Animals of Pauline's Swamp
Burwell brook	New River	Burwell Castle		Paulines Swamp		Demolition	Local walks

Crayfish

It is reported that, at the Swamp Open Day in September 2016, two crayfish were caught in the main pond at Pauline's Swamp - an adult (unsexed) and a juvenile. In March 2017, one juvenile crayfish was caught and photographed.

However, at the open day September 2nd 2018, that that a large crayfish had been caught in July 2015. I was told that this was about 5 or 6 inches long overall - which is as large as the native white-clawed crayfish gets.

The one we photographed looked like a British native White-clawed crayfish (Austropotamobius pallipes) so I contacted the Cambridgeshire Wildlife Trust who contacted the Environment Agency. On March 2nd 2017 two officers from the E.A. and myself spent several hours trying to catch a crayfish - without luck. Traps were laid, and collected again on Friday 24th. But the search proved crayfishless.

I continued, for a few days, to lay my trap either in the main pond or in the neighbouring feeder pond, without luck.

In 2019 the pond dried up completely. There was no evidence of crayfish. It appears that the crayfish were not resident but had been introduced recently and had not survived.

How could crayfish get into this pond?

Introduction by dumping.

Could someone have caught crayfish elsewhere and have deliberately dumped them here? I find this unlikely - there are no nearby sources of crayfish and there is relatively little pond-dipping in this pond. But if this is the method, these will not be British native White-clawed crayfish, but will be Signal Crayfish.

Historical invasion.

Long ago, before the factory was built (around 1957 according to British History on Line) the area was a commercial watercress farm. The springs that were here were capped off by concrete when Tillotsons built the cardboard-box factory. The springs must have fed a significant stream where crayfish were living and able to inhabit the watercress beds. If these are the remnants of such a period, then the pond in the neighbouring property that feeds the seasonal stream should also contain crayfish - it is spring-fed rather than the ground-water-fed pond in the swamp!

However a crayfish trap was put into the feeder pond for 4 days. The only catch was a number of water beetles and a stickleback which was almost certainly infected with Schistocephalus tape-worms. This pond is shallow, overgrown and apparently nearly sterile, so historical invasion seems very unlikely.

Introduction by bird.

It is theoretically possible that a female crayfish with attached young could be caught by a bird. The mother with babies could then have been dropped when the bird visited the pond. The Environment Agency officers agree this is possible - but they are unaware of any such case occurring. If this is what happened this would account for the inability to catch specimens.

So we have three unlikely possibilities. We shall probably never know the truth! But if you have anything to add to the above, please contact me.

Crayfish Identification

• The white-clawed crayfish (Austropotamobius pallipes) - the only indigenous species.
• Signal crayfish (North American) the main cause of the decline of the native crayfish.
• Turkish narrow-clawed crayfish (Eastern Europe)
• Noble crayfish (Astracus astracus) (European) found in South West England
• Red Swamp Crayfish (American) found in Southern England
• Spiny-clawed Crayfish (North American) known in two locations, on in the Midlands, one in the East
• Virile Crayfish (North American) found in River Lee, North London.

There are some pdfs supplied by the Environment Agency to assist in identification:

• Crayfish fact sheet the differences between the White-clawed and the Signal crayfishes.
• Crayfish identification - the six non-native species.
• Crayfish leaflet general hints on crayfish and what to do if you see one.
• Crayfish photo identification these are the types of photo I would need to take to confirm identification!

Other information on crayfish

Diary

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