Triploid Rainbow Trout

mike2

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Sep 9, 2016
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I have been fishing my local reservoir for the last 6 seasons. It is approximately 250 acres, and 40ft deep when full, reducing to around 20 feet when low in mid to late summer.
It has a good head of small wild Browns - a fish of 1lb is a good one, and these Browns feed right through the season.
Every season the reservoir is stocked with 2,500 Triploid Rainbows averaging 1.25lb over the first 3 months of the season. These provide good sport during April, May, June and the first half of July.
As the water warms and the level drops during the second half of July and through August, the Rainbows virtually disappear, and anglers fishing anywhere in the lake, at any depth from either bank or boat are very lucky if they catch one.
This is quite normal during the dog days of summer, but for the last two seasons, the autumn has not seen the return of these Rainbows to feeding. Fry bashing has become a thing of the past, and I have not seen any over- wintered fish caught this season or last.
According to catch returns, there should have been a balance of around 1,500 Rainbows remaining from the stocking after allowing for fish taken and some Cormorant and Heron predation.
The wild Browns are surviving the winter and breeding, but it would appear that the stocked Triploid Rainbows are dying off during the summer.
This has only seemed to start to happen in the last 2 or 3 seasons. I remember very well catching good condition over wintered Rainbows which had actually increased their body weight since being stocked the previous season when I first started fishing this lake 6 years ago.
I am of the opinion that the process of breeding and producing these Triploids is rendering them less and less able to cope with life in the wild. I think they have become "domesticated", vulnerable to predation, and unable to adapt to higher water temperatures and lower oxigen levels during the summer.
Our wild Browns appear to have the genetic make up which gives them an ability to adapt to changing conditions, and instinctively be wary of predation.
I would be interested to hear others views on this issue- has the breeding of Triploids become too far removed from the original stock of wild Rainbows from which they have been generated?
Environment Agency and European policies are clearly against the stocking of wild fertile Rainbows into virtually all UK stillwater fisheries, irrespective of whether they are connected to other river systems, so we appear to be stuck with the put and take practice of stocking Triploids.
Is there anything which can be done to help their viability in the wild?
 
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guest54

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A natural lake/loch without human interference, would have a range of sizes of trout in. What would be the maximum size?, that determines what the water can support. With our stocked fisheries, we put in more trout of a greater size than the water can naturally support, it's a business, what we don't like to think about is that we as anglers support a system that treats those trout as disposable objects, yes we use barbless, we play and handle and unhook the fish carefully, we make sure that it swims away strongly, but the reality is that most of those trout we return so carefully are doomed to die of starvation or disease due to a dramatic loss of condition over winter.
My personal view is that we need to look again at where and when we practice catch and release.
 

fredaevans

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+1 to 54's comments especially this one: "My personal view is that we need to look again at where and when we practice catch and release."

Here where a lake is stocked (most are) it can be a catch and keep requirement to 'thin the hurd.' (Did I spell that right?)

fae

Edit: Dang almost forgot! Welcome to the Board Mike.

Fred
 

campsiefisher

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It has a good head of small wild Browns - a fish of 1lb is a good one

If you had a good head of natural brownies, and a brown of one pound is a good one, that would suggest to me that there is not a huge abundance of natural food to sustain the brownie population thus keeping them all under the one pound mark. If it had a huge abundance of natural food your browns would be bigger.

Every season the reservoir is stocked with 2,500 Triploid Rainbows averaging 1.25lb over the first 3 months of the season.

Throw 2.5k of rainbows into the mix, i'd also have to assume you just made the food chain even more scarce, it also seems madness not to trickle stock if the food chain isn't there.

I am of the opinion that the process of breeding and producing these Triploids is rendering them less and less able to cope with life in the wild.

If your triploid theory was correct, why do you think other venues of mixed and wild stock are thriving with many overwintered specimens caught regularly.

Rainbows at just over a pound are prime cormorant snacks, don't be fooled into thinking you only lose the odd fish, to them.

Is there anything which can be done to help their viability in the wild?

They're not "In the wild" it's a stocked reservoir you have with a head of naturally small brownies, much like most rainbow fisheries.

Best regards
Jim
 
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ohanzee

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has the breeding of Triploids become too far removed from the original stock of wild Rainbows from which they have been generated?

Your reservoir is far from wild rainbow habitat, if anything its closer to a stocked rainbow habitat if that makes any sense, I'm not sure rainbows in the UK make sense in the context of 'wild' or 'natural'.

Why not stock browns, or stop stocking at let the natural population thrive.
 

BobP

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That reservoir sounds very similar to Farmoor in size. A fair bit deeper, and a greater draw-down, but Farmoor produces over-wintered rainbows in large numbers. Actually, it is as good a winter fishery as it is a summer one if you are prepared to adapt tactics.

I would like to know more about the location of this reservoir, what feeder streams there are and the water quality. Is it alkaline or acid for example? That will have a significant bearing on food production and fish survival.

A good indicator would be the stomach contents of the rainbows that are caught a few weeks after stocking.

There is a whole lot more to running a fishery than just chucking fish into it.
 

mike2

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The reservoir is Stithians which is located in west Cornwall, and the earth is very Peat based, with perhaps some Granite substrate. I would accept the argument about the inadequate food supply accounting for loss of fish, but the situation with respect to non survival over winter has only occurred in the last 2 or 3 winters. Prior to that, there was a good rate of survival.
The Rudd population is positively thriving at the moment, producing near specimen sizes of Rudd.
I am getting more and more convinced that the Rainbows currently being stocked are less hardy than thise of a few seasons ago.
 

jeffhirst

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Those small rainbows are cormorant fodder. Also just because coarse fish are present it does not follow rainbows will overwinter. I suspect that those rudd mop up most of the food in the lake. Lakes like Chew and Blagdon have very few over wintered rainbows(except for those feeding on pellets underneath the cages) and if you catch one they tend to be long and thin but with huge tails.
 

BobP

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In any given water body there is only so much food to go round. The rudd are invertebrate feeders and are also predominantly mid-water to surface feeders so if they are thriving that tells me they are very well adapted to the water and are creaming off the bulk of the inverts before the rainbows can get to them, especially in the spring and early summer when the rudd are at their most active.

Triploids, whether brown or rainbow, are better able to make good use of a fertile water as they do not come into spawning condition. On that account and given the right conditions they will feed happily all winter and continue to grow.

I doubt very much that triploiding is having any effect on the Stithians fish as far as their ability to feed is concerned.
 
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guest54

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doubt very much that triploiding is having any effect on the Stithians fish as far as their ability to feed is concerned.

Rudd and Roach can carry big loadings of parasites that have only a small effect on themselves and don't stop them breeding at all, but they may have an effect on trout, gill maggots can reduce a trout's ability to absorb oxygen through their gills, although this in itself may not kill them it can weaken them enough for them to lose condition fast. Have there been any checks on the health of the resident fish, I don't mean the ones you catch, sick fish are unlikely to take your fly. If you think the mortality rate is too high contact the EA and ask for their advice.
 

mike2

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Thanks for that Bob P - your comments about the thriving Rudd are very plausible, particularly as the Rudd epidemic has occurred coincidentally with us noticing the drop off of surviving Rainbows.
Dont know why we should suddenly have a plethora of Rudd though, but we certainly have.
Its a bit chicken and egg really- the Rudd could be thriving because the Rainbows are not feeding in the warmer water conditions of recent summers?
Still no further forth in understanding what we should recommend be done to improve the year- round fishing.
Maybe we should stop stocking altogether and make it a catch and release Wild Brown Trout water.
Or perhaps we could try reducing stocking levels by half, and focusing some effort on improving the environmental ecological conditions by planting and other projects.
Thanks for your interest.
 
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guest54

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Dont know why we should suddenly have a plethora of Rudd though, but we certainly have

Good years and bad years, the Rudd in my pond have spawned multiple times this year, three times by my reckoning but it could be four and their at it again as I type. Last year they spawned twice, it's anyone's guess how many are in there now.
 

BobP

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I would think that the first course of action is to get a health check carried out on all the fish species in the reservoir if at all possible. Rudd, brown trout and rainbows. You would be looking at around 100 fish in total to give you a range of sizes across the species.

The rainbows, of course, will have a health check carried out at 6 monthly intervals on the fish farm, but it would be a useful comparison.

It will cost a bit, but without knowledge of the current health status of the fish, you are groping in the dark.
 
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