Wild welfare: the threats facing wild crustaceans
Decapod crustaceans have been around for over 450 million years (humans have only existed for around 300,000 years!) and in that time, they have adapted to an astonishing array of habitats.  
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Yet human activity and interference are threatening the survival of many species around the world. Alarmingly, around
30% of freshwater decapod crustacean species are now endangered.  
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Crustaceans are vital to the health of ecosystems. So, anything which causes harm to them can have a much greater impact on the overall health of our oceans and rivers. This really matters, as healthy oceans and other bodies of water are imperative to the way humans live now, and in the future.  
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Understanding the threats facing crustaceans is the first step towards ensuring their continued survival. But, to do this, we need to shift how we see these remarkable creatures.  Too often, the welfare of crustaceans living in the wild, is overlooked or ignored - and that needs to change before it’s too late. ​
What are the leading threats to wild decapod crustaceans? 
Our knowledge of the marine environment is far from complete; just 5% of the ocean has been explored by humans. However, we have already been able to identify key areas of concern when it comes to wild decapod welfare. 
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Habitat destruction 
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Overfishing 
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Bottom trawling 
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Pollution 
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Climate change 
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Invasive species 
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Industrial development 
Habitat destruction  
Habitat loss for crustaceans has largely been driven by human activities – think coastal developments, mining, pollution, and destructive fishing practices like bottom trawling. The continued decline of coral reefs is a particular problem, as many decapod species rely on them for shelter and food. Pollutants and sediment from the building of human developments along coastlines can smother nearby coral reefs, causing their collapse. Many crustacean species also rely on rocky shores, estuaries and salt marshes, which are being destroyed by trampling and construction projects. As the human population continues to increase, there’s a worry that the situation is only going to get worse unless we make major changes and become more environmentally conscious. 
Real life story: The Purple Marsh Crab (Afrithelphusa monodosa) is a small freshwater crab species that’s only found in the Upper Guinea forest in Northwest Guinea. They were completely unknown to scientists until recently. A sample was first collected in 1947, but they weren‘t seen again until 2005, when a small group of individuals were found living in waterlogged farmland.   This fascinating, long-legged purple crab hides in swamps and marshy wetlands, only coming out at night to forage. However, the expansion of farmland in Guinea has severely impacted the availability of these vital habitats across the crab’s entire range. Today, there are thought to be fewer than 2,500 Purple Marsh Crabs remaining in the wild.
Overfishing
Fishing is a big industry worldwide, estimated to be worth over £800 million. More than 9.4 million tons of crustaceans are farmed every year alone. While most countries have limits and protections in place to prevent overfishing, too many species are “falling through the net”. Not only are crustaceans regularly captured for the food industry, but they can also be accidentally caught as bycatch. For example, shrimp fisheries are notorious for having high crustacean bycatch, including multiple crab species and mantis shrimp. Many of these are unfortunately discarded due to their low commercial value or because of strict regulatory limits. Aside from the threat to the crustaceans themselves, the animals they eat are also under threat. For example, krill are commercially fished to produce fishmeal and oil for aquaculture.  
Real-life story: Coconut Crab  The coconut crab (Birgus latro) is the largest land crab species in the world, with a leg span of 1 meter! They are renowned for their ability to crack open coconuts with their huge pinchers.   One of the biggest threats to wild coconut crabs is intensive harvesting. Coconut crab meat has an unusual flavour due to the number of coconuts they eat. So, they have become a popular delicacy, particularly across Indonesia. This has led to a drastic decline in their numbers. The price of a Coconut crab can be as high as 800 pesos (around £12.19 per kg), but their rarity could potentially push the price up even higher.  And there’s another problem: hunters tend to go for the largest crabs. This can have a negative effect on reproduction in the wild. Female coconut crabs prefer mating with the largest male crabs or at least ones that are larger than themselves. With the largest males being harvested for their meat, there’s a worry among conservationists that this could cause a reproductive imbalance.
Bottom trawling
Bottom trawling is a form of overfishing. But it’s a highly destructive fishing method that deserves its own section here. Trawling vessels are boats that drag large, heavy nets along the seabed to catch fish, particularly whitefish and shellfish. However, they can cause irreparable damage to fragile habitats, such as coral reefs, and bulldoze muddy sediments, which many crustacean species rely on for survival. This practice also releases huge amounts of carbon, contributing to climate change and ocean acidification.  
While the use of trawlers is heavily regulated in the UK, they remain a significant threat to marine wildlife. For example, in 2024 alone, offshore marine protected areas (MPAs) suffered from over 20,000 hours of suspected bottom trawling. Yet, the UK government rejected an outright ban on bottom trawling in UK waters in 2025.  
Real-life story: Alaska snow crab  Alaska snow crabs (Chionoecetes opilio) are found off the coast of Alaska in the Bering, Chukchi and Beaufort Seas. They were once a popular commodity, but populations faced a historic collapse in 2021, leading to the unprecedented closure of the Alaska snow crab fishery in 2022. Studies have shown that there are multiple causes for the decline of this species, but it all came down to one thing – starvation. A marine heatwave caused their metabolism to increase, but repeated trawling in the area had also decreased their food supply. On top of this, habitat loss and warmer waters caused the crabs to gather in much smaller areas, meaning that they were more vulnerable to being captured by trawling nets.
Pollution
Real-life story: Norway Lobster  The Norway lobster (Nephrops norvegicus) is found in the Northeastern Atlantic and is common around most British coasts. When it comes to seafood, you might know them better as langoustine or scampi.   Various studies have shown that these little orange lobsters are ingesting significant amounts of plastic. For example, a study in the Firth of Clyde, West Scotland, found that more than 80% of Norway lobsters contained microplastics. A further study in the Irish Sea found that Norway lobsters exposed to microplastic pollution had reduced body mass. Adult Norway lobsters can grind up plastics inside their bodies. However, these smaller particles are then released back into the ocean, potentially harming smaller organisms and even their own young.
You’ve probably come across heart-wrenching images of hermit crabs living in discarded bottle tops or seabirds tangled up in discarded fishing nets – pollution is a BIG problem. Abandoned fishing nets, traps and lines, collectively known as ghost gear, can ensnare coral reefs, causing pieces to break off or lead to suffocation by blocking sunlight. Even smaller pieces of waste can cause significant harm. You may think that leaving a single plastic cup or crisp packet on the beach isn’t a huge deal, but crabs can crawl inside them and get trapped. Even if this doesn’t happen, the waste will eventually make its way into the ocean, releasing harmful chemicals into the water. Collectively, over three quarters of a million pieces of litter were picked up from UK beaches by volunteers in 2024 alone, equating to a 10% increase on the previous year.  We can all do our bit to help by making sure we dispose of any waste and taking everything with us when we are done sunbathing on the beach. One of the biggest concerns for the marine environment is microplastics. These tiny plastic particles of less than 5mm in size are found throughout the ocean, from top to bottom. Not only can they cause harm to marine life, but they can also lead to human health risks when we eat contaminated fish. 
Climate change
We know that global temperatures are on the up, which is affecting both land and sea. Studies show that the heart rates of many crustaceans are increasing in response to lower oxygen levels. Some species are even relocating to entirely new areas to escape rising water temperatures. Ocean acidification (caused by an increase in carbon dioxide) also makes it harder for crustaceans to build and maintain their shells, leading to weakness, reduced growth, smaller moults and even death.  
Real-life story: American Lobster  The American lobster (Homarus americanus) is found in the cold, rocky waters off the Atlantic coast of North America. During the 1990s, it was New York State’s most valuable commercial marine resource. However, in 1999, a mass mortality event resulted in a near-total collapse of local stock. The population has still not fully recovered, which scientists think is down to warming waters caused by climate change. In fact, evidence suggests that populations are being driven northwards as they try to find cooler waters.   Lobsters are comfortable in temperatures up to 20oC, but they suffer from stress in anything above that, causing problems with their respiration and immune systems. Ocean temperatures around the world are increasing at an average rate of 0.12oC every year. However, sea surface temperatures in coastal Northeast America are warming at twice that rate. As a result, cases of Epizootic shell disease have increased in American lobsters over recent years, which causes severe shell rot and death.
Invasive species
Every ecosystem in the world is unique, with its own food chain, climate and environmental characteristics. Any changes to an ecosystem can have disastrous effects, which is why invasive species have become such a problem. Many have been accidentally introduced through human travelling, while others have been purposely introduced to be farmed. Whatever the reason, they can severely affect native wildlife and plants.  
Real-life story: White-Clawed Crayfish  The white-clawed crayfish (Austropotamobius pallipes) is one of the UK’s most endangered species. The cause of their decline is the invasion of the North American signal crayfish (Pacifastacus leniusculus). Not only are these new crayfish larger than our native species, but they are also more aggressive, breed faster and damage banks with their burrowing behaviours. Perhaps one of the deadliest consequences of their invasion is that they carry crayfish plague, which is harmless to them but kills white-clawed crayfish.   American signal crayfish were introduced to Britain in the 1960s to be farmed as restaurant delicacies. However, after escaping the farms, they quickly spread across England, Wales and parts of Scotland. The white-clawed crayfish is now classed as endangered on the IUCN Red List. However, conservation groups are working hard to bring these vital ‘ecosystem engineers’ back from the brink of extinction.
Industrial development
As humans, we rely on the natural world for the air we breathe, as well as shelter, materials and energy. But we no longer live in harmony with the environment, often favouring profits over sustainability. For example, oil drilling projects around the world are destroying habitats, releasing toxic chemicals into the air and water, and disrupting local wildlife. In recent years, we have made a shift to more environmentally friendly energy solutions, but these also come with risks. For example, the creation of offshore windfarms can negatively impact marine life, including crustaceans, by exposing them to higher levels of electromagnetic field strength. This impacts their mating and feeding behaviours. Windfarms can also uproot vital habitats and cause intense underwater noise, particularly during construction.   
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The more industrial waste that is dumped into our oceans, the more it affects the PH balance of the water, which can potentially cause further, long-term issues and high mortality rates. 
Real-life story: Whiteleg shrimp  The thiteleg shrimp (Litopenaeus vannamei), also known as Pacific white shrimp, is native to the Eastern Pacific Ocean off the coast of Latin America. Adults live at depths of up to 75m, while juveniles live in estuaries. Studies have shown that when exposed to crude oil, whiteleg shrimp suffered with impaired swimming ability, loss of balance and even death. Furthermore, exposure to high levels of cadmium (a heavy metal present in crude oil and drilling waste) causes the destruction of gill tissue.
This can all make for grim reading but there is some good news – we can all do our part to improve the lives of wild crustaceans. Whether that’s making sure you pick up your waste when you visit the seaside or only eating sustainably sourced seafood. You can even join a volunteer clean-up operation or support us in our mission to protect crustaceans across the UK.  
