How tolerant are pond animals of lack of oxygen?

Since the ice and snow thawed quite a few people have been reporting dead fish and dead amphibians.

What’s been killing these animals?

One obvious answer is lack of oxygen, though it may not be the only one.

The goldfish (Carassius auratus), koi carp (which are a form of the common carp, Cyrpinus carpio) and frogs people have been finding dead are all quite resistant to low oxygen levels, the goldfish especially so.

Goldfish can survive for days to several weeks at 0 degrees C in the complete absence of oxygen – and pretty much indefinitely in cold weather with low oxygen levels.

Even more remarkable is the close relative of the goldfish, the crucian carp (Carassius carassius – so the same genus as the goldfish).

The crucian carp is the fish world champion at staying under the ice in winter and can tolerate literally months without oxygen.

Crucian carp are specialised to live in low oxygen environments. They are happy in very silty ponds, like this field pond in Norfolk, and can survive the under the ice in winter for months without oxygen.

Crucian carp are happy in silty ponds, like this pond in Norfolk, with low oxygen levels. In winter they can survive in cold water under the ice for months without oxygen

In carefully controlled laboratory studies crucian carp have survived four and a half months without oxygen. So resistant are these fish that the first people to report their resiliance – who studied the animals in Finland where most ponds are frozen in winter – were not initially believed.

Both goldfish and crucian carp survive by shutting down their metabolisms, and respiring without oxygen. To do this they need a big energy store: the crucian carp’s is huge, the biggest known in any vertebrate in proportion to its size. The goldfish isn’t so good at this but can still survive for a good time.

Our common frogs (Rana temporaria) are also well known for hibernating underwater. They do it in much tougher climates than the UK as well – ranging north of the Arctic Circle – and can hibernate for 8-9 months of the year.

But to do this they need oxygen and, although frogs can tolerate short periods with no oxygen at all, they’re nothing like as good at it as zero-oxygen tolerant fish. Probably 4-7 days is as much as they can manage, not as long as a goldfish, and nowhere near as long as crucian carp.

So frog deaths due to lack of oxygen are likely to come first, before the kind of fish we commonly keep in ponds.

And a strong candidate for the cause of death is lack of oxygen.

But we can’t yet rule out some of the other possibilities completely: poisoning by hydrogen sulphide, carbon dioxide, ammonia or methane, all of which could be present in de-oxygenated ponds, is still a possibility.

But, although toxic gases are often suggested as a cause of amphibian mortality, the jury is still out on on this: an experienced amphibian ecologist I was speaking to this week was unaware of any data or published reports to back up this idea. This doesn’t mean it doesn’t happen, just the evidence isn’t there yet to decide one way or another.


3 Responses to “How tolerant are pond animals of lack of oxygen?”

  1. jonspond Says:

    Some references
    Comparison of nitrate tolerance between different populations of the common frog, Rana temporaria
    Avoidance of anoxic water by tadpoles of Rana temporaria
    The population ecology of a self‐maintaining colony of the Common frog (Rana temporaria)
    Hypoxia tolerance in reptiles, amphibians, and fishes: life with variable oxygen availability
    Tribute to RG Boutilier: The role for skeletal muscle in the hypoxia-induced hypometabolic responses of submerged frogs

    Just a few papers I have found by searching on google

    Can we find the answer we are looking for?

  2. barry mackintosh Says:

    I am Club Secretary of a private syndicate with three on line ponds in north yorkshire.approx one acre.The oxygenated water is stream fed & supports brown trout.We have recently restocked with crucian carp 6inch & 2-4inch tench. in the empty smallest/last pond in line.The average depth of 4ft with some deeper corners.My concern is to their survival chances following the severe winter.I would appreciate any advice as to how confident to be of them withstanding the harsh conditions,and when to begin an intensive feeding programme to increase growth.

    • Jeremy Biggs Says:

      Hi Barry – I have to say we’re not fisheries experts. Fish people in the Environment Agency, or other fishery manages might be better at answering this question.

      For what it’s worth in theory I’d say Crucians should survive anything the weather can throw at them: the survive zero dissolved oxygen for months (they are truly exceptional creatures in this respect: one of the toughest in the world), and live out the winter under ice in Finland. Tench, I’d guess, will be less hardy but being pond fish are presumably reasonably tolerant. However, they do die of lack of oxygen, or simply the cold, in smaller garden ponds.

      As to feeding: I’ve no experience of that. For us, fish are wildlife and have to live with what nature provides! But presumably, once the water warms up in spring they’d be in a position to make use of the feed to do something with it and put on a bit of extra weight.

      Hope that helps a bit


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

%d bloggers like this: