Having worked in many retail and wholesale environments over the years, I have observed a number of different ways in which businesses display, package, and sell their products. Unfortunately, it's not uncommon to find a retail store with very poor quality controls, untrained staff, and no real understanding of why they do things the way they do. To be honest, it's often the recreational fisherman who has a better understanding of how to package and store his catch.
The biggest mistake that many wholesalers and retailers make, is that they intentionally wash fillets with tap water, or use water as part of their processing method, being ignorant of the detrimental effect that this has on the fillets. I recall working for one retail outlet that had such "quality" controls. We were encouraged to dunk our fillets in a container of water. Their theory was that this removed any residual scales following the skinning and pin-boning process. This is terrible practice as it increases the temperature of the fillet, washes out the natural colours, oils, and flavours of the fish, and exposes it to all sorts of bacteria, since it is being constantly dunked in what becomes a tepid cesspool. It also isn't particularly effective at removing scales.
When retailers use such practices, and then proceed to stack fillets in trays for display, this water drains off onto the bottom of the tray, leaving the fillets sitting in a warm bath of bacteria and water. Some retailers even wash and spray the fillets again each morning when they are retrayed! There is a reason beef, pork, and lamb are not washed or processed around water, and the same logic should be applied to fish fillets.
Certain species can tolerate a bit of water as they have a flesh that allows water to naturally slide off. However, many species such as Pink Snapper, Threadfin Bream, Salmon, Gummy shark, Tuna, and others, tolerate water terribly, acting like sponges. The only time it is really necessary to use water is when there is a significant gut spillage onto the fillet, and even then, water should be used sparingly and quickly dried off.
Leaving fillets in trays, on top of ice, is bad practice for further reasons: if plastic trays are used, coolness is not transferred as effectively --- stainless steel is a superior option; if fillets are stacked too high, the higher layers are left warmer than the bottom layers; and if the fillets are not glad-wrapped, they start to oxidize. All of this reduces shelf-life, especially when combined with the previously mentioned practices.
The best looking and tasting fillets are those that have been dry-filleted. Aside from good aesthetics, they have also not come in contact with massive amounts of bacteria. In my opinion, the best method of storing dry-filleted fish fillets is to vacuum seal. Vacuum sealing prevents oxidization and prevents the fillets from coming into further contact with bacteria. Handling is also easy and clean.
Recreational fisherman spend a tidy sum of money on boats, rods, reels, etc. They ought to also invest in their fillets. A sharp filleting knife, the patience to fillet with care, and a vacuum sealer and bags to store their catch.
I researched vacuum sealers extensively before making my first purchase and happened across a company called LAVA. I now own 2 of their machines and both have worked brilliantly over several years, sealing tens of thousands of packets of fillets and seafood products for my business.
If you are looking for a quality, reliable machine, I highly recommend them. I have received fantastic service from their representative here in Perth: Michael Jonientz. Give him a call and he will be able to answer all your questions.