RELATIVE PERFORMANCE OF 3 BOTTOM GRAZING FISHES (CYPRINUS-CARPIO, CIRRHINUS-MRIGALA, HETEROPNEUSTES-FOSSILIS) IN INCREASING THE FERTILIZER VALUE OF PHOSPHATE ROCK

The bioturbation-induced fertilizer value of phosphate rock by common carp (Cyprinus carpio), mrigal (Cirrhinus mrigala) and singhi (Heterop neustes fossilis) was examined. The bioturbation activity of the commo n carp was highest, even though its body mass was 3 times less than mr igal, and about the same as that of singhi. The relative importance of mrigal and singhi varied depending upon the biomass or number of fish . As a result of bioturbation, the amount of citrate-soluble phosphate and available phosphate of bottom soil was observed to decrease by 33 % and 15%, respectively, whereas the level of orthophosphate of water was increased by 27%, suggesting that citrate-soluble phosphate and/or available phosphate of soil served as a source of phosphate in overly ing water. There was a strong inverse correlation between the orthopho sphate of water and citrate-soluble phosphate or available phosphate o f soil.