Over the past several years, Indonesian freshwater aquaculture has intensified, with a concomitant increase in the use of commercial pellets. To assess the effects of pond aquaculture intensification on nutrient dynamics, we monitored nutrients and fish production in a small-scale fish farm in West Java province. The studied system consisted of semiintensive giant gourami (Osphronemus goramy) production in four small earthen ponds (353-482 m 2 each and 0.46-0.55 m deep). Nitrogen (N) and phosphorus (P) fluxes through the ponds were monitored, and data on fish production and nutrient accumulation in sediments were collected during a 5-month production cycle. Results showed that, on average, 61% total N and 77% P inputs were trapped in the accumulated sediments. Only 15% of total N and less than 3% P inputs introduced into ponds were recovered in harvested fish. Sediment nutrient accumulation increased linearly with total nutrient input. The consequences of intensification of giant gourami aquaculture using this production model are explored in terms of nutrient use efficiency and environmental impact.

Several ecological services and functions are attributed to macrophytes, which may represent valuable resource for the ecological intensification of tropical fish farming. However, considering the multiple potential eco-services provided by macrophytes, the choice of the most appropriate species requires multiple criteria to assess these eco-services. Five floating macrophytes (Eichhornia crassipes, Lemna minor, Azolla filiculoides, Salvinia molesta and Salvinia spp.) were selected for this study. The six eco-services parameters compared among these macrophytes were: productivity (in % of seeded macrophytes), risk of non-productive cycles, nutritional value, impact on water quality, palatability (expressed as the percentage of plant ingested in 4 h) and ease of use. Experiments to determine these indicators were carried out in simple devices (net cages and plastic tanks) partially immerged in earthen ponds. The palatability of fresh macrophytes (whole or chopped) was studied in ponds using Osphronemus goramy juveniles. All indicators were scored from 1 to 5, and the highest score was assigned to the highest performer. These scores corresponded either to the evaluation of a single parameter (e.g. productivity) or to the average from scores of several parameters (e.g. nutritional score). Multiplier coefficients were applied for nutritional value and palatability. Azolla filiculoides showed the best scores for productivity; L. minor for nutritional value and palatability, and E. crassipes for the lowest risk of non-productive cycles and a positive impact on water quality. After integrating the scores in a multi-parameter matrix, A. filiculoides had the best overall score. The results of this approach to select macrophytes are discussed in light of the eco-services provided by macrophytes which may, in turn, promote the ecological intensification of tropical small-scale aquaculture.

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<p align="center"><strong>ABSTRACT</strong></p><p class="Paragraf">Snakehead <em>Channa striata</em> is a local specific fish species and has high economic value. Until now the production of snakehead still reelies on the catch of nature because cultivation of snakehead is still underdeveloped. The main constraint in snakehead fish farming is high mortality on snakehead juvenile rearing phase. This study was conducted to determine the best stocking density on snakehead juvenile rearing to achieve optimal production. The treatments used in this study were stocking density of 1 juvenile/L, 2 juveniles/L, and 3 juveniles/L. Snakehead juveniles with a length of 3.41 ± 0.39 cm and weight 0.28 ± 0.07 g, were reared for 42 days in the aquarium sized 40×40×40 cm with a volume of 40 L. Fishes were fed by bloodworms in ad libitum<em> </em>method. The result showed that the treatments did not affect the survival, growth and the ratio of RNA/DNA of snakehead juvenile. Survival of juvenile snakehead ranged 92.5‒94.58% (P&gt;0.05). The result of water quality measurement showed that it was on optimum condition to supporting snakehead growth at 3 juveniles/L stocking density. Furthermore, recirculation can be use to maintenance water quality for optimum condition. Thus, the rearing of snakehead fish juvenile in the recirculation system can use a stocking density of 3 juveniles/L, and the recirculation system could maintain the water quality in good condition.</p><p class="Paragraf"> </p><p>Keywords: growth, recirculation system, snakehead fish, stocking density, survival rate</p><p> </p><p> </p><p align="center"><strong>ABSTRAK </strong></p><p class="Paragraf">Ikan gabus <em>Channa striata</em> merupakan ikan spesifik lokal dan mempunyai nilai ekonomis tinggi. Sampai saat ini produksi ikan gabus masih mengandalkan tangkapan dari alam karena kegiatan budidaya ikan gabus masih belum banyak berkembang. Kendala utama dalam budidaya ikan gabus adalah tingginya mortalitas pada fase pemeliharaan benih. Penelitian ini dilakukan untuk menentukan padat tebar terbaik dalam upaya memperoleh pertumbuhan dan sintasan terbaik. Perlakuan yang digunakan dalam penelitian ini adalah padat tebar 1 ekor/L, 2 ekor/L, dan 3 ekor/L. Benih ikan gabus dengan panjang rata-rata 3,41± 0,39 cm dan bobot rata-rata 0,28 ± 0,07 g dipelihara selama 42 hari di dalam akuarium berukuran 40×40×40 cm dengan volume air 40 L. Benih ikan gabus diberikan pakan berupa cacing sutera secara ad libitum. Hasil penelitian menunjukkan bahwa penggunaan padat penebaran yang berbeda tidak memengaruhi sintasan dan pertumbuhan dan rasio RNA/DNA benih ikan gabus (P&gt;0,05). Sintasan benih ikan gabus pada akhir pemeliharaan berkisar antara 92,5‒94,58%. Hasil pengukuran terhadap kualitas air pada kepadatan 3 ekor/L masih dalam kondisi optimum untuk mendukung pertumbuhan benih ikan gabus sehingga sistem resirkulasi yang digunakan dapat mempertahankan kualitas air dengan baik. Hasil penelitian menunjukkan pemeliharaan benih ikan gabus pada sistem resirkulasi sebaiknya menggunakan padat tebar 3 ekor/L dan sistem resirkulasi dapat mempertahankan kualitas air dalam kondisi baik.</p><p class="Paragraf"> </p><p class="Paragraf">Kata kunci: ikan gabus, pertumbuhan, padat tebar, sintasan, sistem resirkulasi.</p><p> </p>

Green seaweed Ulva had a high growth rate and spread in all of Indonesian waters. Species Ulva had a complete nutrient content that made it potential to be used as an alternative fish feed ingredient. This experiment was conducted in two series of trial, digestibility measurement of Ulva meal and its effects on the growth performance of the Nile tilapia (O. niloticus). In measuring the nutrient digestibility, a protein rich diet was formulated with a test diet in which 30% of the reference diet was replaced with Ulva meal, used Cr2O3 as an inert marker. Fish with initial weight about 16±0.35 g were stocked with a density of 15 fish per aquarium and collecting faeces is carried out until sufficient sample was available for analysis. The growth trial was conducted using a completely randomized design with four treatments and three replications. The experimental diets were U0 (Ulva 0%), U10 (Ulva 10%), U20 (Ulva 20%) and U30 (Ulva 30%).  The Nile tilapia with an average body weight of 3.42±0.01 g, were stocked into the 60x50x50 cm aquaria with 25 fish in each tank and cultured for 60 days. Fish were fed three times daily on those diets at satiation level. The parameters which evaluated were specific growth rate, protein retention, lipid retention, feed efficiency, survival rate and blood hematology of the Nile tilapia. The results of digestibility measurement showed that Ulva meal had acceptable nutrients as an ingredient in Nile tilapia diet. Protein digestibility of Ulva meal was 87.36%, while lipid was 93.05%. The results of growth trial revealed that fish fed on 10% Ulva meal tended to have highest growth performance than those fed to the control, while the survival rate and fish health seemed not to be affected directly (P>0.05).