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 development of seaweed farming in Nador lagoon (NE Morocco, Mediterranean Sea) offers the best hope for raising incomes in fishing communities. The feasibility of growing red seaweed, Gracilaria gracilis (Gigartinales, Rhodophyta) in off-bottom and floating longline systems was investigated in Bouareg location. Several constraints such as epiphytism and wood borers arose in off-bottom cultures. 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 DGR 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) led 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. The Gracilaria farming may provide supplementary income to artisanal farmers in Nador lagoon.