There have been a number of posts in this forum relating to the perilous situation that trout cod are in.
In my opinion, trout cod are on the brink of extinction despite a couple of decades work to try and bring them back. This is because of a number of factors ALL of which need to be addressed if we are to save this magnificent fish from oblivion.
In no particular order (since they all need to be addressed) I believe these issues are as follows:
Habitat restoration There is no denying that habitat destruction has effected trout cod populations basin wide. Many of the streams that would once have been narrow little tree-lined (shaded) waterways with deep holes, undercut banks all interspersed with little riffles in the upper areas of the Murray-Darling basin are now, due to land clearing and agricultural practice, braod open shallow sand beds with hardly any water and no habitat.
Exotic predators Intordoced top of food chain predators have a devastating effect on stockings of juvenile fish of any species. The fundamental difference between stockings of trout cod and the exotics themselves is the numbers of fish involved. A single stocking of trout cod might involve the release of only a few hundred up to about fifteen hundred fish. Numbers of trout released are typically an order of magnitude greater, making it meaningless to try and compare survival rates. Such small numbers of stocked fish are unable to cope with large numbers of predators. In the (original) natural streams greater habitat is conbined with much lower stock levels since trout cod are much more territorial than trout. This means that today baby trout cod get a double whammy.
Size of stocked fish I was at a workshop at the Arthur Rylah Institute a few years ago that looked at mathematical moddeling that has been done to look at the dybnamics of trout cod stocking. The results were startling, buut sadly corroberated by real world experience. Stocking with fingerling in even ideal locations (and most actual ones are far from ideal) is likely to result in failure in over nine out of ten cases. (Success being measured by the presence of juvenile fish in the years after the five years of stocking ends.) However stocking with yearling fish (at only about one tenth of the number of fish released) effectively reversed this likelihood of survival with success about 8 out of ten. So why do not fisheries release yearling fish? The simple answer is cost.
In summary, it is no good either side talking about only one aspect of the solution - trout control, or habitat restoration or size or whatever. All issues need to be addressed. Like it or not, trout control is a necessary part of the solution. We cannot simply afford to wait until we fix everything else before we look at that part of the problem. Similarly trout control is not the only thing either. But it is one of the things.
Tight lines.
Nick
[ This Message was edited by: Nick_Thorne on 27-05-2004 12:38 ]
[ This Message was edited by: Nick_Thorne on 27-05-2004 12:39 ]
[ This Message was edited by: Nick_Thorne on 27-05-2004 12:40 ]
I'd say it's a bit early to judge the sucess of trout cod stckings. Given the trend to generally lower water levels over the last ten years most fisheries(including introduced trout) wouldn't be self sustaining.We need to wait for some wet years and see what happens before we give up on some of our native fish.
Charlie
The problem is that some people are suggesting the problem for Trout Cod is everything BUT introduced Trout, which is of course is ridiculous.
They will also not acknowledge that there are a handful of upland rivers/streams in excellent environmental condition, where there is no explanation for the disappearance of Trout Cod and other upland natives like Macquarie Perch except a heavy presence of introduced Trout and repeated heavy stockings of introduced Trout.
i am sorry guys i have to dissagree with some of these points put forward.... i for one have fished in the good years as simon knows, it is hard to find a solution as to what really happened to some water ways, take for instance the silver perch around the ACT and the maccas around the small streams i fished in those times, just ask yourself why is it so that fisheries put the majority of native fish into dams these days, than rivers, i do think about it. most of it has nothing to do with trout being the major predator as they were not there in any numbers in the bidgee and still cod and silvers maccas fell off,..... as for tc there has been a success in my area, talbingo which holds stacks of trout and redfin , and the bidgee below where i am now has plenty of tc as well.....
You obviously havent fished areas that have been restocked with trout cod. If you have you would see the how good they do in areas like the upper Murray,Ovens River,Murrumbidgee,and the king rivers are thriving with trout cod thanks to restocking.
A waste of time .I think it is great they are actually doing something.
So i would have a think before you make comments like it is a waste of time.
Actually, I have fished in several areas where trout cod have been stocked. I have also participated in trout cod surveys and I have spoken to some of the scientists working on the trout cod recovery program as well as having seen the tabulated results of all the survey material that has been collated so far.
I have also fed wild trout cod cicadas in the summer in rocky pools in upland water ways, I have kept trout cod in aquaria (under permit of course) and have participated in trout cod breeding programs and cared for trout cod brood stock.
So I do have a bit of an idea about what I am talking about with regards to the species.
There is no question that in some places the trout cod that have been stocked have thrived. Right up until they reach about 45 to 50 cm. Then they seem to "disappear". (I don't suppose angling pressure would have anything to do with that, surely everyone knows that TC are protected...)
What has not happened is any natural breeding in these streams. The way this system works is that you stock with fingerlings every year for four or five years. Then you don't stock and keep sampling for juvenile fish in subsequent years - a sign of succesful breeding in the wild.
The survey results have readily shown the survival of the originally stocked fish (you can see each age class quite clearly in the graph of measured fish in the survey results - right up until when the fish "disappear").
What you do not see is any recruitment after the stocking period ends. Therefore, by definition, the stocking has not been successful, since the aim is to re-establish breeding populations in the wild.
I stand by my original post.
BTW, I do not recall saying that the recovery program was a waste of time. What I was trying to do was point out some of the things that need to be done to make is successful.
Nick
[ This Message was edited by: Nick_Thorne on 28-05-2004 23:20 ]
Hello Nick i do agree with some of your points esspecially with the trout. The comment that they dissapear at 40-50cm is one that got me thinking .I have caught quite a few going over 50cm one around 72cm mark.Just the little ones see content on smashing everything before a big one gets a chance.
Very good and informative post Nick. Really you would think it is all pretty simple in that you
1)Identify a suitable stream/river that has the potential to hold these fish.
2) Confirm there is suitable habitat for the fish to breed and survive in.
3) Confirm the water is of suitable quality and flow to sustain the fish.
4) Remove any fish that may be detrimental to their survival, and ensure that these cannot get back into that particular location. (alive for restocking elsewhere if possible).
5) Stock the fish at a size where they have a fighting chance of survival.
6) Monitor their progress and health.
If all this fails then I imagine there is some sort of problem with either the fish themselves or there is a water quality issue (excluding a catastrophic natural event).
Fisheries may say it is too expensive to stock say yearling fish but I'm sure we would all be happy if it genuinely gave them a fighting chance.
There was something like $950,000 allocated to save a spotted tree frog, something that a lot of us will never see in our life, however if it saves it from extinction so be it. Same to for the Trout Cod, but if it is going to be done lets hope it is done right.
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.I think it is great they are actually doing something.
