[alanw]

I think up to 3 miles out you are still in county (sheriff) jurisdiction, which is also state (F&G) jurisdiction. Out to 12 miles out is US (FBI) jurisdiction. From shore out to 200 miles is still US (Coast Guard) jurisdiction.

To be sure you'd have to ask the county sheriff, DFG, and the Coast Guard. Carrying and discharging are two different things. Most likely the CG would be the ones responding to a discharge call. It's likely you don't even need to use the fishing exception clause to carry/discharge outside of the 3 mile zone.

I'm not a lawyer and probably wouldn't even rely on my own opinions. The best thing to do is pay a gun lawyer for his opinion and have him on retainer.