This study was aimed to analyze the growth performance of African catfish Clarias gariepinus cultured in the biofloc system at high stocking density. African catfish with an average weight of 1.85±0.09 g were cultured in four units of tarpaulin tank at a diameter of 1.72 m and a height of 1.05 m with a volume of ±2,000 L at the different density of 1,000 fish/m 3 ; 1,500 fish/m 3 ; 2,000 fish/m 3 ; 2,500 fish/m 3 . During rearing period, fish were given the artificial feed with protein contents of 28.75% with the frequency of twice a day, as much as 3% of the body weight. The results showed that different treatment of high stocking density in the biofloc system had a significant effect on the absolute growth rate, lipid retention and energy retention (P<0.05) but not significant effect on daily growth rate. The results showed that the highest lipid retention and energy retention were found in the group of fish treated at a stocking density of 2,500 fish/m 3 but declining protein retention and growth in fish occurred. The highest absolute growth rate and daily growth rate were shown by treatment with a stocking density of 1,500 fish/m 3 .Keywords: growth, stocking density, biofloc ABSTRAKPenelitian ini bertujuan untuk menganalisis performa pertumbuhan ikan lele dumbo Clarias gariepinus yang dipelihara pada sistem bioflok dengan padat penebaran tinggi. Ikan uji memiliki berat rata-rata 1,85±0,09 g yang dipelihara pada kolam terpolin berdiameter 1,72 m dan tinggi 1,05 m dengan volume air ±2.000 L sebanyak empat unit dengan kepadatan yang berbeda yaitu 1.000 ekor/m 3 , 1.500 ekor/m 3 , 2.000 ekor/m 3 , 2.500 ekor/m 3 . Selama 40 hari masa pemeliharaan, ikan diberi pakan buatan berkadar protein 28,75% dengan frekwensi dua kali sehari, sebanyak 3% dari berat tubuh. Hasil penelitian menunjukkan bahwa perlakuan perbedaan padat penebaran tinggi pada sistem bioflok memberikan pengaruh yang nyata terhadap pertumbuhan mutlak, retensi lemak dan retensi energi (P<0,05) namun tidak memberikan pengaruh nyata terhadap laju pertmbuhan harian. Hasil penelitian menunjukkan bahwa semakin tinggi padat penebaran terjadinya peningkatan retensi lemak dan retensi energi yaitu pada perlakuan padat penebaran 2.500 ekor/m 3 tetapi terjadi penurunan nilai retensi protein dan pertumbuhan pada ikan. Nilai pertumbuhan mutlak tertinggi ditunjukkan oleh perlakuan dengan padat penebaran 1.500 ekor/m 3 .

Catfish is a species of freshwater fish that contains a source of protein and it has economic value and has become one of the famous commodities in Indonesia. Biofloc can be one alternative waste fixers intensive cultivation for reduce the waste of inorganic nitrogen and also provide additional protein for increase growth and feed efficiency. This study was to determine the effect of high stocking densities on the growth performance of african catfish in biofloc system. This study used completely randomized design (CRD) with different stocking densities in the system biofloc T1.(1000/m3), T2.(1500/m3), T3.(2000/m3), and T4.(2500/m3). Animal trials were using jouvenile african catfish with an average weight of 1.06±0.3g, which maintained in a pool tarpoulin cage with water volume ±2000L for 50 days with feeding ratio 3% of the weight biomass. The results showed a significantly different effect (P<0.05) against the value of hepatosomatic index, absolute growth and daily growth rate, but the result not significant at spesific growth rate. The second treatment (T2) showed the best results than others in the growth rate and daily growth rate with a value of 6.45±3.1g for absolute growth and 0.13±0.06g for daily growth rate. The four treatment showed the best results than others in the hepatosomatic index with value 4.7 ± 1.8%. These findings demonstrate a role of biofloc technology in catfish aquaculture.

This study was aimed to analyze the growth performance of African catfish Clarias gariepinus cultured in the biofloc system at high stocking density. African catfish with an average weight of 1.85±0.09 g were cultured in four units of tarpaulin tank at a diameter of 1.72 m and a height of 1.05 m with a volume of ±2,000 L at the different density of 1,000 fish/m 3 ; 1,500 fish/m 3 ; 2,000 fish/m 3 ; 2,500 fish/m 3 . During rearing period, fish were given the artificial feed with protein contents of 28.75% with the frequency of twice a day, as much as 3% of the body weight. The results showed that different treatment of high stocking density in the biofloc system had a significant effect on the absolute growth rate, lipid retention and energy retention (P<0.05) but not significant effect on daily growth rate. The results showed that the highest lipid retention and energy retention were found in the group of fish treated at a stocking density of 2,500 fish/m 3 but declining protein retention and growth in fish occurred. The highest absolute growth rate and daily growth rate were shown by treatment with a stocking density of 1,500 fish/m 3 .Keywords: growth, stocking density, biofloc ABSTRAKPenelitian ini bertujuan untuk menganalisis performa pertumbuhan ikan lele dumbo Clarias gariepinus yang dipelihara pada sistem bioflok dengan padat penebaran tinggi. Ikan uji memiliki berat rata-rata 1,85±0,09 g yang dipelihara pada kolam terpolin berdiameter 1,72 m dan tinggi 1,05 m dengan volume air ±2.000 L sebanyak empat unit dengan kepadatan yang berbeda yaitu 1.000 ekor/m 3 , 1.500 ekor/m 3 , 2.000 ekor/m 3 , 2.500 ekor/m 3 . Selama 40 hari masa pemeliharaan, ikan diberi pakan buatan berkadar protein 28,75% dengan frekwensi dua kali sehari, sebanyak 3% dari berat tubuh. Hasil penelitian menunjukkan bahwa perlakuan perbedaan padat penebaran tinggi pada sistem bioflok memberikan pengaruh yang nyata terhadap pertumbuhan mutlak, retensi lemak dan retensi energi (P<0,05) namun tidak memberikan pengaruh nyata terhadap laju pertmbuhan harian. Hasil penelitian menunjukkan bahwa semakin tinggi padat penebaran terjadinya peningkatan retensi lemak dan retensi energi yaitu pada perlakuan padat penebaran 2.500 ekor/m 3 tetapi terjadi penurunan nilai retensi protein dan pertumbuhan pada ikan. Nilai pertumbuhan mutlak tertinggi ditunjukkan oleh perlakuan dengan padat penebaran 1.500 ekor/m 3 .

Industry development in Indonesia resulted in sewage and polluting heavy metals such as mercury (Hg). These pollutants will be harm organisms that live at aquatic environment. Fish gills could be damage due to exposure by mercury. To know the influence of mercury’s toxic against aquatic organisms by using toxicity test. An aquatic organism, which is usually used as toxicity test, is nilem fish (Osteochilus hasselti). The objective of the study was to determine the value of LC50-96 hours in a toxicity test of nilem fish exposed to lead acetate; to determine the changes in the fish gill and to determine the concentration of lead mercury which causes tissue damage structure in the gills of nilem fish. The design used completely randomized design (CRD) with four concentrations (0; 0.08; 0.16 and 0.24 ppm) and three replications. The objective of the study was sublethal toxicity test. Lethal toxicity concentration data were descriptive and data from sublethal toxicity test were One Way. The analysis showed that there were highest edema 10% and 17% on day 4 and 12, the highest lamella fusion 35% and 59% on day 4 and 12, the highest hyperplasia 45% and 54% on day 4 and 12, and the highest necrosis the 65% and 80% on day 4 and 12. It was concluded that the value of LC50-96 hours in nilem fish (Osteochilus hasselti) toxicity test was 0,3938 ppm; and damage of fish gill tissue changes started to occur in the lead mercury (Hg) concentration of 0,08 ppm.

Keberadaan bakteri proteolitik pada komoditas akuakultur penting untuk dipelajari, salah satunya terkait dengan praktek budidaya ikan skala kecil di daerah pedesaan. Penelitian ini bertujuan untuk mengetahui keberadaan dan melakukan identifikasi secara molekuler bakteri proteolitik yang diisolasi dari saluran pencernaan ikan nila (Oreochromis niloticus). Sampel ikan nila diambil dari tiga unit kegiatan akuakultur yang menggunakan pakan berbeda di Kabupaten Banyumas yaitu dari Desa Pandak (dengan probiotik, pakan pellet), Desa Beji (tanpa probiotik, pakan tumbuhan) dan Desa Tambaksogra (dengan probiotik, kombinasi pakan pellet dan tumbuhan). Jumlah bakteri, proporsi bakteri proteolitik, dan indeks aktifitas proteolitik diamati dari usus bagian anterior, middle, dan posterior. Sampel isolat bakteri  proteolitik dikelompokkan berdasarkan hasil analisis restriksi 16S rDNA menggunakan software PhyElp. Bakteri dari setiap kelompok diidentifikasi berdasarkan sekuen gen 16S rDNA dengan menggunakan analisis BLAST dan analisis filogenetik. Jumlah bakteri di saluran pencernaan ikan nila dari tiga tempat relatif sama dan cenderung meningkat ke arah posterior. Hasil penelitian menunjukkan ikan nila dari Desa Pandak memiliki proporsi bakteri proteolitik yang lebih tinggi dibandingkan sampel ikan dari Desa Beji dan Tambaksogra. Nilai aktivitas bakteri proteolitik saluran pencernaan ikan nila dari Desa Pandak relatif lebih tinggi dibandingkan dari dua desa lainnya. Bakteri proteolitik dari saluran pencernaan ikan nila dapat dikelompokkan menjadi 15 kelompok berdasarkan polimorfisme hasil digesti fragment gen 16S rDNA. Sampel dari 15 kelompok tersebut memiliki sekuen 16S rDNA yang mirip dengan Pseudomonas aeruginosa (4 isolat), Plesiomonas shigelloides, Escherichia coli, Aeromonas veronii, Klebsiella variicola, Enterobacter ludwigii, Enterobacter hormaechei (2 isolat), Enterobacter cloacae, Bacillus subtilis, Bacillus amyloliquefaciens dan Bacillus sp.