In an ideal world, we'd all have access to a friendly, reputable, neighborhood fishmonger, and could simply leave selecting fish for purchase up to them. Oftentimes these workers are very knowledgable, friendly, and a great resource for tips on both purchasing and consuming the fish at hand. Feel free to ask them questions; it's their job! To determine whether a fishmonger or fish counter is worth buying from (or for selecting any sort of prepackaged fish) try these tips:
For Whole Fish, Check:
- The eyes should be bright, clear, and convex, never cloudy or sunken.
- If the fish has any noticeable odor, it should be briny and of the sea, like seaweed. Anything noticeably pungent, "fishy," or similar to the scent of a beach at low tide should be avoided, as this indicates decay, and the off-putting aroma will only be intensified by cooking.
- One of the best indicators of freshness are the gills: they should be bright red.
- Skin ought to be taut, clean, and glistening, almost as if the fish were still alive. Skin color is not necessarily indicative of the fish's state of decay, as with many varieties the color will fade almost immediately after death.
- The belly should be taut, not swollen or sunken. A distended or shriveled belly indicates that the digestive enzymes from the fish's gut have broken down and essentially digested some of the flesh.
Ideally, fish fillets should be cut to order from a whole fish, as the increased surface area exposed to air and oxygen will speed up decay, oxidation, and the onset of a malodorous fishy aroma. Many fishmongers will do this, particularly if you call ahead; it can be especially handy when looking for unusually sized fillets, like when making gravlax. In circumstances where this isn't possible, check for these signs:
For Fillets, Check:
- The same guidelines for odor apply as for whole fish, but are even more important: fillets decompose more rapidly once cut, and there are fewer visible guidelines (like eye and gill appearance) to go by.
- If the skin is intact, see whole fish guidelines; also take note that the fillets are cut cleanly and that the skin is not ragged.
- The flesh should be firm, robust, shiny, and never dry. If you can, ask the fishmonger to allow you to touch the flesh; if it springs back when gently depressed, it should be good to go. If the edges of the fillet have begun to brown, skip it; this indicates excessive oxidation and decay.
- If a liquid-y mucous covers the surface of the flesh, it should be completely transparent and glossy; a milky, opaque appearance indicates that the flesh has been exposed to air for an extended period of time and is not fresh.
One last note: for an excellent guide on the sustainability of fish and shellfish, check out the Monterey Bay Aquarium's Seafood Watch. It's even downloadable as a PDF and available as an iPhone and Android app (particularly handy for consulting on the go).