I receive an e-mail each week from my main source of seafood. It lists what's available and the price. It's all fresh so the availability and price change all the time. Unfortunately I'm a slave to the current price. It's not a commodity you can stock up on when the prices are down and I can't raise my menu prices when fish costs are high.
Obviously a huge issue. First you have to get it in fresh. One of the reasons I buy in Chicago is the high volume and product turn around. If the fish is whole it's easy to determine freshness. Check the gills, they should be bright pink or red. The redder the better. The eyes should be clear and moist. The flesh should spring back after being poked. If it's fillets you should check the bloodline. Again, bight pink or red. No slime on the flesh but in some cases slime on the skin is fine. (salmon) Also shelf life. The longer it remains a good product the fresher it was when it arrived. All bi-valve mollusks have a tag on them when they arrive indicating origin, when harvest and processor. Odor is also a good indicater but I probably rely on it the least. Last but not least if I'm not satisfied with the quality and freshness I bitch about it. I want them to give the old stuff to my competitor next time.
Second is storage. The fish should be iced down in a perforated container to allow for drainage. The fish shouldn't sit in the water. When the fish is prepped it should have minimal handling and time at room temp.
The fish shouldn't show signs of damage or mishandling. The shrimp and scallops should be of proper size and consistency. Scallops should be sand free. The shellfish shouldn't be opened and still alive. Mussels should react to contact and be relatively clean.
I also get seafood shipped directly from Hawaii and Seattle. The product is gorgeous but expensive. I try and stress to the servers if they see Hawaiian or Seattle fish for a special it is a treat and should be suggested. For the most part the staff are not fish eaters or good actors so it can be difficult.
When ever I do sushi it's when the fish is perfect. Another treat I like to push. I still say I have the best sushi in town.
I'll talk about meat purchasing in another post.