Great Lake - one of our best - for shore
Greg French looks at shore-based fishing at Great Lake
At the beginning of November Great lake was already within .8m of the all-time high level mark of 1035.48 (i.e. 3.89m below full supply) attained in October 1997 - and it was still rising. There is a distinct possibility that this coming summer the lake will edge out over new ground. Such an event dramatically affects trout behaviour.
Flexible anglers familiar with what happens will be beside themselves with anticipation. Those who are only familiar with 80's style fishing are unlikely to reap the best benefits - unless they read on.
Dams, dams, dams
Great Lake was originally a large natural water. It had an average depth of just 2 metres and was weedy throughout. The catchment was small and the outflow at the southern end was often wadeable.
Brown trout were introduced in 1870 and, while no further fish were liberated into the main lake until 1910, very large fish were soon commonplace. From 1890 to 1905 the average weight was stable at 8-10 lb and fish to 18 lb were reasonably common. A drought driven lull in the fishing then prompted the construction of a hatchery at Miena - and releases of browns and rainbows in 1910 heralded an era of regular and intense annual stocking.
A proposal to use the waters of Great Lake for power generation went before Parliament in 1910. By 1912-13 an 2.4 metre coffer weir had been erected across the outflow while the larger masonry dam was completed in 1915. By this time the average weight had fallen to about 5 lb but fish feeding on the flood plains piled on weight and by 1917-18
Great Lake was again the talk of the angling community. A substantial increase in rainbow trout was formally acknowledged in 1920 when, for the first time, the catch of rainbows exceeded that of brown trout.
In 1922 a new 10 metre high concrete multiple-arch dam superseded the old masonry structure. Moreover, the River Ouse was diverted into the lake via Liawenee Canal. Rainbow trout used the spawning shingle and spring-time flows in the canal to best advantage and by the 1930s they had come to outnumber browns 50 to 1 in anglers" bags. Rising lake levels provided a bumper food supply and in the six years after 1922 the weight of the brown trout was restored to pre-1910 levels.
The average weight of the rainbows stabilised at about 5-6 lb (though many weighed 10-12 lb) and provided exceptional sport until about 1940 when the rainbow population went into decline, as did the average weight of both trout species. This has since been attributed to the progressive concreting of Liawenee Canal (from 1933 to 1941) and the consequent loss of the spawning grounds best suited to rainbow trout. Also, increasing demand for power resulted in dramatic fluctuations in lake level, possibly resulting in the destruction of feeding grounds such as rich weed beds.
By 1950 the size and condition of the trout as well as the relative abundance of browns and rainbows was approaching what we are familiar with today. Typical fish weighed 2-3 pounds and rainbows had been reduced to about 30 % of the harvest.
Since 1964-65 the waters of the lake have been diverted north through the Poatina Power Station, eliminating the traditional flows down the Shannon outlet. Also beginning at this time was the pumping of water from Arthurs Lake into Great Lake at Tods Corner.
In 1967 a new rockfill dam superseded the Multiple Arch Dam enabling the lake to be raised by a further 3.4 metres, but the water did not approach this level until 1975.
Although the rockfill dam was raised by a further 6 metres in 1982, the next decade was plagued by drought and the levels of 1975 were not exceeded until the winter of 1996.
Current potential for rises and falls in water level
The 1967 dam resulted in the full supply level being a little over 1033 m above sea level. The 1982 dam increased the potential to 1039.37 m. However, while the normal operating range is now about 21 metres, fluctuations of this magnitude do not occur over one or two seasons. The lake rarely goes up or down more than 1 - 4.5 metres in any twelve month period and net gains or losses from one winter to the next or one summer to the next are even more modest, usually in the order of 0 - 3 metres.
Fishing in the 1980s
While the lake came close to the 1033 metre mark in 1975, throughout the 1980s it fluctuated between 1023 and 1030 metres. During this time the shoreline was a barren expanse of clay and bedrock and the most lucrative feeding grounds for brown trout were the few deepwater weed-beds found off certain stretches of sheltered shoreline. These areas were best targeted by using deep-running lures and/or lead core line and were accessible from the shore only when the lake briefly dropped very low. Shoreline anglers could always find trout cruising along the edges but the catch usually included a disproportionate number of old trout - fish that had been forced off the weed beds by their younger counterparts.
The wet years
Great Lake began rising markedly in 1992 and by early 1994 the water had inundated the exposed clay. As the water began inching out over flats where snowgrass and heath had re-established we had our first glimpse of what lay ahead. The water flushed out a wealth of worms and terrestrial insects and the brown trout moved into the shallows to take advantage of the new food supply. Late in the winter of 1996, the lake exceeded the high level attained in 1975 and it kept rising until Christmas. During autumn and winter the water fell slightly but these losses were regained the following spring and the highest ever level was reached in October 1997.
How does high water affect the brown trout?
High levels fundamentally alter the biological dynamics of the lake. The old weed beds become so deep and starved of light that they slowly die and the fish, especially browns, move into the shallows to feed on drowned worms and the like. Not only do we find more brown trout around the edges but these include most of the prime trout - maidens and fish that have just spawned once. On top of all this the abundant supply of forage food allows the fish to pile on weight quickly.
What about rainbows?
Rainbows have a penchant for deep open water and are most common cruising the edges of drop-offs and in the wind lanes. The most reliable rainbow fishing has always been boat-based and really little has changed. The fish are still there in the wind lanes and, as in the 1980s, anglers still catch a good percentage of the best conditioned fish.
When the lake was very low one of the best situations for shore-based angling was when a strong northerly wind was blowing down the lake. This stirred up the lake bottom close to shore and trout, including a high percentage of rainbows, would cruise along the band of discoloured water where they could easily be polaroided along the edges. While the lake has been high, similar events have occurred on exposed shores and again rainbows have been prominent. But really, high levels are best for brown trout fishing and you should take advantage of the situation while it lasts.
How to take advantage of high water
Flood plain fishing can be good from the very beginning of the season but is at its best when the weather gets warmer from mid spring to mid summer. This is good news because Great Lake usually approaches its annual high levels in December/January.
The hot spots are the sheltered flats in Swan Bay, Christmas Bay, Boundary Bay, Brandum Bay, Halfmoon Bay, Sandbanks Bay, Cramps Bay and Tods Corner. Unfortunately, the snowgrass plains are now completely inundated so you have to fish amongst drowned stands of dense heath and it is inevitable that some fish will break off. Fishing the outer edge of the emergent sticks from a boat offers little relief as there are just as many snags under the water and, in any case, the fish are mostly feeding closer to shore.
Fly fishers should be ever alert for risers (the fish love to sip beetles, spiders and the like from the surface) but a great many fish will be preoccupied with worms. Honestly, when the water is rising over new ground, or just flooding long-exposed sections of lake bed, brown trout have guts so distended with worms that when spooked they can barely swagger out of your way. I guess that most anglers prefer the tailing and savage strikes brought about by low light conditions but for me the highlight is polaroiding in the middle of the day.
Spinning from the shore can be a nightmare since it is difficult to avoid the snags. There are some deepwater banks well suited to spinning but unfortunately the best of the fish will be in the extreme shallows, right in amongst the sticks.
Set rod fishing with live worms is extremely popular and quite productive. However, bait fishers will improve their catch if they don polaroids and stalk fish in much the same way that fly fishers do. Spot your fish, cast the worm a metre of or so in front and then wait for the trout to swim over and engulf your offering. Twitch the bait only if you are convinced that the fish has ignored it.
What if the lake does not rise over new ground?
If the lake fails to rise to an all-time high then there are still consolation prizes. The highest reaches of the last flood line have been exposed for the best part of tw o years now and any gains during November and December will likely result in low-key flood plain sport. Even when the lake begins to drop, brown trout will still be out cruising the edges, as they always do, and sunny days inevitably offer memorable sport for sight fishing enthusiasts.
What about the weed beds?
When the lake is at a sustained high level or as levels are falling, wave action erodes the shores back to clay and stone. At these times the most productive feeding grounds are the offshore weed beds. Weed beds develop in sheltered bays below the low-water level of the preceding few years. Surveys undertaken by the IFC in the mid 1980s (when the lake had been very low for the best part of a decade) indicated that weed beds covered only 5 % or so of the lake bottom, being confined to bays sheltered from erosive wave action between the 1020 and 1024m contours. These particular weed beds would not have fared well while the lake has been at a sustained high level. However, new beds will surely have established nearby somewhere between the 1025 and 1030m contours. The exact location of the beds will (very slowly) oscillate over the years since they seem to fare best at about 5-6 m below the surface.
Remember, when the lake rises suddenly the weed beds are lie deep down and well off shore. The flip-side, however, is that when levels drop suddenly and markedly the weeds are in shallow water relatively close to shore.