Lough Ree Stock Assessment Survey Results

jkchambers

Link http://fishinginireland.info/news/wp-content/uploads/2014/07/ReePreliminarysurveyreport28714.pdf
.
.

Furez

Very interesting report. The relationships over the last 40 years on other waters, between >eutrophication >roach >pike size >zebra mussels <roach <pike size, are well documented here.

These zebra's sure seem to be having a huge impact, wonder how it will all balance out, or even if it will get time to before the asian clam hits.

Budawanny

If I read that Zebra Mussels have improved water quality, reduced the invasive Roach species, and increased the Native trout species.
Did i get that right?

jkchambers

Budawanny wrote: »

If I read that Zebra Mussels have improved water quality, reduced the invasive Roach species, and increased the Native trout species.
Did i get that right?

I only had one quick read of the report. I will carefully read it over the weekend. Zebra mussels generally improve the water clarity not necessarily quality. Roach number do fall off a lot. I dont think they helped increase trout stocks. They compete with younger trout for food on the bottom and this may encourage the trout to surface feed on flies etc which will make them easier to catch

Bio Mech

Budawanny wrote: »

If I read that Zebra Mussels have improved water quality, reduced the invasive Roach species, and increased the Native trout species.
Did i get that right?

In the short term they can remove suspended particles which can clear the water and improve trout catches. In the longer term they lock up a lot of the available biomass, carpet the bottom of the lake and supress other invertebrates and thus turn large areas of lake bottoms into desert. They can also reduce spawning areas for species who don't spawn on plants, reeds etc. Even in moderately fast flowing streams they can adhere to rocks, pebbles etc and prevent Salmonids spawning.

croo

Looks like it might be an interesting read okay.

A total of seven fish species were encountered in the course of this survey -Bream, Eels, Perch,Pike, Pollan, Roach, Rudd and Trout.

I'd never even heard of Pollan!


It's not a topic I would having any expertise in but I remember googling zebra mussels a few years back and I thought I'd read that they were food for roach. I don't remember what site I found that first time but I just did a quick search again and found this site. Which says

Most fish can't eat zebra mussels because they can't crush the shells. A few fish species have specialized teeth and jaws that are strong enough to break the shells of mollusks, and some of them do eat zebra mussels. In Europe the roach, is a major predator of zebra mussels, along with bream, and silver bream. Round gobies and common carp, native to Eurasia, have been introduced to North America, and eat zebra mussels where they occur.

I only glanced at the report but noted

Since the zebra mussel stock became abundant roach standing crops have declined markedly

Why is it that these mussels and have not resulted in a boom for roach (and bream) that feed on them rather than the decline noted in the report? Are our roach different from those in the rest of Europe?

Bio Mech

croo wrote: »

Looks like it might be an interesting read okay.

I'd never even heard of Pollan!


It's not a topic I would having any expertise in but I remember googling zebra mussels a few years back and I thought I'd read that they were food for roach. I don't remember what site I found that first time but I just did a quick search again and found this site. Which says
I only glanced at the report but noted
Why is it that these mussels and have not resulted in a boom for roach (and bream) that feed on them rather than the decline noted in the report? Are our roach different from those in the rest of Europe?

The adult shell are far too big for anything but the very largest (record sized roach) I would have thought. I don't know where that website gets its info. Bream could probably handle them and larger hybrids but not, the majority at least , of Roach.

Roach populations are by nature very volatile as they reproduce in huge numbers. When the conditions are right their populations explode.

Cloudy eutrophic water suits roach. Cover from predators, advantage over competitors (they can tolerate lower oxygen levels), abundance of their preferred food. In clear low nutrient water they don't do quite so well.

uch

Lads if Pollan are so endangered, why did they keep all 28 captured ? Makes no sense what so ever

Bio Mech

uch wrote: »

Lads if Pollan are so endangered, why did they keep all 28 captured ? Makes no sense what so ever

They may have been dead in the nets.

croo

The adult shell are far too big for anything but the very largest (record sized roach) I would have thought

Certainly, I would find it difficult to imagine any roach I caught making any headway trying to munch on your typical mussel but I guess, like most things, they start out small and grow!?

That last link was a US university so perhaps their knowledge on "Europe" is not complete. I had another look and found this Irish document, which is not as emphatic, but none the less says

Opportunities may arise for the roach, an avid benthophagic predator with pharyngeal teeth that are well suited to feed on zebra mussels.

Maybe there is more to the story. Perhaps they can feed on the younger/smaller mussels but, because of the volatility in roach populations you mention, the population of big mussels can expand in those low roach years until we are left large populations of large mussels with no predator. A lot of maybes and questions which probably means I need to go off and read some more

jkchambers

I was at a recent fisheries meeting and, as far as I recall, we were told that roach/bream hybrids and trout will sometimes feed on zebra mussels

Flysfisher

I was under the impression that tench could eat zebras, and were eating them. This may be true as there is evidence to suggest that there are more and larger tench in sheelin where zebras have been present since 2002.
Also I believe that zebras eat or filter all the tiny micro stuff that juvenile roach fry eat hence they ate their food and then a collapse in roach numbers followed.

jkchambers

IFI will be hosting a meeting to present results/findings etc at 7 pm on Thursday 28th August in the Hodson Bay Hotel