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Freddo
Guest
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« Reply #4 on: September 16, 2008, 08:32:29 am » |
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Hi Catch,
I agree with your comments about the Mayor's comments. The way to bring back some positivity is to take significant actions and fix the problem, not to pretend it doesn't exist.
Below is a quick history of the Taupo fishery in terms of fish size and condition problems.
Much of this below is taken (and edited/shortened by me) from the Turangi Trout Centre website so I hope they don't mind me paraphrasing them here.
As you say there was large scale netting and sale (most of the fish were smoked and sold in Wellington and Auckland) of Taupo trout by the government between 1913 and 1920 following a sudden collapse of the fish size in 1912 (basically they had eaten almost all the native koaro and had run out of food, after earlier often growing to 4kg and more) and even with that large scale netting it took seven years for the fish size to recover, but it did eventually, once the trout population was reduced to match the food supply, and during the 1920s the fish size was probably at its largest ever with fish of 5 kg and more quite common.
The golden years were short lived though and by the 1930s the trout population had again outgrown its food supply and the size and condition dropped again. This time the problem was fixed by increasing the food supply rather than reducing the trout population, by the successful release of smelt into the Taupo system. Releases of smelt continued to 1939. By 1942 smelt were a large part of the diet of Taupo trout. The trout size and condition improved yet again.
After WW2 the condition of fish again declined rapidly and in 1951 data from angling surveys indicated anglers were returning 30% of their catch (I suspect it is about 70% at the moment for lake fishermen!), inevitably rejecting the poorer conditioned fish which contributed to the high proportion of older fish in the population. To improve the condition of the trout it was decided that greater harvesting of unthrifty old trout would divert the available food to the younger, stronger growing fish which should improve the average size. A number of measures to increase the harvest of trout were instituted during the 1950s including an open winter season (with some restrictions on spawning waters), an increased bag limit, and anglers were encouraged to kill all fish caught, especially poor conditioned fish. These measures were partly successful, but not fully, so in the early 1960s the bag limit was dropped entirely, lead and wire lines were allowed, and a full all year round season was introduced. This time the fishery responded and in 1963 a bag limit of 20 fish was reimposed.
In the early 1960s an experiment began to test the effects of large-scale hatchery stocking of the lake. This involved releasing up to 100,000 marked rainbow trout per year and then looking at the proportion of stocked to wild fish in subsequent anglers' catches. Not surprisingly the results of this were not positive, as that would only tend to increase the trout population and therefore the stress on the food supply, so stocking of the lake ceased in 1965.
Instead of the widespread netting practiced early in the century to reduce trout numbers and improve size, the same effect had been achieved in the early 1960s through increasing the harvest by angling, the anglers maintaining the balance between trout numbers and the food supply, and that situation was mostly happily maintained until 1990/91.
Since then. and I think all since DOC took over we have had the 35 - 45 cm size limit change, the reduction of the bag limit to 3 from 8, the introduction of up to three flies/lures, and downriggers and jigging being allowed (plus other changes such as weights allowed on lines etc). The size limit and bag limit changes were introduced eventually as a result of a difficult season (low catch rates) in 1990-91, which prompted Doc research over several years (sonar surveys and fish caught surveys etc) that seemed to indicate the angling harvest might be getting too high, with perhaps up to 50% of the annual trout production being caught by anglers.
The next bits are purely my own theory (but I did study Marine Biology at post graduate university level including how fish populations, harvest, and food supplies affect fisheries so some of this may not be just guess work). Anyway, I wonder if perhaps this limiting of the harvest during the 1990s (done in good faith by Doc and based on research) was overdone or perhaps not needed at all, and if we might now be paying for those changes, which may have reduced the harvest and eventually left too many trout for the food supply, especially when the smelt numbers dropped suddenly because of natural fluctuations such as the 1995 warm winter possibly causing the lake not to "turn over" properly? In general over the full history of the Taupo fishery the problem has tended more to be too many trout for the food supply, not too few.
I have a feeling that the downrigging and jigging issues might be side issues, even though with jigging in particular, in my own experience, the fish caught are regularly the prime conditioned large fish, but no more so than the winter/spring caught fish in the Tongariro and other spawning rivers, and the harvest there is very large and no one has ever blamed that for this problem.
I am sure there are simply too many fish in the system for the food supply at the moment and we need to reduce the trout numbers substantially overall which will eventually fix the problem. Another possibility (and Doc has proposed this themselves as a possibility) is that the 45 cm limit might have meant that the spawning runs have now for some years included a lot more small fish than under the 35 cm limit and that we are simply breeding a larger proportion of small fish into the population because of that. For that reason I am disappointed they didn’t try reducing the limit to the old and mostly successful 35 cm limit. It might surprise Taupo river fishers, who mostly target the big winter/spring run fish, that most lake boat fishers happily kept and ate the 35-45 cm fish as they made wonderful eating, and in doing so those boat fishers probably kept the harvest up at levels enough to keep the overall fish size good.
I know it is your moniker here Catch but I strongly feel that in most of the Taupo fishery there is little need for catch and release by most fishermen (it is different for someone like yourself fishing most days of the year, and plenty of people don't like eating trout anyway) as this is not a system like the vulnerable streams with only year round resident fish vulnerable to being overfished (there are no doubt some exceptions to this in some small Taupo waters). This is a system that historically has shown it depends on a quite high level of angler harvest to keep the trout population and food supplies in balance.
Those last bits are just my opinion and you are all welcome to shoot them down (politely I hope).
Hope this is of some interest to the younger ones here such as Geoff_fishie, who might not be aware of the fluctuating history of fish condition and size over the years at Taupo, and of how the fishery has been very actively managed at times to maintain a good fish size.
Cheers.
PS just a techie thing Catch. The "Preview" button when writing a post here doesn't seem to be working.
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