FREQUENTLY ASKED QUESTIONS

 

YABBIES

1.                  How many yabbies do I need to stock my dam?

 

Depends on the size of the dam and the surface area.

For example if the dam is 20 meters wide by 50 meters long, then surface area is 1000 square Meters.   Dam stock yabbies are stocked at 1 per 10 squ mtrs so 100 needed for standard stocking.  This is the standard most people would use to stock their farm dams.

A commercial stocking is 1 per squ mtr so 1000 needed.

If you use 0+ Juveniles stock at 20 per squ mtr so 20,000 required.

 

2.                  How many young per year do yabbies have?

 

Each mature female yabby has approximately 1000 young per year.  In good conditions most yabbies will breed 2 – 3 times per year averaging 350 – 450 young per go.

 

3.                  How many yabbies survive?

 

No easy answer to this one as yabbies are on the bottom of the food chain and everything eats them including themselves.  As a rough rule only less than 5% will survive in the wild.

 

4.                  Do I need a licence to grow yabbies?

 

No.  You can grow all the yabbies you like for yourself or your friends and so long as you do not sell them then no licence required.  If however you want to sell yabbies then you must apply to NSW Fisheries for an aquaculture licence and meet the criteria of all Government Departments before you will receive a licence. 

 

5.                  Why are yabbies different in colour?

 

Yabbies come in all different colours.  As a rule they will generally colour up to the colour most suitable for camouflage in the environment in which they live.  Yabbies can be white or black, blue or green or any combination in-between.  We grow a genetically blue yabby at Port Stephens so most offspring will have some blue in them, the intensity of that blue will depend on the culture conditions.  For example:

Muddy milky coloured water tends towards light brown bodies and light blue claws.

Red clay, muddy dams tend towards bright blues and pinks.

Clear shallow water tends towards blue yabbies.

Clear deep water tends towards dark blue yabbies.

Dams in forests with tannin and surrounded by trees tend towards green and black etc.

 

6.                  Can I swim in the dam with yabbies or will they bite me?

 

Yes, no problem.  Yabbies will avoid you and you should have no problems.

 

7.                  How fast do yabbies grow?

 

Yabbies are cold blooded animals and the warmer the water the faster they can grow.  The more food available the faster they grow also.  In a farm dam generally 12 months to 50 gram, 24 to 100 gram and 5 years to 250gram.  However if lots of yabbies and little food then may never grow bigger than 40gram.  Good aquaculture ponds 12 months to 100gram.

 

8.                  When I walk around the dam I see dead yabbies washed up on the shore, what killed them?

 

Generally they are not dead yabbies, they are moult shells.  Yabbies have a hard exoskeleton (shell) that they must shed to grow.  This is called moulting.  The old shell is a complete replica of the yabby and does look like a whole dead yabby but if you pick it up you will see that it is a empty shell.

 

9.                  Do I need to aerate the dam?

 

No yabbies are very tolerant of low oxygen levels, unless you are going to grow intensive levels of yabbies, no extra oxygen required.

 

10.              Should I add chemicals to clear the water?

 

No.  Yabbies prefer the muddy, turbid conditions and will thrive in muddy dams.  In clear dams they will not thrive and predators will easily capture any left.

 

11.              Do I need to feed my yabbies?

 

No.  As a general rule if you are just growing yabbies for yourself in a farm dam no feeding is required.  Yabbies live on a very broad diet consisting of detrital material such as rotting grass leaves and seeds.  They eat weeds and algae growing in the dam plus a mass of microscopic organisms growing in the dam.  Meat and fish they will also eat if the opportunity arises.  They are opportunity feeders.  If you intend commercial farming growing higher densities than can naturally be supported then feeding is essential, see the Commercial Farmers Manual.

 

12.              Is Water Quality of my dam critical, should I have it tested before stocking with yabbies?

 

As a rule no.  Most dams are fine for yabbies as they are very tolerant to varying conditions.  The main thing to check if you want to is the pH.  Yabbies prefer neutral 7.  Many dams can be low pH and this can be remedied by adding Agricultural Lime.

 

13.              Can I grow yabbies and fish together in the same dam?

 

Yes you can, however, all fish do eat yabbies so the number of yabbies produced by the dam will be lower with fish in it than no fish.  The advantage is that the fish will grow faster with the yabbies as an extra food source.  Silver Perch only have small mouths and only eat small food items so any yabby over 5 gram in size is usually too big for them to eat.  Large numbers of yabbies are easily produced in Silver Perch dams.  Both Bass and Yellowbelly have large mouths and even quite large yabbies are good food.  Yabbies in these dams will build up populations in the shallow water around the edges away from the fish.  As the yabby population increases the young ones will move into the deeper water looking for living space and be consumed.  The fish will not eliminate yabbies from a dam but they will limit the numbers produced.

 

14.              I have eels in my dam, can I grow yabbies?

 

No you can not.  Eels and yabbies do not mix.  There is nowhere in the dam that yabbies can go to escape the eels.  Yabbies are very frightened of eels, they take one look and run for their lives.  Even if the eels do not eat all the yabbies, the yabbies will refuse to live in the same water as eels and abandon the dam.  They will head overland looking for a better place to live, most will die in the paddock.

 

15.              How do eels get into my dam and can I keep them out?

 

Eels are a major problem on the East Coast.  They as a general rule they enter the dam via the overflow.  When the dam fills and then overflows, the eels swim up the overflow and into the dam.  They may be very small when they first enter and most people with new dams go well for the first 3 years then their yabbies just dwindle away to nothing.  This is because the eels that have entered your dam are glass eels or elvers and it has taken 3 years for them to grow to a size that impacts on the yabby population.  Most eels enter in rain/flood events when a lot of water is flowing through the dam.  It is not possible to prevent the eels entry into the dam under those conditions.  Aquaculture ponds are not farm dams so eels can be easily excluded see The Yabby Farmers Handbook.

 

16.              What is the best way to catch my yabbies?

 

There is any number of ways to catch yabbies.  It you have the time then meat on a string is the way to go.  If you want to catch large numbers quickly then we use opera house traps.  These are a collapsible trap which is very economical to buy and work exceptionally well.  There are 2 types of opera house traps, those with an entrance ring and those without.  In the wild you are only allowed to use the ring form of trap and all stores sell those, however they allow the yabbies to escape easily and do not work well.  In private dams you can use the ringless type and they preform exceptionally well, you will however need to purchase them from RBM Aquaculture.   These traps are imported from China.

 

17.              What is the best bait for yabbies?

 

Fresh is best, meat or fish that has a strong scent will attract yabbies to your traps quickest.  Kangaroo meat is good, pilchards and mackerel are good.  We use a lot of dried dog food for everyday trapping and even cans of cat food can be used.  Being fresh is the important aspect to remember.

 

18.              Do yabbies hurt when they bite?

 

Yes, yabbies have very powerful claws with sharp tips.  Take care when handling yabbies and approach them from behind to pick them up.  See The Yabby Farmers Handbook.

 

19.              How do I tell the difference between males and females?

 

Yabbies all look basically the same from the top.  You need to turn them over and check underneath.  Females have two round circular spots on the inside base of the 3^rd walking legs.  Males have two small projections on the inside base of the last pair of walking legs.  See Further Information for a diagram.  Colour plays no part in sex, however males are generally larger than females with larger claws and females are broader in the tail than males.

 

20.              How big do they get?

 

Yabbies grow to a maximum size of 350 gram, however most commonly 250 gram is a large yabby.

 

21.              Can I keep yabbies and goldfish together in my fish tank?

 

No, yabbies do not mind a feed of fish for dinner.  Goldfish are very stupid, they will swim right up to the yabby to say hello, the yabby will just grab it and eat it.  Best fish to keep with yabbies are natives ( Silvers, Goldens, Bass) these type fish are smart and keep away from the yabbies and will happily live in harmony together as long as they are a compatible size.  If these fish are large they will eat the yabby.

 

22.              Can I add more yabbies to the ones currently in my fish tank?

 

Yes you can, but precautions need to be taken.  The yabbies in the tank have established a territory and will defend that territory from invaders.  If you just add new yabbies into this tank then the new yabbies going in will know they are in new territory and not fight very well because they are in the wrong.  Those already in the established tank will fight hard to protect their homes from the invaders so a big fight will occur and lots of casualties.  The only way you can avoid a all out war is to remove the current yabbies from the tank and then rearrange the tank.  Move all the rocks and gravel etc to a completely new position in the tank, then drop both old and new yabbies in together.  Now they are all in new territory, all will cooperate together and get along just fine without any major violence.

 

23.              Do I need a heater in my fish tank?

 

Yabbies are cold blooded animals so  you can heat if you want but it is not necessary.  However the warmer the water the faster they will grow and breed etc.

 

 

 

 

 

 

 

 

 

 

 

 

 

FISH

 

1.                  How many fish do I need to stock my dam?

 

Depends on the size of the dam and the surface area.

For example if the dam is 20 meters wide by 50 meters long, then surface area is 1000 square Meyers.  At 1 mtr deep = 1000 cubic meters of water or 1 Mega Litre (ML).  At 2 meters deep = 2 ML  For a 2ML dam:

Silver Perch and Golden Perch fish fingerlings are stocked at 100 per ML so 200 needed for standard stocking.  This is the standard most people would use to stock their farm dams.

Australian Bass fingerlings are stocked at 50 per ML so only 100 needed.  Bass are ferocious eaters and require lots of food.

 

2.                  How many fish will survive in my farm dam?

 

As a general rule you would usually loose 30% of your fingerlings to predators.  Though these fish are natives and very fast and smart you will loose the odd one this week and next week etc.  This adds up over time and it is not till the fish are large that mortalities due to predation reduce.

 

3.                  What eats my fish fingerlings?

 

Birds are the main cause.  Cormorants or shags are the one that will give you the most grief.  These birds land on the dam, dive down and swim under water to catch your fish.  They are very effective at catching fish.

 

4.                  What can I do to stop predation?

 

Not much, you can shoo the birds away whenever you see them but that is only a short respite.  More shelter in the dam helps as the fish can hide and that makes it difficult for the bird to find them.

 

5.                  Will my fish breed?

 

No.  Unfortunately Silvers, Goldens and Bass are river species and need special conditions to breed.  Your farm dam is not suitable.  You will only get out what you put in.

 

6.                  Should I add extra fish each year to keep the numbers up?

 

Yes, as the fish do not breed the only way you can keep the numbers up is to add extra stock every year or two.

 

       7.       Do I need to aerate the dam?

 

No, fish in low densities ( less than 100/mega litre) are very tolerant of low oxygen levels, unless you are going to grow intensive levels of fish, no extra oxygen required.

 

8.            Should I add chemicals to clear the water?

 

No.  Fish prefer the muddy, turbid conditions and will thrive in muddy dams.  In clear dams they will not thrive and predators will easily capture any left.  In clear water thy may feed better as they can see the food but all Australian native fish are very shy and secretive who do not like to be seen.  In clear water without shelter they will be stressed.

 

 

9.            My dam is covered in floating weeds, is this a problem?

 

Yes it can be, if the weed covers a large portion or even all the surface then oxygen will not be able to enter the dam and the fish will die.

 

10.        Do any fish eat the weeds?

 

Yes Silver Perch are weed eaters and consume vast amounts of weed especially as they get older and larger.  However they will not remove weeds from a dam.

 

11.        Do I need to feed my fish?

 

No. Generally in your farm dam at low stocking densities extra food is not required.  Bass and Yellowbelly are live food eaters so unless you grow worms or yabbies you can not effectively feed them artificially.  Silver Perch eat anything so can be artificially fed if desired.  Many people do feed silvers, they feed a floating food such as bread.  This brings the fish to the surface to feed so you can see how they are growing.  Just through the bread in and the water boils as the fish rush up grab a piece and dive back to the bottom.  Its very spectacular and makes it easy to catch a fish, just add a piece of bread to your hook, drop it in and wham your on.  Be warned the nutritional value of bread in minimal so only use sparingly as large amounts of bread will actually slow growth as they eat that instead of real food.

 

12.        Do I need a licence to grow fish?

 

No.  You can grow all the fish you like for yourself or your friends and so long as you do not sell them then no licence required.  If however you want to sell fish then you must apply to NSW Fisheries for a aquaculture licence and meet the criteria of all Government Departments before you will receive a licence.

 

13.        Can I eat my fish straight from the dam?

 

It depends on the dam and the species.  Generally Yellowbelly and Bass straight from the dam are fine to eat as they are live food eaters.  Silver perch are susceptible to a muddy/earthy flavour which is due to the sediments and algae they consume.  See off flavours & purging in further information.  The best dams for no off flavours are muddy/turbid dams as algae does not grow well in them.

 

14.        What happens when my dam overflows, will I loose all my fish?

 

It depends on the overflow size.  Generally when fish are small they will stay put and not get washed out.  You trouble occurs when the fish are sexually mature at 2.5 to 3 years old.  This is when the instinct to breed will be strongest and if you have flood conditions during the breeding season some fish may well go out your overflow.  Usually it is male fish that wander and it is the females who stay put in the dam.

 

15.       What can I do to keep my fish in the dam?

 

You can widen the overflow so it runs wide and shallow, if the water runs under 150mm deep fish will not normally escape.  You can also mesh your overflows with a large mesh.  Galvanised steel reinforcing or pool fence is used.  Placed at a 45 degree angle to the flow can be very effective if maintained and if overflow is not too large.