Ice-ice disease in cultivated eucheumatoid seaweeds: The perspectives of farmers

Abstract

ABSTRACT Eucheumatoid seaweeds, encompassing the genera Kappaphycus and Eucheuma, are widely cultivated globally, particularly in tropical regions. However, ice-ice disease (IID) poses a significant challenge to their production, causing substantial economic losses. This study aimed to elucidate the factors contributing to IID in eucheumatoid seaweeds, focusing on the perspectives of seaweed farmers in Sibutu, Tawi-Tawi, Philippines. A mixed methods approach was employed, utilizing both one-to-one interviews (n = 96) and focus group discussions. The majority of the interviewed farmers were male, aged between 31 and 60 years, with extensive experience (11‒25 years) in seaweed cultivation. Notably, all participants possessed a familiarity with IID since childhood. Farmers described IID as a pathological condition affecting eucheumatoid seaweeds, characterized by the emergence of white and soft areas on the seaweed thalli. The initial stages of the disease manifest as a pale discolouration of the thalli and the presence of epiphytes or debris. Several environmental factors were identified by the farmers as contributing to IID incidence, including high or low water temperatures, low salinity (particularly after heavy rainfall), stagnant water currents, nutrient deficiencies, inadequate seedling quality, and poor farm management practices. Additionally, deepwater (nearshore) farms were reported to be more susceptible to IID. Farmers noted that easterly winds could exacerbate the disease by facilitating the infestation of epiphytes on the seaweed. Furthermore, the prevalence of IID was observed to be highest during the dry and hot season. Kappaphycus striatus was identified by the farmers as being more susceptible to IID compared with K. alvarezii and Eucheuma denticulatum. The negative impact of IID on farmers’ livelihoods was also highlighted. Some mitigation strategies employed by the farmers included the application of inorganic nutrient enrichments (e.g. ammonium phosphate (16–200, NP-K) and complete (14–14-140, N-P-K) fertilizers), frequent relocation of infected seaweed to different farms, and the cultivation of more IID-resistant species.