I am going to make a giant assumption, that having read part 1 of this story , you are in agreement with me that bass are a problem in the Trout areas here in KZN , and that something needs to be done about them. If you haven’t already agreed with the above, then you probably won’t be reading this anyway.
The biggest issue here, is that nobody knows how bass spread. There are however some theories. I will list those here, and then alongside each theory, suggest an appropriate measure to stop the spread.
Theory no 1: Bass eggs on Duck’s feet:
I find this one hard to believe. But because I don’t know it to be untrue, let me not write it off as nonsense. If this is indeed how bass spread, there is little that can be done (no…. I wont propose shooting all ducks). What does remain true however, is that the fewer waters that have bass in them, then the less chance there is of a duck flying from a bass dam to a trout dam, with an egg stuck on its feet. With this in mind, I propose paying attention to bass invaded waters in the general upland areas, even if they have no prospect of ever being a decent Trout water. By “paying attention to them”, I refer to whichever of the other measures mentioned below which might be practical.
Theory no 2: The farm mechanic stocks bass.
I have a sneaking suspicion that this problem is right up there …one of the main ones. If I generalise, I can say that farmers who are INTERESTED in their Trout fishing on their farms, seem to be less inclined to suffer a bass invasion. I can only assume that they lecture their staff on the value of their Trout water, that they care who fishes there, and by what method, and that they control access. In other words they EDUCATE. KZN does not have a “keep bass out” sign anywhere. I think it is time!
Theory no 3: Bass swim up a flooded spillway.
I believe in this one. We forget how strongly any fish can swim up a current. After a summer freshet, a dam spillway flows strongly through the grass or vlei for a few hours, giving bass a passage up to the next impoundment. One or two of these storms every year, and eventually a bass will swim up. The solution , when bass exist in the dam below, is to put stainless steel mesh barriers across spillways, and keep them clean.
NFFC volunteers erect a bass screen on a spillway in the Kamberg
Theory no 4: Water pumped from one dam or river to another transfers bass eggs.
This is not a theory. We have proof. Eremia dam was invaded this way in 2015, and in around 2013/4 Sourveldt received bass from the little Mooi River that has bass in it. This requires some study on how to screen the pump intake finely enough to stop bass eggs, but without causing suction vortex and pump cavitation. Once we have that worked out, it will be back to “Education” to ensure that the solution is put in place when farmers do have need of water transfer. To get that right, farmers will need to value their Trout fishing resource, as described above.
Those are all my theories.
Next is to understand the enemy to come up with some eradication/control measures. I did some googling a while back, and this is what I learnt about bass:
- They live for up to 15 years, sometimes longer, and breed every year in that lifespan.
- They lay eggs when the water temperature gets to around 18.5 degrees C
- They like to lay eggs in shallower water where the sunlight penetrates to the lake bottom…about 500mm to 1.5 m in depth .
- The male protects the nest and an area of about 3 square meters around it.
- Larger Trout love eating bass hatchlings
- Breeding bass shoal stupidly and expose themselves to danger in the margins when their mind is on breeding.
We can use this information to empower ourselves in the struggle against bass as follows:
- We can stock Trout in bigger sizes, and at the very time when bass are hatching (9 to 12 inch fish in late November). The NFFC already does this on select dams with some measure of success.
- We can wait for the water temperature to get to 18.5 degrees, and then open the valve and drop the water level two metres to fry bass eggs in the hot sun! You can only do this if the water is not needed for irrigation, and if the dam has a valve. The NFFC has been doing this at Eric Kietzke dam with the blessing of the landowner, for 3 years now.
Eric’s dam before :
Eric’s dam after:
We learnt this via the grapevine from farmers in the East Griqualand area who have done the same. We also know it to work, in that the Mearns Weir on the lower Mooi River, which has a constantly changing level has a particularly thin population of bass. There are also American reports of bass struggling to breed in resevoirs where level fluctuates.
- When we have a drought, and dams which we would not normally be allowed to empty, are empty anyway, we can strike with a piscicide (fish poison) and opportunistically win back some waters.
- We can fish for bass, or even cull them with a throw net, when they are shoaling stupidly in summer.
- We could sponsor a masters program to study other methods. I can’t help wondering if shading dam margins, or rigging up vicious looking decoys (like “Billy the bass” on steroids) to scare off potential egg layers, or some other clever things might be possible.
The total onslaught:
My time in the army was a real waste of time. What I did gain was a “balsak” which still serves as an excellent tackle bag, and the concept of the ANC’s so called “total onslaught”. Whether or not the ANC did have a total onslaught strategy or not, I like the concept when tackling a problem as diverse and difficult as the spread of bass. I think we need to borrow the idea, and employ as many of the ideas and tactics mentioned in this article, all at once. I think that only if we do that, are we likely to achieve success in this endeavour. An endeavour that otherwise seems as hopeless as holding back the sea with a fork.
I illustrate my conviction that such a total onslaught is required with this sad story:
When the Spring Grove dam was built above Rosetta, the authorities had the foresight to have an impact study done. That study revealed that the Inchbrakie Falls constituted a natural fish barrier.
That natural barrier protected the Trout fishery above the falls, from an inundation by other warm water species from below. The dam would flood this barrier, allowing warm water species to migrate upstream.
A study was done, and a loss of economic value by such an inundation was calculated, and it was deemed justified to spend something like R10 million building a fish barrier. The dam was given the ‘go-ahead’ with the condition that such a barrier be built.
When the dam was under construction, budgets were being strained, and it is alleged by friends who attended meetings, and heard this first hand, that engineers proposed scrapping the fish weir because “There is no difference between Trout and bass anyway”. Interested and affected parties declared that a lawsuit would ensue if the pre-condition was not adhered to.
So the weir was built.
The lake thrown by the fish barrier on the Mooi River.
My conjecture is that it was built in a “wham, bam, thank-you mam” way. I say that because locals I spoke to had no idea why it was being built. Others who challenged the effectiveness of the proposed design were also brushed off. No signs were erected prohibiting transfer of species above the weir. No public education or engagement was entered into.
And now, not much more than a year after its construction, largemouth bass (seen with my own eyes), and allegedly smallmouth bass (I have not seen them), exist in the impoundment ABOVE the weir.
R10 million down the drain…completely wasted.
If this was a first world European country, the authorities who built the dam, would be forced by a court of law to spend whatever needed to be spent, and do whatever necessary, to reverse the damage they have done.
I for one, am truly saddened.
If you are as concerned as I am about the big bass problem, and if you feel that something should be done, please drop a comment here, or on facebook, or mail me on “truttablog at gmail.com” . In that way we can measure if this problem is worthy of action, or conversely if it touches so few people that it warrants abandonment.
Note that in all this, there is no attack intended on bass and bass fishermen on some wide scale: It is merely tackling bass invading waters in which, to the best of my knowledge, there is no economic or social value attached to bass fishing, but where bass threaten to erode that value found in Trout waters.