Mostly Trapping

Can lion poo or wolf pee drive away the koi-eating otter?
Nov 5, 2019 07:30 ET

(Reprinted from above link)

A year after a river otter managed to gain entrance to Vancouver's Dr. Sun Yat-Sen Classical Chinese Garden and eat about a dozen prized ornamental koi fish, another otter is doing the same thing.

Spokespeople for the Vancouver park board, which maintains parts of the garden and runs the adjacent and free Sun Yat-Sen Park, said they don't know if it is the same otter.

Regardless, after discovering the remains of three koi on October 30 this year (and three more found later), the board decided to partially drain the pond to relocate the koi once again, this time before most of the big fish are eaten while staff try to trap the stealthy member of the Mustelidae family of mammalian carnivores, which includes wolverines, badgers, and weasels.
Workers netted the fish on Friday and Saturday, and the garden remains closed temporarily while live-trapping attempts are carried out.

Trapping failed in 2018, with the otter somehow managing to steal the chicken and seafood bait without triggering the device. Eventually, the otter left. Grating on pipe access and modifications to the garden's gates have also been done, seemingly to no avail.

This time, with no guarantees that traps will succeed, are there any other methods the park board could employ without harming the animal?

What's your poison: lion poo, loud noises, wolf pee, or hot peppers?
A quick look around the Internet shows several other tools for otter control in North America and England (which is the home of the Eurasian otter, similar to Canada's river otter and the most widely distributed otter in the world).

These control methods have been marketed and used (with varying success) for otter problems ranging from feces on docks and in open boats to denning under houses or decks and predation on fish stocks in backyard ponds and hatcheries.

A company called Spark-Away sells a product (run either by regular electricity or solar power and triggered by a motion detector) that it claims imitates lightning and thunder and scares off elk, bears, coyotes, and other "nuisances". It sells for about US$100, and testimonials from satisfied customers include one from someone in B.C. who claims that otters "react as if someone shot at them" when Spark-Away is used.
Readers of a forum on the SportFishingBC website suggested various home remedies—some of which they swore by—to use as otter deterrants, including: mouse traps to give painful but not injurious nips; open containers of ammonia; mothballs (naphthalene); cayenne pepper mixed with vegetable oil; and a radio left on or connected to a motion-sensor switch.
Those who posted on a Trawler Forum website thread titled Otters be Gone! favoured various control methods: a large replica bald eagle with rotating (wind-powered) wings; rock salt spread on a dock; and diluted vinegar sprayed where needed.
An outfit called Wildlife Removal USA says to "forget about using repellents and decoys", insisting that—apart from an impractical (in this case) perimeter fence—"trapping and removal is the only way to deal with them" while acknowledging that "otter trapping is not easy". It recommends live traps baited with "potent-smelling fish" or "oils from another otter". (But if you were able to catch one to obtain its oil, you probably don't need the oil to begin with.)
A website run by Nationwide Wildlife Removal says that salmon "is one of the best baits that you can use to attract otters". It also advises owners of backyard ponds to spread out "hot and smelly spices" to deter otter traffic in the area, although it also admits that "most repellents...do not work" and are "usually a waste of money".
Wildlife Animal Control's website recommends fencing or trapping, declaring fish-based baits to be best (first fresh fish, then oily tinned sardines) but also recommending corn, fruits, and cat food. The site notes that otters "are exceptional beacuse they also have a taste for sweet food, unlike other wild animals". A good way to use that leftover Halloween candy, maybe?
The Washington state-based Living With Wildlife website advises pond and hatchery owners to provide hiding places for their fish, recommending cut conifer trees anchored to the bottom.
And, finally, a fishing club in England protected the valuable fish stocks in its private lakes from hungry otters by formulating a protective spray that uses "very, very pungent" lion feces from the London Zoo as its "key ingredient". Unfortunately, this would probably have the same effect on visitors to the Dr. Sun Yat-Sen garden. In the same vein, someone called "The Pee Man" in the state of Maine told a Canadian with otter problems to purchase and use his "wolf pee". If that didn't work, he wrote, he'd send along some bear pee, free of charge.
Given the fact that the Sun Yat-Sen otter has been spotted in the DTES streets in the neighbourhood, perhaps it is unlikely that the smell of urine will deter it.