Crustaceans diurnal

Blue Mud Shrimp

Upogebia pugettensis

The hidden architect of the West Coast mudflats, the Blue Mud Shrimp builds vast underground networks that support an entire community of marine life. Though rarely seen above ground, these blue-hued engineers are vital to the health of our coastal ecosystems.

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Quick Identification

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Size

10–15 cm (4–6 inches) in length; relatively heavy-bodied for a shrimp

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Colors

Mottled blue-gray, olive-green, or brownish-white; claws often show a distinct bluish tint

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Key Features

Large, equal-sized flattened claws
Dense fringes of hair (setae) on the first two pairs of legs
Soft, flexible abdomen specialized for tunnel life
Cylindrical body with a tough carapace

When You’ll See Them

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Activity pattern diurnal

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Peak hours Activity is tide-dependent; most active when the tide is high enough to cover the burrow entrance.

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Season Year-round, but most easily observed during extreme low tides in spring and summer.

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Diet Suspension feeders that use the specialized 'hairs' on their front legs to filter plankton and organic detritus from the water column.

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Habitat Estuarine mudflats and low-intertidal zones with soft, silty sediment.

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Behavior

The Blue Mud Shrimp is a master architect of the intertidal zone, spending almost its entire life within complex, Y-shaped or U-shaped burrows. These tunnels can descend over three feet into the mud and serve as both a fortress and a food-trapping system. By rhythmically waving its pleopods (swimmerets), the shrimp creates a constant current of water through its home, which oxygenates the sediment and brings in a steady supply of microscopic food.

These shrimp are remarkably social in a passive way, often sharing their intricate burrow systems with 'roommates' such as pea crabs, scale worms, and even certain species of small gobies. Unlike many other crustaceans that are aggressive hunters, the Blue Mud Shrimp is a peaceful filter feeder. However, they are currently facing an ecological crisis along the West Coast due to an invasive parasitic isopod that attaches to their gills, stealing their energy and preventing them from reproducing.

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Camera Tips

Capturing the Blue Mud Shrimp on camera is a unique challenge because they are subterranean. To see them, you must focus on the 'doors' to their world. For those with coastal or estuarine backyards, the best strategy is to use a waterproof action camera or a trail camera with a very close focal range. Look for 'volcano-like' mounds or clean, circular holes about the diameter of a nickel in the mud during low tide. These are the burrow entrances. Mount your camera on a weighted base or a low-profile sand stake, positioning the lens just 6-12 inches from the hole, angled slightly downward.

Because these shrimp are most active when the water is moving, the 'magic moment' for filming is the transition period as the tide comes in or goes out. Use a time-lapse setting or a high-resolution video mode triggered by a timer. As the water begins to submerge the burrow, the Blue Mud Shrimp will often move toward the opening to begin its pumping cycles, and you may catch a glimpse of its blue-tinted claws or its fan-like tail clearing debris from the tunnel mouth.

Light is your biggest obstacle in the murky intertidal environment. If you are filming during a daytime incoming tide, natural light is usually sufficient, but for night-time observations, use a camera with 'No-Glow' infrared LEDs. Standard white flashes or bright lights will cause the shrimp to retreat deep into its burrow. Additionally, ensure your camera is securely weighted; the force of the incoming tide can easily flip a light camera, resulting in footage of the sky rather than the mud.

Lastly, be mindful of the 'ghostly' vibrations. Blue Mud Shrimp are highly sensitive to thumping on the mud. Set your camera and retreat at least 15-20 feet away to allow the sediment to settle and the shrimp to feel safe enough to return to the surface of its tunnel. The best months for this are May through August during 'King Tides' or significant negative tides when more of the mudflat is exposed for easy equipment setup.

Similar Species

Species that look similar or are commonly confused with Blue Mud Shrimp.

Bay Ghost Shrimp

Palish pink or white in color; males have one claw much larger than the other.

Giant Ghost Shrimp

Larger and paler, often found in more sandy rather than muddy sediments.

Frequently Asked Questions

Blue Mud Shrimp activity is dictated by the tides rather than the sun. They are most active when the tide is high enough to bring oxygenated, nutrient-rich water into their burrows, allowing them to filter feed.

You can only attract Blue Mud Shrimp if your property includes an estuarine mudflat. The best way to support them is to maintain natural shorelines and avoid using pesticides or fertilizers that can run off into the water and harm their delicate habitat.

They are suspension feeders, meaning they eat microscopic plankton and bits of organic detritus that they filter out of the water using the specialized 'hairy' bristles on their legs.

They are common only in specific coastal suburban areas along the Pacific Northwest and California, specifically in towns built near estuaries, bays, and salt marshes.

Blue Mud Shrimp are usually a mottled blue-gray or olive color and have two claws of equal size, whereas Ghost Shrimp are typically pale pink or white and males have one significantly oversized claw.

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