RELATIVE PRAWN PRODUCTION AND BENTHIC MACROINVERTEBRATE DENSITIES IN UNFED, ORGANICALLY FERTILIZED, AND FED POND SYSTEMS

Relative prawn production rates in unfed, organically fertilized, and fed pond systems were evaluated. Populations of benthic macroinvertebr ates that potentially serve as forage organisms in these systems were also evaluated and compared with ponds without prawns to evaluate fora ge preferences. Juvenile prawns ((x) over bar = 0.36 +/- 0.02 g) were stocked into nine 0.04 ha ponds at a density of 39520 ha(-1). Prawns i n three ponds were not fed, prawns in three ponds were fed a complete diet, and three ponds received organic fertilization. Three additional ponds (0.02 ha) served as controls (not stocked with prawns and recei ved no nutrient input). Survival averaged 86%, overall, and was not si gnificantly different among treatments. Average weights of prawns fed complete feed or raised in fertilized ponds (36 and 33 g, respectively ) were not significantly different (P > 0.05). Prawns in unfed ponds w ere significantly (P less than or equal to 0.05) smaller (13 g). Avera ge prawn yields in fed, fertilized, and unfed ponds (1261, 1056, 426 k g ha(-1), respectively) were all significantly different (P less than or equal to 0.05). In ponds receiving no nutrient input, macroinverteb rate densities were significantly higher (P less than or equal to 0.05 ) in ponds without shrimp (controls) than in those stocked with shrimp . In ponds stocked with shrimp, macroinvertebrate densities in fed and fertilized treatments were significantly greater (P less than or equa l to 0.05) than in the unfed treatment, but not significantly differen t (P > 0.05) from each other. Insect taxa showed a greater negative re sponse to prawn predation than non-insects. Non-insect taxa demonstrat ed a more positive response to fertilizer and feed than insects. Altho ugh prawn production in organically fertilized ponds was surprisingly high (> 1000 k ha(-1)), economic analysis demonstrated higher net retu rns when prawns were fed a prepared diet, principally due to the produ ction of greater numbers of large, high value prawns.