Climate change has had a profound effect on crustaceans by raising the temperature and acidity of Earth’s oceans.
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New York fisheries yielded about 214,000 pounds of lobster in 2014, down from 9,400,000 in 1996. That shellfish are such a staple of our diet begs the question, “Where did they go?” or, more accurately, “Where has climate change sent them?”
”Shellfish” is often a culinary term to warn those with allergies, describing edible animals like shrimp and clams that sometimes need special care in preparation and cooking. To discuss each of them, we need to clarify terminology.
All crustaceans are shellfish, but not all shellfish are crustaceans. Whereas mollusks consist of clams, scallops, and other soft invertebrates that inhabit shells of calcium carbonate, crustaceans are essentially aquatic bugs. A subset of arthropods, these creatures use many limbs to swim from reef to reef or scurry across the ocean floor.
A key difference between crustaceans and terrestrial arthropods is the presence of numerous facial appendages in addition to limbs. Nightmarishly, certain filter-feeding crabs reach for algae with nets at the ends of “arms” that protrude from the jaw. But there’s so much variation within crustaceans that classification can be tricky.
As crustaceans live in all sorts of freshwater and saltwater habitats around the world, climate change affects each population differently. To discuss the effects of rising temperatures on other important variables is to shed light on how to help different crustaceans endure in centuries to come.
Dive deep into crustacean biology and behavior in this absorbing MagellanTV documentary.
The Main Weakness of Freshwater Habitats: Isolation
The mellow waters of ponds, lakes, and streams are home to some crab species as well as to crayfish. Rising global temperatures will either force crustaceans to new latitudes or draw other species to invade crustaceans’ territory, possibly resulting in several extinctions. Freshwater bodies are much smaller, less common, and more distant from each other than saltwater bodies, so freshwater crustaceans suffer from the particular problem of having nowhere else to go.
As red decapods who scurry across amphibious terrain, crayfish are close relatives of lobsters. The stalk eyes and menacing claws on either side of the crayfish’s sharp snout are reminiscent of its ancestors, though most freshwater crustaceans are much smaller than their saltwater counterparts. Adult crayfish can be as little as 2.5 cm in length.
In terms of color, crayfish range from red or brown to brighter hues of green and yellow. They’re dully monochromatic to avoid detection, hiding beneath rocks or logs and performing most activity at night.
Crayfish also vary in size depending on where they are. Thoroughly celebrated by people of the American Bayou, crayfish also live in parts of Europe, Asia, and even Australia: Tasmania is actually home to the biggest crayfish, which can be as long as 40 cm.
Otherwise, crayfish share their carnivorous diets and mating rituals with saltwater cousins, feeding on bugs, tadpoles, or mollusks and tending to countless larvae inside or outside eggs.
A colony of crayfish (Credit: Kate Estes, via Unsplash)
Crayfish Boils Aren’t the Problem – Disease Is
Despite their popularity as a culinary staple in some regions, American crayfish populations aren’t critically endangered. However, rising temperatures and invasive species have brought new diseases into the crayfish populations of European ponds and lakes.
The future of European crayfish populations will not only depend on how well humanity controls climate change, but also on how well government teams can manage the influx of invasive crayfish species. Freshwater species can’t go any further than their respective watersheds allow. As European ponds and streams dry up, biologists will have to find new places and ways to maintain existing crayfish populations.
Saltwater Crustaceans Suffer from Ocean Acidification
The world of saltwater crustaceans is much more diverse. From the complex mantis shrimp to the hulking Japanese spider crab, saltwater crustaceans engage with the environment and other sea creatures in myriad ways. They suffer from many of the same perils as their freshwater relatives in addition to a real but less imminent threat from climate change: ocean acidification.
As carbon emissions continue or increase across the world, oceans will absorb them, gradually lowering the pH of saltwater bodies. This acidification process will affect saltwater species in different ways, but generally speaking, the primary concern is how well shells will maintain integrity in corrosive waters.
Shrimp Fisheries Are Vulnerable to Ocean Heating
Uniform orange curls in cocktail sauce might not suggest that saltwater and some freshwater bodies contain 2,000 varieties of shrimp in different sizes and colors. These slim, translucent creatures undulate their tails and limbs to swim backward. Feeding on plankton among other small organisms, shrimp are as common a prey for sea creatures as they are for humans. Thus, shrimp engage in mutual symbiosis with many critters, from the most benign anemone to the most menacing eel.
For example, as the Egyptian plover bird earns a snack by cleaning a crocodile’s teeth, cleaner shrimp offer the same service to moray eels. The anemone shrimp suffers from an equally uncreative name, keeping anemones clean in exchange for room and board, though biologists may also refer to these shrimp as Coleman’s shrimp, among other names.
Many aspects of shrimp’s plight are unremarkable in comparison to that of other crustaceans. Shrimp fisheries in the Gulf of Mexico and along the east coast of North America have become hot enough for many Atlantic shrimp populations to collapse. This is not to mention that warmer waters have attracted predators.
A shrimp among coral (Credit: Esperanza Doronila, via Unsplash)
Acidification Thickens Shrimp Carapaces – Why That’s a Problem
The acidification of oceans has threatened shrimp so directly as to arouse a curious physiological response: Shrimp carapaces have actually become thicker to compensate for corrosion. Between less transparency and less mobility, shrimp are becoming easier prey for humans as well as countless other species that also find shrimp delicious.
What’s the silver lining if not the intestinal tract to remove before cooking? Shrimp farms present more opportunities to limit carbon emissions.
How Shrimp Farms Can Reduce Carbon Emissions
Shrimp diets contain large amounts of soy, whose cultivation contributes to deforestation and a decline in soil quality. To counter these issues, shrimp farmers can purchase soy from conscientious vendors and use only the minimum amount of feed necessary to help shrimp reach an appropriate size for consumption.
Maintaining water quality is the other major part of managing shrimp farms. Today’s shrimp farmers use aeration systems to preserve oxygen in otherwise stagnant water. The farmers can either fuel aeration systems with renewable sources or invest in “smart” systems that turn off and on autonomously with sensors. Note that there are also “smart” feeding systems. With enough planning, shrimp farmers can reduce their carbon emissions by half.
Versatile Crabs: Worthy Opponents of Climate Change
Stouter than other crustaceans, crabs are identifiable by their broad shells and short tails. There are thousands of species with different characteristics. Many crabs live in the sea, but some exhibit more amphibious behavior, foraging and scurrying across beaches and shallows such that many species use both gills and lungs to breathe.
Between two breathing options and an omnivorous diet, crabs are nothing if not resourceful. Often relying on dexterous pincers, they commonly engage in mutual or commensal relationships with other aquatic animals, and their diversity includes some of the largest crustaceans in the world. The Japanese spider crab (below) is indeed a crab rather than a Lovecraftian horror.
A hulking Japanese spider crab at Chicago’s Shedd Aquarium (Credit: Dallas Krentzel, via Wikimedia Commons)
Crabs Need More Oxygen
As with other crustaceans, more acidic waters threaten the integrity of crabs’ carapaces, increasing the frequency of molting. But less oxygen in water has been the primary problem for crabs. Warmer water contains less gaseous oxygen, and many crabs have lungs with which to breathe the gas.
Take the Pacific Dungeness crab, for example. It’s a common source of crab meat for Washington State and British Columbia. This population has a complex life cycle, but adults are most vulnerable to the lack of oxygen, especially during summer.
Consider all the oxygen crabs must expend to build new shells and search for food or mates. A specific way to assist the Dungeness crab would be to refrain from eating it altogether, or at least setting traps in early spring and pulling them upon the start of summer.
Durable Lobsters Face Eviction
Lobsters exist in a variety of colors and sizes, but they’re recognizable by their long bodies and wide central tailfins. Their anatomy allows them to excel at crawling and swimming alike. They usually live at the bottom of the ocean, scavenging for an omnivorous diet without much outside assistance.
More than other crustaceans, lobsters are particularly sensitive to higher temperatures. Climate change has caused certain habitats to become inhospitable and others to become more hospitable, but the change in latitude of lobster populations has been easy to observe.
Lobster shows its colorful face (Credit: David Baker, via Unsplash)
Larval Mortality Shifts Lobster Habitat North
Thirty years ago, an American lobsterman could set traps as far south as the Long Island Sound to make a profit. Meanwhile, today’s lobstermen in New England struggle to fare as well as they have in the past, and the lobster populations of Canada are booming.
Researchers emphasize that lobsters aren’t migrating. Larval mortality is simply higher in warmer water, so more larvae are dying in the Long Island Sound, say, than in the Gulf of Maine.
What We Can Do to Preserve Crustacean Populations
Like any organism besides anaerobic bacteria, crustaceans have to adapt to rising temperatures. And if we want to keep eating them, they need our help.
A crab sunbathing on a rock (Credit: Jay Gomez, via Unsplash)
There’s more for biologists to learn, better practices for crustacean farmers to observe, and more conservative trapping solutions for fishermen to implement. As for those of us who live further from the crazy and colorful world of crustaceans, we can always decrease demand by eating something else. If you’re deciding whether to eat shrimp or fish, opt instead for chicken or even a vegetable.
We all need to work together to give wild populations some space. If, for example, lobsters don’t return to New England, human intervention will have to assist them in adjusting to their new homes.
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Ben Sernau is a prolific marketing professional whose articulate content has boosted SEO for businesses across the nation. Between a growing YouTube channel and work for clients, Ben keeps his hands full with a variety of topics. Ben is also an avid gamer, enjoying any topic tangentially related to games. He writes from Mamaroneck, NY.
Title Image: Lobster traps by a harbor (Credit: John McArthur, via Unsplash)
