Home ›

Dead Man's Fingers

Common Name(s) 

Dead Man's Fingers, Green Sea Fingers, Green Fleece, Oyster Thief, Sputnik Weed, and Broccoli Weed

 

Scientific Name 

Codium fragile subspecies tomentosoides (van Goor) Silva

Status
Project UFO has not seen it in Cape Breton waters, but several people have reported seeing specimens washed up on the west coast of Cape Breton Island (i.e. around Cheticamp and beaches of Cape Breton Highlands National Park) - if you come across what you believe to be oyster thief, please mail it (dry) or bring it to Project UFO, Cape Breton University.
 

Description

  • color is pale to dark green
  • branching alga (seaweed) that splits into new branches as it grows, giving it a "bush-like" appearance
  • branches are cylindrical in shape, resembling fingers
  • the long hairs on the fronds give it a soft, fuzzy feel when submerged, however, branches become coarse when washed up on shore
  • can grow to a length of > 1 meter
  • when washed up on the beach, it loses its green color and becomes pale ivory or white
  • for helpful photographs and drawings of Codium, please click here for the ID card from Salem Sound Coastwatch, Massachusetts

 

These samples were found washed up on sandy beaches near Hubbards, Nova Scotia, in 2009. 

Habitat 

Codium is well established in a variety of climates throughout its distribution.  It is found on hard bottom surfaces and rocky shores and grows attached to rocks or attached to other algae.  It usually inhabits the lower intertidal zone, however if this area is likely to freeze during the colder months, it is often found subtidally.  Codium can survive in a broad range of temperatures and salinities and prefers a protected to semi-exposed habitat where is can grow best in low sunlight.  

 

Invasion History 

Many believe this alga to be native to the Asian Pacific, in particular, Japan.  From it’s native range, it moved into Europe and was introduced into England.  It is now present along the shores of Britain, Australia, New Zealand, the Mediterranean, and on the east and west coasts of North America.  It was first reported in the United States in New York in 1957 and spread up and down the east coast where it was then reported in Nova Scotia in 1989.  The Marine Invasive Species in Nova Scotia website based out of Dalhousie University reports that Codium in Nova Scotia was first recorded in Graves Shoal, Mahone Bay, Lunenburg County.  Since then it has spread along the shores of Nova Scotia, Prince Edward Island and New Brunswick.  

 

Regional Sightings 

To our knowledge, Codium has not yet been found on Cape Breton Island. If you snorkel or SCUBA dive, please be on the look out for this unmistakable seaweed. If you are a beachcomber, please scout for dried specimens that look like bleached, fuzzy or coarse fingers. If you think you have seen Codium on your adventures in Cape Breton, please contact us at info@ProjectUFO.ca.

 

Potential Impacts

Sea urchins normally graze on kelp forests in cycles where one dominates the other for a certain amount of time.  At some point the kelp can be completely depleted by the urchins, leaving barren areas. Codium competes with local kelp and is unable to establish itself when kelp is present. However, when these barrens occur, Codium is able to establish itself in abundance.  This also occurs with the introduction of the invasive lacy crust bryozoan, Membranipora membranacea which has the ability to wipe out a kelp forest, creating room for Codium to establish itself.  Once this occurs, the kelp can not re-colonize the area, thus altering the structure of the community.   

 

Dense clusters of Codium make it difficult for larger invertebrates and fish to swim freely and live amongst the branches. Dr. Robert Scheibling of the Marine Invasive Species in Nova Scotia site reports that there is concern that these algal meadows will inhibit the foraging of species such as lobster, as well as concern for the shellfish and aquaculture industry.  This algal species will attach itself to any hard substrate, including shellfish, and if the wave exposure is high, the shellfish can be completely swept away with the plant (i.e. “the Oyster Thief”).

 

Additional websites about Codium in Nova Scotia and around the world