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Much of the world’s population depends on fish as a source of protein,
and that demand is only growing.
But lakes, rivers, and oceans are already overfished,
and many fisheries can’t produce as much as they used to.
Which means that fish farming, also known as aquaculture,
is going to need to ramp up to take the pressures off of wild fish populations.
However, as unsustainable as commercial fishing has been in the past,
aquaculture doesn’t have a sterling reputation either.
Which leads to questions like, is it possible to farm fish more sustainably?
And which one is actually more harmful?
How can we choose what’s best for the environment
without giving up on our sushi rolls and our crab cakes?
Well, as you might be expecting, the answer is not straightforward.
So let’s take a look at some of the positives and negatives
of catching and farming fish to see what comes out on top.
Let’s dive into the environmental impact of wild-caught fish first:
the good, the bad and the ugly.
We’re going to consider a handful of factors: things like greenhouse gas emissions
and direct ecosystem impacts, as well as waste
and overall efficiency of different fishing methods.
The good news is that wild-caught fish don’t require
any extra space or any water to be brought in.
Because, as the term implies, they live in the wild.
They inhabit naturally occurring bodies of water
and eat what is available to them in their environment.
So in comparison to other protein sources, like pork or beef,
they require very little additional resources before being harvested.
They’re also a relatively easy to access source of high-quality protein,
which is one of the reasons at least 1 billion people
rely on fish and shellfish as their main protein source.
And in general, fish and shellfish are pretty eco-friendly protein choices.
For instance, gram for gram, fish contains more protein than nuts.
So the greenhouse gas emissions to produce
the same amount of protein are correspondingly lower.
The problem is that once the world caught on that there were literally
plenty of fish in the sea, commercial fishing operations ramped up.
Those big ships emit a lot of greenhouse gases.
And there are a lot of them.
Worldwide, the total number of fishing vessels in 2018 was estimated at 4.6 million.
Not all fishing operations are created equal,
and the emissions depend on the type of fishing being done.
Shrimp and lobster fishing have higher carbon emissions because
the boats have to travel a long distance between traps,
and constantly stop and start as they place their pots.
Other methods are less fuel-intensive.
Purse seine nets are used to capture large groups of small schooling fish by
literally scooping up the entire school in one net.
They are among the most fuel-efficient ways to catch a lot of fish at once.
Hook-and-line fishing, where a long line is set out with one or more baited hooks,
is also fairly fuel-efficient because the line
doesn’t create any additional drag on the boat.
However, wild-caught fish aren’t just eaten locally.
These harvested fish are shipped all over the world,
and shipping comes with its own set of greenhouse gas emissions.
Looking beyond the greenhouse gas emissions of wild-caught fish,
there are a whole host of other environmental impacts as well.
Net trawling, where large fishing nets are towed behind a ship,
can result in a lot of bycatch.
Bycatch is anything caught in fishing nets that is
unwanted and inevitably is thrown back as waste.
Around 10% of the world’s commercial fishing intake is discarded as bycatch,
which is unfortunately not just small unwanted fish species.
It’s often larger marine creatures like sharks, sea turtles, dolphins, even seabirds.
Fortunately, practices like hook-and-line fishing can limit how many creatures are
caught accidentally, especially when fishers use
a special hook to target the catch they want.
Then we have bottom trawling, where weighted nets
are dragged across the seafloor.
This one is infamous, as it can decimate entire ecosystems found on the bottom,
some of which can take decades to rebound.
Finally, even if we know better now, a lot of wild-caught fish species in both oceans
and lakes have been harvested unsustainably for a long time.
Commercial fisheries took more than the existing population
could replace through reproduction, so these fish species are going to
take a while to rebound, even after unsustainable practices have stopped.
So wild caught fishing methods don’t always get
an “A” grade on their sustainability report card.
It’s been proposed that we should consider supplementing
or completely switching over to farmed fish as a source of protein.
But aquaculture has earned itself a bad reputation as an unsustainable
and environmentally degrading practice.
So… how accurate is that reputation?
Once again, it’s more complex than just saying it’s good or bad.
Now, from a greenhouse gas perspective alone, producing more farmed fish
would be much easier on the planet than producing more beef.
Cows are notoriously inefficient eaters.
Whereas fish convert the food they’re given into biomass very efficiently.
For some species, it’s like a 1:1 ratio.
That means one pound of fish food can yield up to one pound of fish.
So fish farmers get a lot of bang for their buck.
Not only that, but fish and shellfish often require less space
and resources than other protein sources like chicken or beef.
Many shellfish species are grown vertically,
and they are pretty small when compared to other proteins.
And since farmed fish eat what humans choose to feed them,
they can be healthier for us too.
Depending on the conditions they’re raised in,
farmed fish may have lower levels of heavy metals like mercury.
Farming shellfish plays another important role.
Not only are they a great protein source, they also help improve local water quality,
because many species are efficient filter feeders.
When shellfish feed, they pull water through their bodies,
keeping the small particles and pushing the water back out,
so they actually pull a lot of stuff out of the water.
But it’s not all great news for aquaculture.
Fish are often farmed in natural bodies of water,
with only a simple pen separating them from the wild ecosystem.
Horror stories abound of farmed fish escaping their holding pens into
natural bodies of water and competing with wild fish populations.
And unfortunately, that can and does happen.
Not to mention, fish are messy.
They are messy eaters, and then of course
what comes out of the other end is also messy.
The extra nutrients coming from this waste end up building up
in the water at the fish farms.
These extra nutrients can lead to algal blooms and deplete oxygen in the water.
Fish farms can also be a breeding ground for disease.
All those fish sharing the same water and swimming in small spaces
makes it easy for them to get sick.
Which means that farmed fish often have to be given antibiotics.
And if they are once again in a pen in a natural body of water,
the antibiotic can easily diffuse out
into the ecosystem, affecting surrounding waters.
There’s also the possibility that improper antibiotic applications could lead to
antibiotic-resistant bacteria in the water,
which has implications for human health as well.
And in some places around the world,
the farms themselves are putting pressure on the surrounding ecosystems.
For example, in Indonesia, an increase in shrimp farming
is leading to increased mangrove forest loss.
That’s because these coastal trees are being cleared
to make room for more farms.
Finally, some species of farmed fish, like salmon, are being fed wild-caught fish.
These large carnivorous fish require a lot of smaller, wild fish to sustain them.
Not only does this deplete wild-caught resources,
it also kind of defeats the purpose of fish farming in the first place.
But let us return to the topic of greenhouse gas emissions.
Because fish farms might not require giant boats traveling far and wide,
but they still need energy.
How much often depends on the species.
For example, catfish farming can be so resource-intensive that it’s about
as bad as beef, at least as far as greenhouse gas emissions are concerned.
But just like with wild caught fish, the industry has recognized there are
some unsustainable practices, and has implemented many improvements
in order to try and address these issues.
For example, fish pens are monitored more closely
to manage situations where escapes might happen.
And some kinds of fish farms are being moved inland,
where fish can’t escape into the surrounding wild ecosystem at all.
And since they’re isolated from wild populations,
that also helps with the spread of disease.
Plus, antibiotics that are applied stay contained within the fish farm itself.
Aquaculturists who want to be more sustainable
are also being more conservative about antibiotic use.
They’re using antibiotics on an as-needed basis,
instead of administering them to the entire population upfront.
And aquaculturists can also opt to use fish vaccinations
as a way to prevent disease outbreak.
Various improvements can also be made to aquaculture practices
where fish farms are located in natural bodies of water.
Fish farmers can place coastal fish pens in places with high currents,
to help wash away excess nutrients from fish feed and waste.
And better waste management systems overall can be put in place
for those farms that used to drain their fish waste into the surrounding ecosystem.
Finally, new standards have been created to
help ensure more sustainable fish farming practices.
The Aquaculture Stewardship Council has created
a set of best practices to improve fish farming with standardized methods.
It’s opt-in, but fish farms can obtain a certification to signal to consumers
that they are following sustainable aquaculture practices.
In the end, unsurprisingly, there is no straightforward answer
to which is better or more sustainable.
Ultimately, what it comes down to is choice.
Since you can’t say up front that something is better
because it’s farmed or wild caught, learning more about where your fish
comes from can help you to make more sustainable decisions.
And there are already programs in place to help with that!
For example, the Monterey Bay Aquarium Seafood Watch program
helps consumers learn about different fisheries,
and recommends more sustainable ones.
Programs like this one can provide consumers with information about
both wild-caught and farmed fish, so that we can weigh
the pros and cons and make more informed decisions.
Maybe this is a bit more work than saying one way is good and one way is bad,
but it’s not like an issue this big was ever going to come down to black and white.
Basically, the idea is that we can make informed decisions without
making big categorical judgements about what kind of seafood is better.
Which is great, because man, I could really go for some crab cakes right now.
Since moving to Montana it’s just not really been on the menu.
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