Taupō Fishery Focus.

By trout anglers for trout anglers.

Issue 48 – August 2026.

Anglers could be in for a bumper end to the spawning season. While plenty of trout are currently in the main rivers, evidence suggests large congregations of trout are still waiting off river mouths for significant rain before they begin their spawning migration.

Weather can be changeable at this time of year, so anglers need to be adaptable. Periods of rain and elevated flows will allow anglers to use more typical winter tactics, such as heavy nymphs and wet flies. By contrast, low clear conditions will require lighter gear, with finer tippets and small flies.

The Taupō District fishing regulations were updated this season, so ensure you are up to date before you begin fishing.  You can read about some of the changes in this edition of Taupō Fishey Focus. Lake anglers are reminded about the reg changes to the fishing season at Lake Otamangakau – see story below.

Our regular technical update provides a summary of the latest data gathered from the Te Whaiau spawning trap at Lake Otamangakau. This important trophy trout fishery is currently tracking well which offers a solid platform for refinement of the regulations.

Remember to buy your Taupō fishing licence before you start fishing. The online only service delivers an accessible, secure experience, available 24 hours a day, 7 days a week: www.doc.govt.nz/FishingLicence

Tight lines.
James Barnett
Editor

Bag limit increase to enhance trout.

This season saw the introduction of an increased bag limit within the Taupō Fishing District – from 6 trout to 8. In response to questions from anglers, we thought it would be useful to explain why the change was introduced.

Lake Taupō is a complex ecological system. Fortunately for anglers, the trout of Lake Taupō have been the subject of decades of scientific study. The fishery benefitted from the work of Fishery Scientist, Dr. Michel Dedual, who dedicated his scientific career to improving our understanding of the fishery through the introduction of a comprehensive technical monitoring programme. Much of this work continues to this day.

Taupō catchment streams can be described as hyper-productive. Their cold, clean, clear, highly oxygenated waters and ideal substrates provide near perfect spawning conditions for trout. This translates into exceptionally high levels of juvenile recruitment. When high juvenile recruitment occurs in parallel with reduced trout harvest (due to changing angler habits such as an increase in catch-and-release), there is a significant risk the population can exceed the food supply needed to support it. The relationship between trout and smelt is critical here. Unfortunately, history has shown how devastating it can be for the fishery when this balance is lost in Lake Taupō.

Lake Taupō is an oligotrophic lake, which means it is clear and low in nutrients. With restricted nutrient levels, lower-level trophic activity is restricted, which results in reduced zooplankton, when compared to more productive mesotrophic lakes. This is why Taupō smelt tend to be smaller than those found elsewhere.

We know the Taupō smelt population is largely controlled by two key factors – the availability of food (zooplankton) and predation (trout). Given the critical importance of lake productivity and food availability, we have a specific technical programme dedicated to measuring and monitoring it – the echo-sounding monitoring programme.

The echo-sounding measures trophic levels in the lake, which measures lake productivity and helps predict potential impacts on the trout population. Our echo-sounding technology is similar to ‘fish-finders’ used by boat anglers, just far more powerful. A ‘back-scattering coefficient’ helps us differentiate important details such as zooplankton, smelt, bullies, catfish and trout.

Turning our attention to trout, we know more than 90% of rainbow trout in Lake Taupō are pelagic, feeding almost exclusively on smelt for a large proportion of their lives. This means the relationship between rainbow trout and smelt is critical to the Taupō fishery.

Data about rainbow trout size, condition and numbers is captured in a variety of ways. Data from the fish traps, escapement counts and angler surveys, suggest that current trout numbers are relatively high and trout size has declined. Average trout size is an important metric. Smaller trout indicates reduced growth rates and points to a reduction in their primary food source, smelt. In addition, at our fish trap, we have seen a decline in the number of rainbows that have previously spawned. This also points to a reduction in food supply, where trout returning to the lake after spawning have struggled to regain sufficient condition to enable them to spawn again. Angler surveys also confirm fish size is currently down.

When trout size begins to fall (as evidenced through multiple studies) it is a signal that the smelt population is under pressure.

As previously mentioned, direct predation by trout can be a significant factor in smelt population levels, particularly when trout numbers are high. Winter weather can also impact smelt by significantly influencing nutrient levels. Storms agitate the surface of the lake and cause the thermocline, which developed over summer, to break down. This allows water layers to mix, freeing up access to surface nutrients, which in turn increases the production of plankton. When this does not happen, the smelt population can be negatively impacted.

While our echo sounding work offers a powerful insight into the productivity of Lake Taupō, there is still more to learn about how lake currents shift over time and how these currents influence plankton and smelt productivity, and in turn impact trout. We are in the process of developing a technical study to help us understand this.

In summary, Lake Taupō is a very large complex system however the relationship between trout and smelt is clearly understood. Recant data trends suggests the fishery would benefit from increased trout harvest, hence the increased bag limit from 6 to 8 fish. The associated reduction in predation pressure on smelt, will help their numbers to recover and improve trout growth and condition. We will continue our monitoring programmes and modify fishing regulations as needed.

Lake Otamangakau now opens 1 October.

An important reminder to anglers who fish at Lake Otamangakau. Updated fishing regulations have changed the start to the fishing season from 1 September to 1 October. Therefore, the Otamangakau fishery will remain closed throughout September. This change effectively reverts back to previous arrangements, when the season kicked off at the beginning of October.

This change was informed by our review process, where we fine-tuned the regulation changes introduced four years ago to protect the future of this internationally renowned trophy trout fishery. The latest data from the Te Whaiau Stream fish trap confirms the 2022 regulation changes are having the desired effect, with good numbers of large trout recorded. Read more about the latest trap data in a separate story within this newsletter.

In addition to the change to the start of the season, the fixed February closure has also been removed. The fixed closure is replaced with a responsive approach to hot summer weather, where a closure reflects the weather conditions. Therefore, closures will only be introduced when the surface water temperature is predicted to reach or exceed 20 degrees C. More information about the system supporting this will be released shortly.

Compliance matters.

With changes to the Taupō fishery regulations for the 2026/27 season, it is a good time to make yourself familiar with the 2026 Anglers Notice for the Taupō District. Once you know and understand the rules you can focus on enjoying everything the Taupō fishery has to offer.

Our Fishery Rangers regularly patrol rivers and lakes checking you have a licence, and that your gear aligns with the regulations.  There are a few reoccurring themes that Rangers regularly encounter. We want you to get the most from your fishing trip, so knowing the regs and understanding some of the key pitfalls can help prevent compliance related distractions.

(To provide some balance, make sure you also read a viewer’s letter TRM received today – added to the end of DOC’s report…)

When fly fishing, you should pay attention to your leader length, ensuring it does not exceed two lengths of your fly rod. This is especially important when Euro nymphing.

Also check any weight you are using. Ensure only split shot or putty is attached to your leader. Note that split shot can be applied above or below a fly on the leader or a dropper, however, is illegal to use clusters of split shot on a dropper without a fly on it – ‘dropshot rigs’ are not allowed in Taupō.

When fly fishing, Rangers will also check your strike indicators (ensuring you are using natural or synthetic yarn only), the number of fly’s being used (up to three), and that you are using a fly reel and fly line.

So, to avoid unnecessary interruptions to your precious fishing time, please read and understand the Taupō fishing regulations before you start fishing.

Te Whaiau trap summary.

Trap results this year confirm the regulation changes put in place in 2022 are having a positive impact on large trout in Lake Otamangakau. This is pleasing to see and provides a solid platform to fine-tune the regulations for the upcoming fishing season, which begins 1 October.

This year, fish trapping on the Te Whaiau Stream began 28 May and ran through to 24 July. This is the 28^th season spawning data has been collected from this location, providing us with ongoing monitoring data, allowing us to track population changes over time.

Number of trout trapped.
A total of 842 trout were trapped and processed by fishery staff during the 10 weeks the trap was operational. A detailed breakdown can be seen below (Table 1).  Each fish was sexed, measured, weighed, fin clipped, maturity estimated and then released upstream to continue spawning.

To allow the two-month trapping period of recent years to be comparable with the five-month period from earlier years, adjustment formulas are used. Separate formulas were created for the browns and rainbows based upon the historical trapping data (1994-2013). The June-July period alone accounts for more than 95% and 88% variations in the total run of rainbow and brown, respectively. For rainbows, the formula is 1.42*(June + July actual count) +57.46 and for browns; 1.12x(June + July actual count) +445.

With these formulas applied, this season’s April to August run estimate is adjusted accordingly – browns 813, rainbows 701 (Fig.1).

Historically the trends in abundances of rainbow and brown trout in the spawning runs remained similar until the mid-2000’s, when they started to show marked differences. The spawning rainbow trout population steadily increased from 356 trout in 1994 to 1,439 in 2005 but then surged after 2006 to reach a peak of 3,661 trout in 2009. The rainbow trout spawning population then steadily declined towards 2016 returning to a level similar to that of the mid-2000’s. The trap was not operated during the period 2017-2021 but when reinstated during 2022, the spawning rainbow trout run had returned to a level not seen since the mid to late 1990’s. The abundance of brown trout also steadily increased from 329 in 1994 to 1,262 in 2008 and then decreased, but unlike rainbow trout, did not show any sudden changes. The abundance of browns has begun to increase but remains comparable with figures from 2012 to 2016.

Size of trout
The increase in spawning run size was associated with a marked decrease in average weight for both browns and rainbows especially between 2007 and 2013 when the numbers of browns and rainbows exceeded 3,000 trout in total. The increase in spawning biomass was particularly large for rainbow trout which increased from 997kg in 1994 to 7,116kg in 2010 compared to an increase from 790kg to 2,504 kg for brown trout during the same period (Fig.2). The increase in trout abundance was initially caused by an increase in recruitment of maiden fish followed by an increase in the survival of previous spawners. During this time, the average size of the rainbows decreased, indicating that the carrying capacity of the lake may have been reached which had implications for the management of this fishery.

Overall, the browns trapped during late May, June & July 2026, averaged 618mm and 3.0kg (6.6lbs) with an average condition factor of 45.2. These browns were the longest on record, surpassing the previous peak of 617mm in 2023. Similarly, the browns were also the joint heaviest on average at 3kg and matched the big browns trapped in 2023. The longest brown trapped this season was a hen which measured 735mm. The heaviest was also a hen and weighed 4.65kg (10.25lbs).

Since 2022, the average length of browns has ranged between 597mm and 618mm while the average weight has ranged between 2.7 and 3kg. (Fig.3).

The rainbows trapped this season averaged 605mm and 2.9kg (6.4lbs) with an average condition factor of 46.2. In comparison to more recent years, these rainbows were down slightly in terms of their length, where it has ranged between 616 & 619mm. Overall, it was the 9^th longest average since trapping began. Over the years, the average weight for rainbows has ranged from 1.8 to 3.1kg with this year’s average of 2.9kg at the upper end. The slightly shorter but still heavy rainbows made for some excellent conditioned fish, with an average score over 46 – scores not seen since the mid 90’s. The longest rainbow processed this season was a jack measuring 740mm. The heaviest was also a jack and weighed 5.2kg (11.5lbs). (Fig.4).

Trophy trout.
A total of 10 trophy sized trout (exceeding 4.54kg or 10lbs) were trapped this winter; 7 rainbows (4 female and 3 males) and 3 browns (2 females and 1 male).

This equates to 1.5% of the actual rainbow trout run trapped this season (Fig.5) and 0.8% of the total brown trout run (Fig.6). Overall, it was encouraging to see good numbers of fish in the 4kg+ (8 to 9 lbs) range that have the potential to become trophy trout in the near future, if they survive.

The percentage of trophy sized rainbow trout amongst the run has ranged from zero to a peak of 7.9% observed during the winter of 1995 (27 trophy sized rainbows). 1996 actually produced more trophy sized rainbows with 34 recorded but due to the larger population size that year equated to 7.7% of the total run. 2023 saw the most notable increase in trophy rainbows for 18 years with 8 double-figured rainbows trapped. This year was on par with season 2025.

Historically, the physical number of trophy sized browns trapped has never exceeded 2 fish in a single season, even when the trap was operated between April and August. Percentages have remained less than 1% of the actual run up until seasons 2022 and 2023.  However, this season saw 3 trophy sized browns trapped.

Overall, the trout population at Lake Otamangakau has remained relatively stable recently. The size and condition of trout this year was on par with recent years, indicating the current management approach is maintaining a smaller population of larger fish – in line with expectations. Longevity is an important factor for trout here. Lake conditions allow trout to recover well and continue to grow after spawning. Therefore, older trout can be very large. These are the fish that anglers prize, so protecting them is critical to the future of this trophy trout fishery.

 Trout spawning access restored on Whangamata Stream.

Fishery Rangers recently restored upstream access for rainbow trout, running up the Whangamata Stream to spawn.

The Whangamata Stream near Kinloch is a small but important spawning stream for rainbow trout at the northern end of Lake Taupō. A historic water wheel straddles the stream, with a fish bypass running alongside it.

In the past, the stream regularly took a very shallow detour around the water wheel, fanning out, leaving only a trickle of water flowing through each upstream path. This made it very difficult for trout to migrate further, leaving them exposed, particularly during drier periods of when stream levels were low.

After surveying the site and drawing up plans, Fishery Rangers constructed a barrier off-site, before bringing it to the water wheel. Installation involved slotting the new barrier into preexisting rebates in an old concrete structure, then attaching with solid galvanised fixings.

A section of the stream bed was manually dug out to restore the main channel of the stream and direct flow towards the water wheel and trout bypass.

The work has proven a huge success with local residents reporting trout passing freely through the structure as they migrate upstream.

Tongariro suspension bridge nears completion.

The last six weeks have seen excellent progress on the construction of the new suspension bridge spanning the Tongariro River, above the Breakfast Pool. The original Major Jones bridge remains in place and fully operational while construction work continues.

All concrete work has been completed, with approximately 700 tonnes supporting the new structure. ‘Deadman’ anchors now have the connecting rods attached, with all excavations back filled and compacted. The first pair of main support cables are in place. These were flown across the river by helicopter. Bridge hanger clamps were installed prior to flying to reduce the amount of high risk suspended height work.

Work will continue for a further couple of weeks, with completion anticipated mid-September, weather permitting.

Latest e-DNA samples test negative.

Tūwharetoa Māori Trust Board recently participated in a nationwide surveillance programme designed to better understand the distribution of invasive aquatic pest species. They submitted e-DNA samples from key locations around Lake Taupō, which were tested for Corbicula (invasive freshwater clam), Golden mussel, Zebra mussel and Quagga mussel. Tests confirmed no detections for any of these invasive species.

This is great news and reinforces the value of active preventative measures such as the ongoing public education and awareness building programmes. But most importantly, it underlines the benefit of practical tools such as Check Clean Dry.

If you are planning a visit to the Taupō Fishing District, make sure you are familiar with the risks associated with invasive species and are aware of the actions required to protect our very special freshwater fishery. Find details online: Check, Clean, Dry your gear