i just thought i'd point out that there are spines on the gills as well, i usual just cut the line if i cannot see the hook and let them drop back into the surf although i'm not sure i agree with the old boy i saw once who simply clapped it in mid air with two rocks
C'mon lads they're only fish and some way down the evolutionary tree from you! Yes they are poisonous but YOU KNOW ABOUT THEM!
The best advice is to cut your line, as Tozer suggests. I however wrap a cloth around the fish bringing it down from head towards the tail. This will push the spines flat where they cannot spring up and get you!!! Grip the bundle firmly and unhook as usual. JUST DON'T PANIC.
I used to keep Bees. In Summer there are 60.000 in a single hive each one of which (give or take a few hundred drones which buzz a lot but are stingless!) I was severely allergic to bee venom, which would have resulted in death if stung! The secret was not to antagonise the little buzzers and treat them carefully and firmly, just like weevers!!!
We get a lot of Greater Weevers on the boats in Cardigan Bay. Often they grab feathers intended for mackerel and can come up 2 or 3 at a time, so you need to be alert if there are novices aboard. One skipper who once got stung now uses barbecue tongs to firmly grasp (but not squash) them while unhooking. Works really well and the fish swim off strongly upon release.
Having discovered that Greater Weevers are delicious, I keep 'em if a decent size. This time it's easier - fish onto baitboard, sound thwack with fish-clonker, one foot on its head, slice head off including gills & dorsal, grab with pliers and chuck over the side. Wrap with foil, with a bit of butter, and stick on the barby. Yum!
Lesser weevers are trickier as they're pretty small fish. Having said which I rarely catch them because for the target species on the sandy ground where they live I use bigger baits than they can manage. But I do carry two sets of long-handled artery pliers with me, just in case, and if deep-hooked I would just cut the trace at the knot.
i carry a set of artery forceps i 'acquired' from my previous employment as an A/E nurse, i grip the hook with the forceps, and give it a twist, and the fish will drop off back into the surf. i no longer kill any seafish i catch, the way i see it, if i fancy a fish supper, i can always buy it from the fishmonger, that ones already dead innit? why kill one fish if another is already dead? i have spent years hunting specimin carp, (i hold 2lake records, and a complex record) and there is nothing i like better than watching my catch beat that tail strongly as it swims away, ive carried that attitude over to sea fishing. i found a small mark in dorset where i caught 36bass in a few days spinning amd ledgering lug, not a one was killed.