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#1 The Flying Tench

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Posted 14 October 2017 - 02:46 PM

There is an article in the latest Angling Trust mag on identification of fish for record purposes, and it talks of the difficulty of hybrids. Fair enough. But then it says, particularly for roach, rudd and crucians, that 'traces of hybridisation can span generations.' I thought hybrids couldn't breed, so how come the problem can span generations?


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#2 Phone

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Posted 15 October 2017 - 01:32 AM

Tench,

 

I bet you really don't want to know.

Hybridization, polyploid, diploid, and triploid in fishes even confuses me and I'm the guy that makes stuff up.

 

If you are R E A L L Y interested I'll try to find the simple answer - I doubt there is one.

 

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#3 Mark Wintle

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Posted 15 October 2017 - 06:31 AM

The vast majority of fish hybrids are first generation hence 'F1' for 'filial' generation 1. Backcrosses ie a hybrid breeding with a 'pure' fish are possible as are hybrids breeding with each other but, and it's a big but, there tend to be so many genetic defects in the resulting fry that survival rates are very low and the chance of catching a second generation hybrid exceptionally small even in waters with lots of hybrids. Beyond the second generation (F2) the chances diminish even further and the chance of catching a record fish with a 'trace' of another species ie F3, F4 etc. almost non-existent. DNA testing to distinguish a F1 hybrid from pure species is about 99% accurate which is a lot better than checking photos, and with checking a F2 about 96% accurate. I don't think anyone has had access to any F3s to check such is their rarity.

 

I have many photos of hybrids including ones that include silver bream, bronze bream, rudd, roach, chub, bleak, goldfish, crucians and carp and I suspect that all bar a couple are definitely first generation.

 

I think the AT statement is misleading!


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#4 Phone

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Posted 15 October 2017 - 01:57 PM

All,

I couldn't find the article referenced by Tench. "Hybrid" fish are quite common and can be traced for hundreds of generations (F-100).  "Hybrid Zone", is a regions where genetically distinct populations meet, mate, and produce at least some offspring of mixed ancestry. (I forget the exact word - damn!)

 

Multiple generations of many fishes can be fertile.  Carp have been hybridized for 2500 years in China. We know a great deal about carp hybrids.  For example:

The following carp genotypes are possible:

SSnn, Ssnn - scaled  ssnn - scattered SSNn, SsNn - linear ssNn - leather

Carp with genotypes SSNN, SsNN and ssNN are not viable. N gene is lethal in the homozygous state and embryos die in the hatching stage.

 

Perhaps the best source for Tench's question (?) can be found in the FAO.  As I thought about it - I'm not sure what the question is except to say - of course hybrids can breed - or not. 

 

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#5 Vagabond

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Posted 15 October 2017 - 03:41 PM

What Mark says is quite correct.   However, I have noticed a significant change  during my lifetime.   I have fished since the early 1940s

 

50 years ago, most fish populations were wild, and in the wild different species prefer different spawning sites,   That is usually sufficient to keep different species apart at spawning time. Hence hybrids were comparatively rare and "second generation" hybrids rarer still.  

 

Nowadays, far too many fish populations are overcrowded.    Fish hatcheries, commercial fisheries, and many club waters are grossly overstocked in a never-ending race to provide easy fishing, big match weights "bag-up" (odious phrase) headlines etc etc.

 

Hence fish have little choice of spawning sites when crammed into small overstocked waters - they live in a permanent soup of excess groundbait, fish crap and gratuitous milt from all and sundry (barely kept alive by continuous aeration in many cases) - so there is little wonder that hybrids are very common in such places .   Yes, I know different species are supposed to spawn at different times and different temperatures, but that does not always happen.

 

A mixed bag of silver fish from a small still water will contain plenty of mongrels - so with more hybrids, it stands to reason there will be more chances of second generation hybrids - even though, as Mark says, they are usually ill-adapted for survival




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#6 Mark Wintle

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Posted 15 October 2017 - 04:26 PM

The degree of hybridisation in a water can be used to measure degradation of a water, especially rivers that have been dredged.


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#7 Vagabond

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Posted 16 October 2017 - 07:30 AM

The degree of hybridisation in a water can be used to measure degradation of a water, especially rivers that have been dredged.

Interesting, and at the same time, depressing news.    Obvious enough when one thinks about it - dredging removes all the different spawning habitats, leaving a monotonous drainage channel.   A sort of Procrustean spawning bed that all are forced to use.




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#8 Phone

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Posted 16 October 2017 - 12:49 PM

All,

 

OK, I'll get myself into trouble.  I thought the lakes in Ireland are all hybrid (the species in question)?  I remember hearing that once?

 

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#9 Steve Walker

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Posted 16 October 2017 - 12:53 PM

No, not all hybrids. But lots of them.

#10 Steve Walker

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Posted 16 October 2017 - 01:02 PM

All,
 
I couldn't find the article referenced by Tench. "Hybrid" fish are quite common and can be traced for hundreds of generations (F-100).  "Hybrid Zone", is a regions where genetically distinct populations meet, mate, and produce at least some offspring of mixed ancestry. (I forget the exact word - damn!)
 
Multiple generations of many fishes can be fertile.  Carp have been hybridized for 2500 years in China. We know a great deal about carp hybrids.  For example:
The following carp genotypes are possible:
SSnn, Ssnn - scaled  ssnn - scattered SSNn, SsNn - linear ssNn - leather
Carp with genotypes SSNN, SsNN and ssNN are not viable. N gene is lethal in the homozygous state and embryos die in the hatching stage.[/size]
 
Perhaps the best source for Tench's question (?) can be found in the FAO.  As I thought about it - I'm not sure what the question is except to say - of course hybrids can breed - or not.

You have to be careful when talking about "hybrids" - the term is used for both interspecies hybrids, as we're discussing here, and crosses between different strains of the same species. Those different strains of carp are all Cyprinus carpio. When you buy F1 hybrid seeds from the garden store, both parents are the same species of plant, they're just different varieties of it. When they stock "F1s" in godforsaken British carp puddles, they're stocking a cross between a common carp and a crucian carp or brown goldfish. We're talking the difference between a cross of two different breeds of horse, and a mule.