Why Tanzania’s Coast Needs a New Kind of Aquaculture
Tanzania is Africa’s leading seaweed producer, accounting for about 92 percent of the continent’s output and supporting more than 30,000 small‑scale farmers, 80 percent of whom are women. Yet coastal habitats face mounting pressure from warming waters, nutrient runoff, and seagrass loss, while many farmers remain locked into low margins and volatile export markets. Tanzania Digest
The Promise of Restorative Aquaculture
Research led by The Nature Conservancy (TNC) shows that well‑sited, low‑input seaweed farms can absorb excess nutrients, buffer acidification, and create habitat for juvenile fish, effectively turning aquaculture into a form of ecosystem restoration rather than extraction. Their pilot farms in Zanzibar illustrate how simple long‑line systems can generate measurable water‑quality and biodiversity gains. The Nature ConservancyThe Nature Conservancy
Early Results: Environmental Gains and Stronger Livelihoods
- Carbon & Water Quality – Modeling suggests a single hectare of seaweed can remove up to 600 kg of CO₂‑equivalent per crop cycle and locally raise pH, countering ocean acidification. The Nature Conservancy
- Economic Resilience – Government tax reforms and higher farm‑gate prices helped push Tanzania’s seaweed production 52 percent higher year‑on‑year in Q3 2023, with exports topping 10,000 t in just nine months. Tridge
- Women’s Empowerment – In coastal villages like Paje and Jambiani, women‑led “Mwani Mamas” cooperatives now report monthly earnings of USD 250‑300—double local minimum wage—financing children’s education and health care. Vogue
How the Model Works
| Problem | Restorative Solution | Outcome |
| Nutrient runoff & algal blooms | Seaweed uptakes nitrogen & phosphorus | Clearer water, reduced eutrophication |
| Acidifying lagoons | Seaweed photosynthesis raises pH | Healthier seagrass & shellfish |
| Limited jobs for women | Low‑tech farming requires minimal capital | Diversified household income |
| Coastal erosion | Long‑lines dampen wave energy | Added shoreline protection |
Pemba Island, Tanzania Spinosum farm and neighbouring sea stars exposed during low tide in Mjini Kiuyu – North Pemba © Sébastien Jan
Lessons for the Wider Aquaculture Sector
- Pair seaweed with finfish – Integrated multi‑trophic systems let seaweed mop up dissolved wastes from fish pens, improving welfare and lowering treatment costs.
- Measure what matters – TNC’s “restorative metrics” (nutrient removal, carbon drawdown, biodiversity indices) give regulators and investors clear targets.
- Center local ownership – Projects succeed fastest when women’s cooperatives manage day‑to‑day operations and share in higher‑value markets (e.g., cosmetics, bioplastics).
Moving Forward
Restorative seaweed aquaculture isn’t a silver bullet, but it offers a tangible way to meet climate, livelihood, and biodiversity goals in the same hectare of ocean. Expanding pilot farms, securing fair supply chains, and embedding rigorous welfare metrics will determine how far—and how fast—Tanzania’s coastal communities can ride this green tide.
