recovered from each of the green water pools versus an average of
125 animals recovered from each clear pool, representing mortality
rates of 43.9% and 8.9%, respectively (Table 2).

DISCUSSION
 Mortality in postlarval prawns has been attributed to high pH
values (pH 9.0-9.5) (Sarver et al., 1982). Corroborating data from
the chemically adjusted pH experiment suggest that pH values of

 TABLE 2. Photosynthetically altered pH replicates.


 % Mortality

Rep Green Clear

 1 42.1 5.7
 2 51.4 5.0
 3 45.0 15.0
 4 37.1 10.0

 Av9=43.9 8.9
 SD= 6.0 4.6


PROCEEDINGS of the CARIBBEAN FOOD CROPS SOCIETY-VOL. XX


9.0 or greater cause mortality in unacclimatized postlarvae. When
stocking postlarval prawns, waters with pH 9.0 should be suspect.
Waters with pH 9.5 or greater may not be suitable for direct stock-
ing of postlarvae.
 The results of the photosynthetically altered pH experiment
show that phytoplankton activity can be correlated with mortality
in postlarval prawns. It is probable that high pH resulting from
photosynthetic activity of phytoplankton was the primary cause of
mortality in this experiment, although other factors, such as algal
toxicity, cannot be discounted until further work is done in this
area. The difference in total hardness values between the
treatments can be attributed to salt precipitation occasioned by the
high pH values observed in the green water treatment.




References
 1. AQUACOP Centre Oceanologique du Pacifique CNEXO-COP. 1979.
Macrobrachium rosenbergii culture in Polynesia: pH control in experimental pond
waters by photoplankton limitation with an algicide. Proc. World Maric. Soc.
10:392-402.
 2. Boyd, C.E. 1979. Water quality in warm water fish ponds. Auburn Univer-
sity Agricultural Experiment Station. Craftmaster Printers Inc., Opelika, AL.
 3. Fujimura, T. 1974. Development of a prawn industry in Hawaii. Hawaii
Sub-project No. H-14-D. Job completion report to U.S. Dept. of commerce. Na-
tional Oceanic and Atmospheric Association. National Marine Fisheries Service.
 4. Sarver, D., S. Maleca and D. Onizuka. 1982. Possible sources of variability
in stocking mortality in postlarval Macrobrachium rosenbergii. In: Giant Prawn Far-
ming, edited by M.B. New. Elsevier, Amsterdam.


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