Up north I fish around seals and sealions on a daily basis, I have yet (in 30 yrs. of salmon fishing) had a seal take a fish, on the other hand, I lose anywhere from 6 to 15 salmon a year and a handful of paddle halibut to sealions, it seems every season gets a little worse.
I did get a little revenge last season on 1 particularly aggressive bull that had been staying in 1 hotspot all season and was stealing fish on a daily basis, I saw him chasing about a 30-35lbs. king and had just enough time to launch a sealbomb, it hit the water about 10 feet from him and it diverted his attention, he came over to investigate and with mouth wide open and less then a foot away it went off, he porpoised 1 time and disappeared, not sure what the damage was but I think it atleast loosened a tooth or 2 and gave him a headache.
Commercial guys in Ak can legally shoot them (if there interfering with their livelihood), always gets a smile out of me when I hear a distant 12 ga. blast.