Cormorants

Gormley85

Whats the story with the cormorants. I hear some lads saying they destroy rivers and other lads saying they're no worse then herons does anyone actually know how bad they are?

ytpe2r5bxkn0c1

They have been much maligned by anglers for years and blamed for reduced fish stocks. However numerous studies, and I have been involved in a few over the years, show that they do not have a detrimental impact on stocks. They are a native bird and the usual laws of nature apply. Like any predator they take prey but will not wipe out that prey as they would affect their own survival. Many areas have near permanent populations of cormorants and those cormorants would not be there if stocks were wiped out. You might as well say pike wipe out stock of roach, bream etc in a lake.

But I'm sure many will disagree. I can only go on the empirical evidence and the surveys

Gormley85

Nixon Red Lockjaw wrote: »

They have been much maligned by anglers for years and blamed for reduced fish stocks. However numerous studies, and I have been involved in a few over the years, show that they do not have a detrimental impact on stocks. They are a native bird and the usual laws of nature apply. Like any predator they take prey but will not wipe out that prey as they would affect their own survival. Many areas have near permanent populations of cormorants and those cormorants would not be there is stocks were wiped out. You might as well say pike wipe out stock of roach, bream etc in a lake.

But I'm sure many will disagree. I can only go on the empirical evidence and the surveys

Are these studies you did online?

ytpe2r5bxkn0c1

Gormley85 wrote: »

Are these studies you did online?

No. Internal network only. I don't have hard copies here as I'm now retired.

ytpe2r5bxkn0c1

Some mention here
http://www.angling-in-ireland.com/forum/viewtopic.php?f=2&t=1308

Gormley85

Nixon Red Lockjaw wrote: »

No. Internal network only. I don't have hard copies here as I'm now retired.

Ah ok fair enough Just out of curiosity what did you work at before you retired?

J. Ramone

Nixon Red Lockjaw wrote: »

Some mention here
http://www.angling-in-ireland.com/forum/viewtopic.php?f=2&t=1308

I can't see them finding many perch or roach in the Slaney headwaters for instance. Does the report not say more about fish populations in midland lakes? Lough Ramor cormorants won't eat many trout or salmon anyway.

twin_beacon

I have coarse fished areas with lots of cormorants over the years, and always had great catches. The cormorant only really started to get a bad reputation in the angling press with the rise of the UK commercial fishery. Naturally enough these birds started to move onto the commercials, like they would any other lake, but when they started to eat the expensive carp they seemed to cross the line!
in natural circumstances, predator like a cormorant/Heron/kingfisher/pike/perch/ferox..... will never "wipe out" wipe out their natural food source, if they did, they would be extinct a long time ago.

Bio Mech

twin_beacon wrote: »

I have coarse fished areas with lots of cormorants over the years, and always had great catches. The cormorant only really started to get a bad reputation in the angling press with the rise of the UK commercial fishery. Naturally enough these birds started to move onto the commercials, like they would any other lake, but when they started to eat the expensive carp they seemed to cross the line!
in natural circumstances, predator like a cormorant/Heron/kingfisher/pike/perch/ferox..... will never "wipe out" wipe out their natural food source, if they did, they would be extinct a long time ago.

That's exactly It really. Higher stocking density of semi tame fish and they can gorge and do damage to (financially) valuable fish. The problem in the UK was compounded by the fact that a lot of the commercial venues are shallow and are perfect hunting venues for them. I can feel the pain as my garden pond was wiped out by a heron last year

Having said that there have been confirmed cases in the UK where excessive numbers that were forced in land from the North sea and Irish Sea etc (due to falling food stocks) have altered the balance in the short term. With so much choice in nicely packed fisheries there behaviour seemed to change from the natural and they can reduce the numbers in small fisheries to levels below what would sustain them and then they move on. Altered behaviour due to altered ecology as they wouldn't have that transient pattern in the larger waters on at sea.

The damage they do to bankside trees when there in numbers doesn't help there public perception either and leads to the look of a bleak and empty water.

jimbev

I think most preconceptions of thee's birds and herons comes from the ordinary garden pond which they will strip the fish stock after numerous visits

Bio Mech

jimbev wrote: »

I think most preconceptions of thee's birds and herons comes from the ordinary garden pond which they will strip the fish stock after numerous visits

Its the same problem basically with stocked fisheries too which has influenced perception. They can arrive en masse and after repeated visits can lower stock density because commercials are often small and vulnerable to them. When they can gorge they will. In natural waters where the stock is more diffuse (more spaced out and lower biomass per fish) they cant do that damage and so balance is maintained.

Biomass per unit area is huge in commercial lakes and is maintained artificially anyway so its already an unbalanced ecosystem so its a ready made TV dinner for the cormorant. Likewise herons and otters too. They don't do ecological damage in balanced natural waters but if they come across a half acre pool full of artificially fed pet carp its like a free buffet. And of course big carp cost so much owners will have a big issue with any loss.

Zzippy

There's a study here that was commissioned by IFI.

Personally, as with seals and other predators, if there weren't enough fish for them to eat they wouldn't be here. I think a healthy population of predators is a sign of a healthy ecosystem. The only regret I have about cormorants is seeing the damage a colony did to the trees on the island on Screebe Lake once they moved in - a number of years later the trees are all dead, something to do with the acidity in their droppings I believe.