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 What is an Atlantic herring?

 herring distribution

 herring life-cycle

 herring ecology
Atlantic Herring
 Herring Biology: Ecology

What do herring eat?

Moonlit Nights and a Copepod Filled Sea - Calcanus finmarchicus steals the show.

The copepods are a class of crustaceans with over 7,500 species, most of which are marine. [1] Copepods are small (only a few species over 1 mm) and extremely abundant, often dominating the plankton community. They form a link in the food web between the primary-producing phytoplankton and the plankon-feeding fish like Atlantic herring. Almost all fish found in temperate and polar waters rely at some point in their life cycle on copepods and other shrimp-like zooplankton (krill) as a food source. In addition, some larger organisms feed directly on copepods.

fin whale feeding on phytoplankton off Grand Manan island in the Gulf of Maine
Fin Whale feeding on a tidal upwelling of phytoplankton on the north side of Grand Manan island in the Gulf of Maine.

In the Arctic, bowhead whales (Balaena mysticetus) time their migration to coincide with the arrival of a Calanus copepod. The whales use their baleen plates to filter the copepods directly from the water column in enormous numbers. Northern right whales (Eubalaena glacialis) make a similar spring migration to an area west of Georges Bank called the Great South Channel where they feed on dense patches of Calanus finmarchicus copepods that occur there every spring. [2]

In 1926 Henry Bigelow describes the importance of copepods to the Gulf of Maine system in his book, Plankton of the Offshore Waters of the Gulf of Maine.

"The importance of Calanus finmarchicus in the general economy of the Gulf of Maine and all the other seas where it abounds can hardly be over-estimated. Certainly it is no exaggeration to call it the most important single planktonic animal, probably more important in the gulf in its relation to both larger and smaller organisms than all other copepods combined. It is the basic food for the local mackerel, and is certainly a major article in the diet of herring, alewife, and shad while these are at sea.

All the other fishes of the offshore waters of the gulf that eat plankton at all may be expected to feed on Calanus more than on any other single item. Through the medium of the herrings, which are nourished on it, Calanus helps support the finback and humpback whales...It (Calanus finmarchicus) dominates the plankton of the Gulf of Maine at all seasons." [3]

There is no free lunch when Atlantic herring and other organisms feed on copepods. Woods Hole scientist Cabell Davis has studied the movement of copepods through the water column during their escape swimming mode. "We have video-taped the copepod Acartia tonsa swimming at over 1 knot, equal to 50 centimeters per second, during a tow test we did. Since the animals are 1 millimeter long, this corresponds to a relative speed of over 500 body lengths per second." Dr. Davis annotates this fact by pointing out, "An F16 fighter jet travels at about 50 body lengths per second, and a cheetah would have to run 2000 miles per hour to achieve 500 body lengths per second." [4]

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References:

[1] Baretta-Bekker, J.G., E.K. Duursma, and B.R. Kuipers, eds. (1992) Encyclopedia of Marine Sciences, 2nd ed. Springer, New York. 357 pp.

[2] Epstein, A. Gulf of Maine Physics. Oceanus. 39(1): 9.

[3] Bigelow, H.B. (1926) Plankton of the Offshore Waters of the Gulf of Maine. Bull. Bur. Fish. 40(Part 2, Document No. 968):1-509.

[4] Davis, C. (10/2000) Personal Communication. Woods Hole Oceanographic Institution.

 
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