There are several accessories you will need that will improve your fishing adventures no end.
First on the list is rod holders. Rods are literally impossible to transport in a kayak safely and effectively without them. So be sure to get yourself some rod holders.
Never go out on a kayak without a life vest. It doesn’t matter how good you are at swimming you really do need to take a life vest. A whistle or loud horn is also good to have and required by law in some places.
A dry pack is another item that is well worth investing in. Things like phones etc really don’t want to be getting wet while you’re out on the water. Especially if you need to make an emergency phone call.
When fishing there is always those occasions when you will want to stay in one place. For this reason you are going to need to take a small anchor with you. There are some real neat ones available nowadays.
If you are going out onto waters you are unfamiliar with a GPS device such as a watch is a great addition to your kit. Getting your position out to people in an emergency could be the difference between life and death.
A good knife is also a must while out kayaking. You never know when you may need it. Keep the knife safely attached to your body via a strap. If you are unfortunate enough to tip your kayak, you may well misplace your knife. If you manage to get tangled up in doing so, this would be the time you would most need it.