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Goulburn Valley Fly Fishing Centre

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Fish Spawning in the Goulburn! The Facts!

How the system works?

The Goulburn is a tailrace or tailwater river. That is the river begins not high in the mountains a hundred miles away but rather at the wall on Eildon Lake just up the road from us. This water finds its way from the depths of the lake where the sun's rays have long since dissipated and any sediment has long since settled. The out take tower takes water from the very bottom of the lake and drops it into the Pondage Lakes where it is then released into the river in controlled volumes. The Pondage holds about 7,000 Megalitres.

As a result the water that comes out of the lake into the Pondage and then into the river is very cold and clear. In summer when the surrounding natural (un dammed) rivers are low and warm it is high and cold, pumping out irrigation water for the food bowl that is the Goulburn Valley. In winter when the surrounding un-dammed rivers (Howqua, Big, Rubicon, Delatite etc) are high and cold the Goulburn remains low and relatively warm.

The lake's first purpose is for the storage of water for spring and summer irrigation. A long time ago those who settled the area realised that there was a need to store water in the wetter years to help get through the dry ones. This is still the case. What this means is that during late Autumn, throughout the winter and until mid spring there is no need for irrigation releases as natural rainfall meets the demands of farmers. As a consequence the river is maintained at the extremely low level of 130 Megalitres per day as water is held back and stored for summer.

Once the rain tapers off in mid to late spring and the days become longer and warmer, the calls for water from farmers downstream of the lake are magnified. This sees the river come up and stay at levels from 1,000 to 4,000 Meg/Day in spring, up to 10,000 in high summer, tapering off to 1,000 - 4,000 again in the autumn. Water is released until late autumn rains see the demand from farmers drop away.

There is a secondary usage of water released and that is for the generation of power. To maximise the benefits of the water, electricity is generated when it drops from the out-take tower in the lake into the Pondage and also at times when it comes out of the Pondage into the river. This was a state run industry up until the mid nineties when Jeff Kennett carved up and sold it off to the highest bidder. More on this later.

When do fish spawn? What are the triggers?

The Goulburn is predominantly a brown trout river and brown trout spawning is well documented right around the world. They are an autumn/winter spawner depending on climate. Distance from the equator, altitude, rainfall patterns and other factors all play a part in determining when exactly spawning will happen.

Trout spawning activity is largely governed by photo period (The duration of an organism's daily exposure to light). Rapidly shortening days as we go into winter are the key trigger to trout spawning. This usually coincides with the onset of heavy rain which sends rivers into spate (flood). Water temperatures are also a crucial factor. These conditions usually coincide in the second week of June for us in the Goulburn Valley. Some years they occur earlier, some later. But on average it is sometime in June that trout spawning starts in earnest.

Fisheries are well aware of this fact. Nothing illustrates this more than the usage of the fish trap below the Pondage. The fish trap is located at the base of the Pondage wall. It is a simple design but utilises the fish's desire to move upstream at spawning time. Flowing water gets the fish to swim up and into it, where they are then trapped in a large concrete box. Here they can be assessed (measured, weighed and counted) to work out the population of the river. They were also used to strip eggs from wild fish for use at the hatchery at Snob's Creek. Records show that this trap was used in June and July when the bulk of the spawning fish were active.

How can we help the fish to greater spawning success?

When we realise that the vast bulk of the spawning fish in the Goulburn are protected by the current regulations we can start to look at the real ways in which we can help the trout to prosper. So apart from closing the season what else can we do? Well there are a number of things that can help.

The regulations could be a lot more effective. As an example you could impose a zero bag limit from after Easter onwards. This would ensure that when the demand for irrigation water is diminished in late autumn that the fish would be protected while they are 'trapped' in the series of pools that the river becomes once it drops to 130 Meg. I would personally like to see this occur in the Spring until the river reaches about 1,000 Meg. This would also introduce the concept of catch and release to many who have yet to experience it. And this is just for starters.

Perhaps the most important factor limiting spawning success or failure is the timing of water releases. While we know that the demand for irrigation is nil during the winter there is still variations in the river level. You will remember that we said that the electricity industry was privatised. Before this occurred there were very few adjustments to the flow rate at this time of year. Now because it is privatised we see dramatic changes that are driven by the dollar. When the call comes down the line that the price is right the river is switched on and raised as electricity is generated.

This happens throughout the winter as cold snaps hit the city and there is a sudden jump in demand for electricity. The river comes up for a few days and then drops. This can be critical. If this happens at the wrong time you can lose a lot of eggs. If the river runs at 2,000 Meg for a week is then dropped back to 130 Meg all the fish that spawned in that week will have their eggs left high and dry. When this level increases occur in June, it can be catastrophic.

Another important change that could be made would be to the minimum flow rates. At the moment the minimum flow or riparian flow is 130 Meg/day. Most of the gravel bars are exposed and there is but a trickle from pool to pool. Adjusting this to somewhere in the 1,000 to 2,000 Meg would have many benefits for the fish.

Firstly it would mean a lot more food right through the season. The huge drops in level severely restrict the number of macro invertebrates that survive and therefore the number of fish that the river can sustain. This would mean that the river could sustain a bigger head of a fish or alternatively bigger, better conditioned fish.

Secondly it will allow for many suitable spawning sites along the river. At the moment we witness an interesting phenomenon each year. The first of the spawning fish that start at the beginning of June do their thing and move off. Then the bulk of the fish that move up and spawn later on dig up the first redds that were built! Suitable sites are so infrequent that this is a regular occurrence. In a 'natural' (non-tailwater) river the level is constantly rising during this time of year and the fish spawn all over the gravel bars as the flows increase. In the Goulburn they are forced to dig the exact same sections of river. Luckily we do not have a large population of larger rainbows or they would also dig up the eggs of the browns later on as well!

We would like to see higher riparian flow rates set. We would also need to see guarantees from the water managers regarding the maintenance of these discharges. This is because as soon as we get a proper flood event and towns downstream are threatened by the rising waters, the cry from down there will be switch off anything that we have control over. That will see the river between the Pondage and the Breakaway dropping significantly and would see the eggs of the fish that had spawned left high and dry. Agreements would need to be put in place that would see compensation to the fishery for damages that would result.

This may come in the form of money provided for stocking in the short term but preferably it would be money to harvest and rear wild fish eggs in the hatchery at Snob's and then they could be released back into the river as fingerlings. While not a perfect scenario we do realise the constraints placed on the fishery due to the fact that it is a by-product of storage/irrigation lake. However that does not mean that we should not have the best fishery that we can possibly have given the current limiting factors.

End Game

Well for now we are a lobby group divided. As a single strong voice the angling lobby would be impossible to ignore. But instead of uniting and fighting off our opposition on the big issues we squabble over the detail. At the moment the trout fisherman of Australia are under attack. There are moves afoot to try and remove trout altogether. While you may say that this is nothing new, we should be aware that the small group who are pushing for this are organised and politically aggressive while at the same time we are fractured and impotent.

For instance there is a push now to warm the water being released from all of south eastern Australia's deep water impoundments. That is to change the water take out to the top rather than the bottom of these huge lakes. Lake Hume, Dartmouth, Eildon are but three of the main ones they are talking about. These changes will make the water below unsuitable for trout and do nothing to address the problems of the native fish. It will only create a great environment for the carp. Knowing full well the results of such a change to water temperatures why are they proposing this? To eliminate the trout.

This push is backed by the EPA, Australian Conservation Foundation, World Wildlife Fund and various arms of Government. Fortunately for us the cost is so ridiculously large that it should prevent it from ever happening here on the Goulburn. But it is on the agenda and they are pushing it. The view that anything foreign should be removed is a common one within many Government departments. They are even pushing this message into our primary schools and our universities seem to produce voices supporting only one side of the argument. Where are we heading?

The most recent bushfires saw Fisheries guarantee that those fire affected rivers would be re-stocked. This assurance was given after the concerns of trout anglers and local tourism operators made their concerns heard. That was a great PR exercise for Fisheries with all of us out there patting them on the back. Now after the emotion of the disaster has died away somewhat they are saying that they will have to do studies to assess the effects first. This means that it may be two years before any action. What does this say to you? How will this affect the tourism operators who rely on these fisheries? Who will fight the fight for trout when these people are no longer there working in tourism?

There is an even wider push out there to ban fishing altogether. Animal welfare 'nutters' are looking for anything that will support their claims that fishing is cruel! Now is not the time to be bickering about the small issues. It is the time that we should be banding together to fight the real enemy. Instead we seem to be engaged in an endless debate over an issue, which when all is said and done, is just a distraction from the main event.

Last Words

The closed season works but its effectiveness is limited by factors other than the timing of it. It would appear that based on our own observations and those of Fisheries that the vast bulk of the spawning fish occur in June and July. Bringing the dates forward would be of no tangible benefit to the fish.

Instead we should be looking at the bigger picture. If we really want to help the fish get through the rigors of spawning with the greatest amount of success, then lets get serious and go after those that manage the water itself. Lets get appropriate riparian flow rates set and agreements regarding dropping the river at spawning time in place.

Right now we should be banding together. We should be united against the real threat to trout survival which is with the Murray Darling Basin Commission. As long as we fight over non-issues like this we will be ineffective and will be rightly seen as an easy target.

To finish it should be noted that people who understand the spawning process either through long years of experience, scientific study or accurate analysis of all the data overwhelmingly confirm our observations. To quote Rex Hunt in his article on the Goulburn River in Freshwater Fishing Magazine Part Two "I have watched many trout spawning in the main stream around July and August". The facts are obvious to all.

~Antony

 

 

 

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