**2. Current problems in seaweed cultivation**

The phenomenon of grazing by herbivorous fish is very common in all locations of seaweed cultivation (**Figure 1**). In India, especially in Krusadai Island, the production of seaweed farming of *Kappaphycus alvarezii* and *Eucheuma denticulatum* species has decreased around 10% of their growth due to attacks of herbivorous fish such as *Siganus javus* (rabbitfish), *Acanthurus* sp. (surgeonfish), *Cetoscarus* sp. (parrot fish), and sea urchin *Tripneustes* sp. [25]. Therefore, cultivation of *Kappaphycus alvarezii* in a cage can prevent seaweed from being attacked by herbivore. Cultivation with this protection system can be done with modifications in accordance with the topography of the area, and this has been done in several cultivation areas in the Philippines [26].

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**Figure 2.**

cause damage [28].

**Figure 1.**

**3. New innovation method in seaweed cultivation**

*Grazing activity of herbivorous fish (*Siganus *sp.) on* Kappaphycus alvarezii*.*

*Floating Cage: A New Innovation of Seaweed Culture DOI: http://dx.doi.org/10.5772/intechopen.90035*

The use of cage for *K. alvarezii* cultivation can be carried out in areas that have high intensity of herbivorous fish attack. However, the durability of the tools to support cultivation needs to be considered. *K. alvarezii* cultivation activity together with oysters and snapper cultivation activities is an alternative cultivation with a good confinement system [27]. Seaweed *Gracilaria gracilis* can be cultivated in a closed container to avoid various attacks by herbivore such as isopods. These animals are seen to not exist in closed cultivation conditions, thus preventing these animals from entering to eat seaweed. Herbivorous fish are not detected when this type of seaweed is treated with freshwater in an enlargement tank, which does not

Floating cage is a technological design that functions as a seaweed cultivation tool. This cultivation tool can protect seaweed from pests while reducing the potential for ice–ice disease [16, 29, 30]. Various sizes and shapes were developed as tools that can be used for seaweed cultivation. The basic materials of floating cages include PVC pipes, nets equipped with buoys as markers, and weights attached to the raft to facilitate the laying of the raft in the desired area. The shape of the tool is designed like a rectangular box with varied sizes. The surface of the raft is left

*Illustration of floating cage that was used during research (a). Thallus of* K. alvarezii *inside the floating cage (B).*

*Floating Cage: A New Innovation of Seaweed Culture DOI: http://dx.doi.org/10.5772/intechopen.90035*

*Emerging Technologies, Environment and Research for Sustainable Aquaculture*

with tubular netting are better than with the longline method [23].

**2. Current problems in seaweed cultivation**

cultivation areas in the Philippines [26].

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.

The phenomenon of grazing by herbivorous fish is very common in all locations of seaweed cultivation (**Figure 1**). In India, especially in Krusadai Island, the production of seaweed farming of *Kappaphycus alvarezii* and *Eucheuma denticulatum* species has decreased around 10% of their growth due to attacks of herbivorous fish such as *Siganus javus* (rabbitfish), *Acanthurus* sp. (surgeonfish), *Cetoscarus* sp. (parrot fish), and sea urchin *Tripneustes* sp. [25]. Therefore, cultivation of *Kappaphycus alvarezii* in a cage can prevent seaweed from being attacked by herbivore. Cultivation with this protection system can be done with modifications in accordance with the topography of the area, and this has been done in several

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

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**Figure 1.** *Grazing activity of herbivorous fish (*Siganus *sp.) on* Kappaphycus alvarezii*.*

The use of cage for *K. alvarezii* cultivation can be carried out in areas that have high intensity of herbivorous fish attack. However, the durability of the tools to support cultivation needs to be considered. *K. alvarezii* cultivation activity together with oysters and snapper cultivation activities is an alternative cultivation with a good confinement system [27]. Seaweed *Gracilaria gracilis* can be cultivated in a closed container to avoid various attacks by herbivore such as isopods. These animals are seen to not exist in closed cultivation conditions, thus preventing these animals from entering to eat seaweed. Herbivorous fish are not detected when this type of seaweed is treated with freshwater in an enlargement tank, which does not cause damage [28].
