Sorry, its a Native fish thing. If you don't go collecting in the wild it probably isn't that obvious.
I am a member of ANGFA, one thing that is drummed into us on all collection trips is the importance of avoiding bucket burn. Bucket burn is when you take fish from the wild and throw them into a bucket, they get stressed and they swim around and around the bucket glancing off the sides and scrapping away their slime coating. Years of collecting experience amongst the members of ANGFA has found that you have a greater survival rate if you do the following instead.
1 line your bucket with a black plastic bin liner, then fill with water from the creek you are collecting. Add a tablespoon of salt for hygiene reasons. Aerate the water with a battery powered aerator and place bucket in the shade away from the sun.
2. When you catch fish, put them in the lined bucket. When you are leaving either tie up the bag like you would a plastic fish bag or transfer into clear plastic bags and use the black plastic bag to transport the fish home. Darkness is good, its stops them getting stressed.
The same logic should apply to transporting fish that you buy from another hobbyist. Don't use a bucket, put your clear plastic bags inside a dark bag like a woolies grey plastic bag. If you notice when you buy fish from an Aquarium, if its any good, they will put your purchase in a dark plastic carry bag to take home.