If you're doing specimen, maybe you will get a few more responses by posting in the specimen section. Donaldson Dam is usually a favourite for Specimen angling around Gauteng, but I cant comment on it, or any other local venue around Gauteng, but names that come up are places like Emmerentia, Florida Lake, but like I said, can't really give you any more, but maybe you can use the info as leads and follow up.