Doctors and nutritionists often advise patients to reduce consumption of red meat, and replace it with fish to cut undesirable fats and get a boost in omega-3 fatty acids. But not all fish offer the same benefits, and some can actually be dangerous. So which are the best and worst fish to eat?

Resources that can help

Environmental issues plague the commercial fishing industry and hurt the viability of wild-caught fish as a sustainable choice, and mercury contamination in fish can compromise wild-caught as a healthy option. But farmed fish may not be safer to eat, unless the fish are farmed sustainably.

To make things more confusing, environmental conditions, fish farming practices, and commercial fish methods change over time, which means the list of best and worst fish also changes over time. Luckily there are several resources that keep up with the changes.

The Monterey Bay Aquarium offers a quick search by fish and maintains a series of seafood pocket guides for the United States. The Marine Conservation Society in the UK maintains a helpful seasonal guide and the Good Fish Guide, which rates fish from best to worst. The NOAA Office of Protected Resources maintains a separate list of endangered or threatened species.

Fish lower on the food chain

Not every resource judges the health and sustainability of fish in the same way, so there may be slight variations on what each list considers the best or worst. But there is one thing each list has in common: eating fish lower on the food chain is more sustainable and typically safer than larger fish toward the top of the food chain.

This holds true in the case of farmed fish because fish toward the top of the food chain tend to be carnivorous and require wild-caught fish to supply the farmed fish meals. In fact, carnivorous fish can require anywhere from three to fifteen times as much wild-fish protein to eat as they will produce. And wild-caught fish that are higher on the food chain tend to accumulate higher concentrations of mercury, making them potentially unsafe to eat. So for both wild-caught and farmed fish, those lower on the food chain tend to be the best choice.

Best and worst to eat

In general, fish farmed in the US and UK are typically safer than imported farmed fish, and smaller species of wild fish are safer than the larger species.

Best fish to eat: striped bass, catfish, wild clams, wild oysters, Pacific cod (non-trawl), most crab (except red king crab), wild Alaskan salmon, farmed tilapia, monkfish, farmed rainbow trout, mahi mahi (US), Alaskan halibut, and some varieties of canned tuna.

Fish to avoid: Red grouper from the Gulf of Mexico, swordfish, Chilean seabass, blue and striped marlin, Atlantic cod, red king crab, imported mahi mahi, orange roughy, shark, swordfish, farmed Atlantic salmon, Atlantic halibut, imported shrimp, red snapper, wild sturgeon caviar, and several varieties of non-canned tuna.