Interesting to reflect on what others say about the Tongariro River… this was written two years ago in 2014.

Lament of a Tongariro angler

Herb Spannagl goes back a long way with the Tongariro River, so he shared some of his thoughts on the current state of affairs affecting this world-famous waterway.

The writer (left) and fishing buddies with a limit bag of spring spawning run fish.

This this is my 34th year of fishing the Tongariro River, I am reasonably qualified to reflect on the recent changes to this great river from an angler’s perspective.

The 2004 flood of 1442 cumec (cubic metres per second) was the second-largest on record and only slightly smaller than the memorable 1958 flood of 1470 cumec. Both floods had a serious effect on the course of the Tongariro. Although there have been several large floods between those two events (1986 810 cumec; 1995 718 cumec; 1998 913 cumec; 1999 670 cumec; and 2000 670 cumec), the pool changes between 1958 and 2004 generally happened within the existing channel. This changed in 2004 when the great flood brought about significant channel alignments. To quote from the Taupo District Flood Hazard Study of 2011:

A flood of this magnitude has the ability to erode and transport large amounts of material. As a result, significant changes to the form and position of the river are to be expected. The most dramatic change was in an area known as the Breakaway Pool. Here the river created a new channel through what was previously a heavily vegetated island. While this new channel had been developing slowly during previous flood events, the river permanently changed its course during the 2004 flood. This change did not just affect the position of the river. The new channel is approximately 30% shorter than the old, and therefore the gradient of the river has steepened. This has increased the velocity of flow, which has also increased the river’s ability to erode and transport material.

While the above are raw figures, the real impact for us anglers has been the loss of a significant number of good fishing pools. Pools are not only fewer, some old pools or newly formed ones are faster and shallower, providing less fishable water. In summary, the shorter and steeper channel now contains fewer pools and more rapids. Fewer pools automatically concentrate angling pressure, which reduces the time a pool/fish can be ‘rested’.

Flood protection work

The 2004 flood removed a vast amount of material from the upper channel and deposited a great deal of it below the SH1 Bridge. This aggregation in the area of ‘The Braids’, which lies within the boundaries of the Turangi Township, caused significant flooding to properties in several low-lying areas. The resulting flood protection work has all but destroyed the newly created fishery of the braided spawning channels. This further reduced fishing opportunities, especially for those less able to cope with casting heavy nymphs on large pools.

To divert flood waters from the Tongariro Lodge and Lower Herekiki Street, a new channel was dug, which dried up the very popular Honey Pot and Plank Pools, as well as some fish-holding braids. As part of this flood-protection work, large-scale willow removal was performed in the lower delta part of the Tongariro to flush out aggraded sand that has shallowed the river and led to increased flooding of the delta and surrounding lowlands.

From a flood-control perspective this work makes sense, but I am also told by regulars that this tree removal has reduced the backwater-holding areas for migrating fish and the overhanging shelter for large brown trout. Considering that in the early years of the Taupo fishery most of the fishing was done in the Lower Tongariro, what is left down there is only a shadow of its glorious past. Even I can remember great fishing days on many lower river pools, which nowadays exist in name only.

Fishery collapse

As if the above event and its human response were not bad enough for us anglers, in the years following 2005 the lake’s smelt population collapsed, and with it, the rainbow fishery. Rainbows feed throughout the whole water column and take most of their food (90%) in the form of smelt. Browns are littoral feeders, living on a large smorgasbord of creatures ranging from snails to bullies, small catfish, ducklings, koura and even rats and mice. Recently I had the opportunity to discuss this downturn of the rainbow fishery, which makes up 90% of the lake’s trout population, with DoC’s Chief Fishery Scientist Dr Michel Dedual.

Like most anglers, I too have been looking in vain for some major identifiable cause for this calamity. Theories abound, ranging from lakebed volcanic activity to catfish predation of smelt eggs. Some punters have found solace in a bit of DoC bashing, with Michel the most prominent target. I have known Michel for many years and can honestly say that he is just as enthusiastic an angler as he is a brilliant fishery scientist.

Despite such credentials, when it comes to managing the Lake Taupo fishery, not even he can pull rabbits out of a hat. Fortunately, I have enough resource management background to comprehend Michel’s ‘Big Picture,’ understanding that this fishery is constantly influenced by many natural factors that can vary from year to year. What was a real surprise to me was learning that for most of the time the lake’s smelt population is starving, owing to the low level of nutrients in the clear lake water. To get a handle on this, one only needs to look at the size of the smelt in some Rotorua lakes. There, the smelt grow to twice the size of their Taupo cousins in what can best described as a ‘nutrient soup’.

With this primary food source so delicately balanced, it does not take much to tip it over. Apparently, the lack of benthic nutrient upwelling resulting from the thermocline not breaking down during the 2005 winter badly knocked the smelt population. Meanwhile, thousands of trout spawning up the rivers started a new generation of rainbows oblivious that out in the lake there was little food for their progeny to grow. Judging by the small size and dreadful condition of the rainbows in the years following the smelt collapse, one can only conclude that there were too many rainbow trout and not enough food in the lake. This imbalance and the resulting strong competition for food by too many fish further slowed the smelt recovery. Anglers also indirectly prolonged this sorry situation by either reducing their annual angling visits and by misguidedly releasing poorly conditioned fish. In hindsight, DoC could have done more to promote the culling of trout or to conduct netting to bring about a balance between trout and smelt sooner.

The demise of the early run 

In recent years the Tongariro rainbow spawning shifted from mid-winter to spring and early summer. Nobody really knows what has caused this change, although a plausible speculation has it that repeated floods wiped out the progeny of early spawners, leaving late spawners to initiate this trend. I don’t know what impact this change has on the annual life cycle of the rainbow population out in the lake, but as a fisherman I lament the loss of an important winter fishing opportunity.  The late runs now clash with the October start of the national summer fishing season, which may cause some anglers to bypass the Taupo fishery altogether. Fewer anglers also mean less business in a region that relies heavily on tourist visitors. DoC has recognised this and embarked on re-establishing a stronger winter spawning run with an experimental stocking of small rainbows raised from early spawning stock. The next couple of years will show if this trial has been successful.

Hard fishing in clear water

Just as I started writing about this topic, a friend arrived who told me he’d found the fishing tough in the clear Tongariro on a recent trip.

Well, that makes two of us who observed what seems to have become the norm over recent years. Everybody is catching them as long as there is a tint in the water, but once it clears (and that could be a couple of days after a fresh) the fishing invariably gets hard. Looking back over the years, I cannot recall such sudden and regular drops in fishing results. On the contrary we used to dig them out all week long, no matter the colour of the water. If one factors in the tremendous advances in tackle and fishing techniques, one would think that fish have become more vulnerable, but the opposite seems to be true.

With all this lamenting, I am glad that I can finish on a positive note. Since 2013 the fishery has been in recovery mode. So far this trend seems to be continuing through the 2014 season, even though there are still too many small trout running the rivers in my opinion.

We must not forget that unlike the nearby Rotorua put-and-take fishery, Taupo is a wild, self-sustaining fishery that’s at the mercy of many natural and human events over which the fishery managers have little or no influence.

We are lucky to have such dedicated scientists navigate this fishery through this complex maze. They deserve our full support during these difficult times. I am quite confident that the trout will recover soon, but it might take another 50- or 100-year flood to hopefully realign the Tongariro for the better. In the meantime, let’s make the most of what this famous river offers us.

Learn the “Tongariro Roll Cast”

with Herb Spannagl

Sunday 21st August 2016
Tongariro National Trout Centre

10.30am – Tongariro Trout Centre for an introduction and video followed by a demonstration of casting at the Upper Birch Pool
12 noon – Lunch (BYO).  Tea and Coffee making facilities are available on site
1.00pm – We depart for the Tongariro River, with Herb, for hands-on tuition and practice

Anglers must supply all their own gear, waders, typical ‘Tongariro rod’ with a long belly WF or double taper floating line.  Herb will provide the indicators.

This clinic is not suitable for fly casting beginners.

To book please contact the Tongariro Trout Centre
ph 07 386 8085 or email admin@troutcentre.com

This event is always popular so bookings are essential

Please feel free to forward this email to friends or family who may also be interest in this informative casting clinic