could pine needles falling in a pond cause fish deaths

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I can't see any reason why they should, and have not heard of any.

Many of our wild and farmed waters are surrounded by pine forests, and must suffer from needle drop and leeching from the forest banks.

But they still hold a heathy stock of coarse or game fish.

Anybody any info on this ?

Large quantities of any sort of leaves falling into the pond have the potential to cause problems in the long term; a build-up of rotting vegetation will gradually lower the pH, the layer of debris may become anoxic and start to generate hydrogen sulphide, and if it subsequently gets stirred up the combined effect of the oxygen demand of the decomposing debris and the released gases could cause a problem.

By and large, though, I'd say that they are unlikely to be causing an acute problem.

stock being the opperative word
The increased acidity along with released alkaliods from pine needles breaking down has ruined many a Scotish trout stream in pine forestries creating a shortage of truely wild brownies spawning in streams that run into some lochs.I was watching a documentry about the very topic some time back. But can not remember the title May have been one of the Bill Oddie ones.

This post has been edited by five bellies: Apr 3 2008, 08:14 PM

I for one can think of at least four reasons why a fall of conifer needles in your pond could kill fish. Depending on the species, "pine" needles can contain: terpines, phenolics, polyphenols, resins and a whole host of other natural, but nasty chemicals. Pine needles take a long time to break down and compost because of these chemicals in them.