Removal of Large Barra from Dams

[DRJ]

At the recent Northern Fishstocking workshop we had two sessions on what is called dam carrying capacity.

Over the years we have been putting as many fingerlings in as possible to our dams in the belief that the more the better - survival of the fittest etc etc.

Well it appears that the survival of the fittest is in fact how it works. Some preliminary studies of Tinaroo have found that there only appears to be very large barra left in the chain. Great if you only want to catch a very large fish and not very often.

As barra do not breed in the dams it is recommended that they are put and take fisheries. This ensures that the larger fish are removed. Removing the larger fish cuts down on the canibalism of juveline fish as well as leaves room for these fish to feed on other bait species.

It may in fact mean we should be stocking less fish into our dams than we have been to ensure we have a full array of all size fish.

There are many other variables that come into this such as water temp, available food, angler pressure etc.

Regards
Darren

[Redback]

hi there darren

just a thought to your post
i say stock to full potential and possibly grow the fingerlings to a larger size prior to release this will possibly give them a greater chance of survival
its just that ibelieve its a numbers game the more you do stock the greater a chance of fingerlings surviving and growing to adulthood thats what the stocking program is all about
you must remember that these fish have an instinct to breed and will travel down stream when the conditons are right and with tinaroo so prone to flooding the inevitable will happen loss of fish over the wall this and numerous other factorswill all account for the fact that there seems to be only large barra left in tinaroo

cheers cameron

[lordy]

That sounds like the scientish we had speak to us at the annual freshwater fish stocking meeting. They Electro-fished 45+ km and found only 58 barra, about 50 or so of these were in the 80cm-130cm (yes that right only a handful less that 80 and those were less than 40cm). 30 1.5km runs for 58 fish total is hardwork. He was suggesting stocking at 15 and probably 20cm sizes to avoid predation.

The most interesting fact: given the choice of bony bream from 0-30+ cm, barra would prefer to target the 2-8cm (this held true even for the huge 100-130cm fish). Some food for thought in choosing a lure size.

[DRJ]

Hi Redback

You are quite right about stocking at a larger size however the numbers issue is dependent upon a large range of factors. A simple one is that if you have 10000 fish in the dam and only 500 have been removed over the year, the remaining 9500 fish will have grown (requiring more food) and if you then put another 5000 fish in you have increased the demand for the available food by a significant amount. The larger fish will then prey on the smaller fish as well meaning that of the stocking you are likely to lose a significant number. If the 9500 fish that remained were say 700mm in size and you decided to stock your new fish at 700mm (very costly exercise unless done in a very small number) in size to avoid the the canabalism you will reduce your food supply dramatically resulting in loss of condition of fish.

Lordy you are quite right - this was all presented to the fishstocking workshops held over the previous few months.

One of the interesting numbers to come out of the information was that of the early stockings in Tinaroo there is a very high survival rate. The rate of survival of recent stockings was extremely low. We must remember that the survey work done by the DPI teams did not cover all areas of the dam and all depths of the dam but it did give us a snapshot of what it may look like under the water.

What it comes down to is that every dam is different and a thoughtfull stocking program is required for each dam. It will also depend on what sort of fishery the local public and stocking associations wish to create. This could range from a family fishery to a world record fishery and anything in between.

As a result this may involve less fish at larger sizes for some dams and for some others it may mean more fish at smaller sizes.

Darren

[big_george]

The cost of fingerlings.
How much on average does it cost for say 30-50 mm barra against say 100-150mm barra figerlings??1000-10000.
One small catch. First you have to land the big barra to kill them.It's great fun tring. [smiley=2thumbsup.gif]
cheers george.

[DRJ]

Hi Big George

The cost of barra fingerlings basically work out to be 1cent per mm. So a 30 mm fish costs 30 cents (plus the dreaded GST). Have never purchased them greater than 50 mm so not sure if the price changes significantly however I would suggest the rate stays about the same. We try and keep our costs down on stocking by buying them at 30 mm and growing them out to the required size ourselves. We still have the food and running costs but no labour cost.

Regards
Darren

[Fitzy]

That sounds like the scientish we had speak to us at the annual freshwater fish stocking meeting. They Electro-fished 45+ km and found only 58 barra, about 50 or so of these were in the 80cm-130cm (yes that right only a handful less that 80 and those were less than 40cm). 30 1.5km runs for 58 fish total is hardwork. He was suggesting stocking at 15 and probably 20cm sizes to avoid predation.

The most interesting fact: given the choice of bony bream from 0-30+ cm, barra would prefer to target the 2-8cm (this held true even for the huge 100-130cm fish). Some food for thought in choosing a lure size.

Guys, Fisheries don't beat their drums about this, but they can only electrofish to a depth of about 3 meters tops. After that its good old guess work. So if they were to electrofish say Somerset in summer, they would get nothing because every stocked fish ('cept my togas) would be in 25 feet or more. While not invalid info, and a sometimes useful tool, electrofishing doesn't paint the TOTAL picture that they would have us believe it does.
They also did Big W & came to the conclusion that there's no banded grunter there. What a load of crap! Gimme a torch on any night & I'll go catch a dozen in 10 minutes by hand. There's millions of em.

So the moral to this story is; don't pin all your assumptions that an electrofishing survey is a TRUE indication of a water bodies fish carrying capacity or survival rates.

Jeez, I nearly got going on this holier than tho "Precautionary Principle" then too. That's be an essay & a half!

Cheers,

Fitzy..

[DRJ]

I agree Fitzy on the issue that the work is not conclusive and I thought I indended to make that clear in the earlier post (need to work on my writing skills).

What was interesting in regards to Tinaroo was that the anecdotal evidence from those fishing the dam also suggested that there was primarily only large fish in the dam.

The boys from Peter Faust Dam showed us a graph of the local charter operation catch records for the previous 12 months. What was interesting was that the number of fish across the size range was consistent. This suggests that the stocking rate of Faust in the past has been about spot on. What will be interesting is with the possible higher stocking rates due to SIP funding will this change. I know the Faust boys are looking at this issue and I am sure they will do their best to get it right.

Currently the size ranges for Teemburra Dam show more fish at the 540 - 700 range. This would be consistent with the stocking rates and age of fish. MAFSA (Mackay Area Fish Stocking Association) is in the enviable position of being able to use some of the experience of Tinaroo and Faust Dams to try and set our own stocking rates. Unfortunatley the dams are not exactly the same and we need to take into account a wide range of issues before determining this rate.

This type of planning is vital even if to ensure that those who pay for an SIP can catch a fish in the future. It may take some explaining to some that it may not be that we put in as many fingerlings as possible with the funds but maybe a lot fewer but larger.

Now Fitzy about that "Precautionary Principle"..............

Regards

Darren

[big_george]

thanks Darren.
A lot of issues to consider re killing the big girls.Over the winter ,the guildes ,both andy thompson and lindsay #dobe have been #catching large barra[ 1000 plus] and not many small barra..Come spring #the 450-900s start to show up.re the electro fishing.the depth that they used to record their data.It seems they recorded in shallow depths.In faust 2002 we caught the most #of owe fish in 15 - 45 foot of water.The biggest barra[116,26kg] came from 4 foot casting to a snag and the [118,25kg] from 12 foot of water in heavy timber casting.May be 80% of the small fish are out in the deep.Just another thing to consider when considering killing the trophy fish.
cheers George.

[lordy]

Fitzy they electro fished in about the 4m bottom depth range at Tinaroo. Whether they were able to get into snags and stuff I don't know.

[Fitzy]

Now Fitzy about that "Precautionary Principle"..............

Regards

Darren

hahahahaha

GF