Flocculated microalgae concentrates as diets for larvae of the tiger prawn Penaeus monodon Fabricius

Fresh algal culture is a major bottleneck in the aquaculture industry. Substitutes that are cost-effective and simplify hatchery procedures, such as algae concentrates need to be evaluated. Four species of alga – Chaetoceros muelleri , C. calcitrans , a tropical Skeletonema sp. and Thalassiosira pseudonana – were concentrated by flocculation, stored for 6 weeks at 4 °C and then compared with their fresh counterparts as feeds for Penaeus monodon larvae. The algae were fed at either high or low cell densities with no supplements.
Fresh C. muelleri promoted the highest survival, greatest weight gain and fastest development to mysis 1. Larvae fed this diet were twice as heavy as those fed most of the other diets. Concentrated C. muelleri or T. pseudonana promoted similar survival rates to that of larvae fed fresh C. muelleri although development rates were slower. Larvae fed fresh C. calcitrans had high survival and intermediate development, but those fed the concentrate had very poor survival and development. Skeletonema sp., whether in the fresh or concentrated form, was a poor diet for prawn larvae: it resulted in high mortality and slow development. Cell density did not affect survival or dry weight of larvae but did affect development in some cases. Flocculated algal concentrates show promise as replacement feeds for fresh algae.