Aquaculture, the farming of seafood items such as bivalves (clams, oysters), seaweed and fish, has been a contentious subject in the United States. Still a relatively small sector, aquaculture has proponents and opponents on all sides, for varying reasons. A new study from the Nature Conservancy and researchers at the University of Adelaide looks specifically at the climate side of things, and it finds or confirms a few ideal pathways for sensible aquaculture.

There is a wide variety of aquaculture operations, ranging from meticulously ethical to environment-destroying, slave-labor-using chaos farms. It’s a very complex topic; some environmentalists rail against the realities or possibilities of pollution, excess fertilizer leading to algae blooms, escaped animals that out-compete local species and high energy use. Some activists point out the many labor violations that occur around the world (please be careful where you buy your shrimp!). 

The realities of aquaculture don’t always line up with the possibilities, which is why so many are against it, but those possibilities are intriguing. Theoretically, fish farming could ease bycatch and overfishing issues, have lower feed requirements by yield than land animals and could, in the case of bivalves, actually clean the water. That this doesn’t currently happen on a large-scale basis doesn’t mean that it couldn’t. 

President Joe Biden, so far in his tenure, hasn’t said or done much about aquaculture, but a highly publicized letter to the president pleaded with him to establish more rules and permits for offshore aquaculture. That letter was signed—just to add to the confusion of who supports what—by sustainable seafood pioneer Taylor Shellfish Farms and some respected scientists, as well as Cargill and Red Lobster, which mostly want more aquaculture so they can sell more and buy for less, respectively. 

In any case, this particular study takes a closer look at the climate effects of farming three types of marine products: seaweed, bivalves and fish. There’s a lot of interesting stuff in here! Seaweed, for example, can serve as an effective carbon sink, but the whole thing with storing carbon dioxide is that the storage medium—the seaweed—has to actually go somewhere. On land, carbon storage is done in the soil or in plants themselves. If seaweed is acting as that storage medium, well, what do you do with it? The seaweed, write the researchers, could be actively or passively sunk, but what are the effects of that seaweed on ocean floor ecosystems? More research, they say, would be needed.

[RELATED: The Future of Ocean Farming]

Overall, the researchers find that fish farming is, of the three categories, the hardest to optimize for climate-related goals. Fish feed, which is often made from wild-caught fish in the first place, is a major problem, as is the location of offshore fish farms and the emissions (such as diesel fuel) for getting out there. Bivalves, as filter feeders that clean water, are pretty low-impact; the work left to be done on them is mostly in packaging and transportation, at least in the United States, where labor laws are comparatively strict. 

One of the biggest issues actually takes place off the farm entirely: transportation. Some very high-value fish, such as tuna and salmon, are farmed, and those fish must be transported very quickly to their freshness-demanding markets. Rapid transportation via air is not ideal, climate-wise. 

The researchers have a list of six major suggestions, including farming some categories together (like fish and seaweed or bivalves and seaweed), fixing all the infrastructure and transportation issues (good luck with that, especially amidst our worsening supply chain issues), and effectively monitoring the carbon output of all the many different types of aquaculture operations. “Unsurprisingly,” they write, “there is not a single silver bullet solution that works in all sectors and situations.”

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Anne Connor

2 years ago

Vertical aquaculture is a win-win solution. Kelp sequesters carbon and dampens wave energy, protecting shorelines. It also reduces the acidity of nearby water, so shellfish grown in baskets on the same lines as kelp have healthier shells. Plus it creates a habitat for fish. Check out the work of Greenwave.

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