Predator Control – Otters: Unwanted Visitors

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Randy LeFever

What does over four miles of fencing have to do with koi? Our story started a year ago in early November. By that time we had culled through over 5,000,000 fry and grown our (fish) crop of koi, butterfly koi and goldfish as much as we could until spring when the water warms. We had invested many, many man-hours and fed tons of food to get the crop to this point. The “keepers” are in the mud ponds, settling in for the winter, and awaiting harvest in February when the culling and sales will resume. At this point we knew what was in each pond, based on stocking densities, feeding rates, and the size of the ponds.

Last February, we started harvesting for the second cull and found that many ponds had produced only 40 to 50 % of what they should have. Some ponds were missing over 90% of fish stocked! All that time and money spent on food, only to discover that so many of our fish were missing. We’ve always lost some fish through the winter, primarily to Blue Herons, but this was ridiculous.

We soon discovered what the problem was – river otters. Both North Carolina and Virginia have re-introduced them into the wild over the last few years. In the words of one wildlife official, “they’ve done quite well.” It turns out that otters are virtual fish eating machines. If you’ve ever observed them at the local zoo, you’ve seen that they are constantly on the move. All that activity burns a lot of calories, and for otters, those calories come from fish.

The otter can weigh up to 50 lbs. and need to eat at least 25% of their body weight each day to survive. For some perspective, that would be 600 - 3˝ koi or 80 - 6˝ koi per day! As you can see, it doesn’t take many otters to devastate a fish crop. All of our ponds drain into adjacent creeks and rivers where otters live and travel, so we were an easy mark. You can’t much blame them for making themselves at home. They’ve spent their life catching only bass and trout in the river and then they suddenly discover a koi farm where there are wall-to-wall fish of every size and color. Apparently our farms had become a gathering place for otters from miles around.

The next question we asked ourselves was “What do we do now?” We were able to trap a few during their season, but not enough to make a difference. So after much discussion, we decided that if we were going to stay in the fish business we would have to fence them out. Our research showed that otters are pretty wily animals and can climb over or dig under most fences, especially when there is an all-you-can-eat buffet on the other side. So we took the plunge and invested in over four miles of 4´ tall, 3˝ mesh fencing. We added four strands of 7000-volt electric fence wire, one as close to the ground as we could get, another 6˝ above that and two more at the top.

As of this writing, it seems to be working. We’ve seen otter tracks leading up to the fence and none on the other side. We’ve seen evidence of one attempting to dig under, but he was deterred and gave up.

We’ve had customers report that otters have wiped out their display ponds in one night. So if you have any kind of pond relatively close to a creek or river, beware of the otter!

About the Author
Randy LeFever is President of Blue Ridge Fish Hatchery, one of the largest Koi and goldfish farms in the US. He has been involved in the production and distribution of high quality koi and Butterfly Koi on a national basis for over 30 years. He’s credited for naming and introducing Butterfly Koi to the US market in the 1980’s.

Blue Ridge Fish Hatchery 4536 Kernersville Rd. Kernersville, NC 27284 1-800/334-5257 Fax 336/784-4306 Email: Web:

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POND Trade Author - Randy LeFever

Author Randy LeFever

Location Kernersville NC

Company Blue Ridge Fish Hatchery

Bio Randy LeFever is President of Blue Ridge Fish Hatchery, one of the largest Koi and goldfish farms in the US. He has been involved in the production...

Read the full bio.



what is the biggest size fish that otters are likely to eat ,as we are thinking of stocking some carp of 20lb plus which cost £1000.00 +. regards , alan.

1. Posted on December 10th, 2010 at 3:27 am.

By alan of compton lakes.


Hi Alan,

Otters could conceivably take a 20 pound carp. But they really prefer much smaller fish. I think they would leave the big ones alone unless they couldn’t find anything else to feed on.

2. Posted on December 13th, 2010 at 9:53 am.

By Randy LeFever of Blue Ridge Fish Hatchery.


I had a 20 pound, 3 foot long white catfish in my pond along with approximately 15 Koi that averaged about 15 inches. The river otters came in one night and cleaned out the whole pond, catfish, koi and all. Didn't eat them; just dragged them all out of the pond and left them to die, which of course, they all did. They have cleaned out my pond six times since.
I have just installed a 130 foot fence around the pond - 5 foot tall. 2 inch spaced, aluminum fence. It is buried one foot into the ground and sits on top of one foot of concrete. Getting ready to restock. HOPE THIS MAY FINALLY KEEP THE OTTERS OUT!

3. Posted on August 4th, 2011 at 8:43 am.

By Kevin Smyth of none.


Otter have wiped out my Channel Cats three times in the last 5 years. I tried electric fence close to the ground about 2 years ago and it worked until a couple of weeks ago. Now my beautiful 6 to 8 pound catfish are gone again along with the few bass I had with them. I will try your combination of 3" mesh and electric this time. I'll need about 4 to 5 hundred feet and three gates but my pond is very nice and worth the effort and money.

4. Posted on December 22nd, 2011 at 6:24 am.

By Ron Smith Live Oak FL.


Had problems recently.
Installed electric fence
Make sure u get high voltage supply...
Working on second try... Meaning the otter got one more before I learned the high voltage rule..
Zap them hard

5. Posted on January 2nd, 2014 at 3:59 pm.

By Rick.

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