Due to previous report stuff on the nature of Tongariro River spawning runs, TRM have been reminded of the previous experiments using radio tracking by DOC (Department of Conservation are the fishery managers in the Taupo region) that will be of interest to Tongariro trout fishing junkies.
The eventual results may have taken a few years but shattered many preconceptions that anglers previously had about trout spawning runs.
On right are the old Target Taupo magazines from 1995 (issue 19), July 2002 (issue 40), July 2003 (issue 43), November 2003 (44), & March 2004 (45). These still provide great reading. Anglers wish they were still being produced, instead of this computer generated nonsense…
Thank you to DOC contributors over that time – Glenn Maclean, Michel Dedual, Rob Hood, & Mark Venman.
We tried to copy & paste the articles but their layout and wording suffered in the process so TRM have done our own summary. The last article alone was over ten pages so needed reducing to fit modern readers’ concentration span.
We trust the TRM summarised version follows the original experiment and results. As the experiments were spread over 10 years and four issues of TT magazines a lot of info has been necessarily deleted. Some of the charts have not been suitable to copy as well.
Nevertheless, it is still interesting to Tongariro fishos as the trout have not read it and still follow much the same spawning habits.
The stated aim was to analyse how fast the trout move up(and on some occasions down), where they rest in the river, favourite holding pools, runs or riffles, and areas to be avoided, to compare favoured trout holding pools with those favoured by anglers, to understand what makes these areas more desirable, to measure features like water velocity, bed material, depth, presence of cover, etc. Most of these parameters controlled by the flow.
By tracking tagged trout and noting habitat characteristics at different flow conditions DOC could assess what flow would maximise the preferred habitat for migrating trout.
How was it done? About 100 trout were to be caught in a trap in the lower Tongariro between May and September and tagged.
By Michel Dedual
DOC provided reasons for delays and how they were going to do it. They explained the experiment was similar to the 1995 & 1996 project when they attempted to index the Tongariro River run to the run in the Whitikau Stream. (?)
They mentioned the Tongariro runs numbered 60,000 in 1995 with approximately 5000 trout passing through the Waipa trap.
As part of the radio tracking they noticed not all fish tagged and released in the lower river moved further upstream. Two died and some others returned to Lake Taupo. Overall 80% of the fish tagged were tracked.
Of 100 tagged in the lower river 10 were recaptured in the Waipa trap. From this they deduced a total run of 40,000 or 20% smaller in 2002.
The article was followed by a “STOP PRESS” that read the project was delayed due to weather issues and risks of losing tags which cost $300 per tag.
By Rob Hood
The 2003 article mentioned the research programme finally started in 2002?
The project began in late April when 15 trout were tagged and released. In mid-June a further 29 were tagged and released. Of note, 22 were male, indicating it was still early in the spawning run.
Following the first tagging a number were close to the SH1 bridge within 3 days of being released.
Since then they moved steadily upstream covering several km every few days.
The trout then stop and remain in the same area or pool for several weeks. They could have been either spawning or resting.
Of particular note was one trout recorded in Judges Pool at 11am on 16 May and recorded at the Waipa trap at 9 am the next day, a distance of approximately 15 km.
Tagging at the Delta was to continue until July until 65 trout were fitted with radio tags.
Also a further 35 trout were to be tagged above the Fence Pool to ensure there were reasonable number of trout to follow in the upper river.
Conclusions? So what happened? Sorry – you will have to wait until I find the time to continue this gripping nail biting drama… tomorrow? To record this summary has taken far too long and She needs me back in the laundry… (I really need my fix – to go fishing)