Culture of seaweedsmonostroma

Abstract

A species of genus Monostroma cultured and grown in south central Japan along the Pacific coast serves the country as an important source of food. Both in respect of the region where it grows and its ecological characteristics, this is a seaweed that shows striking resemblance with ‘amanori’. The methods of culturing either this species or amanori are also very similar. Most of the species goes into the preparation of a seasoning known as ‘nori tsukudani’. It is also used as the principal ingredient for ‘shirumono’ or soups. In recent years around 1 400 tons (dry weight) of the species has been produced annually, almost 70% of which comes from its main sources. Besides Mie Prefecture, these include Fukushima, Shizuoka, Aichi, and Kagoshima Prefectures. Some basic studies have already been reported on Monostroma and substantial data is available on its morphology, life history, and ecology. These studies, centering on topics like morphology, pattern of growth and life history, indicate that this seaweed belongs to Monostroma latissimum (Kuetz.) Wittr. As for its morphology, it differs considerably according to the environment within which it grows. Furthermore, they may be classified into three types, namely the inner bay, estuary, and outer sea type, according to the external appearance of their mature fronds. To the inner bay type belongs cultured Monostroma as is evident from its leaf frond characteristics. Techniques of growing cultured Monostroma have yet to be developed to the level of ‘amanori’. One has so far depended on nature for seeding Monostroma, though more recent studies have led to the development of artificial methods that have since been applied widely. Artificial seeding of cultured Monostroma consists of culturing in tanks zygotes of the summer generation and artificially inducing adhesion of zoospores emerging in early Autumn on to seeding nets. The technique also facilitates easy retention of the seeding nets. On the other hand, increase in the number of culture nets of late has tended to overcrowd the culture grounds. At times this causes diseases of the leaf fronds and, accordingly, affects both the yield and quality of cultured Monostroma. Studies must now be taken up to stabilize production by installing the exact number of culture nets in the culture grounds according to their expected production. Research is also needed in the field of manufacturing technology for food products using Monostroma to help increase demand for this seaweed.