Estudo comparativo das taxas do crescimento e produtividade de algas do cultivar sacol e das variantes Alvarezii, special e payaka da espécie Kappaphycus, em cultivo no distrito de Nacala, Provincia de Nampula

Abstract

Coastal and inland aquaculture is nowadays a practice in Mozambique, as a result of the various initiatives developed with a view to improving the income of the most disadvantaged communities and consequently contributing to poverty alleviation in these communities. Nowadays, aquaculture does not only represent the farming of fish and other shellfish in an aquatic environment, but also includes the farming of macroalgae, specifically the cultivation of Euchewna sp. and Kappaphycus sp. The provinces of Cabo Delgado and Nampula were the first to benefit from a project consisting of the introduction of seaweed farming. The comparative study of the growth rates and productivity of seaweeds of the Sacol cultivar and the alvarezii, special and payaka varieties of the Kppaphycus species, which is the present work, aims to compare the growth rates and productivity of the four varieties of seaweeds of the Kappaphycus species and to contribute to the better selection of the varieties which best respond to the environmental conditions of the beach of Uissimajulo. The "off-bottom monoline" method of mariculture was used for cultivation as it was considered to be the most appropriate for the environment of Quissimajulo on account of the behaviour of its water (waves in the ocean-continent direction). Scales were used for weighing and salinity and temperature measurements were made using a salinometer and thermometer, respectively. The results obtained showed that the sacol variety showed the best growth with an average growth rate of 2.14%/day and the special variety showed the lowest average growth rate of 0.99%/day. During all the phases the highest growth rate was found in the sacol variety that was 3.27%/day, probably because it is the one in which the medium conditions are favourable and being in agreement with (Hurtado et al.,2000 ) who states that high growth rates vary between (2.3-4.2%/day) when the algae are in optimal environmental conditions, on the other hand, the highest average growth rate was observed in the same cultivar and the lowest growth rate was found in the variety alvarezii and was 0.48%/day. Native species of algae, mainly Uiva sp. contribute negatively to the productivity of the algae in culture, mainly in the last thirty days of cultivation because it is easier to graze the algae in cultivations when they are well developed. This led to the estimation of the weight of the algae as a function of the empty nodes for the determination of the growth rates.(TRAUIÇAO NOSSA)