Oregon Sea Grant

Aquatic Invasive Species Watch

The Japanese dock that washed ashore at Agate Beach in 2012 was covered with more than 125 species of plants and animals. These are some of the invasive species found on it.

European Blue Mussel (Mytilus galloprovincialis)

This mussel can be dark blue or brown and looks similar to Oregon’s native mussels. Originally native to Europe, it became invasive in Japan and is now a major species found on Japanese tsunami debris. It is present in British Columbia, Washington and California, but is not in Oregon. It can mate with native mussels.

Asian/Japanese Shore Crab (Hemigrapsus sanguineus)

This crab has a square-shaped shell with three spines on each side. Its legs have light and dark bands; its claws have red spots. This crab looks similar to one of Oregon’s native shore crabs, but it can be an aggressive predator.

Dead Man’s Fingers (Codium fragile subsp. Fragile)

This green algae with spongy, hairy branches can reach about three feet in height. It reproduces asexually when pieces of the plant break off, allowing it to spread quickly.

Northern Pacific Seastar (Asterias amurensis)

This large, light-purple sea star with a yellow underside can grow up to 20 inches in diameter. Native to the northwestern Pacific, it has become an aggressive invader, overtaking native sea stars in Australia.

Wakame Kelp (Undaria pinnatifida)

An edible, fast-growing kelp native to Japan, its long, dense blades can grow to about 10 feet and potentially shade out the sunlight of Oregon’s native kelp ecosystems.

Skeleton Shrimp (Caprella cristibrachium)

These non-native species can outcompete and replace native skeleton shrimp. Their small heads and long, large claws inspired the creature in the film Predator.

Acorn Barnacle (Megabalanus rosa)

This barnacle is pink to red and sometimes white. It’s found on wood, rocks and concrete. Native to Japan, it grows faster and larger than most barnacles. The waters off Oregon, however, are too cold for it to gain a foothold.

Red Algae (Grateloupia turuturu)

This seaweed has thin, flat, pink to maroon blades that can grow rapidly to 10 feet in length. Red algae can be slimy to the touch, but when reproducing can feel grainy and rough. It can quickly occupy areas, exclude native organisms, and alter habitats.