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 Currently there is a question about the validity of some exotic species in the South African rivers, it is not a question of whether they should be there or not, it is a question about what is to be done about them. The species in question is trout, the humble fish that most of pursue from time to time. Should they be here or not is not for this debate, well not yet.
Let me begin by saying I am not a scientist, nor a researcher of scientific material, however when I heard that there is a project afoot to use a specific chemical to remove trout from a specific river in the western cape, I started researching the process.
Simply put, a few guys, with what I believe are good intentions, are being pig headed to achieve some sort of personal goal. I think these guys have now received so much criticism that they are not listening to anything anyone else might have to say. It is an unfortunate situation, but it is a poor showing from the people we entrust our rivers to. We believe that based purely on education and passion, they will make the correct decisions for the rest of us. We also believe that their supervisor’s, the guys with knowledge, experience and an understanding of the implications of a mistake, will bring sanity to a poor situation. It is not my intention to belittle or degrade these guys, it is simply to say, “Guys wait, have you truly investigated and explored every possibility?” During my investigations I found that there has been a project running the Great Smoky Mountains National Park, by chief fisheries biologist Steve Moore, who is re-introducing the native Southern Appalachian Brook Trout. Without getting too complicated… Although Rainbows Trout are native to the USA, they are contained to certain geographical areas, similar to the way Largemouth and Smallmouth Yellowfish are native to the Orange-Vaal system. Brown Trout are exotic to the USA, so they shouldn’t be there, and then there are cross bread, or un-pure / mixed strains of the Brook Trout (north and south cross), not Cutthroat, that is a pure strain all by itself. The end result is that the Smokey Mountains have Brookies, Pure southern ones and half breeds, Rainbows and Browns in their river system, when only the Brookies belong.
Steve embarked on a eradication program, but realised that there was little or no way to eradicate all the alien species, instead, he found rivers and streams with natural barriers, tested it was a true barrier, and then started on eradicating the fish from above the barrier.They tested that it was a true barrier by electro shocking about 300 meters of river above the natural barrier, clipping the adipose fin and releasing the fish below the barrier. These natural barriers were normally waterfalls of 6 to 8 feet or more. Trout will naturally try and get back to their original territory and after a year, the clipped fish were not found above the falls, the barriers are deemed to be effective. The eradication process was done in 2 methods. The first was to electro shock as much of the river as possible, this was done to try and recover as many Brookies as possible. These fish were relocated to holding ponds and the other fish; Rainbows, etc… were released below the natural barrier. The second was to use a chemical, this is where you prick you ears up… they did not want to use Rotenone, as it’s destruction is well documented, killing everything in the stream, leaving a desert waist land. The rehabilitation of a stream that was in this kind of state, is no overnight process, so this product was rejected. Steve then investigated another chemical called, Antimycin, which does not kill all gilled creatures. I tried to understand the process, but you can Wikki Pedia it, if you want. They tested it and found that it had a 100% success rate on fish, but only killed between 20% and 50% or aquatic invertebrates, with almost no effect on the craw fish and crabs. Thus leaving a stream with a relatively healthy population of life, without the fish… they left the stream for a season to regain its lost insects, and then reintroduced the Brookies, into this pristine garden. They thrived… There are other benefits to using Antimycin, one of which is that it is easily neutralised with a calcium compound, and there tests showed that a properly neutralised piece of water was easily achieved. The park has been working on this for a few years now and to date they have rehabilitated about 15% of the streams contained in the park. Currently Steve is on another project, but interspersed with it, he goes around the States lecturing and training other National Parks members on this process. He has completed a thesis and documents all of his findings, is not time to accept that there might be another approach. Without going into the politics of trout eradication form South African rivers, I am concerned that our fisheries department are jumping in feet first, without due diligence to the process and material to be used. Is it a case of have Rotenone, will use it; or are we man enough to stand up, swallow our pride and investigate another process?? |
