ABSTRAK: Parameter keberhasilan dari kegiatan budidaya rumput laut diukur berdasarkan dari hasil produksi thallus yang dibudidayakan. Metode budidaya yang digunakan dalam kegiatan budidaya rumput laut merupakan salah satu faktor penting yang dijadikan sebagai acuan keberhasilan. Penelitian ini bertujuan untuk mengkaji pertumbuhan dari rumput laut K. alvarezii yang dibudidayakan dengan metode lepas dasar menggunakan net bag yang dimodifikasi. Materi yang digunakan dalam penelitian ini adalah bibit rumput laut K. alvarezii (F2) yang diperoleh dari pembudidaya di Perairan Pulau Kemujan, Kepulauan Karimunjawa. Metode penelitian yang digunakan adalah eksperimen dengan rancangan percobaan berpola Rancangan Acak Lengkap. Perlakuan yang diujikan adalah rumput laut K. alvarezii yang dibudidayakan dengan perlakuan A (satu lapis jaring), perlakuan B (dua lapis jaring), dan perlakuan C (tiga lapis jaring). Penanaman bibit dilakukan selama 42 hari sejak penanaman. Parameter pengamatan meliputi laju pertumbuhan spesifik dan parameter kualitas perairan. Hasil penelitian menunjukkan terdapat pengaruh sistem budidaya lepas dasar menggunakan net bag (P < 0,05) terhadap laju pertumbuhan spesifik K. alvarezii. Metode net bag dengan satu lapis jaring memiliki pertumbuhan terbaik pada 4,95 ± 0,70 %g/hari. ABSTRACT: The success parameters of seaweed farming activities are measured based on the results of cultivated thallus. The cultivation method used in seaweed farming activities is one of the important factors used as a reference for success. This study aimed to assess the growth of K. alvarezii that was cultivated by employing off bottom method in a modified net bag system. The material used in this study was K. alvarezii (F2) seaweed seeds obtained from cultivators in Kemujan Island, Karimunjawa Islands. The research method used was an experiment with a completely randomized design patterned. The treatments tested were K. alvarezii which was cultivated by treatment A (single net), treatment B (double net), and treatment C (triple net). Planting of seeds was carried out for 42 days after planting. Observation parameters include specific growth rate and water quality parameters. ANOVA test results showed that there was a significant influence (P <0.05) on the absolute weight and specific growth rate of K. alvarezii. Results showed that single net bag method given the best growth rate at 4.95 ± 0.70 %g/day.

Highlight Research Mariculture is one of the activities that can pressure the aquatic environment. Mariculture activities are carried out by considering the sustainability aspects of environmentally friendly implementation. The suitability of the location for mariculture activities refers to the geographical and hydro–oceanographic conditions seen from the waters' physical, chemical, and biological parameters. The suitability index produced using multiple approaches (GIS-based AHP) can be used to determine the potential locations for mariculture development.   Abstract Potential mariculture activities in the Dampier Strait Conservation Area, which are indicated by the availability of water space and local commodities, can have a multiplier effect on socio-ecological aspects. Therefore, reasonable development steps are needed to carry out environmentally friendly aquaculture. This study aims to determine the potential use of water space for the development of mariculture activities based on the level of suitability using multiple approaches. Suitability analysis was carried out with Geographic Information System (GIS) based on the Analytical Hierarchy Process (AHP) by considering the area’s characteristics using several aspects seen from the geographical conditions and water quality (physical, chemical, and biological). Based on the suitability analysis results, the potential water space that can be used for mariculture development activities, namely seaweed and pearl oyster cultivation was 1,130.45 ha (0.49% of the overall space allocation 232,588.59 ha). A justification was then carried out to determine a suitable location in terms of its accessibility and environmental friendliness. The analysis has shown promising results in determining potential locations for developing mariculture activities for seaweed and pearl oyster commodities based on sustainable and environmentally friendly cultivation.