All recreational fishers in South Africa are required by law to buy recreational fishing permits with the implication of such a permit being that the fish caught under it may not be sold.

The recreational permit imposes daily fishing limits (as far as quantity is concerned) and limits fishers to certain periods of the year. This ruling was put in place to protect the marine life during breeding periods as well as limit conflict between commercial and recreational fishing.

If you're planning a fishing trip to Cape Town, just take note that there are areas where fishing is prohibited. I'm not familiar with the specific areas, but I know (for example) that the Boulders area in False Bay forms part of a conservation area where even thinking of fishing is subject to a hefty fine. ;)