Author:Â David Freitas
Photos by David Freitas
Common Names:Â Rock Prickleback, Rock Eel, Rock Blenny
Scientific Name:Â Xiphister mucosus
Identifying Features: The Rock Prickleback is greenish-black in color with faint white markings around the base of its tail and light bands on its face. It is often confused with the Black Prickleback which has similar markings radiating from its eyes except they are generally solid black markings with a light border against a uniformily black body. The dorsal fin starts at the back of the head and goes down the length of the body merging with the caudal fin. The Rock Prickleback has very small pectoral fins and is lacking pelvic fins giving it a very eel-like appearance. They are called Pricklebacks because the dorsal fin is mostly composed of hard, spiny rays with sharp tips (the rays support the fleshy fins).
Habitat: The Rock Prickleback lives in rocky areas mostly on the exposed coast with moderate waves. It is very easy to find under rocks at low tide. It is able to stay out of water for 17-23 hours on land if it is kept moist. The Rock Prickleback is found from south-eastern Alaska to southern California.
Food: The Rock Prickleback eats mostly algae, but also eats small fish and crustaceans. It will also eat small chopped up fish or mussels in captivity.
Predators: Likely predators would be various shore birds, the Great Blue Heron, raccoons, and river otters. Humans also harvest the Rock Prickleback and the skeletal remains in middens indicate they were a food source of coastal First Nations for hundreds of years.
Life Cycle:  The Rock Prickleback breeds during the winter. The female lays her eggs in clumps under rocks and seaweed then the male coils up around the eggs and guards them until they hatch.  The Rock Prickleback takes 4-5 years to reach maturity and can live up to 11 years.
References
David W. J. (September 24, 2007). Rock prickleback (South Sound marine life). The Olympian. Retrieved June 8, 2011 from http://www.theolympian.com/2007/09/22/224212/rock-prickleback-south-sound-marine.html
Froese, R. (October 6, 2010). Xiphister mucosus (Girard 1858) Rock prickleback. FishBase A Global Information System on Fishes. Retrieved June 8, 2011 fromhttp://www.fishbase.org/Summary/SpeciesSummary.php?ID=3798&genusname=Xiphister&speciesname=mucosus
Lamb, A., & Edgell, P. (2010). Coastal Fishes of the Pacific Northwest. Harbour Pub.
Stephen S. (2003). Rock Prickleback Xiphister mucosus. MSAP – Marine Species with Aquaculture Potential. Retrieved June 8, 2011 fromhttp://hmsc.oregonstate.edu/projects/msap/PS/masterlist/fish/rockprickleback.html
Young, D. (2011) Marine life of British Columbia Identification Guide, Victoria BC