A live fish is better than a dead one

08 September, 2022

I have just been involved in finishing a film about the overfishing in our world’s oceans. It is frightening to see how people are affected, everywhere, when the fish disappear. How people lose both jobs and their source of protein. But how overfishing has affected the ecosystem, in the ocean, can be a far more serious consequence – long-term.

A live fish in the sea can be better than a dead one on the dining table – for humanity.

Since the beginning of commercial industrial fishing, the fish in the sea has decreased drastically. Today, it is estimated that 90 percent of all the world’s fish stocks are maximally exploited or threatened with collapse.

It is serious that the fish are disappearing because we humans are dependent on the protein from the sea. But there may be a more serious consequence of us taking the fish out of the sea; that it accelerates climate change.

fish
Photo: Tobias Dahlin

The fish poop – and that’s a good thing

When I was little I had an aquarium. The fish weren’t that many at first, but multiplied quite quickly and pretty soon a thick layer of fish poo settled on the bottom. It wasn’t much fun emptying and cleaning that aquarium as often as needed. In the end, the aquarium disappeared and I guess it was my cleaner mother who couldn’t take it anymore. But – what is not so much fun at home, seems to be incredibly valuable in the big “real” sea.

Small marine organisms, phytoplankton, absorb carbon from the water and the air around them in photosynthesis. When phytoplankton are eaten by zooplankton and then by ever larger creatures and fish, the carbon migrates up the food chain. When the fish poop, much of the bound carbon sinks to the ocean floor, where it can be stored for millennia.

This is pretty obvious, when you think about it. But why don’t we talk about the significance of it? It should be more topical than ever? I decide to find out where the research stands today.

fish
Foto: Johan Candert

Dead fish are better in the sea than up on a plate

Daniele Bianchi, a researcher at the University of California and has written a high-profile article in Science about the importance of fish poop.

“The most interesting thing is that we have begun to look at fish and other large marine organisms we have exploited, that they have an integral role in the carbon cycle on Earth. Perhaps the fish is also important for understanding how much carbon is sequestered.

The researchers divide about how much it is eaten, how much it is pooped and how much of it settles on the bottom. But most people agree that fish are important for carbon to stay in the sea.

Silvia Earle, world-renowned marine biologist and oceanographer explains it this way;

– Regarding the great question of our time; climate change, sea life plays as big a role as land life in sequestering carbon. /—/ And when we take whales and turtles and tuna and lobsters out of the ocean, we break the carbon cycle, where carbon goes through photosynthesis and is tied up in marine life. /—/ When we take life out of the sea, we contribute to increasing the amount of carbon dioxide in the atmosphere.

sylvia earle diving
Sylvia Earle. Foto: Johan Candert

Fish as a climate improver

With less fish in the sea, less carbon sinks to the bottom and is stored. That means more carbon in the atmosphere.

Alltså; när vi fiskar upp fisken släpps kol ut i atmosfären och det borde skynda på klimatförändringarna. Men att den slutsatsen innebär att vi borde lämna fisken i havet – är kontroversiell. Daniele Bianchi, forskaren med fiskbajsstudien, säger att det behövs mer studier.

– It’s probably a bit too early to actually say because we really don’t know, but setting fishing quotas has historically been more about economic factors.

But there is another group of researchers at Uppsala and Gothenburg universities, among others, who are already proposing a climate reform within the fisheries.

coral
Foto: Göran Ehlmé

Maximum carbon sequestration

Today, commercial fishing is governed by MSY, maximum sustainable yield. Researchers at ICES, the International Council for the Exploration of the Sea, make calculations and give advice on how much can be taken from a stock at most. After that, states set quotas for fishing. Largely based on financial interests in favor of the fishery.

But, say these researchers, if you only look at how much you can take out of a species, or even several species together, you miss one of the great points of the ocean. They want to complement MSY with a new goal; MCS; maximum carbon sequestration, maximum carbon binding.

– MCS is intended as a new concept – (to) be able to point more clearly to the type of fishing measures that reduce the ocean’s ability to sequester carbon.

So says David Langlet, professor of environmental law at Uppsala University, and one of the co-authors of the article proposing the new MCS concept.

– There seems to be a great potential for the administration to contribute to counteracting climate change. If you have a very short-term perspective, it might pay off to carry on fishing as you do today. But with a longer perspective, it is clear that it does not.

ocean bottom
Foto: Göran Ehlmé

Everything is connected – in every imaginable way, it’s called ecosystem

The importance of overfishing becomes so much greater than that we get fewer fish on the dinner table. The oceans are losing some of their ability to sequester carbon. When we on land have been net emitters of carbon dioxide, the oceans have prevented us from already perishing from heat stroke. And it turns out to be partly thanks to the fishermen. The fish that remain in the sea, that is, the ones we don’t catch.

Silvia Earles recently wrote on her facebook page;

“No sea, no life. There is a climate crisis — but there is also an ocean crisis. We have seen in my lifetime the collapse of the food webs of the great oceans. We’ve taken so much out of the ocean, and we’ve put so (a lot of trash) a lot of horrible things in it that the ocean has real problems.”

Feel free to watch our latest feature film ” Empty Sea – The Hunt Towards the Bottom”

Text: Lena Scherman
Photo: Tobias Dahlin, Johan Candert, Göran Ehlmé

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