The Effect of Photoperiod on Growth and Survival of Juvenile Freshwater Prawn, Macrobrachium rosenbergii in Nursery Tanks

Abstract

To achieve marketable size (> 30 g) in the limited growing season available in temperate areas, post-larval freshwater prawn, Macrobrachium rosenbergii must be grown to a larger size (from 0.01 to > 0.2 g) prior to pond stocking. This is known as the nursery phase. Little research has been conducted on the effects of different management and environmental factors on juvenile prawn growth and survival during this 30-60 day period. The objective of this study was to evaluate the effects of three different photoperiods on growth and survival of juvenile freshwater prawn during nursery production. Four hundred post-larval (PL) freshwater prawns (0.025iö.04 g) were stocked into nine 170-L nursery tanks at 2.3 PL/L with artificial substrate added to each tank at a rate to achieve a density of 430 PL/m2 of substrate. Tanks were randomly assigned to one of the following photoperiod regimens: 24 hours darkness (L0:D24); 12 hours light: 12 hours darkness (L12:D12); or 24 hours light (L24:D0), with three replicate tanks per treatment. Freshwater prawn were fed a trout diet containing 42% protein and 8% lipid according to a feed table. After 60 days, there was no significant difference (P > 0.05) in average individual weight of freshwater prawn exposed to the different light regimens (overall mean 0.86 g). Survival was significantly greater (P < 0.05) in prawn raised under continual light conditions (L24:D0) (72%) than those raised under L12:D12 (59%) or continual darkness (L0:D24) (58%); values for these latter two treatments did not differ significantly (P > 0.05). This study indicates that continual light conditions have a positive impact on survival of freshwater prawn juveniles during the nursery phase.