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Over the past couple hundred years, we've become a little bit too good at catching fish. As a result, we've completely transformed the oceans. A 2021 study estimated that we have reduced the mass of fish in the sea by 60% since 1800, but advances in technology don't have to be exclusively bad news for fish. They can also help make fisheries more sustainable.

A sustainable fishery means the fish population can be maintained even if we're catching a certain amount every year. This means fishers need to be selective about what they catch, scientists need to monitor the ecosystem, and everyone needs to play by the rules, and technology can help us do all of that. So here are three ways that new tech can be a fish's best friend.

When fishers are trying to catch one species, they often end up getting others along the way. This is called bycatch, and it makes up around 10% of all fish caught globally. It's a big problem. You can't limit the number of fish taken out of an ecosystem if you can't control which fish are caught. The worst case scenario is that those unintended catches could be protected species.

The key to reducing this is to make fishing tools more selective, but dragging a net through the water to capture one type of fish and not another is easier said than done. One promising solution is to actually install little illuminated exit signs in the nets. We know that different species of fish respond to light differently. It can signal food or danger, and the responses can vary depending on the light's properties; the intensity, color, flashing rate, and even polarization of light can all affect fish behavior.

Fishers have used lights to attract fish, but studies have found that carefully placed LEDs can also help fish find their way out of a net. A 2020 study placed LEDs on the areas of scallop nets where the mesh was wider and designed to let the unintended catch out. In certain scenarios, like deeper water, the exit lights reduced bycatch by between 25 and 47%, and a 2015 study found that lights on the line of a shrimp trawler had similar results. They saw a 91% reduction in bycatch, and they still caught as much shrimp as they did without the lights.

So it's clear that light signals can have a powerful effect on specific species of fish, but it's also not simple. When the researchers changed the position of the lights on the shrimp nets, it increased the bycatch, which means we need to be careful and learn about what kinds of lights affect what species and in what ways in order to use them effectively.

Now, sustainable fishing is all about catching the right number of fish - too many, and the population can decline. Overfishing can even lead to the sudden collapse of an entire ecosystem. But it isn't easy to count every fish in the sea. We don't even have basic data for over 80% of fish stocks.

One idea is to bring in some help in the form of artificial intelligence. Increasingly, fishing boats are required to have cameras on board to film what they catch. This provides valuable data, but it takes a lot of person power to review those tapes, so scientists have developed systems that use AI to automatically count, identify, and measure the fish that go past a camera. This tells them about how the ecosystem is doing, monitors bycatch, and helps enforce laws and regulations.

Systems like these aren't yet in widespread use anywhere, but they definitely have potential to help us understand what's being caught, and AI could also help us count fish without catching them, for example by analyzing footage from underwater drones or stationary cameras. This is particularly valuable, as it can count young fish that are too small to be caught, so we can see how many fish will grow up to become adults soon.

One of the most important aspects of managing a sustainable fishery is ensuring that enough young fish grow up to be adults, even if a lot of those adults are caught. A 2020 study attempted to use a deep learning program to count young mangrove snappers in over 12 hours of video footage and achieved 95% of the accuracy of a human viewer.

Of course, a fishery's management is only effective if the rules are actually followed. The ocean is a big place, and in some cases, it's all too easy to cheat the system. It's estimated that illegal, unregulated, and unreported fishing makes up 30% of catches globally. This can undermine the sustainability of entire fisheries.

A big part of the solution is to improve the traceability of the seafood supply chain. That lets you know the fish you purchase was caught legally in a sustainable way and it is actually the type of fish it's being labeled as. And it turns out that's a big problem. A 2019 report found that 21% of fish in the United States were not actually the species they were being sold as, so one idea is to use blockchain, a decentralized electronic database most commonly known for powering cryptocurrencies.

Now, you might be tempted to roll your eyes at that, but there's a surprising amount of serious consideration being given to this idea. The advantage is that it isn't controlled by a single organization or country, and it's very difficult to hack since there isn't a single point where records are kept. So the plan is to tag the fish as they're caught with either an RFID tag or a QR code that is scanned at every step in the process from the boat to your plate.

It's already being used in pilot projects to track tuna, and one day, this could even be directly connected to the AI systems we mentioned earlier, which would record the fish being caught to automate and verify the data being entered, but there are still lots of details to work out. In particular, blockchains tend to be notoriously energy-intensive, and a system that tracks sustainable fishing isn't much good if it requires an unsustainable amount of electricity.

So improving our world's fisheries is a huge undertaking with no easy solution. There are a ton of promising high tech ideas on the horizon, but we still have a long way to go. These technologies can be expensive, and implementing them requires governments and fishers to work together, but despite these challenges, sustainable fisheries are an important step towards improving the health of our oceans.

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