Fish should be dispatched as quickly as possible if they are not stoned
outright. A dive knife to the brain is the proper way to do this for
all reef fish in the Gulf of Mexico. Leaving fish alive on a stringer
is just bad karma and asking for a visit from a grey suit since the
fish will still be sending out the vibrations of a wounded fish.
Vibrations which are fr more effective than blood at attracting sharks.
From time to time fish will swim off a freeshaft or tear off a lineshaft, especially if tension is applied to the line instead of the shooter swimming to the fish. When this happens the shooter should make every effort possible to find that fish and recover it. While fish can heal from a grevious looking injuries when shot above the spine they are sure to die when belly shot. Again, a wounded fish swimming around the reef with you is only going to increase your chances to witness a hungry shark up close.
Spearfishing is the most ethical form or marine harvest when done correctly. The secret is the last part, being done correctly. More often than not that means knowing when not to pull the trigger. If you don't know what type of fish it is, don't pull the trigger. If you don't know that the fish is for sure large enough, don't pull the trigger. It is the last one in particular that makes many operators cringe when we see spearguns with measurements marked on the stock come aboard.
Many shooters with good intentions have put these marks on their guns. The problem is that clearly you can't measure the fish before you shoot it and the idea of using it to calibrate your eyeballs underwater likewise doesn't really hold up. many more experience shooters scornfully refer to the marks as "poaching hashes." There should be a legal measuring tape on the boat and that is all that is required. Otherwise these guns announce the owners intentions to shoot questionable fish and measure them underwater without fear of bringing them to the surface for inspection.