178 



Life 



to compilations by the Department of Fish 

 and Game (Staff of Marine Fisheries Branch, 

 1956, etc.)- The same average was obtained 

 for the 16 years between 1926 and 1941 

 (Fig. 236, p. 305). To this must be added 

 about 7000 tons of fish caught annually by 

 men who fish for sport. At an average water 

 content of 20 per cent, the total annual catch 

 is 0.03 million tons dry weight. Tagging 

 work with sardines indicates an exploitation 

 rate of about 28 per cent (Cahfornia Coop- 

 erative Oceanic Fisheries Investigations, 

 1955. p. 20). If we assume an average of 

 5 per cent exploitation for all fishes, the 

 standing crop would be about 0.6 million 

 tons. If the average life span (or turn over) 

 is 6 years, the annual production is about 0.1 

 million tons, dry weight. This is only 3 per 

 cent of the annual production of zooplank- 

 ton and about 0.2 per cent of the annual 

 production of plant tissue, somewhat lower 

 than the generally assumed 10 per cent effi- 

 ciency of conversion from phytoplankton to 

 zooplankton to fish (Pequegnat, 1958). 



Sea mammals serve as a further example 

 of low efficiency, in their case of efficiency 

 of conversion offish to mammal tissue. The 

 population of sea lions (both Steller and 

 California) in southern California was esti- 

 mated by Bonnot and Ripley (1948) to be 

 4000 in 1947, but it has subsequently in- 

 creased to about 20,000. Assuming an av- 

 erage dry weight of 200 pounds, the total 

 weight of sea lions living in the region is 



about 2000 tons. Dolphins and porpoises 

 comprise possibly an additional 1000 tons. 

 Whales are not included because they are 

 for the most part only transient. If the aver- 

 age life span of the mammals is 10 years, the 

 average annual production is only of the 

 order of 300 tons. This is negligible in com- 

 parison with the tonnage of fishes; however, 

 it should be recalled that the balance be- 

 tween plankton, fishes, and mammals exist- 

 ing at present is not a natural one but is 

 much influenced by the present and past 

 hunting activities of man. 



Fairly good estimates (to a factor of 2) can 

 be made of the standing crop of invertebrates 

 living on or in the bottom based on the work 

 of Hartman (1955*3, 1956) and Hartman and 

 Barnard (1958 and unpublished data). A 

 summary given in Table 1 1 shows that the 

 standing crop is about 5.5 million tons (wet 

 weight). The annual turnover of animals in 

 shallow water is believed (but not known) 

 to be about two times each year, judging 

 from the average of 2.44 obtained by Sanders 

 (1956) for both long- and short-lived com- 

 ponents of the benthos in the shallower 

 water of Long Island Sound. For those in 

 deep water it may be once every 2 years; 

 thus the annual production is computed to 

 be about 7.4 million tons (wet weight). 

 Analyses by Vinogradov (1953) show that 

 the common benthonic invertebrates have 

 water contents that average about 80 per 

 cent. The total production of benthos off" 



