A. No. The fish can fend for themselves once they are released. I do have food available if you wish to supplement their food. Care needs to be taken not to let uneaten food build up in the dam as this can spoil the water.
A. The species I stock are all suitable for dams. What is best for you and your dam comes down to what you want to achieve out of the process. Some issues to consider:
What species are native to the area?
Are there practical reasons to support the dams ecology?
Are you looking for something good to eat?
Are you looking for something that is fun to fish?
A. Some species are more compatible than others. There are also other factors to consider such as stocking rates, structure in the dam and the availability of food. Silver perch and Yellow belly are the most popular combination.
A. There are some birds that are a threat to your fish, namely cormorants/shags. The best protection for your fish is to have structure in your dam. You can add additional structure such as logs and branches, PVC pipe or tyres.
A. As the fish grow they will eventually feed off some of your yabbie population. Provided you don't overstock your dam with fish, the yabbies should still be sustainable. Yabbies are no threat to your fish.