I, like a lot of fishos, am pretty fanatical with how I treat my catch.
Agree with most of what has been said. I would add:
1. Bleed fish on capture.
2. Once the blood is drained, placed in salt water slurry and make sure fish is not bent.
3. Fillet over the rib cage, not through.
4. Avoid/minimise any contact the fillet has with fresh water.
5. Small amount of fillets per snaplack bag, and record date.