The Traditional Fisherman's Forum

Not quite so! Mostly sterile is probably more like it otherwise you would not have roach x rudd x roach or bream x rudd x rudd hybrids. Although rare they do exist, same as cru x goldfish x cru!

Rather like humans x humans x humans although they may have different DNA!

I`ll stick with my original premise & Peter Rolfe et al .....

The triple hybrid oddities are just first generation hybrids due to several sperm impreganting an egg at the same time, due to overly close mating between species. As far as I am aware there's no such thing as second generation hybrids, if there were they would be quarters of and not thirds of any particular combination of species! Or perhaps not! A little reading around Google indicates some quite complicated genetics are involved beyond my understanding. Apparently some tetraploid fish hybrids can breed with a parental species to produce sterile triploid's. But this is very rare and thus hybrids are mostly considered as sterile. I think!!!!

Santiago wrote: ↑Thu May 25, 2017 8:16 pm Luckily, the offspring (hybrids) are sterile! Otherwise there would just be one species of a whole myriad of odd looking hybrids and no such thing as roach, bream etc.etc.

Sometimes you get a hybrid that is viable. When the Canary was crossed with a foreign Siskin some of the hybrids were viable. It was by crossing like this that rare colours were put in the Canary. As regards crossing of species the same applies to cage bred birds, you can cross all the finch family with the Canary ie Goldfinch X Canary. You can also cross the finch together to produce hybrids Goldfinch X Linnet, Redpoll X Bullfinch etc. What you cannot cross is say a warbler with a finch or a bunting or Tit with a finch etc. You could probably cross a Thrush with a Blackbird but I have not heard of this cross being achieved. Oh, and a Bearded Tit is not a member of the Tit family and Hedge Sparrow( Dunnock) is not a Sparrow. Some time back I heard of hybrid crosses being offered for sale ie, Goldfinch x Redpoll crossed with a Greenfinch! That's a new one on me. I have never heard of a hybrid being found in the wild, such as a Goldfinch X Linnet, I think you can only force a crossing in controlled caged conditions. Falcons are crossed like this as well, Lanner X Peregrine is an example used in falconry. I am beginning to waffle on here so I will stop.....

Nooo! Interesting these freaks of nature - not the home bred variety tho! Ligers & Tigons!!

Some fish species will not cross as breeding as at a different time - dace & chub (although I have faintly heard rumours of a X being caught/identified).

Just as with fish and possibly all other species (and birds) you can make selective crosses but the resulting hybrids are sterile. Sterile means that they can't mate. Viable just means the hybrids are alive. The very definition of a species is that one species cannot mate with another to produce fertile offspring. However, some very related species are actually only classed as different species because their geography has come to limit their mating potential and examples of this exist in both mammal, fish and birds, where only slight differences are found because over time separate populations have come about owing to geographical barriers and evolution. And if they should now meet, there's a block in mating that might well be merely a minor difference in mating ritual such as a call or flick of a tail. Yet, should they be forced to mate they are so close they would produce fertile offspring. But these examples are rare. The vast majority of interbreeding between two different species produces sterile offspring, such as horses and donkey produce a mule, which is viable yet sterile! It's all part of defining what a species actually is.

I have a copy of the Colin Pitt thesis on fish hybrids and DNA testing and when it comes to cyprinid hybrids this is probably the definitive work. It states that both second generation and back cross (eg roach x bream crossed with roach) hybrids are possible but what tends to happen is that the very high incidence of genetic imperfections in both cases causes development of the fertilised egg, fish fry etc. to fail in nearly all cases long before the resultant fish reaches adulthood. With cyprinid hybrids the ova are more viable than the sperm so a back cross (female hybrid, male non-hybrid) has more chance of succeeding than a second generation hybrid but still few and far between and the likelihood of further generations ever diminishing hence why we don't end up with a 'fish soup' of hybrids. I collect pictures of hybrids and whilst nearly all can easily be identified there are odd ones that would have needed DNA testing to be absolutely sure. DNA testing is reckoned to be better than 99% certain at identifying 1st generation hybrids but this falls to circa 96% for 2nd generation hybrids/back crosses although those figures are far better than what would be obtained through looking at pharyngeal teeth or scale counts. In the lab some hybrids were achieved that don't seem to occur in the wild eg chub x bream although the survival rate was again extremely low. In theory a triple cross is possible eg a roach x bream crossed with rudd....

Some of the rarer hybrids I've seen include bleak x chub, silver bream x bronze bream and silver bream x rudd. Dace x roach is often claimed but all the examples I've seen are just skinny roach. similarly I've seen ide hybrids claimed and although ide ought to be able to hybridise with, say, chub, none have been proven as such in the UK. Roach x chub are rare except for some reason in the Ribble. The hardest 'common' hybrids to identify are roach x rudd and crucian x goldfish, and both of these tyopes of hybrid often catch even experienced anglers out.

Back to crucians, the likeliest wild hybrid is crucian x carp, usually in a small pond where carp have been recently introduced and there is a successfully breeding crucian population.

Speciation isn't a binary, "yes/no" process in many cases; all the many varieties of sea-trout and brown trout are one species, for instance, as are all the breeds of of domestic dog; and the birdie-botherers got their knickers in a royal twist and began to appear worryingly interested in "genetic purity" when the American Ruddy Duck discovered, to its lustful joy, that it could interbreed successfully withe it's Eurasian "cousin", the White-Headed Duck.
Geographic distibution had prevented duckly incest before the interfering hand of man stirred their gene pool; the same hand separated all the different breeds of dog. If a Chihuahua were mated with a Great Dane- - well, one shudders to speculate, but the offspring "ought" to be fertile.

Behaviour, especially preferred mating displays, can also cause and accelerate speciation - the Cichlids of Lake Malawi being a prime example.
Ice-dams, river-course changes, tectonic activities and all sorts of other events and processes can cut populations off from each other, so each develops independently from the other and they drift apart in response to even slight selective pressures; whether man defines them as different species or not depends not on the wonderful accuracy of man's idea of what a species is (or "ought" to be), but on how long the populations had been apart and how intense the selective pressures on them had been.

The nub of the matter being that "Species" and even "Genera" are human attempts to impose order on the chaotic processes of life; the terms should be wielded with caution and awareness of their limitations.

My academic boss ordered a batch of self-coloured (brown) goldfish (Carrasius auratus) because they're cheaper than gold ones, and was most upset when his eagle-eyed technician spotted that one of them flaunted a pair of barbules... it would appear that Cyprinus and Carassius aren't that completely speciated, despite being named not only as different species but as separate genera! One for the DNA analysts to sort out...

Pure conjecture alert, but it seems likely to me that roach, rudd and bronze bream are all extremes of one population that spread out to exploit small, shallow stillwaters (rudd), small rivers (roach) and large, slow rivers and big lakes (bream) and occasionally having their gene-pools stirred up by the accidents of post-glacial geography/geology. Discuss, when bored...

I`m actually finding this vet interesting folks. Daceace & Vole, where to you stand on dropping the carp tag and just being called a crucian?....

"Crucian" seems too obvious an adjective for my inner revolting pedant to accept as a noun; and as they are so inter-fertile with Cyprinus I'd say they were more definitely "carp" than "crucian".
Which is no help, because we'd still need a common name for goldfish-carp. And brown goldfish-carp...and F1 carp... and how sure are we that F1's are infertile? If they're not, what'll we call their babies... and how will we tell?