4 hidden dangers lurking in your favorite saltwater fish

Seafood might be a dinner favorite, but behind every flaky bite lies a deeper story about our oceans. From sushi-grade tuna to everyday canned sardines, our choices ripple outward affecting everything from our health and government subsidies to the ecosystems that stabilize our planet. According to the USDA, 45% of Americans eat seafood weekly, adding rich nutrients to their diet. Yet because most of us live far from the coast, the consequences of what ends up on our plate are easy to overlook. Evaluating if seafood deserves a place in your diet is a powerful way to put pressure on the policies and commercial practices that overlook the wellbeing of animals that keep our planet thriving. Ready to consider your options?

In today’s issue:

• Early Adopters: algae & niche fish

• Health: Powerhouses of nutrition

• Industry: Byproducts of your favorite fish

• Environment: Contaminants everywhere you look

• History: Empty oceans reached at record speed

EARLY ADOPTERS

Early adopters are cautious about saltwater fish, and for good reason. Concerns about contaminant levels, bycatch, and overfishing have led many to explore cleaner, more sustainable options. Many people are turning to algae oil as a source of omega-3s, the key nutrients often credited to fatty fish. Since fish get their omega-3s from algae in the first place, going directly to the source offers the same essential nutrients without the environmental cost and moral dilemma tied to commercial fishing.

For those who still want to include fish in their diet, look for wild-caught, single-line fish. In particular Atlantic mackerel and Atlantic herring are great options that offer strong nutritional value and are high in Selenium, which mitigates mercury toxicity, naturally low in the North Atlantic (2019). These fish have a a lighter environmental footprint when sourced from responsible fisheries like Patagonia Provisions. However, since saltwater fish can still contain heavy metals and other pollutants, even the cleaner varieties should be eaten in moderation.

HEALTH

Powerhouses of nutrition

Seafood provides a unique combination of nutrients. Per serving, the most popular saltwater fish provide over 10% of the Daily Value for both Omega-3 fatty acids & protein, without any carbs. As far as healthy fats are concerned, saltwater fish don’t produce omega-3s themselves. Instead they consume algae, the original source of omega-3s, or smaller organisms like krill and plankton that feed on algae. Unfortunately, healthy fats aren’t the only thing fish absorb from their food chain.

Fish absorb nutrients from the water around then and the food they eat, which also means they take in harmful substances the same ways. Water pollutants, like mercury, arsenic & microplastics, are more easily absorbed by fish than airborne pollutants are for land animals. This makes water quality crucial to fish health and also makes it difficult to detect when contaminant levels are unsafe.

At the same time, saltwater fish are rich in micronutrients and fit well into a low-carb diet. Many popular saltwater fish contain more than 15% of the Daily Value per serving for 20 micronutrients, as shown in the table below:

INDUSTRY

Byproducts of your favorite fish

In 2022, the fishing industry pulled 2.58 trillion fish from our oceans. Roughly 40% were discarded, often dead or dying, because they were not the intended species, commonly called bycatch. This widespread bycatch practice has persisted for over 50 years with little to no consequences, except for the ocean itself. It plays a major role in overexploiting nearly 80% of global fish populations, putting marine biodiversity at serious risk.

This decline has consequences for bycatch species like whales, dolphins, sea turtles, and certain fish that serve as keystone species. These animals play a vital role in maintaining a balanced ocean ecosystem by regulating populations of other marine organisms. When their populations are drastically reduced or wiped out, it can trigger widespread disruption and even ecosystem collapse. Much of their decline is tied to the fish we choose to eat and the industrial methods used to harvest them:

In addition, the US depends on a global supply chain involving 13+ countries to meet the demand for the most popular saltwater fish. The table below illustrates just how heavily we rely on international trade partners to support current consumption levels:

ENVIORNMENT

How does mercury get into the fish?

Mercury enters the atmosphere mainly through the burning of fossil fuels, particularly high from coal-burning power plants, mining for gold & producing metals. Once airborne, mercury settles onto oceans, rivers and lakes through rain, snow or dust. Once in water, bacteria transforms it into methylmercury, a highly toxic bioavailable form of mercury. As larger fish eat smaller ones, mercury accumulates at each level of the food chain, a process called biomagnification. Regularly eating fish, even those with low mercury levels, can cause it to build up in your body over time. For commonly consumed fish, mercury levels per serving typically range from 0.01 ppm to 0.39 ppm. To reduce the risk of exposure, it’s best to eat smaller fish or avoid fish entirely.

While the oil and gas industry is a significant source of mercury in ocean fish, the agricultural sector also poses serious risks to marine ecosystems. Runoff from synthetic fertilizers and chemicals flows into rivers and eventually reaches the ocean, where excess nutrients fuel massive algae blooms. These blooms deplete oxygen and increase acidity, creating dead zones where marine life struggles to survive. The US is responsible for 15% of the world’s 500 dead zones, including the second largest—an area of 6,700 square miles where the Mississippi River meets the Gulf of Mexico, according to NOAA.

HISTORY

Empty oceans reached at record speed

After WWII sonar technology, originally developed to detect underwater mines, torpedoes and submarines, was adapted for commercial fishing. This innovation enabled fishing vessels to locate fish with precision, revolutionizing the scale and speed of ocean harvests. Today, more than 440,000 industrial boats use sonar to sweep the seas, dramatically increasing catch rates and adding pressure on marine ecosystems. On average, vessels can harvest the following amount of fish:

1. Purse Seine + Sonar can harvest 75 tons of fish a day

2. Midwater Trawls + Sonar can harvest 30 tons of fish a day

3. Bottom Trawls + Sonar can harvest 30 tons of fish a day

4. Longlines +Sonar can harvest 10 tons of fish a day

5. Gillnets + Sonar can harvest 7 tons of fish a day

6. Single-line + Sonar can harvest 1 ton of fish a day

How fast we are harvesting life from our oceans isn’t a coincidence. In 2019, the US subsidizes the global fishing industry with $21 billion to enhance their harvest rate and directly promoting overfishing. This level of industrial efficiency has pushed many saltwater species to record lows compared to their 1970 population peak:

1. Cod (Atlantic): 97% decline

2. Tuna (Bluefin): 85% decline

3. Grouper: 65% decline

4. Haddock: 60% decline

5. Swordfish: 60% decline

6. Snapper (Red): 60% decline

7. Tuna (Albacore): 50% decline

8. Halibut: 50% decline

9. Herring: 50% decline

10. Mackerel: 40% decline

11. Tuna (Yellowfin): 40% decline

12. Sardines: 30% decline

13. Anchovies: 30% decline

14. Pollock: 20% decline

In truth, the ocean has always been humanity’s life support system. It gives us food, supplies the air we breathe, and helps regulate our weather. No civilization has ever survived without a healthy ocean, and its a bit fishy to put the modern era to the test.

TIGHT 5

• Fish oil: requires 450 g of fish to produce 100 g of fish oil.

• 3.8%: The US consumption of the global seafood supply.

• 93%: of Earth’s CO₂ is stored in our oceans.

• Marine Plants: can store 20X more carbon than the same area of rainforest.

• Swordfish: are the fastest fish in our list, reaching a top speed of 60 mph.

PUBLIC SERVICE ANNOUNCEMENT

Thanks for tuning in to learn about small changes that add up to make a big difference. When changing your lifestyle, consider professional advice (not me). I am a member of the Amazon Affiliate program and do make a commission from your purchase without any added cost to you. Your contributions allow us to continue making content.

Got a topic you’re curious about?

Just reply to this email—we take suggestions seriously and most of our best ideas come from community members like you. Go ahead, hit reply and tell us what food you’d like us to evaluate next. We’re listening.