A study was conducted on the taxonomy, ecology, and yield, as well as properties of polysaccharides, of the marine algal genus Gracilaria. Eight species (G. corticata, G. crassa, G. edulis, G. fergusonii, G. milladertii, G. salicornia, G. verrucosa and Gracilaria sp.) were identified and reported both from intertidal as well as sublittoral zones. Of the eight species studied, G. corticata and G. salicornia were the most variable morphologically, depending on prevailing physiological and ecological conditions. With respect to their distribution along the coast, G. salicornia was the most common followed by G. corticata and G. crassa. Studies on their seasonality showed a general single growth peak for the genus, between the months of September and December.

Based on their availability in adequate quantities, six species (G. corticata, G. crassa, G. milladertii, G. salicornia, G. verrucosa and Gracilaria sp.) were investigated for their agar yield and quality. The effects of morphotypes, habitats and seasons on the quality and quantity of agar extracts were studied. Native agar yields from hot water extracts ranged from 8.1% - 30.3% dry weight, with G. verrucosa and G. salicornia yielding the highest and lowest amounts respectively. From 1.5% solutions of native agar the highest gel strength was recorded from G. verrucosa (220 g cm^-1), also having the highest content of 3, 6 anhydrogalactose (23%). On the other hand, extracts from G. corticata gave the lowest gel strength (<60 g cm^-2) and the lowest 3, 6 anhydrogalactose content (14.5%). Other chemical and physical properties of the extracts, such as melting and gelling temperatures, sulphate contents, and effects of alkali treatment, were also studied.

Implications of the results obtained from this study are discussed with respect to seaweed farming in the Kenyan waters. Considering their agar yield and quality, G. verrucosa and G. crassa are recommended for further culture experiments, which were beyond the scope of this study. These two species are viewed as possible candidates for commercial food agar production if they can successfully be cultivated on a large scale.