How many fish does a dam lose in an overflow situation?

[rayken1938]

I thought that we lost a lot at NPD with just a few days overflow untill i had a look at the Hinze dam construction site www.hinzedamstage3.com/.
They have a time lapse camera set up on the overflow and I reckon that the dam was in an overflow situation for around 142 days this year. 5/2 till 28/4 and 14/5 till 14/7.
gotta feel sorry for the local stocking assn.


Cheers
Ray

[loophole]

i know a heap of bass tilapia spangleds and cattys went over kurwongbah last time it flowed

[mylestom]

Maybe we should just be happy that they did overflow and systems were running. Thats is the basic principle of river systems. Stocking, while it is great for fishing folk is not the be all and end all of the dam/impoundments/weirs and the system.

We should be grateful for the use of the these (impoundments) for stocking and fishing purposes.

Yes some stocks were lost, but they can be replaced, same as the farmers having to destock and restock with drought. It is part of the overall cycle.

Helps to be able to see what the original purpose of the impoundment were designed for and the permission granted to stock in not a right but a privilige.

This is not being critical (of stocking groups) who do a fantastic job, mostly with limited funds and members.

But in the overall scheme its just better for the dams to be overflowing.

Regards

Trev

[rayken1938]

Another plus is for the fishery below the dam walls if the fish can enter an enviorament where they can breed but I think that a sustained overflow such as Hinze experienced would to my mind result in a overpopulation below the dam wall.
Probably wouldnt matter if they constructed an effective fish ladder when they build a dam. That way everyone would benefit as fish ( Bass) could then pass downstream to breed and then come back to fatten up ready for next year.
Cheers
Ray

[Luc]

As far as bass is concerned, the timing of the overflow is important. If it occurs as bass are nearing their breeding time, then many will take the big plunge as they have S..X on the brain.

At other times, many will be trying to push as far upstream as possible rather than go over the wall.

Re Kurwongbah, as at the time the bass were still immature, while some would have been lost over the wall, most would have stayed in the dam or pushed further up.

Luc

[aussiebasser]

I don't think its the intention, or the hope that fish which escape during an overflow actually breed. The limited gene pools of stocked fish could very well create problems in a breeding situation. It's pretty easy to tell the escaped impoundment fish from the natural river fish anyway. Within a few weeks the escapees will be skinny while the naturals are still healthy. Please don't kid yourselves that stocking groups releasing Bass into impoundments are doing anything to help the natural population in the rivers. The released fish are for a put and take fishery, not a breeding program.

[Luc]

Granted that the stocked fish are not put in for a breeding program, but, if they're ready to breed and the dam overflows, they will do so.

At the recent PRFMA lungfish rescue, while many bass still sported injuries from going over the wall, they were in good nick. None of the ones I saw looked undernourished!!

Luc

[warrior]

we lost nearly all of our bass over the wall last summer here at lenthalls dam catches have been very slow since but it did stock the river below and we will be putting another 30,000 in in november ,we are very lucky here though as we have a very healthy population of mid size barra to keep us entertained

[shayned]

I don't think its the intention, or the hope that fish which escape during an overflow actually breed. The limited gene pools of stocked fish could very well create problems in a breeding situation. It's pretty easy to tell the escaped impoundment fish from the natural river fish anyway. Within a few weeks the escapees will be skinny while the naturals are still healthy. Please don't kid yourselves that stocking groups releasing Bass into impoundments are doing anything to help the natural population in the rivers. The released fish are for a put and take fishery, not a breeding program.

While I agree to a point on this statement it is oversimplified and does nothing to deal with the various situations where fish stocking occurs.

I agree with Luc in our observations from multiple river systems the statement refering to condition of escaped fish in a few weeks is not supported by the available evidence.

The gene pool statement really is another generalisation. It does not take into account breeding program protocols nor the condition of existing wild fish stocks in a system or for that matter the number of stockings or numbers of various suppliers with varying brood stock and the collection and breeding protocols for a particular impoundment and river system.

While issues such as domestication can be a real problem as has been seen overseas, no reference has been made to the safeguards employed to allow for overflow events in our systems nor the fact that with the large number of barriers in place in our catchment areas, Bass were close to non existant in many areas before the stocking program began.

[Fitzy]

Am a little hesitant to discuss this in a public forum as I know there are those will use this discussion as ammo.
I would hope that any fish going over the wall in any stocked dam would not breed. Based on my experienced, there is not enough of a focus placed on genetic spread from the aquaculture industry as a whole. A big dump of hatchery bred fish into a system could easily overwhelm the existing population. Whatever local diversity that exists could be smothered in one swoop.

As for lake bass losing condition once going thru the wall (under or over), I've seen some very poor conditioned bass in several systems after a flood event. It wasn't in weeks, but in proceeding months it can be clearly evident that big females (over a decade old) that have been conditioned in one environment can & do struggle with their new environs. Can go from mastifs to greyhounds.

Anyway, not keen to go into it too much here,, but a short reply offering my 2 cents.

Cheers,

fitz..

[Mike Delisser]

As for lake bass losing condition once going thru the wall (under or over), I've seen some very poor conditioned bass in several systems after a flood event. It wasn't in weeks, but in proceeding months it can be clearly evident that big females (over a decade old) that have been conditioned in one environment can & do struggle with their new environs. Can go from mastifs to greyhounds.


Cheers,

fitz..

I agree Fitzy, I've been fishing a stream populated by bass that went over a dam wall earlier in the year and now some months later I doub't their condition would allow them to breed sucsessfuly.
Cheers
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