Concept of triangular raft design: Achieving higher yield in Gracilaria edulis

Abstract

The study describes utility of triangular raft design and the associated cluster arrangement in improving yield of commercially important agarophytes Gracilaria edulis. This simple modular design is cost effective, expandable, maneuverable, requires no specialized skills for assembly and could be easily practiced at individual cultivator level. Although, the average daily growth rate achieved in triangular raft (5.01±0.64%day−1) was quite comparable to conventional square rafts (4.58±0.25%day−1), the biomass yield per square meter in former was considerably higher (59.49%) than latter. Analysis of variance (ANOVA) showed that the raft shape significantly affected the biomass yield per square meter (F=16.58; p=0.001) but not DGR (F=3.847; p>0.05). The projected per hector earnings were 2.4 times higher in case of triangular raft than square rafts. The mean drag coefficient values were 1.72 and 2.51 for triangular and rectangular configurations respectively. Thus triangular configuration was subjected to less force on the front face (more stable) than the rectangular configuration. The method appears to be superior for cultivating the algae having fragile fronds such as species of Gracilaria which are more susceptible to breakage in response to wave action. The scaled-up experiments are underway to ascertain its utility for year round farming.