The Koi Weren’t Jumping For Joy

Growing up in Hawaii, I spent many weekends and summer vacations going spearfishing with my friends. In fact, my family’s business is Kaya’s Fishing Supply on Kekaulike Street in Honolulu, so my ohana consumes fish on a regular basis.

Fish was and still is my favorite food. It was quite ironic, then, when I started to get requests from people who needed medical help for their sick fish. Steaming moi and preparing it Chinese-style I could do, but repairing an injured fin posed quite a challenge.

Having very little knowledge in the area of fish medicine, I traveled to the East Coast for additional training.

I decided to start small and just concentrate on one type of fish, koi. Upon my return, I was all set to get my feet wet, so to speak.

Mr. Kendal had a beautifully landscaped home with a 1,500-gallon pond. He called me one day requesting a house call to inspect his koi. One by one, his fish were dying, and on the day that he called, Mr. Kendal lost his largest prized koi. He was definitely distraught over the situation.

It was my first fish case and I was excited with trepidation. Would I sink or swim? Did I bite off more than I could chew? Should I just cut bait?

Arriving at Mr. Kendal’s house, I took a quick assessment of the environment and the arrangement of the pond. The water looked pristine, but I did some routine testing to verify water quality. This testing took some time, and as I watched the koi I couldn’t help but notice their agitation. Given any moment, one of his remaining seven koi would swim to the bottom and scrape its body on the pond’s floor. When doing so, its body would “flash” in the sunlight, which made the activity very noticeable.

Sharing my observations, Mr. Kendal responded, “I only noticed the flashing recently. But that’s not my concern, Doc. Over the past couple of weeks, the fish have been doing a lot of jumping. It’s rather entertaining, but on occasion they would land outside of the pond on the deck. If I’m not there to put them back in, they die. I’ve already lost five fish.”

I explained to Mr. Kendal that the flashing and jumping may be related.

Using a sock net, I caught one of the koi in the pond and gently placed it in a container filled with fish anesthetic. Within minutes the koi rolled over onto its back indicating that it was sedated enough for close inspection.

Covering the poor koi was a large population of parasites. Being new to the world of fish medicine, I collected a handful of the organisms to take back to the hospital for identification. The sedated koi was then placed in fresh water to revive and then returned to the population.

After scouring the medical texts I identified the culprit as argulus, otherwise known as fish lice.

Yes, fish can have ukus, too.

These nasty critters latch on to the fish, inject digestive enzymes, then suck up liquefied fish meat for their meal.


Treatment for Mr. Kendal’s koi involved slowly adding salt to the pond until the salinity reached a point that killed the adult lice.

To prevent the Argulus eggs from hatching, we then treated the water with lufenuron, which is used to sterilize fleas on cats and dogs.

Within a week the koi were happy and no longer excessively flashing or jumping.

Treating koi has added another dimension to my appreciation of fish. Do I still enjoy macadamia nut-crusted onaga, or lemon and capers with a white wine reduction on opakapaka?

You bet.

Even though I work on the wild side, I guess I still need to satisfy my hungry side.

Pet Tip:
One of the most important things an owner can do is maintain good water quality for their pet fish. Commercial kits are available to help.

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