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.
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
