Phase V – Blue Growth Initiative through Farming of Silver Pompano (Trachinotus blochii) and Rabbit Fish (Siganus sutor) for Food Security and Improved Livelihood in East Africa (BLUEGRASI)

The Blue Growth Initiative (BLUEGRASI) was an ambitious research project aimed at enhancing food security and improving livelihoods in East Africa through the farming of Silver Pompano (Trachinotus blochii) and Rabbitfish (Siganus sutor). This initiative recognized the pressing need for sustainable aquaculture solutions in the face of rapidly growing populations and the challenges posed by traditional land-based agriculture, which increasingly encountered shrinking arable land and unpredictable climate conditions.

This research, aimed at breeding and producing seeds for silver pompano (Trachinotus blochii) and rabbitfish (Siganus sutor), examined their growth performance, survival, and feed utilization under formulated feeds and cultured at various stocking densities and culture systems. The study also evaluated their farming cost compared to other cultured species and their impact on community livelihoods. Rabbitfish brooders and juveniles and silver pompano brooders were collected for breeding purposes. The silver pompano brooders were injected with a gonadotropin-releasing hormone. The silver pompano were fed with five experimental diets containing 5% and 10% effective microorganisms (EM) and 5% and 10% of both EM and shrimp meal and randomly stocked in hapas at one (PSD1), two (PSD2), three (PSD3) and four (PSD4) individuals/m3. Both trials were conducted for eight weeks. Twenty rabbitfish per hapa were fed on four feeds in which fishmeal was replaced by black soldier fly larvae (BSFL) at 0, 50 and 75% with a control. The rabbitfish fingerlings were stocked at 1.5 (SSD1.5), 2.5 (SSD2.5) and 3 (SSD3) individuals/m2 for ponds and 12 (SSD12) and 24 (SSD24) individuals/m3 for cages and fed at 5% for 112 days for cages and between 108 and 144 for ponds, respectively. A site hydrodynamics study was also conducted. A total of 323 respondents, including fish farmers, fish traders, fishers, and others, were interviewed to understand their income, fish price and preference. We also assessed the economics of producing rabbitfish in ponds and cages. A socioeconomic and livelihood study involving milkfish and Nile tilapia farmers was conducted by using a semi-structured questionnaire. Results indicated that the rabbitfish brooders in the first experiment were infected by ectoparasites, whereas in the second experiment, they were too immature to breed. Similarly, no eggs were produced for silver pompano because the brooders were immature. Feeding did not affect final body weight (FBW), daily weight gain (DWG), feed conversion ratio (FCR), and survival rate of silver pompano (P > 0.05). The silver pompano juveniles reared at PSD1 attained a significantly higher FBW, DW,G and survival rate and better FCR than other stocking densities (P < 0.05). The results for the rabbitfish feeding trial are currently under review in a journal and thus cannot be shared. The rabbitfish reared in the pond at SSD2.5 attained significantly higher FBW, DWG, and survival rate than other stocking densities (P < 0.05). However, the rabbitfish cultured at SSD1.5 and SSD3 had a statistically comparable survival rate (P > 0.05). The rabbitfish reared in cages at SSD24 attained significantly higher FBW, DWG, and survival rates than those cultured at SSD12 (P < 0.05). The results on site hydrodynamics indicated that, the water currents speed ranged from 0.344 m/s to 1.113 m/s, wave heights ranged from 0.35 m to 2.7 m. Fish traders earned a higher monthly income compared to other occupations, while the hospitality industry earned the least monthly income. Rabbitfish and silver pompano attracted a higher price/kg (25-35%) compared to milkfish and Nile tilapia grown in seawater. All value chain actors indicated a higher preference for rabbitfish compared to milkfish, silver pompano, and Nile tilapia grown in seawater. The ponds generated relatively higher benefits than the cages. Nile tilapia farmers earned a higher monthly income compared to milkfish farmers. Both farmers farm fish to obtain income, employment, and food. Findings show that, any of the feeds tested may be used for rearing silver pompano under similar study conditions, while inappropriate stocking density may impose negative effects on feed utilization and growth both for silver pompano and rabbitfish. Fish traders earn more money when rabbitfish is a preferred fish. Nile tilapia farming is profitable compared to milkfish farming, while both provide income, employment and food security.