FISHERY BULLETIN: VOL. 71, NO. 4 



For comparative purposes, the caloric content 

 of five genera of sea grasses collected in various 

 areas of the world and knov^n to be eaten by 

 green turtles there, are provided in Table 2. All 

 of the samples from the South Pacific were burn- 

 ed according to the methods of Lieth (1968). It 

 is likely that these values would be about 8% 

 higher if independent ash determinations were 

 made with a muffle furnace. Although green 

 turtles were not actually seen feeding around 

 Fulanga in the Lau Group of the Fiji Islands, 

 leaves of Halodule uninervis collected in Novem- 

 ber 1970 around Fulanga registered 4.02 kcal/g 

 dry wt, ash free when combusted by the Lieth 

 (1968) method. T. testudvium around Grand 

 Cayman Island is currently collected by a 

 special underwater harvester and along with 

 specially prepared food pellets is fed to captive 

 green turtles in the turtle farm on Grand 

 Cayman. Likewise, on some of the Tonga Islands, 

 Syriugodium and Halodule wrack washed up 

 on the strand in large quantities after storms is 

 fed to captive turtles kept in kraals. The findings 

 reported in Tables 1 and 2 show that the caloric 

 content of leaves of various kinds of sea grass 

 are similar despite the fact the samples were 

 collected at different times of the year and at 

 widely scattered places. However, some inter- 

 area differences are evident in that the energy 

 content of tissue of five genera from the Gulf of 

 Aden (Table 1) averaged about 0.15 kcal/g dry 

 wt, ash free, higher than the four genera from 

 the South Pacific (Table 2) as measured by the 

 Lieth method. 



The caloric content of sea grasses reported in 

 this paper are very similar to the value of 4.41 

 kcal/g dry wt, ash free reported for Phyllospa- 

 dix scouleri by Paine and Vadas (1969). The 

 caloric values are also similar to some of the 

 benthic marine algae collected off the coast of 

 the State of Washington where the modal values 

 of green, red, and brown algae were respectively, 

 4.90, 4.75, and 4.45 kcal/g dry wt, ash free 

 (Paine and Vadas, 1969). For 32 samples of 

 aquatic monocotyledons, Cummins and Wuy- 

 check (1971) give a mean of 4.77 kcal/g dry wt, 

 ash free and for 359 samples of aquatic algae 

 they list a mean of 4.63 koal/g dry wt, ash free, 

 but none of their samples were sea grasses. 



The number of calories in the standing crop of 



Table 1. — Caloric values of sea grasses (leaves only) at 

 Khor Umaira. The plants were collected on 28, 29, and 30 

 July 1972. 



' Caloric values in parentheses were obtained using methods 

 of Lieth (1968). The other three caloric values are based on 

 independent ash determinations: see text for explanation. 



sea grasses at Khor Umaira can be estimated by 

 referring to the regression lines in Figures 2 

 and 3. For example, assuming that leaves of 

 C. serrulata represent 3.01 kcal/g dry wt (Table 

 1) then a pasture with, say, 50% cover contains 

 about 453 kcal/m^ (Figure 2). 



There are extensive sea grass pastures in 

 some shallow coastal waters (for distribution 

 see den Hartog, 1970) but before turtle ranch- 

 ing can become a reality, studies are needed on 

 the energy provided by epiphytes and animal 

 prey. It is likely that green turtles obtain some 

 nutritional value from the epiphytic organisms 

 on the sea grass leaves. Allen (1971) has pro- 

 vided detailed information on the energetics 

 of epiphytic algae and bacteria in a lake eco- 

 system. Further, the digestive processes of 

 green turtles ought to be examined in relation 

 to the protein content of sea grasses and other 

 food. Occasionally, it has been observed that 



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