374 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1950 



interference, these minute forms of life are eaten in fantastic quanti- 

 ties by other ocean dwellers. The zooplankton, for the most part, live 

 by eating the phytoplankton. They may then sink to the bottom, 

 where they provide food for shrimps, crabs, womis, mollusks, and 

 smaller invertebrate animals (which in turn may be eaten by larger 

 invertebrates or by bottom-living fishes like flounder and cod) , or they 

 may stay in the surface layers — only to be eaten by such fishes as 

 herring, menhaden, sardines, or mackerel, or, paradoxically enough, 

 by the largest of all marine animals, the whalebone or baleen whales. 

 The phytoplankton and zooplankton, the bottom invertebrates, the 

 fishes, the whales — all eventually meet their fate. If they escape pre- 

 dation, they die a natural death and release their inorganic matter 

 for use once again in the continuous cycle of life in the ocean. 



Or these plankton, these bottom invertebrates (shrimps, oysters, 

 clams), these fishes (herring or flounder), these whales, may be re- 

 moved from the sea by man for his use. 



The question, then, is this : at what stage in the cycle is it best to 

 take "the harvest of the sea" ? G. A. Riley, writing in the October 1949 

 Scientific American, directed attention to this problem in exemplary 

 fashion : 



. . . the fishes and other large animals in the sea represent the end product 

 of a long and complicated food chain. Through a series of predations, the tiny 

 bits of plant life are transformed into successively bigger bundles of living ma- 

 terial. But all along the way from plants to fishes there is a continual loss of 

 organic mattei*. During its growth to adulthood an animal eats many times 

 its own weight in food. Most of the organic material it consumes is bi'oken 

 down to supply energy for its activity and life processes in general. It follows 

 that the total plant matter in the sea outweighs the animals that feed upon it, 

 and the herbivores in turn outweigh the carnivores. Fish production is believed 

 to be of the order of only one-tenth of 1 percent of plant production. 



To put it another way, we can say that the average annual 

 phytoplankton crop in well-known fishing areas is roughly 500 to 

 1,000 times as great as the commercial catch of fishes; in short, if an 

 acre of sea bottom yields 50 pounds of fish a year, the phytoplankton 

 production in the overlying waters in that period might be 25-50,000 

 pounds. At a given time the phytoplankton crop might be only 

 about four times the weight of the fishes, but the microscopic plants 

 grow and multiply so fast that the production in the course of a year 

 is hundreds of times as much as the fish production. And if the 

 annual phytoplankton crop is of this order of magnitude, the zoo- 

 plankton crop — the next step in the chain — is perhaps 100 times the 

 poundage of the commercial fish catch in the course of a year. Clearly 

 then, by harvesting the fishes, which are at the end of the chain, we 

 are working at the most inefficient level. 



Unfortunately, however, nothing can be done about it. There 

 have been devices for the collection of plankton on a limited scale 



