Influence of cultivation densities and harvesting rates on the environmental parameters, growth and productivity of eelgrass, Vallisneria spiralis

This study was conducted to evaluate effects of planting density and harvest rate on the growth and yield of eelgrass (Vallisneria spiralis). Experiment 1 aimed to evaluate the effects of different planting densities including three treatments of eelgrass planting density with three repetitions: 1) 0.25 kg/m2; 2) 0.50 kg/m2 and 3) 0.75 kg/m2. The results showed that the growth rate (3210 mg/day) and increase in biomass (83 g) when planted at a density of 0.50 kg/m2 were similar to those when planted at a density of 0.75 kg/m2 (P > 0,05), however, the yield was high (0.896 kg/m2) when eelgrass was planted at a density of 0.75 kg/m2. Experiment 2 evaluated effects of different harvest rates, including 4 treatments and was also repeated 3 times per each treatment: No harvest and harvest 15, 25, 35% total biomass/time after every 15 days of planting. The results of the 15 and 25% harvest rates did not differ in growth and yield of eelgrass (P > 0.05), however, the 35% harvest rate clearly reduced growth rate, biomass increase and productivity of V. spiralis.