Culture of Gracilaria edulis was undertaken using a floating raft method to improve biomass production.
Research on seasonality of growth, growth rate differences in different localities, subtidal (off-shore) and
intertidal (near-shore) cultivation and seasonal occurrence of epiphytes was carried out. Lowest biomass
(1.5±0.1 kg fresh wt m−2) and daily growth rate (DGR) (2.6±0.1%/day) were obtained during January–February
which were significantly different (Pb0.001) from other maximum growth periods. The range of biomass
(1.6–2.6 kg fresh wtm−2) and DGR (3.6–5.9%/day) was higher at Ervadi than Thonithurai, but not
significantly different (PN0.05). Cultivation in subtidal region gave significantly higher biomass (12.5±0.9 kg
fresh wtm−2) and DGR (7.4±0.4%/day) than those from intertidal region (4.4±0.4 kg fresh wtm−2) and
DGR (5.1±0.1%/day). Epiphytes are reported to cause severe problems for the growth of Gracilaria. A maximum
of 15 epiphytic algae recorded in April and August and minimum of 7 in February. The findings presented here
indicate that G. edulis can be cultivated successfully for 8 months each year with maximum growth rates during
November–December. Cultivation in the subtidal region, harvest after 60 days of growth, periodical weeding of
epiphytic algae improved the yield further.