Spinning for Brown Trout on Lough Corrib

The biggest loss is to flyfishers. Here are some of the factors that have been at work in my opinion:

The roach are now established. The larger trout can eat roach which are compact and nutritious, and more satisfying than a tiny fly. A 5lb brown taking one 5 ounce roach every second evening at dusk does not help fly fishers. Anyone out there using using 8" lures for trout?

Zebra mussels significantly reduce tiny organisms that both trout and coarse fish need to survive and grow, so after zebras are established, the mortality of all young (year 0 class) fish increases, and the numbers of adult fish eventually reduces. They grow bigger due to there being fewer of them, so zebras function as a reducer of other fish numbers, as a result of competition for food at the young fish stage.
Some coarse fish consume zebras, and these may thrive, but in fewer numbers. Tench and bream caught are for example bigger in recent years. However a link to zebras is not proven as far as I know, also climate warming will also contribute to coarse fish (warm water species) growth. Warm water is a bad effect on cold water species, like trout, putting them deep in refuge from over hot temperatures.
Therefore climate change is a factor that messes up traditional surface fishing techniques for trout. The cool of the night they come up, but drifting with wet flies is not the best at that hour.

You could say about the changes just mentioned, that Corrib and Mask have taken a slight shift in the direction of Ree or Derravaragh; And Ree, Derravaragh, Derg, Ennell and Sheelin have taken a slight shift towards being coarse fishing lakes ..... so much so that Derravaragh is pretty much now a coarse lake. Trout are now fewer, bigger, more fish eating in their habits, and harder to locate than they used to be. This change is particularly noticeable on Lough Conn.

Then you look at the number of anglers nowadays compared with 30 years ago. They don't all return their catch .....

Finally, in the catchment of many lakes, the OPW have dredged the gravel out of the spawning streams in "land reclamation" programmes, which were actually political vote getting projects.
These projects have been ongoing for 50 years now. You can dig up a lot of river bottom in 50 years with a Hymac.
They have a major effect on all fish stocks, but especially game fish which need fast water and gravel, both are which removed in OPW widening and deepening operations.

Water quality has gotten worse over 30 years, and may be getting better now. It helped destroy many waters, but is probably not worsening the situation any more. But midge species have been favoured by enrichment for a long time, which are easily eaten under the surface, and harder for fish to catch on the surface. Midge eating trout taking suspended midge pupae in a layer underwater require different fly fishing presentations, which works against the traditional over the front of a drifting boat lough style. Adaptable anglers do well with suitable techniques.

Next we get to genetic quality. What do you think happens when you kill the healthiest and fastest growing trout within a population for 50 years? At the same time returning the weak small ones to reproduce and make the next generation ...... year after year culling the strong and releasing the weak ...... you end up with dwarves, that's what!
We now need catch and release for decades, with both big trout and pike culling the weaker trout to make the genetics of the stocks good again. But it's hard to allow predation when we already know that total numbers are down so much. So the simultaneous rehabilitation of streams, and acceptable predation levels are all we can stand. Sorting this out will take many decades.

jkchambers wrote: »

.... At a meeting of anglers in Galway in February to discuss the Corrib survey one angler suggested that instead of ban on the taking of trout under 14 ins(I think that was the measure) there should be a reversal to a ban on the taking of trout over that length.

This would be the correct thing to do in my opinion, to slowly allow the genetic stock to be restored to longer lifespan-larger trout.
They have evolved to deal with death at a young age from angling harvest, so we now have fast growing short lifespan trout, (ferox are an exception as they live longer than ordinary trout).

The natural state would be for trout that increase size a little slower, and also live a lot longer, and get to larger sizes in their life. But that depends on a reduced mortality rate. As long as we have a great number of anglers, this means catch and release.
Encouraging anglers to kill and remove smaller trout (or any other species of fish) does not automaticaly mean removing the weaker genes. This is because the anglers would be focused on small young trout, not small older trout.
But predation and disease are going to do their job over time, if we let them do it.

In Irish lakes, if zebras reduce small fish numbers, it would be relatively easy to cull perch in their spawning time by dropping bushes in the water, on which some eprch spawn, and then removing the bushes with the spaw attached, thus reducing the amount of perch spawn success, and their numbers before they start to eat all around them. Not intending to eliminate them, but to reduce their biomass(numbers) a certain % amount. This reduced predation on small fish would balance against small fish death due to shortage of plankton from zebra infestation. I'm sure research would produce some guideline on effect of fry predators (perch) vs fry food competitors(zebras) and their relative effect on fry survival.

Is perch spawn reduction necessary on fertile loughs in the first place? Probably not.
But in the less fertile lakes I believe a programme of % perch reduction might benefit all other fish numbers, bream, tench, rudd, including bigger perch! Big fish numbers are a function of the strength of the year class from when they were born. More baby bream this year = more 10lb bream in 12 years from now. The question is: are the adults too many in numbers and stunted, or too few and enormous? Does the lough have too many fish and it needs more predators, or too few fish and need some sort of a predator reduction (perch spawn removal)?
When we look at this aspect of a lough biosystem, we find ourselves talking about maintaining a balance in quantity of good spawning area for each species, which is definitely the way forward in the future.
If we arrange for adequate spawning area for each species of fish, the fish will to a large extent look after themselves for the rest of their life.
The trout probably suffered most due to dredging operations down the years and need much help in this regard.
The fishery biologists are paying great attention to this approach now as a result of research findings.

When we say "predators" people assume we are talking about pike.
But not necessarily. Perch are a predator and an insectivore, as is trout.
So perch both compete with young trout for food items, and also eat baby trout.
Perch made a cycliclical high in numbers over the past decade, and seem to outnumber the trout by 50:1.
It will be interesting to see what changes occur (in the other species) when perch eventually swing back into a cyclical decline.

And then there is the roach, introduced into those lakes at or about the same time trout began their one way decline ...... roach are likely what pushed arctic char over the edge in Corrib.

If trout anglers were in the habit of recording numbers of all species caught, over the seasons, (instead of just trout numbers caught) the decade long struggle between different species for resources would be very clear.
But since they don't keep such detailed logs the fishery surveys are all we have.