Anglers often notice things about fish that scientists and naturalists miss. Please contact me with details of any crucian behaviour that you think might be unusual or remarkable. In that way we can perhaps add to the general understanding about this fish.
For example, if this winter proves to be really severe we may find crucians surviving where other fish die from winter kill. If you have first hand experience of this please let me know.
Another example: do crucians live and thrive only in still water? - If you know where they can be caught from a river, please tell (it's certainly the case that some crucians can be found in the River Thames, as Justin Gray's magnificent 4lbs 2oz crucian from 2014 shows). What about canals? - Do they any hold crucians?
How common is it that crucians feed at night?
Have you watched them spawning? - how did they behave? When did spawning begin? Did it happen just the once or was it repeated throughout the summer?
It's often stated that crucians don't feed in winter. You'll often read that that they "hibernate" "in the mud". Our experience here suggests that's not always so and that they can be caught, mainly after dark, way into the winter, like carp. Have you found the same?
Crucians often feed in very shallow water. Do you have any experience of that?
Can you suggest why crucians "roll" on the surface - can you tie it in with feeding, for example?
Do the crucian shoals consist of fish of about the same size, or are they of mixed sizes?
Do crucians feed with other species so that you end up with a mixed bag? Or do other fish crowd them out - or vice versa?
Have you noticed shape changes in your crucians over the years? Any suggestions why? Can this be linked to predators being added to your lake or pond, for example?
These two photos show very well how a fish's environment can affect its colour. Martin Bowler's beautiful big crucian is from a clear and weedy lake; Dave Redwood's from a muddy commercial pool.
Mark Wintle sent this up-date on his aquarium crucians.
I've noticed that the crucians have been pulling off the leaves on the plastic plants in the aquarium. As replacement plastic plants cost £8 each, I gathered a big handful of willow moss, Canadian pondweed and hornwort when out fishing, washed it, and placed it in the aquarium. The crucians love it. They chew on it, burrow into in it and look for food underneath it. It also seems to have improved the water quality in the tank, and the crucians seem more active as a result. They've grown tame enough to nibble on my fingers when I feed them.
So, aquarium crucians do eat plants. Do they in the wild, too? And they are tameable!
If many of the crucians in our swim feed like this, it's not surprising that the float does strange things. Photo by Mark Wintle.
JAA() - I agree, I've seen my crucian in a tank do the same and so fish a modified lift rig with a no. 8 'tell tale' and a very light float, which has a very thin cane antennae. You see exactly that, a slight dip, which I take to be the fish's body pushing the line and then a lift. You wait for the lift...
Mark Wintle sent me some observations on his aquarium crucians:
I've kept a 20 gallon aquarium for many years, and mostly kept goldfish. I've also had tiny tench and rudd in the tank, though no longer have them. When I helped do DNA testing on crucians I kept one of the fish in the tank to see how it recovered from scale removal and fin clipping.
Scales were replaced in about 6 weeks, and the fin re-grew in about 8 weeks though there was a slight scar. When that crucian died after about 2 years I got another one of similar size to keep the goldfish company. But eventually the goldfish died so Peter has kindly let me have three tiddler crucians to keep the other crucian company.
I love watching the crucians in the tank. They know how to 'beg' when hungry - they come to the front glass and shake their heads.
They feed in different ways. The original crucian went beyond vertical in feeding - the cause of crucians pushing the line to create finicky bites - but its replacement prefers to feed at about 40-50 degrees to horizontal. The replacement also prefers to feed moving upstream against the flow of the filter. This means that as he sucks up and spits out the aquarium gravel he slowly builds a sloping gravel bed. If I re-level the gravel he will put the slope back inside a couple of weeks. He isn't very big - maybe 5". He will also take food from my fingers, and will surface feed.
The newest arrivals are smaller - 3" fish. They are quicker off the mark at feeding time but the bigger one will push them out of the way, though they sometimes nip his tail in return. They also pick and blow the gravel but having smaller mouths can only pick up one stone rather that three or four at a time. They also feed at the same 40-50 degree angle, although one of them will feed vertically sometimes.
The filter is adjustable to change the flow. The crucians don't like flow at all so the filter is set to the minimum flow. If the flow is increased they find the quietest corner and sulk.
Before the introduction of the tiddlers there was a lot of silkweed on the plastic plants but the new fish have eaten all of the silkweed and pulled off many plastic leaves.
Mark told me on the phone that his crucians will often pick up a piece of food, lift slightly off-bottom and then remain in that one spot, chewing in the meantime. Translate that into fishing terms and it becomes a slight lift bite and then a motionless float. Quite often I've found that if I strike a second or two after that, I hook the fish, and we all know that it's quite common to hook into a crucian without having had a recognizable bite at all. Perhaps this is the reason why.
After a heavy and prolonged shower, out came the sun and the crucians immediately began to rise - yes, rise - to a hatch of flies. They were definitely taking insects from the top and chasing nymphs sub-service. A one-off, I wonder?
A thought from Mark Wintle:
"A Dorset lake was stocked a decade ago with 100% mirror carp and genuine (DNA-tested) crucians. After 5 years the two species interbred and the resultant F1 hybrids are 100% fully scaled. Are there any known examples of F1 crucian x carp that are mirror-scaled?"
I observed the following at the Wetland:
I thought that the pipe that carries the water from Pond 5 to Pond 6 (the one with small pike in) was not flowing properly. When I lifted up the screened end in Pond 5 I found crucians struggling to escape. They'd obviously swum up the pipe to get into Pond 5. There were 16 of them. Today there were another 12.
Out of curiosity I checked the feed between Pond 5 and Pond 4. On the first day I found just one rudd. Today, nothing.
So, what's the explanation? My current theory is that the crucians were anxious to escape the attentions of the pike in Pond 6. I know that something similar happened at a two-lake fishery near here, where the owner put crucians into a pike lake and found most of them in the eel-trap shortly afterwards, where they'd tried to escape from the lake. That was downstream; in my ponds the movement was upstream. But in my pond the downstream exit was screened so the fish had no option but to go into the pipe at the top of the pond.
Is this another example of how crucians can disappear from a water? Has anyone a similar experience? Please let me know.
Mark Wintle sent me his thoughts on some of the above: