Throw Your Fresh Fish Away Immediately If You Notice This
While there's a definite difference between the taste of perfectly ripe fruits and those that could use a bit more time, nothing bad will actually happen if you bite into a peach that's a little less than juicy. It may yield an unpleasant texture, but there aren't really any potential disastrous outcomes. That's not the case with seafood — when it comes to fish, the fresher, the better, and you never want to be eating one that has gone bad in any way.
For those who may not know exactly how to tell if your fish is a bit past its prime, there's a relatively simple trick you can use. This little tip is the reason that New York Magazine suggests buying fish with the head still intact rather than purchasing pre-cut filets (and, as a bonus, you can cut the fish exactly the way you need for whatever recipes you're making).
As Best Life explains, you want to take a look at the eyes of the fish you're about to cook. If you detect any cloudiness or opacity, or if they seem white-tinged in any way, you need to toss it and get another one. According to New York Magazine, the eyes of a fresh fish should be clear and bulging.
Other ways to tell if your fish isn't fresh
If you're not sure if the fish you've purchased to cook has cloudy eyes or not, or if you bought the fish sans eyes, there are a few other ways to gauge its freshness.
The first is the odor — while the scent varies according to the type of fish you're preparing, as Better Homes & Gardens explains, it should be relatively mild. If a few filets make your kitchen smell awful, they're likely not very fresh. Another trick that can be used for any fish, even filets with the skin removed, is to press it with your finger. According to Taste of Home, fresh fish should essentially bounce back from where it's pressed — if that little fingertip dimple remains, it's a sign you may be better off tossing it.
And, if the fish you're considering purchasing or cooking has the skin still on, there are a few other things you can examine. As NDTV Food suggests, check to see that the scales aren't loose and that the skin doesn't look dull in any way. You should also take a peek at the gills — if they're discolored or brownish rather than the bright pink or red hue they should be, that's a bad sign.
Don't risk your health — if you spot any of these warning signs, it's time to buy some new fish.