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Question for riprap

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#1
Rip, I am one of the bass anglers who hate killing bass, after I read your posts about culling and all that kind of things, I realy do understand the reasons for culling the smaller bass. My question to you , what is the reason why small mouth bass dissapearing in waters as soon as barble appears. Voelvlei dam, once a prime small mouth dam with allmost nothing left since barble introduction, the Breede river, once one of the best fishing distinations in SA for small mouths, since the appearence of barble the small mouths really strugles. What worries me about the Breede river smallies is the ones you catch are really big but there are absolutely no juveniles. The largies on the other hand are doing very good. Barble starting to be a problem in Kwaggas, I really hope the smallies will survive. I've read lots of articles about smallies in other dams in SA that just can't grow in numbers where burble are present.
What do you think about my observations.
I really believe electroshocking barble will be the only way to go to reduce there numbers.
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BWG
#2
Firstly, we need to know about the species itself, which can be found here compliments of the Zandvlei trust:
[Image: Catfish.jpg]

<!-- m --><a class="postlink" href="http://www.zandvleitrust.org.za/art-zvnr%20in%20and%20around%20the%20reserve-african%20catfish%20project.html">http://www.zandvleitrust.org.za/art-zvn ... oject.html</a><!-- m -->

Herewith an interesting article written by the late Erwin Schroeder, when he was the SABAA conservation officer:
Of great concern is that SABAA don’t appear to have a full time portfolio position in this regard!?

<!-- m --><a class="postlink" href="http://sabassfishing.co.za/conservation/esa_where/esa_where_have_the_bass_gone/esa_where_have_the_bass_gone.html">http://sabassfishing.co.za/conservation ... _gone.html</a><!-- m -->

Herewith another interesting article from the same author with regards to Small Mouth management:

<!-- m --><a class="postlink" href="http://sabassfishing.co.za/conservation/bassafrica_smallies_control/bassafrica_smallies_control.html">http://sabassfishing.co.za/conservation ... ntrol.html</a><!-- m -->

Herewith just one example of some work being done to remedy such situations:

S A BASS June 2008
ECO-WATCH
by Eugene Kruger
HARTIES REMEDIATION PROGRAMME : Leave those Long Lines!
As published before the Department of Water Affairs in conjunction with the
North West Province has embarked on a R35 million remediation programme in an attempt to restore the dam to its former glory.
One objective of the programme entails reducing the total fish biomass in the dam, an action headed by the well known ecologist and fish authority Professor Gert Steyn of Aquatic Weed Control en Eco Dynamics consultancies.
The reason for reducing the biomass is that the extremely excessive over population of fish in the dam produces countless millions of fry in the water which feed on the zoo plankton in the dam. In turn the zoo plankton feed on the algae, so the less zoo plankton, the more algae.
The species that are the major cause of this unhealthy situation are the canary kurper, barbel and carp. Interestingly enough, another well populated specie is the smallscale yellowfish; blue kurper are still present and of importance to bassers is the proven fact that bass represent no significant factor, other than a canary kurper predator. Indeed, as was seen at the March SA Bass Cast-for-Cash at Harties, numbers of bass were brought to the scales that had regurgitated small canary kurpers into the weigh basket.
“People are not catching canary kurper because they are so over populated that they are all very stunted,” Professor Steyn explains. “The canary is a highly aggressive fish and with their extreme numbers have a significant effect on the dam,” he adds.
Barbel and carp are the easiest to target, and commercial harvesting started already in January, using long line methods. The harvesting contract was allocated to a nearby duck farmer and barbel are being harvested for sale locally. Trot lines are set at night and removed in the mornings.
The numbers of carp must also be greatly reduced. “Bear in mind that a 1,5kg barbel can produce some 100 000 eggs and a carp about 10 000 per kilogram mass, which gives some perception to the over production of biomass in the dam,” Professor Steyn explains.
A barbel egg hatches after about 24 hours and a carp after about 36 hours, so during spawning time millions upon millions of barbel and carp eggs are deposited. “Even if just a small percentage reaches maturity it results in a massive increase to the dam’s biomass,” he points out.
It is important however, to note that the problems associated with Harties are not only caused by excessive fish biomass. “A completely natural set of factors also come into play in such a dam,” he says, “namely that when a dam is newly built it is deep with clear, clean water. As the dam level rises new feeding grounds are made available to fish and other aquatic organisms. This is known as the oligotrophic stage. Then, as the dam ages it eventually reaches the eutrophic stage, with much warmer water, silting, shallower depths and with excessive vegetative growth, such as can be seen in the large reed and weed beds in many dams.
With no manmade intervention the initially beautiful dam becomes just a shallow wetland, and in such a habitat only a few species can survive, among them barbel and carp. “What we are now attempting is to do is to halt the ageing process and to return the dam to its oligotrophic state,” he says.
An initial commercial harvest target is set at around 300 tons of fish a year, but this will be monitored continually. When compared to the 500 tons harvested a year from Bloemhof Dam, this does not look excessive but will help to reduce the biomass.
“It is important for anglers to note that the fishery part of the remediation programme is being implemented not only to contribute to the overall ecology of the dam, but to promote a healthy
fish population of all species, “Professor Steyn explains. * Bassers are therefore requested not to take out trot lines if they should come across them in the dam as they are perfectly legal and part of the remediation programme. Also, buoys have been placed where certain underwater activities are being undertaken (see also May issue).

It’s a pity that this thread, on our site, didn’t continue. Maybe someone wants to pick it up again?
<!-- l --><a class="postlink-local" href="http://www.bassfishing.co.za/bassingnews/modules.php?name=Forums&file=viewtopic&p=66183">modules.php?name=Forums&file=viewtopic&p=66183</a><!-- l -->

If you feel like a long but worthwhile read, you may be interested in the following thesis entitled, “ASSESSING THE IMPACTS OF INVASIVE NON-NATIVE AFRICAN
SHARPTOOTH CATFISH CLARIAS GARIEPINUS”:
<!-- m --><a class="postlink" href="http://eprints.ru.ac.za/2959/1/KADYE-PhD-TR12-30.pdf">http://eprints.ru.ac.za/2959/1/KADYE-PhD-TR12-30.pdf</a><!-- m -->

This is a lot of info, perhaps too much, but hopefully it will satisfy some of your curiosity, Breedesmallie.
[Image: big_fish_eat_little_fish.jpg]
BIG FISH EAT LITTLE FISH....
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#3
Thanks Rip.Some very good reading. Barbel in the top 100 worst invasive species world wide, that says a lot. The only way they can controle it is a gene manupulated virus for barble. I once read a artickle somewhere that the Ausies are doing it with unwanted species. ???
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#4
Completely different senario in KZN and North where Barbel are indigenous and Bass thrieve in their company. All to do with rain fall in the Cape I believe.
The more I learn about fishing the more I realise
how much more I have to learn about fishing.
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#5
Here is what i have found over many years. Our winter rain with irrigation is very big factors

With the over population of small carp in our dams which leads to breading beds being eradicated. So when the new spawn born they in open water. Now with less cover comes less successful breeding and it continues down the line.

With catfish being dominant and no predators for them, they hamering the bass on the nest. With less new spawn it can only go backwards.

I have found previous bass water where catfish took over bass dissappear ed. I have removed large numbers and have found the bass coming back as they flow in from non catfish waters.
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