Sea Raven

(Hemitripterus americanus)

Sea Raven

Distribution

The sea raven, also known as the whip sculpin, gurnet, puff-belly, scratch-belly, and sea hen, ranges along the Atlantic coast of North America from Hamilton Inlet, Labrador, southward to Strait of Belle Isle and Gulf of St Lawrence. Sea Raven are present but uncommon around Newfoundland, becoming more common in Nova Scotia waters, in the Bay of Fundy and embayments such as Passamaquoddy Bay, and southward to Chesapeake Bay.

Habitat

Sea ravens live on rocky or hard bottoms, occasionally swimming up to the surface waters. Most live in waters deeper than 2 m and more shallow than 90 m. Preferred water temperatures range from the upper limit of about 14 degrees Celsius (eg. in the Gulf of Maine) to near the freezing point of salt water (-1.8 degrees Celsius) eg. off Newfoundland and in the southern Gulf of St Lawrence.

Food

Sea ravens are voracious feeders, and will eat any available bottom invertebrates, including crustaceans and molluscs. Sea urchins have been found in the stomachs of sea ravens taken in Newfoundland waters. Their wonderful camouflage comes in useful when they stalk and capture other fishes such as herring, sand lance, and silver hake. Interestingly, when they themselves are captured, sea ravens will often distend their abdomens by gulping water or a mixture of water and air and may then float belly up. The water can usually be removed by burping these fish (taking care not to get the fingers bitten), after which, they will be able to swim normally. Although sea ravens can reach lengths greater that 60cm, adults around 30 cm are more commonly found.

Antifreeze Production - Type II Antifreeze

Antifreeze production in this species shows some interesting variations from the pattern commonly found in species occupying temperate waters. Firstly, sea raven have antifreeze proteins present in their plasma year-round. Secondly, while some individuals show a seasonal cycle of antifreeze production with levels increasing to maximum values in the winter (like ocean pout), other individuals have constantly high levels all year round. This pattern is most commonly observed in fish inhabiting polar oceans. However, the animals used in studies that established this pattern in sea raven came from New Brunswick - Atlantic Canadian - waters, which although cool, are certainly not polar!

References

Fletcher,G.L., M.H.Kao, and K.Haya. 1984. Seasonal and phenotypic variation in plasma protein antifreeze levels in a population of marine fish, Sea Raven (Hemitripterus americanus). Canadian Journal of Fisheries and Aquatic Sciences. 41: 819-824.

Ng,N.F.L., and C.L.Hew. 1992. Structure of an antifreeze polypeptide from the sea raven - disulphide bonds and similarity to lectin-binding proteins. Journal of Biological Chemistry. 267: 16069-16075.


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