I do not know about non edibles in the breede river but I know there are some monster spotted grunter there! Good baits from what I have hered is: pilchard, chocka (cut like worms) and mud and sand prawn and live mullet.
In the gourids river I have caught a Big ray( did not measure it as I took to long to look for my phone for a photo, and in the end my phone was in the car

) wing span was about 1.2m but not sure!
Always good to chat with the local fishermen in the area.
I fished allot at gourids estuary and rocks, stillbay and vleesbay area.
