Why letting goldfish go wild is a bad idea: They become giant pests

[Viktor Jarikov]

Another one of those. We need to up our awareness efforts as a community.

http://mashable.com/2016/08/16/giant-go ... SE_Xl5ZsqL

You may think dumping goldfish into a river is a harmless act, but in reality the fish can become destructively big.

Researchers from the Centre of Fish and Fisheries at Murdoch University have been trying to control goldfish for 12 years in the Vasse River, located in the southwest of Western Australia.

An invasive species, the goldfish is causing havoc for native fish and its surrounding ecosystem, which is why Stephen Beatty and his fellow researchers spent a year studying the little-known movement patterns of the goldfish in the wild. The results of the study, now concluded, has been published in a paper in the journal, Ecology of Freshwater Fish.

Beatty told Mashable Australia that the study was conducted because of the sharp rise in aquarium species, such as the goldfish, being detected in the Vasse River in the last 15 years. That's all thanks to people letting them go in local waterways.

"We think it's a major factor, people letting their aquarium species go. Unwanted pets, basically. They can do quite a lot of harm," Beatty said.

Goldfish are omnivores in the wild, and they can have destructive feeding habits. They deteriorate the quality of water by stirring up sediment on the bottom of river beds, dig up vegetation and also consume anything edible that comes before them — including native fish eggs.

On top of that, the goldfish compete for space and resources with native fish, and have been responsible for introducing disease.

Most startling is the fact that goldfish in the wild can grow to massive sizes, and they have an unprecedented ability to travel long distances. One goldfish found by researchers weighed 1.9 kilograms (4.1 pounds), while another was tracked travelling a marathon 230 kilometres (142 miles) in a year.

"We didn't think goldfish were that mobile," Beatty said. "What this study shows is that they are quite mobile, but I think it's mostly to do with with feeding and foraging."

Beatty said they were able to discover evidence of goldfish undergoing migration into nearby wetlands, where they are reproducing — a.k.a. a spawning migration. It's a discovery which will help researchers figure out how to stop the invasive species.

"It gives us better clarity on how to control them. That wetland has only a small opening, so we think we can manufacture some sort of trap to catch them when they go in to breed," he said.

Other removal methods include nets and electrofishing, but Beatty admits it can be difficult to remove an alien species without damaging the local fish population. As always, prevention is the cure.

"The key thing is if you've got unwanted pets, you can see if the pet shops will take them back. But if you're going to euthanise them, putting them in the freezer is the most humane way," Beatty explained.

"But just letting go of a pet, no matter how innocuous you think it is in your aquarium, or how pretty it is, can potentially cause a lot of damage. Not all fish you let go will form a self-maintaining population, but we're finding more and more that do."

[catfishchaos]

We should introduce a group of

Silurus glanis

to eat the goldfish

[Bas Pels]

While I do agree goldfish - or any species - should never be put into the wild, putting them into the freezer is by for not the most humane way to euthanise them.

One can use colvis oil (I do hope I got the English word right, English is not my native language) but personally I would prefer using a knife.

Making a cut directly behind the head, deep enough to cut the spine will kill immedialely

However, in a cold winter I have used the cold water outdoors. That is 4 C, and putting fishes into 4 C from 20 C will kill immediately too. Obviously, this only works for small fishes - but is ideal for large groups of small fishes, for instance I once had a litter of cichlids with a partly missing dorsal fin

[bekateen]

We should introduce a group of

Silurus glanis

to eat the goldfish

Yeah, that'll work about as well as introducing Marine toads to Hawaii and Australia to control agricultural pests like locusts. As funny as a rubber crutch, I like to say

Cheers, Eric

[Viktor Jarikov]

more of the same https://www.yahoo.com/finance/news/peop ... 53896.html

[bekateen]

Victor, for some reason, your link didn't work for me. Here is the same story with a different link:
http://finance.yahoo.com/news/people-du ... 53896.html

And I'll add one more report of the same problem, but from 2013: http://blogs.usda.gov/2013/03/07/super- ... ake-tahoe/

[Viktor Jarikov]

Thanks. My link still works for me, FWIW.

[Fundulopanchax76]

I propose after killing not wanted gold fish, to throw them in a pan with boiling oil, fry them and then eat them ! I think they will be tasty ! lol

[Viktor Jarikov]

I am sure they are tasty. After all, they are a differently colored Carassius carassius that is caught and eaten all over Euroasia. I spent my younger years catching them and carp in Belarus and I am sure they inhabit Bulgaria too, probably in every significant body of water.

The only small concern of mine would be that they are raised for ornamental fish trade and as such they can be treated with medicines, etc. that are not approved for fish intended for human consumption. Such medicines can be based on heavy metals, e.g., copper. Heavy metals (IDK is all of them or most of them) accumulate with age, having entered an organism, they never leave it. I think it happens with mercury for sure.

[Bas Pels]

For mercury Victor is absolutely right, for lead and cadmium too. Copper is excreted slowly, but so slowly that one can ignore this.

However, while I would not advise anyone to eat contaminated fish, these heavy metals all collect in different places in the fish, but none of them collect in the muscle

That is, gutting a fish will remove more than 90 % of the heavy metals

[Fundulopanchax76]

So guys which medicine for aquarium fishes contains heavy metals ?

[Bas Pels]

It really is easier to find out which do not

[Viktor Jarikov]

Here is one list of the most common ones. It's not long, so one can quickly go through these granted there is interest: http://www.fishchemical.com/FULL-PRODUC ... egory.html I've been buying from these guys for 6-7 years. Every label says "For ornamental fish only. Not for fish intended for human consumption". Surely they have to overkill it but there must be a bit of something behind it. How big a bit, that's the question.

...However, while I would not advise anyone to eat contaminated fish, these heavy metals all collect in different places in the fish, but none of them collect in the muscle

That is, gutting a fish will remove more than 90 % of the heavy metals

Good point, Bas. Thanks. IIRC, mercury, cadmium, and Co. accumulate in bone marrow in humans but fish don't have bone marrow, so must be internal organs. Anyhow, it's a small concern albeit it could involve more than just heavy metals, e.g. potentially harmful metabolites of these medicines may stay in a fish a while too.

In fact, everything we eat is contaminated and bottom-feeding fish and especially apex predatory fish in particular. One of the reasons people do not favor carp and catfish is because they are bottom feeders (albeit they say if we knew on what foods farmed tilapia and shrimp are raised in SE Asia, we couldn't bring ourselves to eat them either).

So all in all, I believe this is just something to be aware of, not worry about. My $0.02.

[Fundulopanchax76]

Yes, and chicken and beef and pork are contaminated with hormones and antibiotics. So you will never run away from this !