Floating Cage: A New Innovation of Seaweed Culture

*Ma'ruf Kasim, Abdul Muis Balubi, Ahmad Mustafa, Rahman Nurdin, Rahmad Sofyan Patadjai and Wardha Jalil*

## **Abstract**

Eucheumatoid cultivation continues to expand with a variety of methods that can increase production. This chapter will discuss an innovation in seaweed cultivation of the genus *Eucheuma*, which is the prime marine commodity in the tropical regions of the world. Research conducted during 2015-2017 and 2019 in Southeast Sulawesi Province, Indonesia, provided an overview of the use of floating cage that showed very significant growth results. The research result showed that the growth rates of *Eucheuma denticulatum* and *Kappaphycus alvarezii* in floating cage seemed faster and resulted in better thallus morphology. Daily production of *E. denticulatum* and *K. alvarezii* that were cultivated in floating cage was higher than daily production of *E. denticulatum* and *K. alvarezii* cultivated on longline. Specific growth rate (SGR) of *E. denticulatum* and *K. alvarezii* cultivated by using floating cage method was also higher than *E. denticulatum* and *K. alvarezii* cultivated by using longline method. Moreover, the cultivation by using floating cages produces good growth rates with no effect of herbivore attacks.

**Keywords:** *Kappaphycus alvarezii*, *Eucheuma denticulatum*, floating cage, longline

#### **1. Introduction**

Seaweed cultivation is a good activity for improving the welfare of coastal communities. Several countries in Southeast Asia such as in the Philippines [1] cultivate seaweed with a fairly high production. *Kappaphycus alvarezii* is a type of macroalgae that is widely cultivated by the community. The morphological form of this species looks very bright and has many branches. This species has large primary thallus, and the color of the thallus is darker than that of thallus branches that look bright from the maintenance of vegetative branches [2]. Old branches of *Eucheuma denticulatum* that has been cultivated for more than 4 weeks are seen to spread. This distribution is thought to be a major factor causing this species to grow on coral reefs in Kaneohe Bay, Hawaii. Meanwhile, some of the most widely cultivated species are *K. alvarezii*, *Eucheuma striatum*, and *E. denticulatum* [2]. *E. denticulatum* has been widely cultivated in several countries such as the Philippines since 1971 [3–5]. The production of *Eucheuma* species continued to increase very rapidly in the initial cultivation process in 1971 with initial seedlings of less than 1000 Mt. of dry weight up to 100,000 Mt. of dry weight [3]. Two countries in Southeast Asia which intensively cultivate *E. cottonii* species are the Philippines and Indonesia. Specifically in Indonesia, until 1990, this seaweed production reached 6 Mt. per year of cultivation area [6]. Seaweed species of *Eucheuma* sp. is a group of lower plant known as seaweed and has a fairly rapid growth in nature [1]. Philippines is a country that has succeeded in developing a generative regeneration system, making the development of seaweed *Eucheuma* sp. quite fast [7]. Seedling growth tends to be rapid with changes in weights that continue to increase every week [8]. Meanwhile, Fiji Island has begun developing *K. alvarezii* aquaculture in their surrounding waters since 1970. Cultivation K. alvarezii are simple with poles and ropes and then develop to date using the longline method [9, 10]. Tuvalu has begun developing the cultivation of seaweed since 1977 [11], while Malaysia has developed cultivation since 1978 [4]. In Indonesia, the cultivation has begun to develop since 1985 [12, 13], while in Maldives, it has begun to develop in 1986 [14]. Furthermore, India and Tanzania have begun developing cultivation since 1989 [15–17], and several countries such as Vietnam, Brazil, and Venezuela have begun developing during the 1990s [18–20].

Cultivation of *K. alvarezii* developed quite well and provided a fairly good growth related to various physical chemical environmental factors that existed especially in the Yucatan region of Mexico [21]. Although well developed, growth of *K. alvarezii* species fluctuates seasonally especially in the northwestern coast of India [22]. The production value of the *K. alvarezii* species also depends on the cultivation method used. A closed method protecting *K. alvarezii* from various herbivorous attacks will be better than open methods. This happened in the waters of the south coast of Rio de Jeneiro, Brazil, illustrating that cultivation techniques with tubular netting are better than with the longline method [23].

Currently, various problems continue to afflict cultivation activities carried out by the community. One thing that really stands out from the various problems that exist is the low quality and low production of seaweed. There has been a decline in the quality of seaweed after 20 years of seaweed production in the Pacific region. Specifically in Indonesia, the low production of seaweed cultivation is caused by low quality of seeds, poor cultivation methods, intensity of attacks of pests and diseases, and marine environment that is impacted by global climate change [24]. Increase in population of herbivorous fish in the seaweed cultivation areas around the Mediterranean waters correlated with the species of epiphyte that existed. Current phenomenon that some unprotected cultivation sites provide food opportunities for herbivorous fish [25]. Recently, many studies have been done, but there are no appropriate actions and solutions to overcome the existing problems. Each stage of seaweed cultivation has its own specific problems. For this reason, it is very important to conduct a thorough and integrated research to approach every problem, starting from getting good quality seeds, good maintenance patterns, and biological, physical, chemical, and ecological factors related to seaweed resistance to the economic value of each production results that affect the selling value of seaweed.
