The effects of substrate orientation and color on survival and growth of freshwater prawn Macrobrachium rosenbergii

Post larvae (PL) freshwater prawn (Macrobrachium rosenbergii) were reared in rectangular and circular tanks to determine the effects of orientation and color of added substrate. In the rectangular tanks (400L), 2000 prawn, with a mean initial weight of 0.05 grams per animal, were nursed for 65 days at 25.5°C (78°F). Brown polyester mesh netting (6 X 6 mm) was added to each of the six tanks, increasing the surface area of each tank by 99% (9335 cm²). In three tanks, substrate was arranged in horizontal rows; the other three tanks had substrate arranged vertically. There were no significant differences in survival of prawn between the horizontal (56%) and vertical (53%) substrates. Differences in growth were also insignificant. Final mean growth was 0.34 grams on horizontal substrate and 0.34 grams on vertical substrate.

In the 400 L circular tanks, polyester mesh netting material (6 X 6 mm) was used in four horizontal substrate pieces per tank, increasing surface area by 186% (21677 cm²). Three tanks contained the addition of brown substrate and the other three contained tan substrate. Prawn were stocked at 1950 per tank, with an average initial weight of 0.1 grams per prawn, and nursed for 60 days. There were statistically significant differences in survival rates between brown (46%) and tan (40%) colored substrates. There was a slight difference in prawn growth between the substrate colors, but not statistically significant. Prawn on tan substrate had a final mean weight of 0.37 grams while prawn on brown substrate weighed 0.34 grams per animal. As the prawn grew larger, they became more aggressive and more cannibalistic, which resulted in decreased survival rates and increased size of the survivors.