Florida: Land of Flowers and Koi Predators

"White-faced heron.(Egretta novaehollandiae)" by Bernard Spragg is marked with CC PDM 1.0.

Florida is Spanish for “land of flowers” and for koi hobbyists, it also represents a land of abundant predators. “I never had a need to keep koi,” said Jan Brown, past president North Florida Koi Club. “I wanted to grow water lilies. I did grow water lilies. I also grew designer mosquitoes and here’s where the long, slippery slide into koi keeper begins.” Along with the flowering foliage, water gardens, and koi came predators, many that are found elsewhere in the United States and notable exotic invasive species, especially in South Florida.
The Great Blue Heron may be one of the best-known koi predators which have an interesting history of its own. A century ago, herons nearly disappeared as a result of hunters killing them to harvest their plumes for women’s hats. They made a dramatic comeback from near extinction in part because of the proliferation of koi in hobbyist’s ponds. The heron has religious significance in Japan dating back to the Heian period (700 to 1100 A.D.) and the Shinto Sagi-mai or White Heron Dance as it is also known. The dance is still performed today by dancers in heron-shaped costumes.

File:Senso-ji Shirasagi-no-mai 20130414.jpg” by Tak1701d is marked with CC BY-SA 3.0.

“Koi are a large fish but it seems to be a game for the herons to spike them in the head, often resulting in death by blunt force or a secondary bacterial infection invading the wound,” wrote Doug Ward, Tropical Koi Club’s former vice president, and aqua-culturist.
While they may harm koi, harming these birds is strictly prohibited by way of numerous laws including the Migratory Bird Treaty Act, which was entered into with Canada, Japan, Mexico, and Russia.
“Yesterday the netting over one nursery tank was removed to enable routine maintenance,” said Joe White, Florida East Coast Koi and Water Garden Society president and AKCA director. “In the evening, I realized I had not put the netting ring back over the tank and hurriedly laid it on the tank with minimal fastening. In the morning this visitor attracted attention by its loud clucks and sounds of thrashing as it tried to escape from under the protective netting. The bird had successfully maneuvered his way into the tank through an open area. A dead, apparently regurgitated, three-inch koi was floating on the water surface. Mr Green Heron flew away once freed from the tank’s enclosure. Hopefully, the bird will breakfast elsewhere from now on.”
Around Florida, such stories are nearly as common as sightings of these magnificent predators themselves. “I lost four of my oldest and largest koi,” said Frank Scanlan. “They were about five years old and the largest probably 15”+ were lost to a Blue Heron that was frequenting our pond in Coral Springs, Florida. I ended up running several monofilament lines randomly across the top of the pond about three feet above the surface. I haven’t noticed any fish missing since.”

A watchful eye in the Southeastern United States is always a fair warning for those wishing to keep their fish predator-free. Egrets, relatives of the heron, also enjoy Florida koi as do a variety of other wading and diving birds including spoonbills, ibis, storks, and anhingas. “ For coastal residents, the list of koi terrorists include the full gamut of Atlantic and Caribbean/Gulf sea birds, which are fully capable of munching on a medium-sized koi,” according to Ward. “A couple of pelicans could clean out a pond in minutes and leave nothing but a buuuurp! Gloria Estefan can explain that better than I. She got cleaned out at her place.”
There are plenty of other classes of predators such as reptiles that threaten koi around Florida ponds. “In come the snakes,” said Ward. “Brown water snakes, moccasins, red rats, Florida kings, and our vast collections of exotics (semitropical South Florida) ranging from pythons and boas to any other snake found anywhere in the world. All snakes are capable, agile swimmers and like the taste of fish.”
Yet, do snakes actually cause much concern for Florida koi hobbyists? “I found out snakes enjoy koi as much as herons,” said Brown. Several other koi hobbyists in Northeast Florida reported problems with snakes.
“We had recently stocked our pond with small koi, and Bill, my husband was out by the pond when a brightly-colored snake slithered out from behind some rocks and dove right in after a fish,” said Dianne Cassidy. “Upland out of the pond came the snake with the fish that was too big for it to swallow. Bill took after the snake that proceeded to leave the koi flapping on the bank.” The fish survived and the snake took off down a storm sewer to hunt its quarry elsewhere. Sarah Schlesinger, a First Coast Koi, Goldfish and Water Garden Club member, also did battle with a snake living in one of her several ponds. After numerous small fry went missing, she identified the culprit that was sharing the pond one day while she cleaned the submersible pump and filter. That snake’s koi consumption ended that afternoon. Chris Smith, another North Florida proud father of two young children and numerous koi was so alarmed by snake eggs found under his pond waterfall that he poured a concrete slab around the entire structure and sealed the crevices to prevent any further encroachments of the natural order.
Some area predators are warm and fuzzy mammals, which include raccoons and even bobcats. “Raccoons are expert fisherman,” said Ward. “Our entire cichlid facility is covered with chain link and electrified at night!” There are some other sneaky varieties of predatory mammals that can clean out a koi pond population quickly.
“We ruled out all the usual predators, raccoons, cats, small boys,” said Brown. “I was convinced we had been found by an otter. My husband, Doubting Paul, was not convinced. We tried beefing up the netting, lights, electric fence, and the ultimate last resort,…a radio tuned to a 24-hour religious station. I now have a great affinity with Carl the groundskeeper in the movie Caddy Shack. Remember Doubting Paul…he remained not convinced until the morning he checked the trap we set to find an otter, with koi on its breath, snarling at him.
Great, I thought, got rid of that problem. I restocked, which was the most fun of the whole ordeal, upping the quality of my koi. There was nearly a year of calm at the old pond until another swimming weasel found me. These otters, by the way, have to travel over two miles from the nearest large body of water, up a shallow creek to get to my pond. The creek is so shallow they must walk the last half mile.
This time, the survivors went to board at another club member’s pond. They stayed there for eight months. In the meanwhile, we tried trapping without any success. When we figured it was safe to bring the fish back, I was so happy to see them back home. So was an otter. It took 10 days for him to find them again — even with two surveillance cameras with an interior monitor, a motion and heat-sensing floodlight with an interior alarm.
In spite of the indignity, I am sure the surviving koi are suffering, they now have to share a 1500-gal pond with the goldfish the otter didn’t eat after we moved the koi the first time. Now the pond is covered with heavy gauge hardware cloth held down with steel spikes driven in the ground. Concrete blocks sit on top of the edging. It’s a koi maximum-security prison. Sing Sing for Sankes, if I had any left.

Otters playing in the water II” by Tambako the Jaguar is marked with CC BY-ND 2.0.

I go down to the empty pond and admire the plants and enjoy the sound of running water…and I plot. Maybe a steel trap there…a tiger pit over there…electric plates.”
The cosmopolitan nature of the South Florida human inhabitants is matched only by their wildlife variety. “In South Florida, we probably have the most diversified collection of koi slaying predators in the United States,” said Ward. “Southeast Texas would be a close second.
Alligators are a common predator in the western sections of Southeast Florida and the eastern areas of Southwest Florida where the Everglades and manlike are attempting to see “whose territory” it really is! Turtle species include alligator snappers, soft-shell, and sliders, all of which are fish eaters. I have sliders in my pond and should a fish get ill, and slow down, the sliders will have him in a second. Don’t keep turtles and valuable koi together unless you have a large pond. Mine is 28,000-gal and the new one is 60,000-gal so everyone has some space to co-exist. The turtles came on their own, as did the walking catfish. I did not put them there.

We also have lots of iguanas of various types and they are all fast swimming, fish-eating machines. I could figure out what was doing the fish in until Todd Hardwick saw the bite on a fish. I lost several large koi to a big iguana a few years back and finally had the great pleasure of blowing him off the fence with a shotgun. It was nearly 6’ long. I suppose this makes Florida seem like a jungle in the Amazon and in some ways it can be,” concluded Ward.
So, remember when you visit the land of flowers there are also koi predators in those bushes!

NOTE: Article was originally published in KOI USA Nov/Dec 2005 issue by John Hawley, Earth Works Content Manager.

For ideas on how to address koi predators you may be dealing with and for comprehensive solutions to your specific lawn, garden, pond, and landscaping needs, contact Earth Works of Jacksonville online or at 904-996-0712. Earth Works operates a retail Garden Center/Plant Nursery in Jacksonville and provides landscaping, hardscaping, water features, lawn care service, lawn spraying, and drainage solutions.

Earth Works proudly serves clients in Northeast Florida, including Jacksonville, Ponte Vedra Beach, Atlantic Beach, Neptune Beach, Jacksonville Beach, Nocatee, St. Johns, Fleming Island, Orange Park, Middleburg, Green Cove Springs, Amelia Island, Fernandina, and St. Augustine.