Understanding diseases and control in seaweed farming in Zanzibar: procedures and sampling for demersal (bottom and beam) trawl surveys and pelagic acoustic surveys

This study identifies the causes of the die-off of seaweed types Eucheuma denticulatum, Kappaphycus striatum, and K. alvarezii in the farming areas of the Zanzibar archipelago and provides recommendations to protect the farming ecosystem, control ice-ice disease, and boost the seaweed industry. The main causes of the die-offs are severe epiphyte infestation and a high incidence of ice-ice disease, triggered by high temperatures and high-light intensity/irradiance.

Format: Paperback / softback
Length: 59 pages
Publication date: 30 December 2020
Publisher: Food & Agriculture Organization of the United Nations (FAO)

This comprehensive study delves into the causes behind the significant decline of seaweed species, including Eucheuma denticulatum (commonly known as spinosum), Kappaphycus striatum, and K. alvarezii (both referred to as cottonii), observed in the farming regions of the Zanzibar archipelago. By examining these die-offs, the study offers both short-term and long-term recommendations aimed at safeguarding the farming ecosystem, combating the spread of ice-ice disease, and mitigating the infestation of epiphytes.

The primary factors contributing to the die-offs are severe cases of epiphyte infestation, coupled with a high prevalence of ice-ice disease. Farmers in the Zanzibar archipelago have long noticed a seasonal pattern of intensification during the hot-dry season and a subsequent decline during the wet season. High temperatures, along with high-light intensity/irradiance, have been identified as critical triggers for the occurrence of ice-ice and the flourishing of epiphytes.

To address these challenges, the study proposes several recommendations. Firstly, strict quarantine procedures should be implemented to prevent the introduction and spread of harmful organisms. Additionally, the farming of E. denticulatum and K. striatum should be relocated to deeper waters (2-5 m) using longlines or the raft method, whenever practical. This move aims to mitigate the impact of epiphyte infestation and provide a more conducive environment for seaweed growth.

Furthermore, if lagoon farming is continued during the hot-dry season, the study suggests using a freshwater shock or a commercially available anti-fouling agent to effectively eliminate epiphytes. This measure will help maintain the health and productivity of the farming ecosystem while minimizing the negative effects of epiphyte infestation.

By implementing these recommendations, the study aims to safeguard the farming ecosystem, promote the growth of seaweed industries, and contribute to the sustainable development of the Zanzibar archipelago. The findings and insights provided in this study offer valuable guidance for policymakers, farmers, and stakeholders in the region.

Weight: 202g
Dimension: 209 x 297 x 7 (mm)
ISBN-13: 9789251326015