Opportunities for the development of seaweed farming as a supplementary income for small-scale fishermen in Nador lagoon: Experimental cultivations of Gracilaria gracilis (Stackhouse)

Abstract

The feasibility of growing red seaweed, Gracilaria gracilis (Gigartinales, Rhodophyta) in off-bottom and floating longline systems was investigated in Bouareg location. The weight gains of G. gracilis in off-bottom cultures tested in winter were low. The lowest daily growth rate (DGR) was recorded in sheet-lines (1.91 % day -1 , p < 0.01) while the highest"s RGR were observed in net-lines and ropes-lines (2.72 and 2.77 % day -1 respectively, p < 0.01). Plants of G. gracilis grew well in the floating longline culture tested at spring. The weight growth rates ranged between 2.54 and 4.26 % day -1 . The highest growth rate in Nador lagoon was observed in treatment stocked with 0.6 kg m -2 . The high stocking density (0.8 kg m -2 ) leaded to low growth most probably due to stress on the seaweed when competing for space and resources. Over a 60-day cycle, the harvest of G. gracilis cultivated on floating longline system in Nador lagoon was estimated at about 101 t FWT ha -1 year -1 . With 8:1 as wet to dry ratio, the production yield per cropping was estimated at 3,156 kg (DW) per ha. However, the total sales per year was estimated at about $ 6,564 per ha.