Does anyone know why the Parks and Wildlife pamphlet says to immediatly remove the intestines from tilapia and grass carp if caught?

I would assume that is because these are non-native species that can be invasive if not regulated. Removing the intestines would insure no live fish are transported to other waters.

Speaking of Tilapia guts. My water is aproaching 50, should I see Tialpia swiming funny or anything as there going to die or do they just sink. Would like to collect some if possable.

Last year mine started off acting sluggish in shallow water. When they died they sank. I could see a few of their white corpses on the bottom and my dogs dragged a dozen or so into the yard.

They will start getting slow when the water temp drops into the 50's either your bass or catfish should clean them up which helps them through the winter also putting lbs. on them as well. We raise tilapia, if your interested on some info on them you can visit our site @ http://www.boatcycle.com

I wholeheartedly endorse Boatcycle. Ken Hale has been a friend for a long time, well before he started advertising in PB. He and his son, Kirk, are reputable people. They sell much more than tilapia. It's a pleasure to do business with them.

I don't have a clue why they might want grass carp intestines removed, but grass carp have more intestines than any other fish I've ever cut open.



And welcome to Boatcycle. Lots of good info on your website.

EEEEEWWWWW!!!

ha....only on pondboss....

nice pic ken.....see what happens when yer a vegetarian?

It's my understanding that grass carp don't actually digest the cellulose, they simply extract the juices and the nutrients contained therein.

Evidently vegetation needs to travel a long distance through the GC gut for this to be accomplished.

thinking about what bruce just said, maybe they (parks and wildlife) want the intestines removed to reduce the chance of spreading aquatic weeds around.....maybe the seeds or plant parts able to propagate survive that long intestinal trip?

Nasty. I've just reaffirmed why I am not in the medical field and also why I don't clean fish. I am a wussie.

Sorry guys!

I had no idea that the sight of fish guts would affect people who are otherwise so engrossed with the other aspects of fish and fishing.

I guess this means I probably shouldn't post my holiday headcheese recipe at Thanksgiving time.

I am told that opening and exposing the guts will allow the fish to decompose in a manner as to return all the nutreants this fish removed during it's life cycle back to the fishery, ie, turtles, crawfish,other fish and so on,all the way up and down the food chain.

I would like to see them use those guts on fear factor. Eat all of it RAW...

That's an interesting comment. Do you think that it's because some "higher-up" organisms get to eat before the bacterial decomposition sets in? Stands to reason.

By the way...Welcome to the forum.

Now I'm confused. I've been repeatedly told that grass carp have a very short digestive trac and that is why they fuel algae by their excretement. At least that is what someone from the Michigan DNR said and I've seen in publications.

Yes, I've seen the "short gut" reference as well.

I guess I don't really know what it means to have a short gut, because that picture has what looks like a long and complicated digestive tract. Maybe I'm just interpreting it wrong.

I did find scientific literature that says specifically that grass carp do not digest cellulose. Digestion of cellulose I believe involves use of specific types of bacteria, which the grass carp don't have.

So what does it mean to have a "short gut"?

I don't see where GC have a short gut compared to other fish.

From Dr. Griffin's talk at Arlington, pretty much all fish have short guts compared to mammals. CC, with a gut length:body length ratio of 2:1, have the longest gut:body ratio of any fish he cited. (By comparison, the big cats have some of the shortest ratios among mammals, at about 4:1).

In general,the gut:body ratio is higher for low protein/high plant matter diets. Given that GC eat almost solely on plant matter, I would expect their gut:body ratio to be higher than that of catfish.

I wonder if GC get most of their nutrition from the invertebrates living in the vegetation they eat? If so, then there should be a strong correlation between the type of vegetation GC prefer to eat and the average densitiy of invertebrates in a particular type of vegetation. Sorry, just wondering out loud as it's been pointed out thet GC don't have the bacteria to actually digest cellulose.

I didn't intend to hurt anyone's brain. Lots of pretty good ideas but now I'm more curious than before.

Thanks Bruce, I'm not sure but that's what I was told by a marine biologist back in the early 70's. You can test this by putting a whole dead fish in an aquirum and watch the water foul over a period of time. If you cut him open he will eaten by everything in the tank. Large and small.

From the following quote from an SARC publication on grass carp it seems perhaps the short gut comment is relative to other herbivorious species, and not in comparison to omnivores or carnivores?

That said I can't see any other species having much longer intestines!

"The reason grass carp are so good at controlling aquatic vegetation is they
have a very short gut in comparison to othe herbivores. The short gut
decreases retention time (less than 8 hours) in the gut, and reduces
digestive effciency to only 60 or 70 percent, so they eat more vegetation."

http://govdocs.aquake.org/cgi/reprint/2003/729/7290120.pdf

Got the following email from Don Garling professor at MSU specializing in aquaculture. Thought you would find this of interest. Thank you Don!

Cecil:

Their (Grass Carp) digestive efficiency is even lower than the DNR statement you
cite. It is because they are herbivores and are similar to many other
herbivorous fishes. FAO reports grass carp digestive efficiencies of 40%
or less. Juvenile grass carp consume as much as 30 to over 70% of their
body weight per day and at the higher rates retain much less because feed
remains in their intestinal track for as little as 30 minutes. It is
basically sped through the tract by newly consumed material. So, it is
retention time that is much less than other herbivores.

There is a published report that grass carp can absorb nearly 74% of the
phosphorus that they consume. Unfortunately, the authors checked excreted
fecal phosphorus collected from tanks for phosphorus. It has been shown
that about 90% of fecal phosphorus can be lost from feces in water in 60
minutes. As a result, they probably have phosphorus uptake nearer to
10-15% at best.

Combine those factors with an inability to eat algae:
high intake of grassy plants + rapid passage rates + low retention of P = algae

It is usually bluegreen algae because it can fix its own nitrogen which
also becomes limiting under the above scenario.

Don Garling

M Spinhirne is right. They are trying to control the spread of those species.