A fishery management problem

[Vagabond]

One of the waters I fish can best be described as a small estate lake. Water lilies, marginal rushes, tench, crucians, gudgeon, a few roach, perch.

 

Nice tench, four to nearly six pounds. I caught quite a few around the turn of the century. Crucians to a couple of pounds. However, recently both numbers and average size of both tench and crucians have declined. There are no carp present, but unfortunately someone introduced bream and the last three years have seen a plague of skimmers.

 

The decline in tench and crucian was due to a simple case of overcrowding by these hoards of skimmers we thought.

 

The management agreed with me that it would be a good idea to net some (most!!) of the bream out and sell or donate them to another fishery/club.

 

Accordingly, the EA were called in to do a health check

 

Bad news - the EA found the fish are infested with gill maggot and can't be moved.

 

What to do ? My own ideas are

1. Dig a deep trench and put any skimmers caught into it (have a "skimmer match" or three in the summer to help fill the trench) - grow runner beans on the result.

 

2. Try to improve the water quality (a cause of gill maggot) by restricting the amount of groundbait used (there are matches held there at which IMHO far too much groundbait goes in) Rotting surplus groundbait is a probable contributory factor to the poor water quality.

 

3. Try to kill off the gill maggots. A Google search throws up various organophosphorus compounds as recommended (by aquiculturists with a vested interest in selling them) for adding to the water for this purpose - These are nasty compounds, and I would like to know of anyone's experience in using them on a lake or pond. They kill other invertebrates besides gill maggots, and (again IMHO) are not good substances to have hanging around in the environment.

 

 

Anyone have any further suggestions?

Edited January 7, 2010 by Vagabond

[Dick Dastardly]

Dave I do know that you can still get consent to transfer fish which have a "Notifiable Disease" to another water which has the same so worth asking them again.

 

I m pretty sure Im right in saying "Gill maggoty" is just a common name for Ergasilus. Also if truth be known allthough no parasetic infestation is desirable the real problem is if Ergasilus gets into smaller artificial trout waters as the female parasite burrowing in the gills of the fish causes an obvious reduction in the gills performance,With trout in small stocked waters which often suffer reduced DO levels in warm water this can prove fatal.

 

With course fish it rarely proves so and in practice neither does it on the big reservoirs,some of the best of which I can tell you for a fact has the "problem".

Edited January 7, 2010 by BUDGIE

[Dick Dastardly]

Oh as an add on the only cases of effective treatment of the problem Ive seen has been in small stew ponds/holding tanks and never in a reasonable sized natural water.

Edited January 7, 2010 by BUDGIE

[Vagabond]

Thanks for prompt response Budgie - I will look into asking the EA again.

 

Yes, I would be surprised if any natural water were wholly free from Ergasilus - it would seem likely that the level of infestation would be related to water quality and to stock levels.

[Dick Dastardly]

Exactly Dave.They are just so touchy over it because of the trout issue.Last time I physically transferred fish with Ergasilus from infected water to infected water was back in the 90's so like I said best to check with the authorities first but they had no problem then and I know of others having done similar at around the same time,Just sorry that I'm a bit out of the loop these days so cant direct you to the right individuals.

[Newt]

Slightly off topic but did you really return to the UK during the middle of the worst weather in some years (and possibly the worst ever)?

[Vagabond]

Slightly off topic but did you really return to the UK during the middle of the worst weather in some years (and possibly the worst ever)?

 

Yep, as a veteran who walked ten miles to school in the winter of 1947, along a railway track with huge drifts either side, and ten miles back after being "rewarded" with a free school dinner, a bit of snow holds no terrors for me. That day in 1947 was the ONLY occasion I experienced of my scheduled steam train failing to turn up.

 

1947 was worse than 1963, but of course most of the media people were still unborn in 1947 (or in 1963 for that matter) So they are saying this current snow is "the worst on record" - an indication of how inward-looking they are.

 

Too early to say how bad this lot will become eventually, so it is pointless comparing with 1947 yet. Will tell you at the end of March.

[John Weddup]

Hi Vagabond

 

just to add and agree with what budgie has said.

 

This gill infestation is so common that being involved with 4 local clubs and fish stocking etc its very rare to find a stillwater that has not got the infestation.

 

Also as budgie says you can move fish into another stillwater that has the same problem. The fish seem to live happily with it.

 

Skimmers are very costly to buy. Even with the infestation they have a value to another club.

 

I am not so sure the skimmer population would expand on its own that much to overcrowd the lake. Introduced over population could occur obviously.

 

I wonder therefore if the loss of tench is a bit deeper.

 

One of our local fish suppliers was telling us that he once netted a small pit that was a prolific tench fishery. It was going to filled in due to development so it was netted fully. It was easy to net so he was confident in removing most fish.

 

He only got 30 tench.

 

The conclusion is that the tench must have been caught many times to allow good catches. But also you only need to lose a few for it to become a difficult water to catch tench.

 

They may well have been old fish and died naturally. (of course it could be otters or eastern europeans)

 

regards

 

john

[lutra]

I am not so sure the skimmer population would expand on its own that much to overcrowd the lake. Introduced over population could occur obviously.

My local club put around 30 bream (around 4lb) and about 30 carp (up to 10lb) in a small lake (3 acres) about 12 years ago. They grow well for about the first 6-7 years with the bream getting to 9lb and 1 or 2 carp making 20lb+. Then about 6 years ago we started to catch skimmers which wasn't a problem to start with as there wasn't to many and they were growing well, but 6 years on its a different story. The place is now skimmer city (1 a cast), the carp have lost weight and look like death and i don't know of the better bream being caught in the last year or two.

[Tigger]

My local club put around 30 bream (around 4lb) and about 30 carp (up to 10lb) in a small lake (3 acres) about 12 years ago. They grow well for about the first 6-7 years with the bream getting to 9lb and 1 or 2 carp making 20lb+. Then about 6 years ago we started to catch skimmers which wasn't a problem to start with as there wasn't to many and they were growing well, but 6 years on its a different story. The place is now skimmer city (1 a cast), the carp have lost weight and look like death and i don't know of the better bream being caught in the last year or two.

 

 

 

That's the type of place where a few pred's would be handy...cormorants, pike etc . It would be specimine city then LOL.