[Trevor]

Just fished a session at Rutland Water and one of the fish was stuffed with eggs. Can anyone explain this when trout can't breed in stillwaters.

[Jim Eddie]

Trevor
Geneallythese days Rainbows are Tripliod, the process involves heating the eggs so that the fish are asexual, neither male or female, so therfore do not produce egss or milt.
However this processis not 100% sucessful and male and female trout are produced. For the eggs to be viable they need to have the correct type of gravel for the female to make a redd, then you need a male to fertilise them, you then also need a flow of water to keep the eggs at a constant temperature.

 

Jim   
 

[Trevor]

Thanks Jim, heard of tripliod trout but didn't know what they were.

Trevor

[Rob Brownfield]

I have caught very black Rainbows from a "local" loch that, at the time, had not been stocked with Rainbows for a good number of years. These fish produced both milt and eggs. They were few and far between, but they were there.

The water has been taken over by a club and is now regularly stocked, but the odd "black" fish is reported.

Steve Parton had a lot to say about the subject of Rainbows spawning but not surviving a wee while back, basically saying that the stock fish used in the UK are a very poor strain and that is why they rarely survive to adulthood. He sites quite a few still waters in Engalnd and Scotland that have spawning Rainbows, but mortality is high if not total due to their inherient weakness. He has an interesting theory that we should import a whole heap on new eggs from the US, from various locations, to improve the genetic make-up of British Rainbows. He is right, farmers have to do this with stock animals from time to time, so why not fish?

Mill of Criggie had spawning Rainbows for a while, and they apparantly survived, although the spawning gravel runs in the feeder streams have been destroyed, I believe.

Lastly, Rainbows can and do spawn in still waters all over the world, with some waters having no feeder streams at all, but rely on springs bubbling up from the lake bed to supply cool water and a constant flow.

[Trevor]

Very interesting Rob, maybe odd fish spawn in reservoirs like Rutland Water where they have 'boils' then??
The point that has been made about farming seems like a valid one to me if the future of good quality fish is to be preserved.

thanks

Trevor

[Hamish Young]

Jim has pretty much nailed it there.

Triploid fish (trout, in particular) were developed principally for the 'table' market where fast growing fish with a low food to weight conversion ratio year round is a prime requirement. From the egg treatment process (which can be shock, heat or chemical but more likely pressure vessel today) to first feed there is little to differentiate between triploid and diploid (normal fish) but in my experience from that stage on triploid fish tend to be harder feeders with a better survival rate.
All of the methods of creating triploid fish have their drawbacks and I recall from college days that around 10% of the fish would end up 'conventional' after the egg treatment process. These days, particularly with pressure treatment, that figure is apparently more like 1% but I'm sceptical if it really is that low. Then again, I've been out of that field of work for 20 years or so and all is possible.
It is worth noting that a triploid fish is also sometimes called 'all female' and as an 'all female' they will go on to produce eggs. However, they seldom make any attempt to spawn and the eggs are generally absorbed back into the fish. That's why we find eggs in the fish, even though they can't 'use them'.

I recall reading somewhere, and I don't recall who the quote was from (maybe it was me ), that the average 'bow in the UK has more in common genetically with a banana than it does with it's wild kin in North America. Whilst that amuses me no end it's not really true as 'bows in the UK have been selectively bred to begin with and subsequently 'managed' to produce table fish. Remember, the table market (particularly in England-shire) is the driving force in trout farming and whilst there is a healthy market in producing stock fish it is of secondary interest to most producers; we the anglers live with the legacy of that work.

So whilst Robs suggestion that some 'fresh blood' is a valid one for the production of 'sporting' fish the facts are that the principal commercial driving force have what they want and it is unlikely that will change any time soon. Rob is also quite correct to assert that trout (of all types) can and do spawn in still water all around the world. Not a first choice, I'm sure, but if you want a shag then force majeure takes over.....

H

[Peter McCallum]

I had a discussion many years ago with Dr Andy Walker, from faskally, who said they had observed rainbows spawning in several places and that the young survived and grew on, however the second generation spawning never produced young.

There are many lochs where trout spawn in the shallows and the wave motion provides enough oxygen for the eggs to survive and hatch out.

[Derek Roxborough]

The Bows in the Uk are supposedly hybrid between Shasta and Kamloops , this was supposed to diminish the migratory tendency,we can see both brown and Seatrout spawn at the lochside in suitable locations in this area, they manage to redd and spawn you can go round some lochs in the spring and see where the redds were, some lochs here with a decent head of trout have no proper spawning burns but still manage to breed, easgach 1

[Trevor]

Quite strange really how all this genetic modification goes on in fish & meat farming but yet so many people are outraged at modification in fruit & veg.

Thanks for your input everyone in this topic, it has been very helpful, as a new forum member as well as being reasonably new to fly fishing i feel that you guys can teach me quite a bit. I'll post another topic in due course which i need help with.

Thanks & a happy new year, Trevor

[Hamish Young]

Quite strange really how all this genetic modification goes on in fish & meat farming but yet so many people are outraged at modification in fruit & veg.

Thanks for your input everyone in this topic, it has been very helpful, as a new forum member as well as being reasonably new to fly fishing i feel that you guys can teach me quite a bit. I'll post another topic in due course which i need help with.

Thanks & a happy new year, Trevor

All the best to you and yours for 2013 Trevor.

Just to be clear though, what we've discussed in this topic with regard to fish is not genetic modification. That's a whole different subject which we don't need to go into right now..... interesting though it is

H 

[Marc Fauvet]

Just to be clear though, what we've discussed in this topic with regard to fish is not genetic modification.

good on ya for pointing that out mate.