In Zanzibar, two edible red seaweed species are commonly used for food: Spinosum and Cottonii, also called ‘Elkhorn sea moss.’ Both species can be found wild in the coastal area and are also farmed intensively. In addition to these two species, a variety of other edible red seaweed species grow there.
Spinosum (Eucheuma denticulatum)
Spinosum is the most essential edible red seaweed species in Zanzibar. The thallus ranges from 35-74 cm / about 14-29‘’ long. These plants have a cartilaginous feel and structure. On their branches, thorn-like structures can be seen. Depending on the light conditions during growth, the color can be green, brown, red, purple, or a mixture of these colors. It forms carpet-like mats with rhizoids that attach the algae to the available substrate. Spinosum grows in shallow waters, which can run dry on low tides. 80-90% of farmers in Zanzibar prefer the Spinosum species when farming seaweeds. This high preference for Spinosum is attributed to its lower susceptibility to diseases, appropriateness for women farmers to plant in shallow waters, and the ability to grow with fewer inputs among resource-constrained farmers.
Elkhorn sea moss or Cottonii (Kappaphycus alvarezii)
K. alvarezii is greenish to brown but can sometimes be deep purple. Its appearance resembles Spinosum’s, but its thallus is not spinous. The gelatinous content of Cottonii seaweed is superior to Spinosum and commands a slightly higher price. However, Cottonii exhibits a higher incidence of disease and die-offs due to its greater susceptibility to environmental fluctuations (global warming) than Spinosum. The challenges are further compounded by the necessity of growing the Cottonii species in deep waters, in which women are vulnerable to the risks associated with deep water.
Wild red seaweed collection on Zanzibar beaches
Wild red seaweed harvesting dates back a long time in Zanzibar. It was a prominent activity in Tanzania long before seaweed farming began in the region. Approximately 4,000 tons of dry, wild-harvested red seaweeds were exported annually from Tanzania in the 1950s. This level of wild harvest and export continued until the late 1970s, when overharvesting led to the collapse of wild populations and ceased this business.
Besides E. denticulatum and K. alvarezii, several other native red seaweed species were collected. These include several Gracilaria species (G. salicorniaw, G. corticate, G. debilis, G. edulis) and others in the genera Gracilariopsis, Gelidium, Pterocladia, and Gelidiella. These seaweeds were not only eaten but also Agar was produced from them.
Nowadays, all these species of red seaweed can again be collected in their specific growth communities and ecosystems. Due to seaweed farming and wave action, seedlings are often separated from their mother plants. Spinosum and Cottonii red seaweed grow wild on most beaches of Zanzibar by vegetative propagation. For survivalists, this is an easy-to-collect food source in intertidal lagoons.
Seaweed farming in Zanzibar
Commercial farming of red seaweeds can be traced back to 1989 when two private enterprises imported Eucheuma seaweeds from the Philippines. These companies subsequently established two pilot firms in the villages of Jambiani and Paje on Unguja Island (Zanzibar). Subsequently, seaweed cultivation has expanded to various Unguja and Pemba Island regions, with Pemba currently responsible for 80% of the overall seaweed yield.
The production system is an off-bottom peg and line farming system in near-shore tidal lagoons (maximum water depth 1 m). It typically involves small, individually owned farms with 100 to 1000 lines (5–10 m in length). Seedlings are knotted on these lines with tie-ties (small twines).
After about six weeks, the newly grown red seaweed plants can be harvested. At low tide, the harvest is packed into woven PU bags, carried to the beach, and dried on sand, rocks, or drying racks.
After 2-3 days of drying, the red seaweed is finally packed and sold to traders, who sell it to big dealers for export. Red seaweed farmed in this way is usually not eaten by the farmers but is used as a cash crop. The farmers I saw preferred to eat seaweed from wild species freshly collected in the lagoon.
Red seaweed in the kitchen
Red seaweed is not only prepared in the kitchen; many also eat pieces of it raw as a snack.
We met a lady on the beach while she was eating raw pieces of seaweed. When asked how she usually prepares red seaweed, she said as a salad.
At our favorite beach restaurant, we requested Mama Coconut to prepare Red seaweed salad for dinner.
In combination with fried Bonito steaks and chips, this salad tasted gorgeous. The crispy, cartilaginous seaweed pieces complemented each other perfectly with tomatoes, onion, and the dressing.
(Laptiste, 2022) stated in her thesis, ‘…In Zanzibar, I asked a chef and a waitress at the hotel where I was staying, two taxi drivers and a seaweed farmer to explain how seaweed was utilized. It was only the seaweed farmer who told me that she uses the seaweed in very small quantities to give flavour to her meals. The other people told me that they believed the seaweed was inedible…’
I propose that the author of this statement visit the ‘Coconut Restaurant’ at Shanuo Beach, Michamvi (GPS: S 006° 9.049, E 39° 31.065) and enjoys the E. denticulatum seaweed salad there. It would be an eye-opener and reverse her questionable initial research.
Nutritional value
(Vairappan & Kawasaki, 2008) evaluated the suitability of Kappaphycus alvarezii and Eucheuma denticulatum as seafood salad. The approximate compositions, amino acids, fatty acids, minerals, antioxidant potential, and antibacterial activity against food-borne pathogens were studied. Findings from this investigation indicated that E. denticulatum has the ideal qualities of an organic marine salad.’
The protein und fat contents are low, but carbohydrates and crude fibres are high, as can be seen from the table above.
Also, the mineral composition is interesting, as – although E. spinosum grows in seawater, it’s chloride (Cl) and sodium (Na) contents are really low. On the other hand, it is a good provider of zinc (Zn) and potassium (K).
Lessons learned from edible red seaweed in Zanzibar:
- There are two species of edible red seaweed collected from the wild and also farmed in Zanzibar.
- The most preferred species for food and export is Eucheuma denticulatum.
- E. denticulatum makes a perfect salad.
- This red seaweed provides plenty of carbs, fibers, zinc, and potassium.
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