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Grass carp and Their Impact on Bluegill or, How to Have Smaller Bass

Imagine that you were shopping for a new car, and a car dealer told you that he had the perfect car for you: this car has a twelve-year limited warranty, it’s more comfortable and nicer to look at than any car you have ever seen, and you can buy it for $2,000 less than any other car in its category. It has a maximum speed of thirty miles an hour, but everything else about the car is unparalleled. Would you buy that car?

Imagine that you have a small growth the size of a pebble on your right shin. The doctor tells you that it’s benign and completely harmless other than being unsightly; the doctor says that at times, the growth may enlarge to the size of a golf ball, but most of the time it will stay that smaller size; the doctor tells you that the growth won’t impact your life in any way other than being an inconvenience when you want to wear short pants or a bathing suit. Then the doctor recommends that you have him amputate your right leg at the knee, and tells you he has a sale right now on wheelchairs and can get you a great deal.

Would you take that doctor’s advice, or would you leave his office with all due haste and report him to the state medical licensing board?

Every fisheries biologist knows that bluegill numbers are key when it comes to growing trophy largemouth bass. Bluegill are the backbone of the forage base in any bass pond; this goes all the way back to Homer Swingle, the founder of the Auburn University fisheries program and the inventor of pond management as a science. Swingle did dozens of experiments ranging from pond construction to fertilization to weed control to fish population dynamics, and one of the things he found was that bluegill and largemouth bass were the best combination of gamefish for stocking into farm ponds: the bluegill provided the most reliable source of consistent and high-quantity forage in the right sizes for good growth for the bass, and the bass provided population control of the bluegill to where they wouldn’t overpopulate.

Every lake and pond consultant who sets up a trophy-largemouth pond starts with lots of bluegill; some of the better consultants now stock up to 3,000 bluegill fingerlings per acre in ponds for which the goal is to grow largemouth to the largest possible sizes. Not only are bluegill stocked at high densities in trophy-bass ponds, but most consultants also rely heavily on supplemental feeding of the bluegill with high–protein pellet food, even when bluegill fishing is not a priority, because bluegill fed a fishmeal-based diet with a protein content of at least 40% produce 80% more offspring than non-fed bluegill.

Needless to say, bluegill numbers are a big deal in a trophy-bass pond, and anything that interferes with said numbers should be avoided like the plague. What would you say, then, if I told you that all of our competitors working in Tennessee, Alabama, Georgia, Kentucky, and MIssissippi are routinely giving advice as bad as the two imaginary scenarios we outlined above to every new pond client they take on?

Every lake and pond management company and every fish hatchery we’re aware of in the above-referenced states sells grass carp, and is recommending them to every new customer they acquire. We have made posts before on the harmful side effects of grass carp; but lest anyone think we exaggerated, here’s a study we just recently came across:

https://afspubs.onlinelibrary.wiley.com/doi/abs/10.1577/1548-8659%281978%29107%3C172%3AEOGCAC%3E2.0.CO%3B2

This study is new to us; as noted above, we have made other blog posts about grass carp, but those posts were based mainly on the harmful effects grass carp have on the food chain of bluegill, and came mostly from our own firsthand observation over many years’ time. We have seen grass carp wreck feeding programs in every pond we’ve ever seen that had them; we have seen them decimate invertebrate populations. No one disputes that grass carp will interfere with pellet feeding; everything from state and university publications on pond management to the websites of more than one of our competitors acknowledges this. There are multiple government publications that note that grass carp are omnivores and will consume aquatic invertebrates; some of these publications also note that grass carp will consume the eggs and larvae of bass and bluegill. But every publication we have seen downplays the significance of these adverse effects when discussing grass carp in ponds.

Imagine that a pond consultant was stocking your pond, and recommended 3,000 bluegill per acre; he told you that you needed lots and lots of bluegill to grow big bass. Then he went on to say that once a month from May through September, the months in the South when bluegill fry will be hatching out, his team would show up to seine your pond and remove half of all the bluegill from the pond so the bass had less to eat and you would need to stock more fish that his team was ready to sell you. What would you say to that consultant?

For us, it was a simple decision: any fish that interferes as heavily with the bluegill food chain, both natural (invertebrates) and man-introduced (pellets), as do grass carp, is a fish we’re not going to recommend for our clients’ ponds. This was not based in theory, but in the actual and profound negative impact, both on bluegill and largemouth, that we observed over and over again in every pond that we worked on that had grass carp. We used to sell grass carp, mainly for customers who don’t fish and just wanted the easiest, cheapest method of controlling most bottom-rooted aquatic weeds; now we don’t even sell them, because they have done so much harm to so many ponds that we feel that they shouldn’t even be legal.

Why, then, do not a few but all of our competitors, and beyond that most private lake and pond consultants throughout the U.S., continue to recommend grass carp to every new client they meet? Because grass carp are easy. They’re very effective at controlling a wide range of aquatic plants; they don’t control every plant, unlike what some unscrupulous fish dealers will tell you, as there are many species of plant they won’t consume; but the ones that they do eat, they will eat into extinction in your pond, and your pond will look like a golf course pond. They’ll also wreck the food chain in said pond and cut the fishery potential by half, sometimes much more than that.

The study we linked to above was originally published in 1978, before pond management as a business in the private sector even existed. We have made many posts claiming to be in a different category, both in terms of knowledge and in terms of results, than all of our competitors; we have the fish photos to prove our claim in terms of results, and will soon have an entire new section on this website devoted to success stories we have had on ponds across the Southeast. If you doubt our claim that we’re simply more knowledgeable, by far, than all of our competitors, read just the synopsis of the study we linked to, and then ask yourself why every other lake and pond management company and every other hatchery that sells largemouth and bluegill in this region is stocking a fish that will reduce bluegill numbers by 50% in all of their clients’ ponds.