fish dying

[carobry]

lost 4 big fish this winter. had water checked today and all ok. anyone else lost more than the usual amount this year? frog life booming!

[Dogghound]

Has the pond been frozen for long periods of time?

[lipase]

yup I lost lots of sticklebacks! Fortunately my bullhead are alright and atleast one weather loach remains. I read somewhere on the waterlife forum that a new theory about why the fish die has been thought up as opposed to just oxygen starvation?

Frog life is definitely booming; I saw 3 or 4 clumps of frog spawn today in a ditch!

[Dogghound]

Decaying matter uses up oxygen, the frozen surface prevents oxygen diffusing through the surface from the air and you end up with low levels of oxygen in the pond.

[carobry]

did try and break the ice daily. will wait till the summer b4 replacing the fish. stood last nite and listened to the frog chorus going on in and around the pond.only have frog spawn though (lots of it). thinking of getting a set of night time binoculars so i can watch the goings on without disturbing them all!

[Rashmika]

It might sound daft, but putting a ball in the pond helps enormously.

I was trying to keep the ice off by using a boiling pan seated on top of it, but I was having to do it everyday. The ball trick worked perfectly, as long as you remembered to put it back before the pod froze over again.

[lipase]

Originally Posted by Rashmika

It might sound daft, but putting a ball in the pond helps enormously.

I was trying to keep the ice off by using a boiling pan seated on top of it, but I was having to do it everyday. The ball trick worked perfectly, as long as you remembered to put it back before the pod froze over again.

You're a genius, I was there trying to pour boiling water through 5 inches of ice. Ended up resorting to having a fire in a quality street tin which didn't work that well either. Didn't think about using an object to prevent it in the first place

[Malcolm Banks]

The latest work on WL ponds (mentioned on another thread) appears to debunk the concept that oxygen levels can be maintained by making a hole in the ice (On BBC site but sorry, can't get the hyperlink to work). If oxygenating plants are still green (as were many at the bottom of my pond) over the winter, they still have photon-trapping chlorophyll and so will still produce O2 by photosynthesis. The ice acts as a seal allowing build up of O2to beneficial levels for pondlife in general (although no doubt this is moderated by the extent of the negative effects of other decaying plant/animal matter). Making holes in the ice is ineffective at significantly increasing PO2 at the bottom of the pond.
The article did say though that ponds with fish or with high concentrations of decaying plant material were excluded from this beneficial effect.
Is this because fish have a higher O2 demand than a torpid frog, or is there another reason (higher susceptibillity to toxins??) Maybe Dogghound can help
M

[Dogghound]

Originally Posted by Malcolm Banks

The article did say though that ponds with fish or with high concentrations of decaying plant material were excluded from this beneficial effect.
Is this because fish have a higher O2 demand than a torpid frog, or is there another reason (higher susceptibillity to toxins??) Maybe Dogghound can help
M

I think the issue with a frozen pond is that detritus in the bottom of the pond decomposes and uses oxygen, the plants still produce oxygen and the water contains some dissolved oxygen but when this rate is slower than the rate of decomposition and respiration (using oxygen) of organisms in the pond then the oxygen level reaches a critical point in which death occurs. Fish not only use up oxygen but they also produce lots of waste which contributes to the drop in oxygen (i.e further decomposition, nitrate input). To futher the damage fish often cloud water stirring up the bed blocking light to plants. Prolonged thick ice also inhibits photosynthesis which further reduces oxygen. It is important to consider if the pond size can sustain the number of fish. Frogs require less oxygen than fish as they can drop there metabolic rate lower than a fish, so fish (especially large ones) feel the affects first. Frogs can suffer though, alot is dependent of the individual pond.

I can explain further if you like, I assume this is what you mean

[Malcolm Banks]

Yes thanks for this Dogghound, a most comprehensive response
M