Growth and survival of post-larval giant tiger shrimp Penaeus monodon feeding on mangrove leaf litter biofilms

Abstract

Biofilm associated with decomposing mangrove leaf litter is a food source for shrimp post-larvae (PL). PL of giant tiger shrimp Penaeus monodon foraging on leaf litter of Rhizophora mucronata with developing biofilm at 1, 3, 4, 6, and 8 wk of decomposition were tested for specific growth rate (SGR, %) and percentage survival (SR, %). Biofilm was analyzed for species composition, abundance, and biomass of microalgae and epifauna. Microalgal biomass increased with the progress of litter decomposition. Diatoms, especially Navicula sp. and Nitzschia sp., dominated the first 6 wk of litter decomposition with a percentage cover of 88 and 99% during the third and fourth weeks, respectively. Cyanobacteria dominated in the 8 wk old biofilm with 61% cover. Copepods dominated the epifauna during the first 3 wk of litter decomposition. In the 4 to 5 wk old litter, polychaetes were most abundant whereas nematodes were dominant in litter that had decomposed for 8 wk. PL foraging on 4 wk old litter had a higher SGR (1.6 + or - 0.5%) and SR (39.8 + or - 4.8%) coincident with the maximum abundance of microalgae and epifauna. The study illustrated that nutritionally rich biofilm for PL shrimp is: (1) developed during the fourth week of mangrove leaf litter decomposition and is dominated by diatoms, polychaetes, harpacticoid copepods, and oligochaetes; and (2) limited by the collapse of the epifauna and subsequent colonization by cyanobacteria in mangrove leaf litter decomposed beyond 4 wk.