This study aimed to evaluate the growth and yield of carrageenan from Kappaphycus alvarezii (Doty) cultured at different depths of water. The study lasted for 49 days, using two strains (green and brown), three initial weights (50, 100, 150 g), and five levels of depth (1, 2½, 4, 5½, 7 m). The results showed significant differences between growth rate and yield of carrageenan on the three treatments (P<0.01). The highest growth rate of both morphology types of green and brown occur on the same weight and depth i.e., at initial weight 100 g and depth 2½ m, respectively at 5.68 and 6.05%/day. The yield of carrageenan is likely to increase in depth with the highest value at a depth of 7 m, respectively 17.12% at green type and 14.63% at brown type. The results showed that reducing growth may increase the yield of carrageenan by the increasing of water depth. Based on these results, this study can be applied to another location as long as the quality of water allows farming activities.

The aim of this research is to determine the amount of trash fish the fish need for growth, and possible saving strategies through reducing the amount of feed until the minimum requirement is reached. Bubara fish C. ignobilis was reared in aquatec floating cages, each cage measuring 3 m × 3 m × 3m. In this study, the fish were reared in four smaller bags, with the size 1.5m × 1.5m × 1.5m placed in one large bag. As many as 75 fish with varying sizes were placed in a small bag, while 20 selected fish were allowed to measure. Fish that are placed in small bags vary in size with a length of 9.56 - 11,125 cm (TL) and a weight of 6.5 - 8.7 g. Each small bag was given different treatments, successively as follows: three day fasting - three day eating (T3), four day fasting - four day eating (T4), and five day fasting - five day eating (T5). Fish are fed 10 -15% of the total biomass, at 8:00 a.m. and 5:00 p.m. daily for 70 consecutive days. Every week, the measurement of waters parameters is carried out to determine the condition of the waters that support aquaculture activities. The results showed that there was weight gainned in the three treatments which were stated based on the absolute growth rate in weight (AGR): 0.65 g.day -1 in T3 treatment; 0.77 g.day -1 in T4 treatment; and 0.80 g.day -1 in T5 treatment. Bubara fish C. ignobilis also had the best survival rates during the rearing period even though they were treated without food with the survival rates of 90 - 95%. The efficiency of feed utilization as stated by the FCR shows that the treatment without food (fasting treatment) can be used as a mode to reduce feed spending. Treatment without food is also able to increase the number of small intestinal villi to expand the absorption surface, so that more feed is used compared to those left to rot at the bottom of the bag.

Cultivation of Kappaphycus alvarezii has been carried out by inverted pyramid method in the deep water of Saparua Bay. This study aims to analyze the daily growth rates (DGR), biomass productions (Y) and carrageenan yields (YC) of the green and brown strain of K. alvarezii with different water depth by inverted pyramid method in deep seawaters. K. alvarezii with an initial weight of 100 g were planted successively at the water depths of 1, 3, 5, 7 and 9 m during four growing seasons that last for 49 days in every season. The results showed that the highest daily growth rate and biomass production were on the green strain at the depth of 1 m and brown strain at the depth of 3 m, which were 4.18% and 749.29 g/m2 then 4.19% and 754.51 g/m2, respectively. Both of DGR and Y in brown strain was higher than the green strain at the surface layer. While the highest carrageenan yield were on the green and brown strain at the depth of 9 m, which were 16.53% and 14.85%, respectively. Seaweed cultivation in deep waters has a positive impact on carrageenan yields in line with the increasing depths while the growth rate and the biomass production can be achieved higher at the lower depth.

Abstrak : Secara konvesional, budi daya rumput laut memerlukan wilayah besar pada perairan dangkal, tetapi tidak semua air cocok untuk pembiakannya. Penelitian ini bertujuan untuk menguji pengaruh beberapa parameter kimia yang cocok untuk tumbuhnya ganggang merah Kappaphycus alvarezii di perairan laut dalam. Penelitian ini difasilitasi dengan beberapa rakit gantung yang ditempatkan secara diagonal, satu di bawah yang lain, pada kedalaman 100, 250, 400, 550 dan 700 cm. Pemotongan tunas dari strain hijau dan coklat digunakan sebagai bibit awal dengan berat 50, 100 dan 150 g. Semua tunas diikat pada tali nilon dengan diameter 1 mm yang sudah diatur pada tali dengan diameter 5 mm yang kemudian akan ditempatkan horizontal pada rakit gantung. Ruang antara dua tali panjang dan dua rumpun rumput laut diatur pada jarak 25 cm. Hasil penelitian menunjukkan bahwa sebagian besar dari laju pertumbuhan harian berkurang dengan meningkatnya kedalaman air. Rata-rata tertinggi dari laju pertumbuhan harian (DGR) dari kedua strain pada berat 100 g yaitu 5,28 ± 0,24% untuk hijau dan 5,45 ± 0,18% untuk cokelat. Analisis varians (ANOVA) dari DGR menunjukkan interaksi antara strain dan berat awal, antara strain dan kedalaman, dan antara berat awal dan kedalaman yang signifikan (P <0,01), namun antara strain, berat awal dan kedalaman tidak ada yang signifikan (P> 0,05). Zat kimia yang berhubungan dengan DGR berdasarkan analisis regresi multivariat yaitu salinitas, pH, amonium dan magnesium