Production Performance and Nitrogen and Phosphorus Mass Balance in Biofloc-based African Catfish Intensive Culture at Different Densities

This study aimed to evaluate the production performance and nitrogen and phosphorus mass balance of biofloc-based intensive African catfish Clarias gariepinus culture at different densities. African catfish with an average body weight of 2.64 ± 0.06 g was randomly distributed into 12 units of round tank with a working volume of 2 m3 of water and maintained for 8 weeks. A completely randomized experimental design with four treatments (in triplicates), i.e. a control treatment at a fish density of 500 fish m-3 with regular water exchange and without organic carbon source addition, and biofloc treatments (BFT) at three different densities, i.e. 500 fish m-3 (BFT500), 750 fish m-3 (BFT750), and 1000 fish m-3 (BFT1000). Biofloc systems were performed with a regular addition of tapioca flour (40% C). The production performance between biofloc system and the control was not significantly different, however water and nitrogen utilizations were significantly more efficient in biofloc system than those of the control. The highest fish specific growth rate was observed in BFT1000 and BFT500 (6.01% day-1 and 5.96% day-1, respectively) (P<0.05). Fish density significantly affected the fish growth performance and productivity in biofloc systems, but not nitrogen and phosphorus utilizations. In conclusion, higher fish density significantly increased the production and water utilization efficiency in biofloc systems, but has no effect on nitrogen and phosphorus utilization efficiency. Furthermore, increasing the fish density could significantly reduce the fish survival and require more efforts to control biofloc biomass in the culture system.

PENDUGAAN DAYA DUKUNG PERAIRAN UNTUK BUDIDAYA IKAN DALAM KERAMBA JARING APUNG DI WADUK PONDOK, NGAWI JAWA TIMUR

Waduk Pondok seluas 407 Ha berada di Ngawi Jawa Timur, beroperasi sejak 1995 dan merupakan waduk serbaguna. Kegiatan budidaya ikan dengan keramba jaring apung (KJA) di Waduk tersebut sudah berkembang, hingga mencapai 126 petak pada tahun 2016. Penelitian ini bertujuan untuk menganalisis tingkat kesuburan perairan, total fosfor yang terlepas dari KJA ke peraian dan mengestimasi daya dukung perairan untuk KJA. Tingkat kesuburan perairan dianalisa dengan nilai index status trofik (TSI). Estimasi daya dukung perairan untuk KJA menggunakan pendekatan model keseimbangan total fosfor (P) yang terlepas ke parairan. Hasil penelitian menunjukkan bahwa perairan waduk Pondok sudah termasuk dalam katagori perairan eutrofik dengan nilai TSI 62,1.Total P yang terlepas ke perairan sebesar 15,04 kg ton ikan. Daya dukung perairan untuk KJA adalah 195,2 ton /tahun (130 petak KJA). Jumlah KJA di Waduk Pondok ada 126 petak (189 ton) atau sudah mendekati daya dukung perairan, sehingga jumlahnya tidak dapat ditambah lagi.Pondok Reservoir as large as 407 hectares is located in Ngawi, East Java. The Reservoir was functionally started in 1995, is a multipurpose reservoir. Fish culture in Pondok Reservoir in 2016 reached 126 cages. The aim of this research is to evaluate the trophic status, the total of phosphorus released into the waters from floating net cage, and carrying capacity of the reservoir for fish culture. Trophic status of reservoir was analyzed trough calculating the TSI (Trophic Status Index). A phosphorus mass balance model was used in assessing the carrying capacity of the reservoir. Research hypotesis in this research is Pondok reservoir has reached eutrophic status, and cages number in Pondok reservoir has alreday exceeds carriying capacity. Pondok reservoir have been categorized as eutrophic status, with the value of TSI 62.1. Total P released to the waters is 15.04 kg P / ton of fish. The carrying capacity of Pondok Reservoir for fish culture is 195,2 ton / year (130 cages). The number fish culture in Pondok Reservoir is 126 cages (189 ton), has already approaching maximum number can not be added anymore.