" and likely a state record by weight, but we didn't have a scale to verify. The state record at the time was under 50 lbs. and we estimated this one somewhere between 50 and 60.
Posted By: Shorty Re: What is the Life span of Grass Carp? - 01/29/09 04:09 PM
Here are my thoughts on the longetivity of GC, this is based on an over enthusiatic Carp fanatic that will remain nameless from other forums. His claim was that common carp in general lived longer and got bigger in colder northern waters. He was always complaing that in southern waters it was rare to see common carp over 15-20 lbs but in northern waters trophys were much more common, if true this likely holds true for GC as well.
Posted By: MrSandman Re: What is the Life span of Grass Carp? - 01/29/09 05:05 PM
Steff, That fish is gigantic! What a great photo. Fortunately my GC are triploid. I started buying them as soon as they were made legal in Ohio in 1987. Thanks for explaining the mortality formula. Now it makes sense.

Shorty, I wonder if the carp fanatic's notion on size is true. Just look at the monster from a southern state in Steff's picture above.
Posted By: Bernie H. Re: What is the Life span of Grass Carp? - 01/29/09 05:58 PM
MrSandman,I,ve stocked triploid GC since they were first made legal in KY. Ponds had to be viewed by a state biologist or a conservationist officer to determine the surface area before a permit for a set no of GC were issued. Since the 80,s the restrictions have been greatly loosened,and you can buy them from fish haulers in any amount. I agree with Greg Grimes,I think the triploid will live in my area for only 15 to 18 yrs. Each year,I,ll lose 3-4 dead usually in the early spring or late fall. To maintain weed control, I have to restock every few years ten more GC.While thirty per acre sounds excessive to me,I have to believe most of your original stock are dead,IF they were truly triploids.
Posted By: Dave Willis Re: What is the Life span of Grass Carp? - 01/29/09 06:45 PM
Csteffen - thanks for posting that! I'm used to seeing 20 or 30 pound grass carp, but that is huge. You know what really struck me -- those are the largest scales I have ever seen on a grass carp. Makes sense, of course. \:\)
Csteffen that is an amazing GC. That is huge, it sure looks like it would weigh in the mid fifties. What a neat picture.
Posted By: Greg Grimes Re: What is the Life span of Grass Carp? - 01/29/09 06:55 PM
GC get huge in the south as well. Csteffen proofed that (nice pic) but here's more proof. I got one that would make these look small and owner claimed it was only 8 years old. It had to be over 75 lbs. They will abotu knock you down. We haev had them jump int he shock boat several times b.c they ae so big they sense the shock way out and if lined up right come at you.

http://www.lakework.com/photo_gallery/gallery2/v/Client+Fish/P1010881.JPG.html
http://www.lakework.com/photo_gallery/gallery2/v/Client+Fish/Troy12-26023_1_.jpg.html

http://www.lakework.com/photo_gallery/gallery2/v/Client+Fish/Picture+083.jpg.html

COmmon Carp quite large as well. This is from Kentucky actually
http://www.lakework.com/photo_gallery/gallery2/v/Client+Fish/P1010032.JPG.html

Posted By: LRunkle Re: What is the Life span of Grass Carp? - 01/30/09 12:33 AM
Sandman, in response to your question about the invasiveness of yellow water iris: my experience of probably 18 years with yellow water iris is that it does not invade out into the lake to a significant degree. What it does do is claim shoreline by spreading laterally. It has been pretty slow to cause problems at my place although we have had to spray glyphosate a couple of times where it took over. It outcompetes some of the plants I prefer as marginals such as pickerel rush, thalia (American water canna) and Louisiana swamp iris (I have a big stand of Black Gamecock that it tries to invade). On the good side it stabilizes shoreline like a concrete wall so I have it planted where the Oklahoma winds try to erode my shore. The mature root system is like a network of interlocking 2"x4"s.
Posted By: catmandoo Re: What is the Life span of Grass Carp? - 01/30/09 04:13 AM
 Originally Posted By: csteffen

So over 20 years you would expect just under 40% of the fish to die.

I added the situation with all the fish surviving to show an exception to the rule for a VERY unlucky pond owner . These numbers are for diploid fish though (thanks for filling in that gap Dr. Willis). You should try to find out if your grass carp are diploids or triploids to determine if these numbers even apply.




 Originally Posted By: Greg Grimes
Guys this is totally contradictory to my experience and education. I have always been total they live no more than 10 years. Well we proofed that wrong back in 2003 with some that had to be 18 years old, but total major exception to the rule. 100 years is just insane. Maybe it is due to being triploid as required in GA maybe it is due to warmer climate thus not living as long. I have literally stocked 100’s of ponds with grass carp. The natural mortality is very high, within 3-5 years the number is always half of what was stocked. We make sure to use 10-12 inch but sure of them may be expensive bass food btu this does not explain this low of a number.


Please don't take anything I'm about to post as anything but the questioning of conventional ideas and teachings. I'm an electronics engineer, not an aquaculturist.

But, if researchers didn't challenge what I learned in college in the 1960s regarding electronic data transfer theory, we wouldn't be posting on PondBoss.com today. The 300 baud modem would still be our maximum data speed for DSL.

From the data presented by csteffen, I think we can safely assume that over 60% of diploids can live longer than 20 years. That puts us back into the 1980s when diploids were still in fairly common distribution in the US.

[I really love the picture of the big "minnow" hugging csteffen! What a classic picture!]

Warden Lake, the WVDNR lake I mentioned above that is near me, and with a serious overpopulation of very large grass carp, could easily be filled with diploids that are now in excess of 30 years old.

I don't know what is in my pond -- diploids or triploids. As far as I can tell from old receipts, six "grass carp" were stocked in 1993 by the previous owner. When we bought this place about four years ago, I was pretty certain that there were four grass carp in the pond. Two years ago I removed two of them. To the best of my knowledge, two were still living in the pond as of this past October. So, I can only assume these two are at least 15 years old.

From my viewpoint, we just don't know how long grass carp really will live in ponds. I think it is considerably longer than 10 years, diploid or triploid. I also don't believe it is anywhere near 100 years.

In any case, I plan to stock on the far more conservative side when I replace the two grass carp left in my pond. I plan to remove both of them this spring. I'm now thinking that I will replace them with two grass carp and two koi (I have one huge tiger-striped orange-and-black koi now, which I plan on keeping -- it is a true friend that follows me around the pond).

I hope to at least outlive the new grass carp.

Good fishn'
Ken
Didn't I see a post here that they are often badly injured by electrofishing?
Posted By: Greg Grimes Re: What is the Life span of Grass Carp? - 01/30/09 01:31 PM
Dave it seems due to size and shape they shock well. We have broken the backs of very few fish over the years overall but on much higher % of grass carp. The one in the pciture I posted above had a broken back due to electrofishing.
Maybe JHAP could do some fine tuning on the GSF Society's Death Star. ZAP!
Posted By: CJBS2003 Re: What is the Life span of Grass Carp? - 01/30/09 02:02 PM
Personally I am a fan of breaking their backs with an arrow over electricity, but that's just me... HAHA
Posted By: MrSandman Re: What is the Life span of Grass Carp? - 01/31/09 04:56 PM
LR, Thanks for the info on the yellow water iris. I'm still undecided as whether to get some. I already have a full compliment of marginal plants, mostly in the form of smartweed and cattails. The grass carp don't seem to like them that much. I noticed that smartweed has a distinctly hot, peppermint-like taste. Maybe they're too spicy for the GC.

But, I no longer have any weeds where the water exceeds 6" or so. The GC ate 'em all. The shoreline vegetation doesn't seem adequate in competing for nutrients. That seems to be the reason why my water tends to be so murky green in the summer. I don't miss the algae mats but I do miss some of the American pondweed and the chara. Chara (although a bit of a nuisance when fishing) especially seemed to make the water clear. Now there are only traces of these plants in the shallowest places of the lake where the GC can't reach.

I guess I better exercise and eat more healthy so I can outlive those 20 + year old GC. For sure I'll be fishing for them this year to hasten their demise.
© Pond Boss Forum