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Which seafood is the most nutritious and consumes the least carbon?

Calling all seafood lovers: For a low-emission, healthy diet, consider eating oysters, anchovies and salmon…but maybe avoid shrimp.

These are suggestions from a new study that compared the nutritional and emissions impact of different seafood species, including bivalves and small pelagic forage fish, that would be a nutritional match for meat, albeit with remarkably low emissions. .

Countries that consume diets heavy in beef, chicken and pork will need to switch to environmentally sensitive foods to meet climate goals. But when it comes to dietary alternatives, fish has often been overlooked amid increasingly sophisticated plant-based protein substitutes such as pea protein burgers and soy-based chicken nuggets.

Where consumers are called for replacing red meat with fish, seafood is often treated as a unit, regardless of the vast differences in nutritional value and emissions impacts between different types, the researchers of the new. Nature Communications Land and Environment say exam For example, the output of emissions can have a significant impact on how fish are caught, or if they are farmed, what food they receive.

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The news aims to fill this information gap, thus helping to encourage more efficient use of fish to move diets in a more sustainable direction.

The researchers compared 41 species of shellfish, along with the nutrient density of each species and the impact of emissions. This created a scorecard of the most nutritious and least nutritious fish, which could then be measured against their emissions in each case.

The results generally supported previous research findings that fish, on average, have a smaller emissions footprint than common animal protein sources such as beef and pork. Interestingly, the results also revealed that 50% of the fish species surveyed had higher protein levels than beef, chicken and pork.

These overall benefits of seafood can be boiled down to one striking comparison in the study: beef has below average seafood nutritional value, but has a larger carbon footprint than any other species surveyed by the authors.

However, the real interest of the study lies in fish species where exceptionally high levels of nutrients overlapped with low emissions, because these have the potential to reduce dietary impacts without harming nutrition, the researchers reasoned.

There, they identified wild-caught salmonid species, including pink salmon and sockeye, smaller forage species including mackerel and anchovy, and farmed bivalves such as mussels and oysters, with the lowest greenhouse gas emissions per nutrient density ratio.

In fact, the researchers estimate that these three groups represent “35% of the available food density” and account for only 6% of the GHG emissions associated with the production of all the species evaluated.

And yet, despite these impressive credentials, these species are far from the most widely consumed.

In fact, we catch large quantities of the most nutritious and environmentally sensitive forage species, such as anchovies, to crush and turn into powdered feed for farm animals to meet our protein needs.

Meanwhile, some of the fish that appear most often on our plates – such as pike perch and hake, which fall under the unknown category of “white fish” – have some of the lowest nutritional scores.

For more evidence of the misuse of seafood, just consider octopus, squid, tuna, farmed and wild-caught shrimp: while these are the most desirable and expensive seafood products, they have the highest emissions profiles and are weighed frequently. researchers found it at the lower end of the nutritional scale.

Higher emissions were typically associated with wild-caught species that require a lot of fuel to catch, such as species caught with fuel-intensive long-haul fleets. Another driver of high emissions was how the species were fed, specifically how much feed, energy and filtration was required to grow the species. For example, a species called Amur catfish was high in emissions, while farmed mussels require minimal inputs.

By distinguishing fish species based on nutritional benefits and emissions, the research helps identify points of action for the future. Some of the low-hanging fruit would be increased fuel use efficiency and reduced energy inputs in aquaculture.

More difficult to achieve, but even more important, would be to increase the consumption of lower-impact, more nutritious fish species instead of red meat, perhaps with the help of new dietary guidelines that support the consumption of certain species.

This should also move us away from the incentives and subsidies that currently encourage boats to catch industrial quantities of forage fish just to feed animals, instead of using those incentives to encourage more sustainable catches of forage species to directly feed humans.

With so many eye-catching meat alternatives on the market, we’re forgetting about fish as a useful tool to steer our diets in the right direction, researchers suggest. “Although there are many hurdles to overcome, we have the opportunity to reshape seafood production and consumption towards species that optimize nutrition while minimizing climate emissions.”

Ziegler et al. al. “Evaluating the nutritional diversity of seafood in conjunction with climate influences provides more accurate dietary advice.” Nature Communications Earth and Environment. 2022

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