Md. Mohidul Islam
Marine Fisheries & Technology Station, BFRI, Cox's Bazar 4700, Bangladesh
Jakia Hasan
Marine Fisheries & Technology Station, BFRI, Cox's Bazar 4700, Bangladesh
Hypnea musciformis, Enteromorpha intestinalis, Padina tetrastromatica
Cox’s Bazar coast, Bangladesh
Pest Management
Seaweed culture sites: Experimental culture sites of seaweeds were setup on intertidal zones of St. Martin’s Island of Teknaf Upazilla (N20°37.043, E092°19.715), Inani of Ukhia Upazilla (N21°13.941, E092°02.596) and Bakkhali river estuary under Sadar Upazilla (N21°28.500, E091°57.941) of Cox’s Bazar district, located in the north-eastern coast of the Bay of Bengal. The St. Martin’s Island characterized by sandy and rocky bottom and protected by the coral reef with slanting; where wave action is weak (Hossain et al. 2007). On the other hand, Inani beach has sandy bottom with large numbers of boulders, pebbles, broken covers etc. (Umamaheswara 1974). The Bakkhali river estuary site is mostly sandy to muddy bottom (Hena et al. 2013). The culture experiment was conducted for a period of 90 days in a season during January to April of 2016 to 2018.
Seaweed culture system: Natural fibered coir rope (made from coconut husk with 16 mm diameter) was used as culture material (4mx4m sized horizontal square net). The mesh size of the coir rope nets was maintained at 20 cm. in a bamboo frame. Four corners of the seaweeds culture nets were tied with bamboo pole or rocks and plastics floats were placed 50 cm above from the sea bottom.
Most abundant 3 types seaweed species like green seaweed Enteromorpha intestinalis, brown seaweed Padina tetrastromatica and red seaweed Hypnea musciformis were selected for culture experiment. Seeding was done by inserting the young fragments of E. intestinalis, P. tetrastromatica and H. musciformis with an average of 4±0.5 kg fw (fresh weight) and 5 cm length in the twists of the coir ropes with short length of string at a density of 35-40 seed/m2 for E. intestinalis and H. musciformis and 10-15 seed/m2 for P. tetrastromatica. During culture period, partial harvesting of seaweeds was done after 15-20 days culture period. At the end of 90 days experimental trials, mean biomass of seaweed was recorded for E. intestinalis and H. musciformis and expressed as wet weight of seaweed per unit culture area (Kg/m2). For P. tetrastromatica 60 days culture trial was maintained. Seaweed biomass was estimated with the following formula:
Y= (Wt− W0)/ A
Where: Y = biomass production; Wt= wet weight at day t; W0 = initial wet weight; A = area of 4 m2 net.
Water quality parameters: Water depth, water temperature, salinity, dissolved oxygen, pH, Alkalinity and water transparency of each culture sites were recorded at the time of partial harvest. Temperature was recorded by using a cellcious thermometer, salinity with a hand refractometer (Atago, Japan) and pH with a portable pH meter (HANNA Instruments USA). Dissolved oxygen in sea water was recorded immediately after sampling by method following APHA (2000) and water transparency was measured by using a Secchi disk (30 cm in diameter).
Statistical analysis: All data were analyzed by using Predictive Analysis Software (PASW), Statistics 18 and Microsoft Office Excel 2013. One-way ANOVA was conducted following Tukey’s HSD post-hoc for multiple comparisons. The level of significance considered was p < 0.05.
Bangladesh J. Zool. 49 (1): 47-56, 2021 ISSN: 0304-9027 eISSN: 2408-8455
Journal