Fish Spawning in the Goulburn! The Facts!
How the system
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
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
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
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.
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
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.
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
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.