I have a carp problem, and as a secondary question to my other post (http://forum.nanfa.o...?showtopic=7494), I was wondering if anyone were aware if there is any way to distinguish between diploid and triploid grass carp, Ctenopharngodon idella? I know that studies have shown no significant differences of external morphometrics of diploid and triploid specimens through a varied range of ages and size/age classes, but I am wondering if anyone is aware of any differences that could be ascertained from examining the internal anatomy.

Obviously I would assume if samples of gonadal tissue were sectioned on a microtome you could look for the presence or absence of active gametogenesis, but I don't have that good of a lab, I have no training in histology, and I know it won't be deemed worth the expense of sending samples to the veterinary lab for histopathology on the company dime. Based on what I've read it doesn't look too promising, but if anyone is aware of any methods or could point me towards a good reference it would be most greatly appreciated.

Thanks,

You can't tell just by looking at them. If they are not triploid, they were illegally imported into the state. There was a man busted a year or two ago in the San Marcos area that was bringing in reproductive grass carp in from Arkansas (where they are legal). The seller in Arkansas became suspicious and reported him to the authorities. Hopefully, the dealer's attitude is common and people that sell them in states where they are legal want nothing to do with Texans bootlegging fish. See my other post on grass carp, too.

Saw the other post already- thanks for the info, I kind of suspected there was no way to tell them apart. I remember that case- as I recall it was a golf ball diver who introduced them into a ridiculous number of ponds all within a mile of the headwaters of the San Marcos river/Spring lake (aka one of, if not the most, ecologically sensitive areas of the state), never heard what happened to him but I hope he got the book thrown at him...that river is already chock full of Hypostomus spp., goldfish, and other invasives, viable carp would have been an ecological disaster considering that a species of endangered wild rice still grows there abundantly...

Edited by BLChristie, 22 April 2009 - 11:55 PM.

Use Coulter Counter of flow cytometer to measure diameter of red blood cell nucleous. Find a grass carp suppleir that breeds their own and see if they can run your sample along with their they do almost daily. Most use Coulter Counters which are relatively cheap to run. All they need is a properly prepared blood sample that can be shipped via mail.

I would be supprised if you do not already have an established / self-sustaining grass carp population in your area. A few of the states in the midwest with requirments for triploids have have diploid populations established in their waters for at least 15 years (personal observation). Law only restricts trade, no actual control measure as intended.

Edited by centrarchid, 27 April 2009 - 08:46 AM.

It's surprising, but we don't have a bad grass carp problem here. I've sampled every major basin in the state, and never caught a grass carp. Common carp, plenty, but no grass carp. I had a conversation with a few friends one day out sampling, and none of them, all with much experience, had caught any either. They are stocked in some lakes, but I rarely electroshock on reservoirs, so I know I've missed out on catching them there. I'd also suspect tha as you go east your chances of catching them go up, but that's just a guess.

You cannot send the blood sample through the mail. It needs to be fresh, although we have not experimented with the use of chemicals that would keep the blood from coagulating, and that might work. Even then, the blood needs to be taken from a live fish, anticoagulants don't work retroactively. There is a new technique that works with fish that are reasonably fresh and dead. You take the eyeball out, that can be stored frozen or kept cool, then the analyst uses flow cytometry on the eyeball fluid. It is not an expensive technique, but more difficult than a coulter counter. Flow cytometry is more accurate than a coulter counter though. Coulter counters have been known to make mistakes, especially on fish that are only partly triploid, which occurs sometimes (some cells triploid and some diploid).

It's surprising, but we don't have a bad grass carp problem here. I've sampled every major basin in the state, and never caught a grass carp. Common carp, plenty, but no grass carp. I had a conversation with a few friends one day out sampling, and none of them, all with much experience, had caught any either. They are stocked in some lakes, but I rarely electroshock on reservoirs, so I know I've missed out on catching them there. I'd also suspect tha as you go east your chances of catching them go up, but that's just a guess.

Grass carp are known to be established in the Trinity River (Journal of Freshwater Ecology (1997) 12(2): 281-289) and also in Lake Texoma, where they are somewhat highly abundant, in my experience. They definately are recruiting there. Also, there were many triploid grass carp stocked into the lower Rio Grande.

I caught a grass carp from the Nueces River near Corpus Christi, on hook and line. It hit a minnow, which is strange, but maybe not so strange when you consider there isn't any real vegetation in the Nueces for grass carp to eat. If they are abundant enough to catch on hook and line, there must be a few of them there. But with the number of big gator gar in that river, it is a wonder any could survive.

I have a carp problem, and as a secondary question to my other post (http://forum.nanfa.o...?showtopic=7494), I was wondering if anyone were aware if there is any way to distinguish between diploid and triploid grass carp, Ctenopharngodon idella? I know that studies have shown no significant differences of external morphometrics of diploid and triploid specimens through a varied range of ages and size/age classes, but I am wondering if anyone is aware of any differences that could be ascertained from examining the internal anatomy.

Obviously I would assume if samples of gonadal tissue were sectioned on a microtome you could look for the presence or absence of active gametogenesis, but I don't have that good of a lab, I have no training in histology, and I know it won't be deemed worth the expense of sending samples to the veterinary lab for histopathology on the company dime. Based on what I've read it doesn't look too promising, but if anyone is aware of any methods or could point me towards a good reference it would be most greatly appreciated.

Thanks,

Back in the mid-eighties, I messed around with trying to look at variable response to anesthetics. MS-222 was pretty much the same, but I found that quinaldine knocked most of the triploids over long before the diploids in the same batch. Was not 100% though, so not a very useful technique. No paper published on it, and I don't think I could even come up with the data after 25 years.

Grass carp are known to be established in the Trinity River (Journal of Freshwater Ecology (1997) 12(2): 281-289) and also in Lake Texoma, where they are somewhat highly abundant, in my experience. They definately are recruiting there. Also, there were many triploid grass carp stocked into the lower Rio Grande.

I caught a grass carp from the Nueces River near Corpus Christi, on hook and line. It hit a minnow, which is strange, but maybe not so strange when you consider there isn't any real vegetation in the Nueces for grass carp to eat. If they are abundant enough to catch on hook and line, there must be a few of them there. But with the number of big gator gar in that river, it is a wonder any could survive.

If they are recruiting in Texoma, I'll blame Oklahoma. The state stocks triploids because of the Hydrilla problem all over. Bass fishermen declare war on them and kill them. The circle of fisheries management... The Nueces by CC is below Lake CC, where I bet they are stocked, and possibly reproducing from earlier stockings. Still, in mainstem rivers and tribs, you hardly ever see them outside the direct influence of a reservoir.

I have data in hand with 298 collections on the mainstem Trinity and its tribs between 1931 and present that record 2 captured grass carp. It's river and trib data, so doesn't take reservoirs into acount. If they are established, they are making it in reservoirs.

If they are recruiting in Texoma, I'll blame Oklahoma. The state stocks triploids because of the Hydrilla problem all over. Bass fishermen declare war on them and kill them. The circle of fisheries management... The Nueces by CC is below Lake CC, where I bet they are stocked, and possibly reproducing from earlier stockings. Still, in mainstem rivers and tribs, you hardly ever see them outside the direct influence of a reservoir.

I have data in hand with 298 collections on the mainstem Trinity and its tribs between 1931 and present that record 2 captured grass carp. It's river and trib data, so doesn't take reservoirs into acount. If they are established, they are making it in reservoirs.

I don't doubt you are correct. In fact, there appears to be some debate over whether the trinity river population still hangs on. They are still in Texoma, though. Texas rivers just don't have ideal habitat for grass carp recruitment, because they don't have the flood plain access.

You cannot send the blood sample through the mail. It needs to be fresh, although we have not experimented with the use of chemicals that would keep the blood from coagulating, and that might work. Even then, the blood needs to be taken from a live fish, anticoagulants don't work retroactively. There is a new technique that works with fish that are reasonably fresh and dead. You take the eyeball out, that can be stored frozen or kept cool, then the analyst uses flow cytometry on the eyeball fluid. It is not an expensive technique, but more difficult than a coulter counter. Flow cytometry is more accurate than a coulter counter though. Coulter counters have been known to make mistakes, especially on fish that are only partly triploid, which occurs sometimes (some cells triploid and some diploid).

I have not done process but at least one triploid glass carp producer does determine ploidy of suspended blood samples shipped via mail. Sample are not shipped as coagulated blood. For the purpose of science or more stringent legal considerations, I agree, flow cytometry is more reliable.

I have not done process but at least one triploid glass carp producer does determine ploidy of suspended blood samples shipped via mail. Sample are not shipped as coagulated blood. For the purpose of science or more stringent legal considerations, I agree, flow cytometry is more reliable.

Yeah, in theory it would work if you kept the blood from coagulating and could be sure that particles were not coalescing. The coulter counter works on particle size, and the size differences in question are pretty small (triploid cells are bigger because they have to contain more DNA, but not a heck of a lot bigger). I'd want evidence that using anticoagulant works before I'd rely too heavily on it, but in theory it should work. Our problem is that fish are often dead when they are brought in by a commercial or recreational fisher, so once the fish is long dead you can't reliably get a good uncoagulated blood sample. That's why the new eyeball technique is cool - manager cuts out an eyeball and ships it cold or frozen and there is no need for blood sampling equipment, anticoagulants, whatever. If they have a pocketknife, a ziplock bag, and an ice chest, we're in like Flynn. Recent grass carp captured in the Canadian portion of the Great Lakes were found to be triploid with this technique, for example, and without it, we'd have been SOL as far as knowing whether the fish are potential spawners.

Why can't fisheries understand that two wrongs don't make a right...?