How much fishing gear gets lost at sea?

The planet has an estimated 60 million fishermen. To do their job, they use nets strung between boats and across rivers, long lines armed with thousands of hooks, trawl nets that get dragged across the seafloor, holding pens for aquaculture, and, of course, good old fashioned lobster and crab pots. Together they feed over three billion people. But in the course of doing that, massive amounts of gear goes overboard contributing to huge environmental impacts. The scale of those losses, which Australia's Denise Hardesty has now managed to calculate, will almost certainly make your eyes pop out. Here she is speaking with Chris Smith...

Denise - So we set out to ask how much fishing gear is lost to the world's ocean. So we went out and spoke with fishers in seven countries around the world and used a lot of different types of gear. So we asked fishers, who fish with fishing line, like long lines with different types of trawl nets or fishing nets that are designed to catch your fish in that way. And also with pots and traps. So we really spanned the full breadth and depth of the world's commercial fisheries

Chris - And is the metric. Then you say to them, how much gear do you buy in a year? And you assume that what they are buying is to replace what they've lost.

Denise - It's not about asking the fishers 'how much fishing gear do you buy each year?' and then subtracting out how much has been lost. Because many of the fishers that we interviewed, they're not the ones that own the companies that are making those decisions. What we did instead was ask the fishers, How long do you spend at sea? How much gear gets lost? How often does it get lost? When and why and where? Under what conditions do you lose that fishing gear? And then we coupled that with information about how much fishing effort happens around the year from an independent data set. And that allowed us to match or to marry those two really different types of information together to make that estimate of how much fishing gear is lost to the global ocean

Chris - And how much is?

Denise - So for one single major fishery a year around 740,000 kilometers of fishing line alone is lost. And with that, our 14 billion hooks. If you wanna put that in perspective, that's about circling the earth more than 18 times for that fishing line or going from earth to the moon and back. We also estimate around 3000 square kilometers of gill nets, 75,000 square kilometers of another type of net called Purse Seine nets. And over 25 million pots in traps each and every year.

Chris - Of course, many of these are man made plastics and polymers, aren't they? So they're going to be adding to the global ocean plastic problem, but they're not going to go anywhere. They're just presumably gonna build up in the sea somewhere.

丹尼斯,所以他们会鱼不加选择地。一个nd we call that ghost nets. When these abandon or lose commercial or other fishing nets are lost at sea because they just continue to fish indiscriminately. And what this means is they're catching fish, they're catching turtles and whales and dolphins and you know, other marine mammals costing lots in terms of biodiversity impact, as well as having quite a substantial potential impact on the global fisheries and on global food security. Because if we capture these fish and they die in the nets, but they aren't making it to people's dinner plates, then we're actually not able to utilize not only the protein benefit, but the economic benefit from fishing.

Chris - My mind is boggling with these numbers that you're coming up with. This is quite terrifying in terms of how much is therefore out there. Do we actually have evidence that this buildup is doing, as you say, and having a knock on effect on species and so on?

Denise - Well, one thing that we know from some previous works on looking at ghost nets in one particular part of Australia was we estimated that around 10,000 turtles a year are killed or captured by nets just in that particular area. So we do have evidence from that study and from other separate bodies of work from other researchers around the world that have highlighted particular problems in particular small areas. What we've done now is really show what that looks like at the global scale in terms of how much is lost. And you know, you said that's really confronting and when we think about it, that's 25 million pots and traps each and every year. 14 billion hooks each and every year. So you know, this is accumulating in the oceans and it's also getting caught up on sensitive coral reef beds. It's getting washed ashore in damaging sensitive marine and coastal ecosystems and habitats such as mangroves. It's smothering our reefs, it's causing quite a lot of damage.

Chris - What can we do about it? When scientists back in the mid 1980s spotted an Australia-sized hole in the ozone layer over Antarctica very promptly, they were able to galvanize action. They got the Montreal protocol together, we banned CFCs as the cause and hopefully have arrested the progression of the ozone hole. What can we do about this?

Denise - Well, that's a really great point. So what can we do? I think the first thing to do is to not only understand how much is lost out there, but to also really unpack why and when it is that fishing gear gets lost. And so that's what we did. And what we find is that smaller vessels on average lose proportionately more gear. We also find that fishers that are fishing on the bottom of the ocean tend to lose more gear than those fishing in the midwater or on the surface of the ocean. And we also understand a bit more now about why and when we're losing gear. So when there's bad weather and fishers aren't getting that much money, they tend to fish in marginal conditions. As we start to see a reduction in the amount of fish in a particular area, we may have more fishers crowding into fishing in a smaller area.

Denise - And that means we can see conflicts between different gears and between different fishers. And when there's conflict, when lines or nets run over one another, they may end up getting caught or tangled and being cut apart. And so some of the things that we can do is to ensure that fishers have the best equipment possible. We can look at potential incentives to reduce fishing gear losses, and so we can provide buyback programs or low cost loans for fishers to replace their gear before they're so close to end of life that they're likely to get lost.