Ornamental Pear Tree Causing Deaths?

[The Masked Shadow]

Hi,

I have 2 outside bodies of water. A 55g patio tank and a 42g patio pond. A few of the pond fish have died, and they seem to be really dopey before they die. It couldn't be from the water quality because there aren't too many fish in the pond/tank, and I do frequent wc, plus the plants for filtration, so the next thing would be the tall Ornamental Pear Tree. In the winter, it sheds its flowers by the thousands, creating a layer of petal snow 2-3" deep. It also sheds its leaves. I am wondering if it could release some toxin just like oak trees, but more extreme?

 

[fishdance]

Could be lack of oxygen from decaying organic matter but toxicity is very easy to test. Throw some leaves into a bucket with some test fish...

 

[The Masked Shadow]

Ok. I’ll see and let you know.

 

[The Masked Shadow]

So, I have 2 trees, similar in look, but flourish in different seasons.

Bad news -

One is pyrus calleryana, or Callery Pear, which is illegal in some states, and is considered an invasive species. The inedible fruit is high in cyanide. There is nothing about leaves and flowers, but that leads me to my next thing.

The other is one of the few species of Pyrus. Almost all are poisonous, both flowers and leaves. The leaves are poisonous, and are included in Poisonous Plants of Washington state. The leaves are said to be poisonous to humans, cattle, horses, sheep, goats, swine, poultry, but not to pets. This seems a little bit suspicious. Why not dogs and cats? What does pets mean? I bet they didn’t test it on fish. If I noticed my fish acting weird, I am going to take an ‘absolutely wild guess’ and pin it on these 2 trees.

Does anybody know any other plants that are poisonous to fish in general? Is cyanide bad for fish?

 

[jjohnwm]

There's cyanide, or at least a precursor that can be converted into cyanide when eaten, in apple and pear seeds...but apparently you'd need to eat hundreds of apple seeds to get anything resembling a dangerous dose of the stuff. My personal S.W.A.G. (Scientific Wild-Ass Guess) is that these things are listed as dangerous to livestock because those animals are herbivores who would be likely to ingest significant quantities of the seeds while gorging on fallen fruit, whereas dogs, cats, people, etc. would not. In any case...is acting "really dopey" a symptom of cyanide poisoning?

It seems possible that evolving seeds that are toxic might be a reproductive strategy of the plant. A herbivore eats a bunch of seeds, wanders off, gets sick and either dies or regurgitates the seeds, and the plant is thus spread?

Now, since the simplest answer is usually the correct one, try this: your pear tree is creating a "petal snow" that blankets the area 2 to 3 inches deep (that is some big pear tree!). If that much dead plant matter falls in your tank, it decays, creating not only a possible ammonia spike but also a condition known to ice fishermen as "winter kill". This happens at the end of the winter under the ice, when the previous year's dead aquatic vegetation decays and all that bacterial action uses up too much of the available oxygen. Fish start to die, and even more pollution and oxygen-depletion occurs.

Maybe this happens in sunny California as well, minus the ice. All those petals fall into the tank and rot, killing your fish. We could call it Surfer Dude Winter Kill if we need to coin a phrase.

It might behoove the Surfer Dude in question to simply net out the petals daily, even if they aren't immediately toxic. The simplest problems often have the simplest solutions as well.

 

[xenacanth9]

+1
That sounds about right.