Out of the Frying Pan, Into the Fire
Taylor Houston | April 2020
Mangrove forests stretch across latitudes near the equator. They spread their seeds at the edges of Florida, South America, Africa, India, Australia, and many more. With turquoise and aquamarine water sparkling against the bottoms of leaves on the mangrove trees. The mangrove trees reach over long, winding rivers and over the shore. You look over at the trees and notice a crab about the size of your hand climbing up the bark. You think to yourself: I never thought crabs could climb trees.
Small chirps and long-droning caws ring in your ears from above your head. The heat can feel like a dense, hot fog running across your skin and into your lungs but the shade of the mangrove trees and the subtle breeze coming in from the sea provides some relief. You stick your feet into the warm, shallow water and begin to walk until the water reaches your knees. You see burrows in the muddy sand, large holes in shallow water and on land. You search for whatever has caused this and in the blurry water you see it—a large mud crab. It looks a bit brown, and as the light penetrates through you can see that it’s almost a blue color. It’s large claws look heavy and threatening, paired with a menacing, yet seemingly wise stare. However, despite its abundance in some places, it's only a couple steps, or crab walks, away from being a concern of conservationists.
Visiting the North Carolina coast, you’re used to seeing small crabs burrow and create little holes that you might be able to stick the tip of your pinky finger into, but nothing like this. The mud crab, or Scylla serrata is a species well dispersed across the mangrove forests of the world. As young crabs they eat detritus, or dead organic material floating at the bottom of the forest and ocean floor. As juveniles the mud crab acts as a cleaner, ridding the mud and sand of the waste on top and recycling the nutrients. As they grow older, their diets become carnivorous and they begin to eat things like oysters, barnacles, fish, worms, and even other crabs. From small sweepers of the forest floor to large, pinching predators.
If you are fortunate to see a wild mud crab for yourself, you should know that the mangrove forest is probably doing well. They are a sign of ecosystem health; they’re cleaners, they’re regulators, and they’re aerators. While they are quite tolerant of salinity and temperature changes, their range in travel and in diet allows scientists to study bioaccumulation, that is the accumulation of toxic substances up the food chain, and what toxins may be present in the water. Since they eat both the gunk of the ocean floor then move onto small animals as they age, they give a good sign as to what is bioaccumulating through the mangrove trophic levels, or simply levels of the food chain. They are also food for other animals in the mangrove ecosystem, such as the marsh mongoose, a species in decline. Not only are these large crustaceans predators to be feared but they are a reliable source of food for others. Their ecosystem services are countless. Yet, their ecosystem is under threat.
Mud crabs aren’t just yummy to the birds of the mangrove forests, who usually go for the young. A much more dangerous predator and ruthless killer creeps along the mangrove riverbanks and shores: humans. Humans have been able to change their landscape amazingly and quickly without much in their path to stop them. The “Anthropocene” is what some environmentalists and geologists are posing should be the name of the new epoch that we have transitioned into, one that has been drastically and globally changed by the actions of humans. From their influence on the climate to their direct destruction of the earth, they leave their trail of blood and bones behind them, along with the shells of crustaceans. You aren’t likely to see a mud crab in person, probably due to its habit of burrowing during the day and only being active at night. However, if you’re a fish food fan, chances are you’ve seen it on a porcelain dinner plate dressed in garlic butter with a lemon on the side. When researching mud crabs, most of the links that would come up were recipes, good restaurants for mud crabs, or what wine pairs best (answer: a buttery chardonnay). Due to their large size, chefs along the coast and around the world desire them for their large claws and thick legs to get the most meat and charge the most money.
The mangrove forests are major hunting grounds for fisheries and this has made them sensitive and prone to destruction. They barrel in with their boats, ripping apart riparian zones, dragging pollution behind them, and large fishing nets catching everything in their path. As the shadow of the fisherman’s boat lurks over the crystal blue waters the mud crab knows to remain in its burrow. The excavating of mud crabs directly from their burrows through shoving one’s upper-half into the ground is the traditional form of crabbing for mud crabs. Commercially, the nets are thrown from the side of the boat. Those crabs who aren’t fast enough will get caught in the grasp of the unforgiving grim reaper of the sea dragging its hands across the sand and mud, picking up anything and everything in its path.
Commercial fishing poses a huge threat to marine life, especially ecosystems that are already sensitive. Vacation beach homes, piers, on-the-shore restaurants, gas stations and gift shops encroach into mangrove ecosystems and dismantle them. These forests teeming with life and sequestering carbon need to be preserved. The lives of the wildlife they contain, such as the mud crab, the marsh mongoose, and the tree-climbing mangrove crab aren’t worth a corny gift shop with cheap souvenirs or the rampant overfishing for fancy palettes.
From what I have read, I haven’t heard stories of mud crabs being removed from an ecosystem entirely, so no one really knows what that would look like. Their numbers are still doing fine, but they are vital to mangrove forests, so if they continue to be commercially fished and overfished or their habitat becomes compromised, we could see dramatic loss of these crabs. They recycle nutrients as young crabs by eating the dead organic matter and turning it into ammonia, aerating the soil with their burrows, keeping herbivore populations level, and possibly even controlling what types of trees and how many grow in a certain area due to seed eating. They are food for animals that are already starting to feel the effects of the damage done to mangrove forests, keeping those populations alive and fed. If they are lost, mangrove ecosystems could fall out of balance and possibly collapse.
Stories similar to this one are happening all over the globe, and most of the time it goes without witnesses or news reports. The Anthropocene will be a dark time in Earth and human history, with extinctions like those of the past and worrisome unpredictability. We should have done better years ago. The action against climate change must be now, and that doesn’t mean only cutting out carbon emissions, but cleaning up and stopping the spread of pollution, protecting sensitive, threatened ecosystems like mangrove forests as well as the ones that look just fine, establishing full and just equality and access for all, and the list goes on.
Mud crabs deserve a healthy, clean, and safe habitat to live in, thrive in, and engage with a community of many other crabs, fish, birds, beetles, and others. All Earth’s creatures deserve protection and respect, because without them, humans cannot exist.
Sources
Alberts-Hubatsch, Hilke, et al. “Life-History, Movement, and Habitat Use of Scylla Serrata (Decapoda, Portunidae): Current Knowledge and Future Challenges.” Hydrobiologia, vol. 763, no. 1, Nov. 2015, pp. 5–21., doi:10.1007/s10750-015-2393-z.
Lindquist, Erin Stewart, et al. “Land Crabs as Key Drivers in Tropical Coastal Forest Recruitment.” Biological Reviews, vol. 84, no. 2, 2009, pp. 203–223., doi:10.1111/j.1469-185x.2008.00070.x.
Mirera, Do. “Intertidal Mangrove Boundary Zones as Nursery Grounds for the Mud Crab Scylla Serrata.” African Journal of Marine Science, vol. 39, no. 3, 1 Oct. 2017, pp. 315–325., doi:10.2989/1814232x.2017.1371640.
Mondal, Asish, et al. “Performance Evaluation of Mud Crab Scylla Olivacea (Herbst, 1896) Co-Culture with Different Fish Species in Confined Brackishwater Ponds.” Aquaculture, vol. 522, 14 Feb. 2020, p. 735125., doi:10.1016/j.aquaculture.2020.735125.
Oosterom, Jake Van, et al. “Investigation of the Mud Crab (Scylla Serrata) as a Potential Bio-Monitoring Species for Tropical Coastal Marine Environments of Australia.” Marine Pollution Bulletin, vol. 60, no. 2, 12 Oct. 2009, pp. 283–290., doi:10.1016/j.marpolbul.2009.09.007.
Polidoro, Beth A., et al. “The Loss of Species: Mangrove Extinction Risk and Geographic Areas of Global Concern.” PLoS ONE, vol. 5, no. 4, 8 Apr. 2010, doi:10.1371/journal.pone.0010095.
Rumisha, Cyrus, et al. “Genetic Diversity and Gene Flow among the Giant Mud Crabs (Scylla Serrata) in Anthropogenic-Polluted Mangroves of Mainland Tanzania: Implications for Conservation.” Fisheries Research, vol. 205, 26 Apr. 2018, pp. 96–104., doi:10.1016/j.fishres.2018.04.015.
“The IUCN Red List of Threatened Species.” IUCN Red List of Threatened Species, www.iucnredlist.org/.
Taylor Houston | April 2020
Mangrove forests stretch across latitudes near the equator. They spread their seeds at the edges of Florida, South America, Africa, India, Australia, and many more. With turquoise and aquamarine water sparkling against the bottoms of leaves on the mangrove trees. The mangrove trees reach over long, winding rivers and over the shore. You look over at the trees and notice a crab about the size of your hand climbing up the bark. You think to yourself: I never thought crabs could climb trees.
Small chirps and long-droning caws ring in your ears from above your head. The heat can feel like a dense, hot fog running across your skin and into your lungs but the shade of the mangrove trees and the subtle breeze coming in from the sea provides some relief. You stick your feet into the warm, shallow water and begin to walk until the water reaches your knees. You see burrows in the muddy sand, large holes in shallow water and on land. You search for whatever has caused this and in the blurry water you see it—a large mud crab. It looks a bit brown, and as the light penetrates through you can see that it’s almost a blue color. It’s large claws look heavy and threatening, paired with a menacing, yet seemingly wise stare. However, despite its abundance in some places, it's only a couple steps, or crab walks, away from being a concern of conservationists.
Visiting the North Carolina coast, you’re used to seeing small crabs burrow and create little holes that you might be able to stick the tip of your pinky finger into, but nothing like this. The mud crab, or Scylla serrata is a species well dispersed across the mangrove forests of the world. As young crabs they eat detritus, or dead organic material floating at the bottom of the forest and ocean floor. As juveniles the mud crab acts as a cleaner, ridding the mud and sand of the waste on top and recycling the nutrients. As they grow older, their diets become carnivorous and they begin to eat things like oysters, barnacles, fish, worms, and even other crabs. From small sweepers of the forest floor to large, pinching predators.
If you are fortunate to see a wild mud crab for yourself, you should know that the mangrove forest is probably doing well. They are a sign of ecosystem health; they’re cleaners, they’re regulators, and they’re aerators. While they are quite tolerant of salinity and temperature changes, their range in travel and in diet allows scientists to study bioaccumulation, that is the accumulation of toxic substances up the food chain, and what toxins may be present in the water. Since they eat both the gunk of the ocean floor then move onto small animals as they age, they give a good sign as to what is bioaccumulating through the mangrove trophic levels, or simply levels of the food chain. They are also food for other animals in the mangrove ecosystem, such as the marsh mongoose, a species in decline. Not only are these large crustaceans predators to be feared but they are a reliable source of food for others. Their ecosystem services are countless. Yet, their ecosystem is under threat.
Mud crabs aren’t just yummy to the birds of the mangrove forests, who usually go for the young. A much more dangerous predator and ruthless killer creeps along the mangrove riverbanks and shores: humans. Humans have been able to change their landscape amazingly and quickly without much in their path to stop them. The “Anthropocene” is what some environmentalists and geologists are posing should be the name of the new epoch that we have transitioned into, one that has been drastically and globally changed by the actions of humans. From their influence on the climate to their direct destruction of the earth, they leave their trail of blood and bones behind them, along with the shells of crustaceans. You aren’t likely to see a mud crab in person, probably due to its habit of burrowing during the day and only being active at night. However, if you’re a fish food fan, chances are you’ve seen it on a porcelain dinner plate dressed in garlic butter with a lemon on the side. When researching mud crabs, most of the links that would come up were recipes, good restaurants for mud crabs, or what wine pairs best (answer: a buttery chardonnay). Due to their large size, chefs along the coast and around the world desire them for their large claws and thick legs to get the most meat and charge the most money.
The mangrove forests are major hunting grounds for fisheries and this has made them sensitive and prone to destruction. They barrel in with their boats, ripping apart riparian zones, dragging pollution behind them, and large fishing nets catching everything in their path. As the shadow of the fisherman’s boat lurks over the crystal blue waters the mud crab knows to remain in its burrow. The excavating of mud crabs directly from their burrows through shoving one’s upper-half into the ground is the traditional form of crabbing for mud crabs. Commercially, the nets are thrown from the side of the boat. Those crabs who aren’t fast enough will get caught in the grasp of the unforgiving grim reaper of the sea dragging its hands across the sand and mud, picking up anything and everything in its path.
Commercial fishing poses a huge threat to marine life, especially ecosystems that are already sensitive. Vacation beach homes, piers, on-the-shore restaurants, gas stations and gift shops encroach into mangrove ecosystems and dismantle them. These forests teeming with life and sequestering carbon need to be preserved. The lives of the wildlife they contain, such as the mud crab, the marsh mongoose, and the tree-climbing mangrove crab aren’t worth a corny gift shop with cheap souvenirs or the rampant overfishing for fancy palettes.
From what I have read, I haven’t heard stories of mud crabs being removed from an ecosystem entirely, so no one really knows what that would look like. Their numbers are still doing fine, but they are vital to mangrove forests, so if they continue to be commercially fished and overfished or their habitat becomes compromised, we could see dramatic loss of these crabs. They recycle nutrients as young crabs by eating the dead organic matter and turning it into ammonia, aerating the soil with their burrows, keeping herbivore populations level, and possibly even controlling what types of trees and how many grow in a certain area due to seed eating. They are food for animals that are already starting to feel the effects of the damage done to mangrove forests, keeping those populations alive and fed. If they are lost, mangrove ecosystems could fall out of balance and possibly collapse.
Stories similar to this one are happening all over the globe, and most of the time it goes without witnesses or news reports. The Anthropocene will be a dark time in Earth and human history, with extinctions like those of the past and worrisome unpredictability. We should have done better years ago. The action against climate change must be now, and that doesn’t mean only cutting out carbon emissions, but cleaning up and stopping the spread of pollution, protecting sensitive, threatened ecosystems like mangrove forests as well as the ones that look just fine, establishing full and just equality and access for all, and the list goes on.
Mud crabs deserve a healthy, clean, and safe habitat to live in, thrive in, and engage with a community of many other crabs, fish, birds, beetles, and others. All Earth’s creatures deserve protection and respect, because without them, humans cannot exist.
Sources
Alberts-Hubatsch, Hilke, et al. “Life-History, Movement, and Habitat Use of Scylla Serrata (Decapoda, Portunidae): Current Knowledge and Future Challenges.” Hydrobiologia, vol. 763, no. 1, Nov. 2015, pp. 5–21., doi:10.1007/s10750-015-2393-z.
Lindquist, Erin Stewart, et al. “Land Crabs as Key Drivers in Tropical Coastal Forest Recruitment.” Biological Reviews, vol. 84, no. 2, 2009, pp. 203–223., doi:10.1111/j.1469-185x.2008.00070.x.
Mirera, Do. “Intertidal Mangrove Boundary Zones as Nursery Grounds for the Mud Crab Scylla Serrata.” African Journal of Marine Science, vol. 39, no. 3, 1 Oct. 2017, pp. 315–325., doi:10.2989/1814232x.2017.1371640.
Mondal, Asish, et al. “Performance Evaluation of Mud Crab Scylla Olivacea (Herbst, 1896) Co-Culture with Different Fish Species in Confined Brackishwater Ponds.” Aquaculture, vol. 522, 14 Feb. 2020, p. 735125., doi:10.1016/j.aquaculture.2020.735125.
Oosterom, Jake Van, et al. “Investigation of the Mud Crab (Scylla Serrata) as a Potential Bio-Monitoring Species for Tropical Coastal Marine Environments of Australia.” Marine Pollution Bulletin, vol. 60, no. 2, 12 Oct. 2009, pp. 283–290., doi:10.1016/j.marpolbul.2009.09.007.
Polidoro, Beth A., et al. “The Loss of Species: Mangrove Extinction Risk and Geographic Areas of Global Concern.” PLoS ONE, vol. 5, no. 4, 8 Apr. 2010, doi:10.1371/journal.pone.0010095.
Rumisha, Cyrus, et al. “Genetic Diversity and Gene Flow among the Giant Mud Crabs (Scylla Serrata) in Anthropogenic-Polluted Mangroves of Mainland Tanzania: Implications for Conservation.” Fisheries Research, vol. 205, 26 Apr. 2018, pp. 96–104., doi:10.1016/j.fishres.2018.04.015.
“The IUCN Red List of Threatened Species.” IUCN Red List of Threatened Species, www.iucnredlist.org/.