What is plankton?

Plankton are small organisms that dwell in oceans, seas and bodies of fresh water. Plankton are defined by their movements and their size. Although they are capable of swimming vertically in the water, they have little ability to swim horizontally and thus are carried about by currents.

They are usually small in size generally microscopic (microns, 1/1000th of a mm). Plankton are the most abundant form of life in the ocean. In fact, all other marine life is dependent upon plankton. The plant forms and many protozoans are known as phytoplankton.

“Plankton” is from a Greek word for “wanderer.” It is a collective term for the various organisms that drift or swim weakly in the open water of the sea or freshwater lakes and ponds. Plankton is composed of viruses, bacteria, phytoplankton, zooplankton and the pelagic larvae of many marine invertebrates and fishes. This group displays a wide range of behavioral capabilities that bridge the transition from being a passive particle to being able to determine vertical and horizontal position in the ocean.

Plankton can range in size from microns to meters. The smallest plants living in the ocean are the phytoplankton, which vary in size from about 5 microns to 50 millimeters. Single-celled plants called diatoms, constitute more than half of the phytoplankton in the ocean.

Plankton can be divided into two large groups: planktonic plants and planktonic animals. The plant plankton or phytoplankton are the producers of ocean and freshwater food chains. They are autotrophs, making their own food, using the process of photosynthesis. Phytoplankton are producers, transforming sunlight into food energy.

The animal plankton or zooplankton eat food for energy. Zooplankton is food for many secondary consumers.
What is plankton?

Anadromous fish of Shad

Shad are anadromous fish (ascend rivers to spawn) that spend the greatest part of their lives in ocean waters as far as 50 mile (80.5 km) from shore. Shad are plankton eaters and are said not to eat fish.

They range from the Gulf of St. Lawrence to Florida on the East Coast, but are caught in significant numbers only from New York southward. They were brought, some years ago, to Pacific waters, and some are now caught in California. Shad are caught in rivers and their estuaries with drift grill nets. Aboard the boats, they are neither eviscerated nor iced, since they are brought to shore shortly after removal from the water.

Shad are used almost entirely as the fresh product, with only small amounts being frozen. They contain many small bones, but can be filtered to eliminate most of them from the flesh. The roe (unfertilized eggs), which prior to spawning is held together by a thin membrane, is highly prized. It is sold fresh, or packaged in moisture vapor-proof material and frozen to be sold to the restaurant trade and in this state, may be stored at 0 degrees F for 6 to 8 months. Longer storage under this condition usually results in a rancid product due to oxidation of the fats contained therein.
Anadromous fish of Shad