If a fish is introduced into a system where it was not previously then it is an alien. So even if the fish is indigenous to a region exists in river A and is introduced into river B then its an alien. Even if the rivers are 10m from one another. So even though barbel are indigenous they've made their way into water systems were they are not supposed to be. If i catch a yellowfish in the Vaal for instance and put it into my farm dam....then its an alien in that dam regardless if its indigenous to the region or not.
i read in the sunday paper that they are going to
- Thread starter leonard williams
- Start date
couta-koppie
Senior Member
Hey-ya Tr0ut, Boggom and Ryan. Did you guys see the big Raggie that neilg caught? Pls go to his 500kg raggie post in saltwater angling.
Cheers
CK
Cheers
CK
Trout nobody is disagreeing with you on that fact.......
I just want the place where you got 80% of the dams in SA have become infested with Barbel..........
Me thinks you have a hidden agenda and reading between the lines have some form of investment in a trout syndicate or something similar along those lines...............
I just want the place where you got 80% of the dams in SA have become infested with Barbel..........
Me thinks you have a hidden agenda and reading between the lines have some form of investment in a trout syndicate or something similar along those lines...............
[color=#006600]Tr0ut[/color] wrote:
a farm dam with no fish is a virgin dam.
alien fish =fish which origin is not from that province.i disagree with your statement
a farm dam with no fish is a virgin dam.
alien fish =fish which origin is not from that province.i disagree with your statement
Lets pause a while and think about the other introduced species in this part of the world - cattle, sheep, all the crops such as wheat - almost all the surviving groups of people were also "introduced" (in the sense that they did not evolve with the landscape) and pushed the locals into oblivion and/or the Namib.
Good thing? bad thing? or just evolution happening before our eyes?
Good thing? bad thing? or just evolution happening before our eyes?
Tintin Welcome to Sealine
Please fill in location in your profile bud...Thanks.
Your comment has validity but there is more land than water and it is easier to manage land based animals than our water bourne ones.......
Anyways such is life - guess some of us just want a sustainable enviroment for generations to come....
Please fill in location in your profile bud...Thanks.
Your comment has validity but there is more land than water and it is easier to manage land based animals than our water bourne ones.......
Anyways such is life - guess some of us just want a sustainable enviroment for generations to come....
Ryan i agree. We have to ensure that our indigenous fish species are protected for the future. I quote Dr Janice Limson: "No conservation concern is small, be it the Sei whales, the coelacanth, a species of butterfly, the Eastern Cape Rocky, the Knysna seahorse or the myriad indigenous fish and other aquatic species being eradicated by the alien species such as trout, bass and translocated catfish, which have become aliens outside of their home range."What about lesser-known species? What about the species that are already lost to the planet, species we will never quite have understood? What about species that went extinct yesterday, and species that will be going extinct tomorrow?"
[color="#006600"]tintin[/color] wrote:
Please TrOuT and tintin, if you want to argue the case of alien species in a landscape, at least acquaint yourselves with an understanding of alien vs invasive, domesticated vs feral and crop/stock management vs population dynamics. If you have the ability to spew forth rubbish through your keyboards it should not be too difficult to master the tool of Google.
couta-koppie urges us to comply with neilg's suggestion to love and let live. Surely these two gentleman do not expect such altruism in the case of drivel as in the above post? How does one debate with someone to whom the concept of reasonable argument seems to be as alien as trout in Timbuktoo? Education springs to mind but how does one educate someone with an IQ that can be counted on the fingers of a unilateral amputee. Does someone who equates human (cultural) diversity to species (biological) diversity use fish slime as fuel for their brain cells?
Please TrOuT and tintin, if you want to argue the case of alien species in a landscape, at least acquaint yourselves with an understanding of alien vs invasive, domesticated vs feral and crop/stock management vs population dynamics. If you have the ability to spew forth rubbish through your keyboards it should not be too difficult to master the tool of Google.
Andre Laas
Sealiner
Hi Guys
Unfortunately this is a complicated matter that even scientists are fighting over like cats and dogs. If you look up the definition for “alien species†in 100 reference works, you would probably get 50+ different “definitionsâ€. In simplest form, it is mostly species that has been introduced (intentionally or unintentionally) into a body of water that is beyond its natural distribution. This is however where the paw-paw and the fan meets. Where exactly is the “boundaries†of “natural distribution†Scientist are still regularly finding species in places that is outside of an animal’s “natural distribution range. A very recent example would be the 4m Zambezi shark that were “discovered†in the Breede River, the most South Westerly locality for this species known to science. Can we say that that Zambezi was “alien†or “introducedâ€?
In some instances it is easy, like the case with Carp, Bass and Trout. These are species that have been introduced into areas where there is absolutely no possibility of “chance introductions†by any means (e.g. Eggs clinging to the legs of wading birds, etc.). These are species that have physically been moved, by humans, over large geographical boundaries that prevents the natural distribution of the species. This is an “alien†species in truest form. The problem with such alien species, is that they come into an environment that is usually devoid of factors that usually keep their numbers under control (Predation, disease, habitat limitations etc). They can then out-compete populations of indigenous species (for food, space, habitat, breeding grounds), rendering them as “invasive aliensâ€.
Then you get the difficult cases, like catfish / baber. These fish are indigenous to South Africa as a country, but they have a certain natural distribution within the country. Thus, it has the potential to be “alien†when introduced into a body of water far beyond it’s “natural distribution†(defined by humans) by means of human intervention. BUT catfish have a unique ability and adaptation for survival. It has a lung-like organ, allowing it to breath out of water for extended periods, it has a (relatively) thick, leathery skin (when dry and devoid of mucus) that is resistant to abrasion and desiccation, and it’s pectoral fins have been adapted to act as “legsâ€. Thus, these fish have the ability to travel significant distances between water bodies and in this way it has the ability to increase its natural distribution range. There are many cases of “virgin†farm dams that produced catfish, even though they were never introduced into the dams by humans. Is a barbel in such a dam either alien (never used to be there) or invasive (it invaded the dam from outside)?
And then, just for fun, I can cast in a conundrum........ Say catfish distribution is only limited by food resources (we know they can handle a variety of habitats, and have a relatively wide temperature tolerance etc). Under normal conditions, the distribution of these fish may have been limited due to lower breeding success due to lower abundance of suitable food resources (catfish can eat insects, but in order to grow to their normal proportions, will need larger food sources = fish, birds etc.). Thus, a pair of catfish manage to get into a stream or dam on the edges of its natural distribution, and successfully spawn. Initially the baby catfish can nourish themselves on insects etc. However, as these catfish grow bigger, they will need more food, and insects just won’t cut it alone anymore. Now they will start targeting fish in their new surroundings. However, if they cannot manage to feed on the local fish (due to the minnows being too fast to catch, or not occurring in high enough density) a lot of the catfish will starve, and the condition of the remaining fish will be too poor to successfully keep on breeding, and with time they will disappear from that water body, and the natural order in that water body will be repaired. BUT, say this water body on the edge of the “natural†distribution of the catfish have been stocked with “alien†species like the carp, bass or trout? Now the catfish will be able to feed successfully on these aliens because they are slower than the indigenous species, or occur in such high densities that the cats actually manages on taking out the weak and injured. Now these cats will be enabled to successfully breed and settle into that “new†environment. Are the catfish than still alien???
Before you shower me with rocks.... I am not saying that catfish in for instance the Eastern Cape have walked there or ended there by natural means in those areas, and that they are not “alien†in those waters, I am merely trying to illustrate how grey the boundaries of “alien†and “invasive†can be, and that this is a complex matter without clear-cut answers. If I would for instance present my above “views†at a scientific conference, I would start a fight like you have never seen on Sealine!!!
At this stage I do not think that anybody has the right answers for these problems. We will also not get answers while we do not even know exactly what the questions is, and how big the questions is. We will not know the questions, until we get more experts working on the matter. It is a disgrace how little freshwater fish biologists and fisheries scientists we have in SA, not that we have a shortage of skills in this area, or a shortage of eager candidates for the job! There is just no funding available, and even the keenest graduated aquatic scientist cannot follow his/her passions if there is no chances of making a living out of it.
To get back to the point..... We know that alien species causes problems for our indigenous species, and it is important to investigate the matter further. But we also know that the mega litres of raw sewerage and other “alien†filth running into our waters are causing much worse problems, and is a severe hazard to our indigenous fish, all other forms of aquatic live, livestock and to US as humans. Isn’t the latter matter more worthy of intense investigation and discussion????
Unfortunately this is a complicated matter that even scientists are fighting over like cats and dogs. If you look up the definition for “alien species†in 100 reference works, you would probably get 50+ different “definitionsâ€. In simplest form, it is mostly species that has been introduced (intentionally or unintentionally) into a body of water that is beyond its natural distribution. This is however where the paw-paw and the fan meets. Where exactly is the “boundaries†of “natural distribution†Scientist are still regularly finding species in places that is outside of an animal’s “natural distribution range. A very recent example would be the 4m Zambezi shark that were “discovered†in the Breede River, the most South Westerly locality for this species known to science. Can we say that that Zambezi was “alien†or “introducedâ€?
In some instances it is easy, like the case with Carp, Bass and Trout. These are species that have been introduced into areas where there is absolutely no possibility of “chance introductions†by any means (e.g. Eggs clinging to the legs of wading birds, etc.). These are species that have physically been moved, by humans, over large geographical boundaries that prevents the natural distribution of the species. This is an “alien†species in truest form. The problem with such alien species, is that they come into an environment that is usually devoid of factors that usually keep their numbers under control (Predation, disease, habitat limitations etc). They can then out-compete populations of indigenous species (for food, space, habitat, breeding grounds), rendering them as “invasive aliensâ€.
Then you get the difficult cases, like catfish / baber. These fish are indigenous to South Africa as a country, but they have a certain natural distribution within the country. Thus, it has the potential to be “alien†when introduced into a body of water far beyond it’s “natural distribution†(defined by humans) by means of human intervention. BUT catfish have a unique ability and adaptation for survival. It has a lung-like organ, allowing it to breath out of water for extended periods, it has a (relatively) thick, leathery skin (when dry and devoid of mucus) that is resistant to abrasion and desiccation, and it’s pectoral fins have been adapted to act as “legsâ€. Thus, these fish have the ability to travel significant distances between water bodies and in this way it has the ability to increase its natural distribution range. There are many cases of “virgin†farm dams that produced catfish, even though they were never introduced into the dams by humans. Is a barbel in such a dam either alien (never used to be there) or invasive (it invaded the dam from outside)?
And then, just for fun, I can cast in a conundrum........ Say catfish distribution is only limited by food resources (we know they can handle a variety of habitats, and have a relatively wide temperature tolerance etc). Under normal conditions, the distribution of these fish may have been limited due to lower breeding success due to lower abundance of suitable food resources (catfish can eat insects, but in order to grow to their normal proportions, will need larger food sources = fish, birds etc.). Thus, a pair of catfish manage to get into a stream or dam on the edges of its natural distribution, and successfully spawn. Initially the baby catfish can nourish themselves on insects etc. However, as these catfish grow bigger, they will need more food, and insects just won’t cut it alone anymore. Now they will start targeting fish in their new surroundings. However, if they cannot manage to feed on the local fish (due to the minnows being too fast to catch, or not occurring in high enough density) a lot of the catfish will starve, and the condition of the remaining fish will be too poor to successfully keep on breeding, and with time they will disappear from that water body, and the natural order in that water body will be repaired. BUT, say this water body on the edge of the “natural†distribution of the catfish have been stocked with “alien†species like the carp, bass or trout? Now the catfish will be able to feed successfully on these aliens because they are slower than the indigenous species, or occur in such high densities that the cats actually manages on taking out the weak and injured. Now these cats will be enabled to successfully breed and settle into that “new†environment. Are the catfish than still alien???
Before you shower me with rocks.... I am not saying that catfish in for instance the Eastern Cape have walked there or ended there by natural means in those areas, and that they are not “alien†in those waters, I am merely trying to illustrate how grey the boundaries of “alien†and “invasive†can be, and that this is a complex matter without clear-cut answers. If I would for instance present my above “views†at a scientific conference, I would start a fight like you have never seen on Sealine!!!
At this stage I do not think that anybody has the right answers for these problems. We will also not get answers while we do not even know exactly what the questions is, and how big the questions is. We will not know the questions, until we get more experts working on the matter. It is a disgrace how little freshwater fish biologists and fisheries scientists we have in SA, not that we have a shortage of skills in this area, or a shortage of eager candidates for the job! There is just no funding available, and even the keenest graduated aquatic scientist cannot follow his/her passions if there is no chances of making a living out of it.
To get back to the point..... We know that alien species causes problems for our indigenous species, and it is important to investigate the matter further. But we also know that the mega litres of raw sewerage and other “alien†filth running into our waters are causing much worse problems, and is a severe hazard to our indigenous fish, all other forms of aquatic live, livestock and to US as humans. Isn’t the latter matter more worthy of intense investigation and discussion????
[color="#ff6633"]Critter[/color] wrote:
I mean, really!
Andre Laas
Sealiner
[color=#006600]Boggom[/color] wrote:
I should be honoured to be counted in the ranks of Lord Kelvin by somebody
[color="#ff6633"]Critter[/color] wrote:
Ernst Mach (of Mach number fame): "I can accept the theory of relativity as little as I can accept the existence of atoms and other such dogma";
Lobsang Rampa: "Einstein and people like Einstein said that the world was flat. Einstein and people like Einstein said Man would never travel faster than the speed of sound"; and
T.H. Huxley: Next to being right in this world, the best of all things is to be clearly and definitely wrong'.
Of course, Lord Kelvin was also quoted to have said: "Radio has no future".
Honoured indeed.
Austere ranks indeed, also filled by the likes of:[color="#006600"][/color]
I should be honoured to be counted in the ranks of Lord Kelvin by somebody
Ernst Mach (of Mach number fame): "I can accept the theory of relativity as little as I can accept the existence of atoms and other such dogma";
Lobsang Rampa: "Einstein and people like Einstein said that the world was flat. Einstein and people like Einstein said Man would never travel faster than the speed of sound"; and
T.H. Huxley: Next to being right in this world, the best of all things is to be clearly and definitely wrong'.
Of course, Lord Kelvin was also quoted to have said: "Radio has no future".
Honoured indeed.