How to Identify 15 Crab Species Found in Alaska Waters

Identifying crabs in Alaska’s coastal waters is essential for enthusiasts, fishermen, and researchers aiming to understand local marine biodiversity, ensure sustainable harvesting, or simply appreciate the fascinating variety of crabs in this region. Alaska’s cold, nutrient-rich waters host a diverse range of crab species, each with unique characteristics. This guide will help you recognize 15 common crab species found in Alaska by their physical traits, habitats, and behaviors.

What You’ll Need

• Field guide or identification book on Alaska marine life (optional but helpful)
• Magnifying glass or hand lens for close examination
• Notebook or device for taking notes and photos
• Camera or smartphone for capturing images
• Protective gloves (if handling live crabs)
• Access to tide pools, beaches, or boat for offshore observation

Step-by-Step

1. Familiarize Yourself with Alaska’s Crab Families: Start by learning the main crab families present in Alaska waters, such as the Dungeness crabs (family Cancridae), king crabs (Lithodidae), snow crabs (Oregoniidae), and Tanner crabs (Chionoecetidae). Knowing the family helps narrow down identification.
2. Observe the Crab’s Size and Shape: Note the size of the crab, from small pea crabs to large king crabs. Look at the overall body shape—whether the carapace (shell) is broad and rounded or spiny and angular. For example, king crabs have a spiny, triangular carapace, while Dungeness crabs have a smooth, oval-shaped shell.
3. Examine the Carapace Color and Texture: Colors vary by species and often change with age or environment. Dungeness crabs are usually reddish-brown, snow crabs are pale white to light orange, and king crabs display red-orange hues with spines. Texture may be smooth, bumpy, or spiny.
4. Count and Inspect the Legs: Crabs have 10 legs total (including claws). Check the length and shape of walking legs—some species have long, slender legs (like the snow crab), while others have shorter, thicker legs (like the Dungeness). Also, note if the legs have spines or are smooth.
5. Identify the Claws (Chelae): Look closely at the claws—their size relative to the body, shape, and color. King crabs often have one claw larger than the other, while Dungeness crabs have claws of similar size. Some crabs have smooth claws; others have serrated edges or spines.
6. Check for Distinctive Markings or Features: Some species have unique characteristics such as spots, stripes, or spines on their carapace or legs. For example, the graceful decorator crab often carries algae or debris on its back for camouflage.
7. Note the Habitat and Location: Different crab species prefer various habitats. Dungeness crabs are often found in sandy or muddy bottoms nearshore, king crabs in deeper, rocky areas, and pea crabs as tiny parasites inside mollusks. Habitat clues can help confirm identification.
8. Use a Field Guide or App to Cross-Reference: Compare your observations to photographs and descriptions in a reputable Alaska marine species guide or identification app. This helps confirm species and avoid confusion with similar-looking crabs.
9. Photograph the Crab from Multiple Angles: Take clear, close-up shots of the carapace, legs, claws, and underside if possible. Photos assist with later identification and can be shared with experts or online forums for verification.
10. Record Your Findings: Document your observations including date, time, location, water conditions, and any behavioral notes. Keeping detailed records improves your identification skills over time.
11. Recognize the 15 Common Crabs in Alaska Waters: Here are brief identifiers for each:
    • Dungeness Crab (Metacarcinus magister): Large, reddish-brown, smooth oval shell, broad claws.
    • Red King Crab (Paralithodes camtschaticus): Very large, spiny red-orange shell, long legs, one claw bigger.
    • Blue King Crab (Paralithodes platypus): Blueish shell with spines, similar shape to red king crab.
    • Golden King Crab (Lithodes aequispinus): Yellow-gold spiny shell, smaller than red king crab.
    • Snow Crab (Chionoecetes opilio): Long, slender legs, pale orange to white, smooth shell.
    • Tanner Crab (Chionoecetes bairdi): Similar to snow crab but darker and stockier.
    • Hairy Hermit Crab (Pagurus hirsutiusculus): Small, hairy legs, uses discarded shells.
    • Graceful Decorator Crab (Oregonia gracilis): Long legs, carries algae on back.
    • Pea Crab (Pinnotheres pisum): Tiny, smooth shell, often found inside mollusks.
    • Box Crab (Lopholithodes mandtii): Thick, square-shaped carapace with spines.
    • Scarlet King Crab (Paralithodes camtschaticus variant): Bright red color, large spiny shell.
    • Spiny King Crab (Paralithodes brevipes): Smaller, more spiny than red king crab.
    • Broad Toothed Hermit Crab (Pagurus granosimanus): Large claws with broad teeth, inhabits shells.
    • Fuzzy Hermit Crab (Pagurus trigonocheirus): Hairy claws and legs, small size.
    • Slender King Crab (Paralithodes camtschatica): More slender legs, less spiny carapace.
12. Practice Regularly: Identification improves with experience. Visit different locations and seasons, observe live crabs or specimens, and compare with your notes.

Common Mistakes

• Relying Solely on Color: Crab colors can vary widely due to molting, environment, or age, leading to misidentification.
• Ignoring Habitat Clues: Not considering where the crab was found can cause confusion between species that look similar but live in different zones.
• Miscounting Legs or Claws: Failing to distinguish claws from walking legs or miscounting can lead to errors.
• Not Using Multiple Features: Relying on a single trait like size or shell shape instead of a combination can be misleading.
• Disturbing or Handling Crabs Improperly: Rough handling can harm crabs or cause defensive behavior, making identification harder.

Tips

• Bring a waterproof notebook or use a phone app to jot down observations immediately.
• Use binoculars or zoom lenses to observe crabs without disturbing them.
• Join local marine biology groups or forums for advice and verification of tricky IDs.
• Learn molting cycles as some features change dramatically during this time.
• Wear gloves when handling crabs to protect yourself and reduce stress on the animal.
• Visit tide pools at low tide for easier access to diverse crab species.
• Compare juvenile and adult forms, as some crabs look very different at various life stages.

Troubleshooting

If you cannot confidently identify a crab, try these approaches:

• Take Detailed Photos: Capture multiple angles, close-ups of claws, legs, and the underside. This allows for later analysis or expert consultation.
• Consult Experts: Reach out to local universities, fisheries offices, or online marine identification communities with your photos and notes.
• Use Multiple Resources: Cross-reference several field guides or apps to compare descriptions and images.
• Observe Behavior and Habitat: Note where and how the crab moves or feeds, as behavior can be a key indicator.
• Wait for Molting or Growth: If possible, revisit the same crab at a later time, as features may become clearer after molting.
• Handle Crabs With Care: If handling is necessary, do so gently and release the crab promptly to avoid stress or injury.

Frequently Asked Questions

How can I tell the difference between king crabs and snow crabs?

King crabs have a larger, spiny, often triangular carapace with robust legs, while snow crabs have a smoother, more oval carapace with long, slender legs.

Are all crabs edible in Alaska waters?

No. While many crabs like Dungeness, king, and snow crabs are edible and commercially harvested, some species are too small, protected, or not palatable.

When is the best time to observe crabs in Alaska?

Late spring through early fall offers the best conditions for observing crabs in tide pools and nearshore waters, as crabs are more active and accessible.

Can I keep any crab I find?

No. Alaska has strict fishing regulations and permits governing crab harvesting. Always check local laws before collecting crabs.

What is the easiest way to identify juvenile crabs?

Juvenile crabs can look different from adults, so focus on carapace shape, claw size relative to body, and habitat. Using a detailed field guide helps.

Do crabs change color over time?

Yes, crab coloration can vary due to molting, diet, environment, and age, so color alone is not a reliable identification feature.

By following these steps and guidelines, you will gain confidence in identifying Alaska’s diverse crab species and deepen your appreciation for the region’s marine ecosystem. Remember to respect wildlife and local regulations while exploring these fascinating creatures.

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