Nila strain Larasati generasi kelima (F5) merupakan nila hasil perkawinan silang antara nila strain Kunti F5 betina dan Nila strain Pandu F5 jantan. Penelitian ini bertujuan membandingkan nila strain Larasati F5 dengan tetuanya berdasarkan laju sintasan (survival rate/SR), berat, panjang total, tebal, laju pertumbuhan spesifik (specific growth rate/SGR), dan nisbah konversi pakan (feed convertion ratio/FCR). Perhitungan heterosis menggunakan dua konsep perbandingan. Nila yang digunakan merupakan generasi kelima berumur 4 bulan. Ikan dengan strain dan jenis kelamin berbeda dipelihara secara terpisah selama 1 bulan pada kolam berukuran 20x10x1 m3, kedalaman air 70 cm dan debit air ± 15 liter/detik. Ikan yang ditebar pada setiap kolam berjumlah 450 ekor. Pemberian pakan dengan pelet (kandungan protein minimal 30%) sebanyak 3 kali sehari dengan metode ad libithum. Parameter yang dihitung adalah SR, SGR, FCR dan heterosis. Ikan diukur pada awal dan akhir pemeliharaan. Pengukuran kualitas air dilakukan pada awal, minggu kedua, dan akhir pemeliharaan. Heterosis dianalisis secara deskriptif. Heterosis hasil perhitungan dengan konsep I untuk SR 1,02%; panjang total 12,5%; berat 44,5%; tebal tubuh 9,6%; SGR berat 4,1%; SGR panjang 11,82%; SGR tebal 9,95%; dan FCR -1,5%. Perhitungan konsep II untuk SR 1,29%; panjang total 13,2%; berat 46%; tebal tubuh 10,3%; SGR berat 4,89%; SGR panjang 12,68%; SGR tebal 11,60%; dan FCR-1,7. Kualitas air kolam masih sesuai untuk budidaya ikan nila dengan kisaran suhu 26 – 29˚C, oksigen terlarut 2,7 – 3,5 ppm, pH 7,1 – 7,3, dan debit air 15 – 20 liter/detik. Heterosis Nila Larasati F5, pada karakter laju sintasan, berat, panjang total, tebal tubuh, laju pertumbuhan spesifik, dan nisbah konversi pakan menunjukkan peningkatan performa dibandingkan dengan tetuanya

Tilapia Larasati strain fifth generation (F5) was the strain of cross-breeding between Tilapia Kunti strain F5 female and Tilapia Pandu strain F5 male. The objective of the research is to compare survival rate (SR), weight, total lenght, thickness, specific growth rate (SGR), and feed convertion ratio (FCR) of Tilapia Larasati strain with their parents. There were two concept comparation to obtain the heterosis. Tilapia F5 by aging of 4 months was used as the research object. Tilapia separately cultivated by strain and sex for 1 month in pond sized 20x10x1 m3, water depth 70 cm and water discharge ± 15 liters/sec. The fishes were stocked in each pond was 450 fishes. The fishes were food 3 times by ad libithum method. Feed used was a commercial pellet with a minimum protein content of 30%. The fishes were measured at the beginning and the end of maintenance. The parameters were determined SR, SGR, FCR and heterosis. Water quality was measured at the beginning of the maintenance, the second week, and the end of the maintenance. Heterosis was analyzed by descriptive analysis. The result showed that heterosis based first concept were SR 1.02%, total length 12.50%, weight 44.50%, thickness 9.60%, SGR of weight 4.10%, SGR of length 11.82%, SGR of thickness 9.95% and FCR -1.50%. The result showed that heterosis based second concept wereSR 1.29%, total length 13.20%, weight 46.00%, thickness 10.30%, SGR of weight 4.89%, SGR of length 12.68%, SGR of thickness 11.60%, and FCR -1.7%. The water quality were eligible to be used for tilapia farming with range of temperature 26 – 29˚C, dissolved oxygen 2.7 – 3.5 ppm, pH 7.1 to 7.3, and water discharge 15-20 liters/sec.Tilapia Larasati have better characters than their parents which were shown by positive value of heterosis, and negative value of FCR in heterosis.

Kata Kunci : Heterosis, laju sintasan, pertumbuhan, populasi, tetua.