because they are turned reddish-orange by 

 stomach enzynnes. Fishermen report that pain- 

 ful sores develop on their hands after handling 

 mackerel containing red feed, which is known 

 to them as "red pepper." The presence of this 

 food in the stomachs of mackerel causes 

 rapid and extensive breakdown of the surround- 

 ing flesh within 24 hours after the fish have 

 been caught and packed in ice. Fishermen 

 occasionally experience heavy losses from 

 such spoilage. 



The herring, one of the most abundant fish 

 in the world, occurs on both sides of the Atlan- 

 tic and the Pacific Oceans, where it feeds 

 while young on small planktonic forms--dia- 

 toms, Peridinium , Crustacea, larvae of worms, 

 pelecypods (bivalve mollusks: e.g., oysters 

 and clams), and gastropods (univalve n-iollusks: 

 e.g., snails). Among the crustaceans eaten by 

 herring, the Calanus , red feed, has a very 

 great influence on the economy of the herring 

 industry of the United States and Canada. In 

 these two countries small herring are canned 

 as sardines. When a catch of herring is to be 

 canned, it must be inspected for red feed, and 

 if Calanus was injested recently enough to be 

 present in the alimentary tract, the fish must 

 be held until both stomach and intestine are 

 cleared of the red feed. 



Menhaden are among the few fishes that 

 throughout life feed chiefly on diatoms and 

 Peridiniuni (two of the most common plank- 

 tonic forms). They also feed on the most 

 minute crustaceans. 



Many fishes prefer one or more groups of 

 plankters to the exclusion of others. The 

 stomachs of fish often contain only one or a 

 few species, even when other organisms of 

 similar size are known to be in the particular 

 locality where the fish were feeding. Whales 

 that feed on plankton also are selective. They 

 roam the seas to locate massive bloonns of 

 their favorite organisms. The reasons for these 

 food preferences and the bases of selection 

 (sight, taste, odor) are not fully understood. 



Food for Man 



The value of plankton as food for fish and 

 other aquatic fauna has long been recognized, 

 but the value of phytoplankton as a primary 

 source of food for man, and the tremendous 

 potential economic importance of its industrial 

 culture, have only begun to be appreciated. As 

 the human population grows, the need for addi- 

 tional foods will increase. Even now, many 

 peoples of the world are underfed while an 

 enormous aquatic resource remains undevel- 

 oped and is wasted. 



Large deposits of the remains of diatoms 

 like the one at Lompoc, Calif., are mute evi- 

 dence that long ago greater quantities were 

 produced annually than were consunned. Al- 

 though excess production of other connponents 

 of the plankton has not been demonstrated so 



dran-iatically, their numbers also surpass the 

 needs of their natural predators. Here in 

 America little consideration has been given 

 to the possibility of using this surplus for 

 human food. Fortunately we are capable of 

 producing more land-grown foods than are re- 

 quired to supply the needs of the present 

 population. 



In some European and Asian countries such 

 as Germany, England, Japan, China, and India, 

 however, scientists have given much serious 

 thought to the use of plankton for food. As 

 early as 1939, the German State Biological 

 Institute of Helgoland was "investigating the 

 possibility of harvesting plankton of the sea as 

 a new food source to make Germany more 

 independent of foreign imports." The Insti- 

 tute found the nutritive value of zooplankton 

 equivalent to that of the best meats, and the 

 nutritive value of phytoplankton equal to that of 

 rye flour. An English scientist, William A. 

 Herdman, who became interested in the flavor 

 of zooplankton, reported in 1891 that he had 

 eaten copepods boiled in butter; he liked the 

 preparation and stated that the flavor was 

 similar to that of lobster. H. Tamiya, who has 

 done extensive work in Japan on man's use 

 of planktonic green algae, found that blanched 

 algae are palatable and that man can convert 

 30 to 50 percent of the algal material to his 

 bodily needs. During World War II, the United 

 States made intensive studies of plankton as 

 food and recommended its use as food for 

 downed aviators or shipwrecked persons. 

 Plankton nets were made part of survival kits. 



An unprecedented increase in the world pop- 

 ulation during the past century has caused 

 scientists to estimate that by the year 2000 

 J;he total will rise from the present 2.7 billion 

 to 7 billion people. Agriculture and known 

 natural resources may be developed ade- 

 quately to sustain a population of that size, 

 but segments of this horde no doubt will sxiffer 

 protein and fat deficiencies as they do even 

 now. Looking to the future, one can envisage 

 a world with 50 billion or more people. Some- 

 time during this tremendous expansion, a 

 critical worldwide food shortage is certain 

 to occur. Then, or before- -depending upon 

 current technical knowledge--harvest or cul- 

 ture of phytoplankton must be undertaken to 

 ensure survival of the populace. 



Man is not likely to compete soon with fish 

 for the plankton of the sea. Collection of 

 plankton there is impractical now because the 

 tiny creatures rarely are sufficiently con- 

 centrated to support a commercial enterprise. 

 On the west coast of Scotland, where the growth 

 of plankton is particularly rich in the lochs and 

 estuaries, a total of 525 pounds (dry weight) 

 of plankton was procured with 10 nets hung 



* The nets were necessarily of fine mesh cloth in order 

 to catch plankton but the exact size of mesh and dimen- 

 sions of the net were not given in the article published. 

 The amount of water filtered was not measured. 



