The Magic of Tailwater Fisheries

By Zane Mirfin, Fish & Game New Zealand Magazine - Issue 35, 2001

 

The Magic of Tailwater Fisheries

TOP ANGLER AND GUIDE ZANE MIRFIN COVERS SOME OF THE BACKGROUND ISSUES AND FISHERIES POTENTIAL ASSOCIATED WITH TAILWATER FISHERIES, BOTH NATURAL AND MAN-MADE, HERE IN NEW ZEALAND AND INTERNATIONALLY.


Some of the great trout waters of the world have been the product of massive engineering schemes that have literally made a silk purse out of a sow’s ear and created trout fisheries where none existed previously.
In the mid-1990s, I was fortunate to fish many of the great tailwater fisheries of North America. Having spent 2 1/2 years of my life in the United States in my formative years, fishing virtually every day, in close to a dozen States, I consider it a privilege to have travelled into the future and observed how I believe many of our New Zealand fisheries will possibly evolve.

Many will not agree, but the success of the Americans with many of these superb fisheries is irrefutable, with many tailwater fisheries producing a far superior fishing experience than that currently available in many New Zealand rivers. Anyone who criticizes American trout fishing hasn’t done much fishing on the wonderful diversity of water available. Sure, there are plenty of anglers about on most American tailwaters with public access, but for high densities of free rising trout the fishing is often of extraordinarily high quality. Do we condemn the Tongariro when it is seasonally congested with anglers?

Tailwater fisheries by my definition are those waters flowing from lakes, reservoirs, or impoundments. Many significant tailwater fisheries around New Zealand are totally natural in their origins, draining freely from lakes that have relatively low human modification and no dam structures present.

Spectacular natural tailwaters in the northern South Island, for example, include the upper Buller below Lake Rotoiti, the Gowan River below Lake Rotoroa, the upper Arnold River below Lake Brunner, and the Hurunui River below Lake Sumner.
But take a look at any map of New Zealand and the opportunities to fish natural tailwater areas are immediately obvious.

These rivers at times hold large numbers of resident browns that thrive in the highly fertile waters draining these lakes. Buffered by the lakes from major flood problems, such rivers are inherently stable habitat sustaining high aquatic insect biomass, which in turn promotes significant trout production. Such rivers often act as important trout nursery areas for young juvenile fish in their upper few kilometres. These fish subsequently mature and stock the entire river system and tributaries to the benefit of anglers. Many of these tailwater areas within the first kilometre or so of a lake are renowned for their prolific caddis populations, which create large evening mating swarms and explosive fishing, with slashing, swirling rises and the water surface literally boiling with rising fish.

Despite the hyberbole, some of these areas are in trouble nationwide. For example, the Nelson Lakes and Lake Sumner are protected in Conservation land, but lakes such as Brunner are situated in farming country and are being exposed to insidious rot through cumulative contamination and pollution by nitrogen fertilizers, pesticides, erosion, animal effluent from farmland, and human waste from Moana township. Hence, they are not faring so well and the future of such fisheries is bleak.

In addition, fish populations in such natural tailwater areas, protected or not, are often very vulnerable to angler exploitation and can require careful management from Fish & Game to protect fish stocks. Smaller, more naïve fish are often given some protection by low bag limits.

The most impressively managed natural tailwater I have ever fished was Idsjostrommen, near Gimdalen in southern Sweden, which is widely rated as Sweden’s best wild grayling fishery. Privately leased and open to anglers on pay-per-visit basis, the river is limited to eight anglers per day maximum and covers perhaps three kilometres of water. During the winter, grayling live in the depths of the lake, which freezes solid in the harsh Swedish winter. But during the short northern summer, the adult grayling migrate downstream into the highly fertile waters of Idsjostrommen to take advantage of the “midsommer” hatches of caddis and mayflies. This fishery is strictly catch and release and the densities of large catchable grayling were nothing short of incredible.

Fishing a dry fly imitating the pale yellow duns was magic. But one morning when the fish inexplicably stopped rising, I tried a double nymph rig with phenomenal success. Every cast a coconut! The Swedes do not understand the mechanics of nymph fishing as we do here and I knew when the resident river keeper told me to cease fishing because I had caught too many grayling that I had really impressed the typically dour Swedes. My friends back there inform me that the fishing has improved further since I was there in 1996, with record size grayling, due to the continuing management strategy and that the legend of the Hare & Copper lives on!

To my mind, though, the really interesting man-made fisheries are those in the United States. In the west, south, and east, water demand for energy generation, urban consumption, and agricultural irrigation has always been greater than in New Zealand. Being a continental climate with cold winters and dry, hot summers, as opposed to our more maritime climate with less temperature variation between seasons and year round rainfall, the demand for water is extremely high.

Many thousands of waterways have had major dams built for various reasons, many of which destroyed existing fish populations and fisheries.
A classic example is the desecration of the mighty Columbia River, with hydro-electric dams throughout its length blocking access to spawning grounds and nursery areas and thereby obliterating the annual runs of millions upon untold millions of Pacific Salmon, which had ascended this river system since the beginning of time. However, dams in many other areas actually improved fishing by storing water in dry, arid, or very warm parts of the country. Without such dams, many significant cold water trout fisheries would not exist. As an example, take the Flaming Gorge Reservoir, origin of the world famous Green River tailwater fishery, with as many as 23,000 fish per mile in the seven mile “A” stretch immediately below the dam.

Often these dams have created significant fisheries in the reservoirs or impoundments themselves and many of the better tailwater fisheries downstream have fertile stillwater catchments above them.

As Ernest Schwiebert, wrote in his 1979 classic Trout: “...the best trout lakes combine several primary factors — fertile water chemistry, good light penetration, extensive food-shelf shallows, and a deep-water bowl extensive enough to accommodate thermal stratification in summer and to provide enough oxygen to prevent winterkill.”
While this is undoubtedly true, many reservoir fisheries only remain highly fertile for a short number of years when high fertility results because of recent water inundation.
New Zealand hydro lakes such as Aniwhenua, Otamangakau, and Dunstan are prime examples of reservoir fisheries riding a productivity high in their early years. Whereas impoundments such as the Cobb, Hawea, and Tekapo are on a downward cycle due to fertility collapse and intermittent water coverage of prime littoral zones because of hydro-electricity generation. Unfortunately, reservoirs and their downstream tailwater flows are inextricably linked.

Fisheries like the Cobb were once prime rainbow fisheries with high numbers of 3-4lb fish in the 1970s. But as the reservoir aged, the fertility declined and trout size and productivity declined markedly. Low rainfall of recent summers hasn’t helped either, with low lake volumes and high demand for electricity during winter cold snaps. The Cobb Power Scheme, owned now by Natural Gas Corporation, is used for peak demand supply to the Wellington market and was virtually run dry over the winter, down to as low as 0.5% volume. An unfortunate side effect of this activity, apart from being extremely difficult for the reservoir fish, was the constant fluctuations of water volume down the Takaka River, which reamed out fish and insect populations. More importantly, these flows flushed iron deposits and other toxic compounds that had accumulated on the dam bottom, on a deadly mission down the Takaka on those cold winter nights. The water colouration was noticeable as far down as Takaka township nearly at the sea and trout populations were deleteriously effected.

The lower Arnold River, below the Arnold Dam, has suffered a similar collapse over the past two years. Although the reasons are not yet understood, it may be similar to the Cobb River experience. Being the most important trout stream in terms of popularity on the West Coast, this is not good news for anglers.

Another tailwater situation gone horribly wrong is the Maitai River, which flows through the heart of Nelson. Due to the growth of the city and a lack of reliable water supplies, the Nelson City Council obtained consents for a water storage dam in the North Branch of the Maitai River in the late 1980s, despite much opposition from environmental groups. When built, it was subsequently found that the reservoir water was of such low quality it was virtually unfit for the use intended and remains so. Poor soil types, excessive rotting vegetation, and low oxygen levels in the reservoir are the major reasons for the poor water quality. After this problem was encountered, Nelson City Council applied for yet more consents to extract water from the better quality South Branch water. To make up the water volume it is legally taking from the South Branch, the NCC substitutes the poor quality dam water to make up minimum flow requirements negotiated by environmental groups. So although the water volume flowing down the river is more stable than in years past, the quality is not. When coupled with massive degradation due to exotic forestry in the major spawning and nursery tributaries of Sharland and Packer creeks, it was inevitable that one of New Zealand’s earliest trout fisheries would collapse. No one can blame the NCC; it needed the water for its citizens. But scenarios such as this will become all too common in New Zealand in the years ahead.

Problems also occur in hydro lakes such as Hawea, which are adversely de-watered at times. It is easy to understand power company resistance to more stringent resource consents when each metre of lake level in which they can operate is worth $40 million over the lifetime of the Hawea Dam. Locals tell me that Hawea currently operates over a 15 metre level, but applications for 25 metres are being considered.

On the positive side, we have some very successful man-made tailwater fisheries in New Zealand. Prime examples are the Tekapo River draining Lake Tekapo in the Mackenzie Country and the Waiau River flowing between Lakes Te Anau and Manapouri in Fiordland. Both these rivers are veritable fish factories, with large stocks of brown and rainbow trout available to anglers. These have been fine success stories!

By contrast, the Americans have resolved many issues surrounding reservoirs, minimum and maximum flows,
and the creation of prime trout fisheries and we could avoid “re-inventing the wheel” by studying their often innovative solutions in regards to water utilization.
Many new dams in the States are specifically designed to provide tailwater fishing opportunities. Increasing understanding of trout ecology and technological advances has allowed fisheries to be designed almost like golf courses, with some fantastic success stories. Water flow in many American states is regulated so the flow is constant and regular, which provides stable trout habitat free from flooding or drought during summer.
More importantly, the water can be taken from a series of valves down the dam walls and the water released into the river can be selected for optimum temperature and oxygen levels, which benefits the fishery immensely. In short, many overseas tailwater fisheries have had artificially near-perfect conditions created, similar to an aquarium, for trout to thrive. In some acidic waters, innovative authorities have even added automated releases of lime to raise the alkaline pH to maximize trout productivity — this could work well on our acid West Coast streams, for example.

Many of these rivers are almost like insect farms, with massive regular hatches of insects that most Kiwi anglers would not believe. I can remember a massive hatch after dark in Montana one night of large white Mayflies. I thought it was snowing at first and couldn’t believe seeing the petrol pump attendant, where we stopped for gas, sweeping them up into big piles!

Different rivers have different insect characteristics, with hatches I’ve encountered including Trico’s (#20-22 black Mayfly), Baetis (#18-22 grey Mayfly), various Mayflies such as pale Morning Duns, Blue Wing Olives, Callibaetis (all # 14-16) Green Drakes (#10), and Hexagenia (#4-6). Then there are numerous caddisflies (#10-16), salmonflies (#2-8), stoneflies (#2-12), as well as terrestrials, such as hoppers, crickets, and ants. These rivers also hosted significant populations of scuds, sowbugs, crustaceans, blood worms, midges, sculpins (dependent on each river) and were often a veritable chemical soup of aquatic life. No wonder the fishing was so great, because many rivers had thousands of fish per mile. For example, the San Juan River in New Mexico with 17,000 trout per mile and the Green River in Utah with 23,000 fish per mile in its “A” stretch. The Frying Pan in Colorado, a very small river that was easily waded, had 3-4000 per mile, or one fish for every foot of bank on each side of the river!

An important food source in many American tailwaters is the Mysis shrimp, which thrives in deep reservoirs and lives on phytoplankton. Many populations of this small white shrimp (#18-22) have been established in such dams and they would probably work well here in New Zealand. If environmentalists argued about the ecological impact of introducing Mysis shrimp, they could hardly fail to notice the massive impacts bought about by damming the river in the first place! Fish, particularly rainbows, bulk up big time on this high protein food source, which is sucked through the turbines of the dam into the river below.

Because the fish populations are so dense, anglers need less area to fish. There were times when I guided on the Frying Pan that we would virtually stand in the same place all afternoon to rising trout and catch perhaps as many as 30 in one pool. All these trout were small right? Not always, in the Taylor and Frying Pan rivers, rainbows over 20lb are regularly caught.

Fish in such popular rivers have become almost tolerant of human presence and these fisheries can take enormous fishing pressure, as the trout can look after themselves. More importantly, these type rivers take pressure off more fragile fisheries.
The Missouri in Montana was one of my favourites and I fished it often. Nymph fishing always worked well, although the technical “match the hatch” trico fishing with 7x tippet was unsurpassed. There were so many bugs on the water at times, getting a fish to actually see your fly was virtually impossible.

The mighty Bighorn is an interesting tailwater that needs to be accessed by boat below Yellowtail Dam because of access difficulties across a Blackfoot Indian Reservation. This river has brought prosperity and jobs to all local towns surrounding it. George Custer may have lost his last stand at the Little Bighorn, but this river is a winner. Dead drifting scud imitations in prime locations caught some beautiful brown trout.

Montana’s Madison offers weeks of pocket water fishing for mostly browns, although there are some great rainbows to catch too. The Beaverhead, also in Montana, is another great tailwater, with current access problems being negotiated by all important stakeholders. Tim Tollett, who runs the Frontier Anglers Flyshop sent me an email about the Beaverhead recently and I quote from it in part:

“Before Clark Canyon Dam was built on the Beaverhead, it would run dry in August. Once there was water in the system for the entire year, the fishing went crazy. The Beav has got to be one of the all-time best trout streams in the world due to this dam. Clark Canyon is also very good as a lake fishery, producing average fish of 5lb. If the people that build these dams do it right, you’ll have a fabulous lake to fish, as well as an unreal tailwater fishery. But as we all know that doesn’t always happen. One thing I have noticed is that water must come from the bottom of the dam to allow for cool water temperatures to produce a quality tailwater.”

The San Juan has some of the consistently best rainbow fishing in a dry barren, stark environment. It was possible to catch as many trout as you wanted some days; it all depended on motivation. Sixty to eighty rainbows that could peel you into the backing were possible — I couldn’t remember how many I caught some days.

The Green in Utah offers epic fishing and large numbers of boat-drifting anglers. Guide numbers are strictly controlled with certain operators holding quota rights to such rivers. There are special launch wardens at the upper launch ramp under the dam to avoid delays with angler congestion. Sometimes it was difficult to find a designated camping spot free in the upper sections, but everybody caught lots of fish.

Northern California had some epic tailwater fisheries. The Fall River resembled a giant spring creek, with placid flow, springs, and giant weed beds, and had to be accessed by boat and outboard motor. On dark, the Hexagenia Mayflies would emerge, with the duns resembling miniature sailboats as they were outlined against the dwindling light. Long presentations, down and across with a #4 dry fly that felt like one was casting a sparrow on the end of the line was the way to go and great rainbows stripped off line as they dived for the weed beds below. During the day, trout could be caught with sink tip lines and nymph patterns along the edges of drop-offs and weed beds.

The Pitt River, a boisterous boulder studded pocket water river in California with plenty of strong mid-size rainbows, is a fine tailwater fishery with great nymph fishing and wilderness stretches that required long walks. It was rare to see other anglers during the day. Sometimes when I’m struggling during a guiding day in New Zealand, I wish I had a Pitt or a Frying Pan river nearby to save my bacon!

Idaho’s Henry’s Fork is a magic place, with the Snake River draining Island Park Reservoir.  The catching was tough, but the challenge great and 2-3 fish per day was pleasant technical fishing.  This river had a major ecological disaster when sediment was flushed from the dam in the late 1980s, but it recovered over time.

One of the more interesting American tailwaters is the Chattahoochee River, which flows through the heart of Atlanta City in the southern state of Georgia. The “Hooch” among other southern tailwaters has created habitat for trout in a warm water US state where bass and bluegills are the principle freshwater sporting fish. The Chattahoochee has major daily fluctuations in flow, which can be analysed in advance by calling a hotline phone number that records the daily water release times for public safety and recreation. Trout were not large, but reasonably numerous, with plenty of wildlife and relatively remote sections. The outfall of Atlanta City’s sewage treatment pipe was the hottest spot on the river, with dozens of trout hovering around the pipe succumbing to small red bloodworm imitations.

Colorado’s Black Canyon of the Gunnison is a great western tailwater with exceptionally clear water and plenty of browns and the Taylor River was another fine tailwater with huge rainbows like you never see in New Zealand. But they were very selective and anglers needed to fish for them with 6-7x tippet and #22 Mysis shrimp imitations. Hooking these huge visible rainbows was hard work, but landing them even more futile. High quality sight fishing right off the road. Taylor Park Reservoir also had some impressive pike fishing. Lower down the Taylor, a tributary of Blue Mesa Reservoir, there was an annual run of kokanee salmon — a form of land-locked sockeye. In fall, the water would be pink with vast schools of migrating fish and you could catch fish until your arm fell off.

Should we be attempting to create opportunities like this in New Zealand? What can we learn from all of the above? My belief is that technology and expertise is available worldwide to create designer fisheries of very high quality. A recent Nelson Mail quoted a 42% shortfall of electricity generation within the next decade, while demand for irrigation and town water supplies continues to grow, exacerbated by the past few dry summers. Take degradation of existing fisheries by agriculture and increasing numbers of tourist and local anglers and there is going to be some extreme pressure on existing fisheries.
I’ve always viewed New Zealand’s fishing resource like an apple pie. As the resource shrinks, the pie gets smaller and, with more angling pressure on what remains, the slices get smaller year by year for all of us. Not all anglers desire a wilderness experience and as our lowland waterways come under increasing strain, fisheries managers will have to examine new and innovative ways of maintaining and enhancing quality angling opportunities for licence holders that are accessible for all.

Instead of fighting all dams and exhausting time, money and effort, perhaps our fisheries managers should be drawing up a list of what rivers we must save at all costs. Then, on many dam proposals with less important rivers that we will inevitably lose, they could work with developers and government agencies to create conditions conducive to tailwater fisheries.

When I took Cawthron Institute scientist Dr. John Hayes to view the devastation of the Maitai fishery in Nelson last year, we were discussing how most trout habitat research focuses on causes rather than on remedial action. I bet with all the technology and knowledge now available in New Zealand and internationally, scientists like John would dearly like to accept a big challenge by attempting to create a fishery from scratch.
Schwiebert was quite the visionary when he wrote: “Tailwaters may be a prelude to the future, particularly near major cities...since the simple demand of future populations for potable water will unquestionably require more and more reservoirs to store seasonal rains and spring runoffs, and as such we will probably see many more tailwater fisheries created in years to come.”

The insatiable demand for water is occurring here and now for irrigation to supply agriculture and horticulture, for industry, for electricity generation, for town water supplies. This trend will not abate and it is our role as anglers to save what wild unspoiled rivers we can, such as Buller and Rangitata. But we must also be pragmatic and work within the frameworks of the inevitable development to create new and exciting recreational fisheries opportunities into the future.

We are only limited by our own imagination and lack of vision. While some doors to traditional freshwater angling may close in future, others will be opened by using the resources we have to best advantage for all to enjoy and treasure.