Spirulina (Arthrospira fusiformis (voronich.) kom. & lund 1990) culture and its use as a protein source for Rufiji tilapia (Oreochromis urolepis urolepis Norman, 1922) mariculture

With global capture fisheries having levelled off for over a decade now, aquaculturecould play a more prominent role in providing human food if substitutes tofishmealaresuccessfully established at a lower trophic level, preferably from outside the human food chain.As spirulina species are worldwide known for their high crude protein content, the present study investigated growth requirements of locally found spirulina species (Arthrospira fusiformis(Voronich.) Kom. & Lund 1990) and its potential in substituting fishmeal in the growth of Rufiji tilapia (OreochromisurolepisurolepisNorman, 1922).The effect of the spirulina meal was assessed by substituting 0(Control), 5, 15, 25, 35 and 100% of fishmeal for O.urolepisurolepisartificially grown using full strength salt water in 100 L containers for 60 days.Arthrospirafusiformiswas isolated from Momela Lakes in Arusha National Park, Tanzania. Its optimum growthwas found inZarrouk mediumat pH 10,temperature 32°Cand light regime of 3.5 klux (p< 0.05).Oreochromisurolepisurolepisfryfed with 5% fishmeal substitute exhibited most superior final weight,8.48g, average daily weight gain,0.132 g, specific growth rate, 4.47, feed conversion ratio,2.08 and protein efficiency ratio, 1.37 (p< 0.05).It appears that the Momela lake spirulina may be an appropriate growth-stimulating plant protein when used as feed additive in Rufiji Tilapia mariculture.