Penampilan fenotipik suatu organisme ditentukan oleh faktor genetik dan dipengaruhi oleh faktor lingkungan tempat organisme tersebut hidup. Dalam beberapa kasus, interaksi antara faktor genetik dengan lingkungan juga berpengaruh terhadap penampilan fenotipik yang dihasilkan. Penelitian ini bertujuan untuk mempelajari interaksi antara faktor genetik dengan lingkungan, daya adaptabilitas dan stabilitas penampilan fenotipik khususnya bobot individu pada empat varietas unggul ikan nila yang dipelihara di tiga lokasi berbeda. Ikan nila varietas GMT, merah NIFI, NIRWANA dan BEST dipelihara di tambak payau di Indramayu, kolam air tenang di Sukamandi dan karamba jaring apung di Waduk Cirata, Kabupaten Cianjur, selama empat bulan pemeliharaan. Benih ikan nila diberi pakan pelet komersial dengan kandungan protein kasar 28%-30%, sebanyak 10%; 7,5%; 5%; dan 2,5% dari biomassa ikan masing-masing pada bulan pertama, kedua, ketiga, dan keempat. Pakan diberikan dengan frekuensi dua kali setiap hari. Hasil penelitian menunjukkan bahwa bobot ikan nila secara nyata dipengaruhi oleh faktor genetik, lingkungan, serta interaksi antara kedua faktor tersebut. Selain ikan nila GMT, tiga varietas ikan nila yang diuji mempunyai adaptabilitas lingkungan relatif sempit, serta stabilitas penampilan fenotipik karakter bobot individu relatif rendah. Hal ini mengindikasikan bahwa pengembangan budidaya ikan nila GMT dapat dilakukan di semua lokasi, sedangkan ikan nila merah NIFI, NIRWANA, dan BEST akan optimal jika dilakukan di lokasi tertentu saja.Phenotypic performance was determined by genetic and environment factors and their interaction. This study was conducted to examinethe present of interaction both of genetic and environment factors, adaptability, and stability of phenotypic performance of four varieties of tilapia which maintained in three different location. GMT, red NIFI, NIRWANA, and BEST tilapia strains were reared for four months in net cages in Cirata reservoir in Cianjur, in earthen ponds in Sukamandi and in brackish water ponds in Indramayu. All fish were fed with commercial pelleted feed contained of crude protein 28%-30%, about 10%, 7.5%, 5%, and 2.5% each day in 1st, 2nd, 3rd, and 4th month, respectively. The results showed that tilapia’s phenotipic performance especially the average body weight was significantly affected by genetic factor, environment factor, and interaction both of them factors. Except the GMT, all tilapia strains used in this study have narrow phenotypic adaptability and stability, especially in average body weight. This results indicated that GMT tilapia strain can be farmed in various areas, but red NIFI, NIRWANA, and BEST tilapia strains are most likely in a specific location.

Langkah awal yang dilakukan dalam rangka pembentukan varietas ikan nila toleran salinitas adalah koleksi dan karakterisasi varietas-varietas ikan nila yang akan digunakan sebagai sumber-sumber genetik pembentukan varietas tersebut. Beberapa varietas ikan nila yang telah dikoleksi antara lain ikan nila Nirwana Wanayasa, GMT Sukabumi, GIFT Sukamandi, BEST Bogor, dan red NIFI. Kegiatan ini dilakukan dengan tujuan untuk mengetahui keragaman morfologi antara beberapa varietas ikan nila hasil koleksi tersebut serta menduga hubungan kekerabatannya berdasarkan tingkat keragaman dan kemiripan antar populasi. Karakterisasi morfologi dilakukan menggunakan metode truss morfometrik dilanjutkan dengan analisis komponen utama (principal component analysis) dan analisis pengelompokan (cluster analysis). Hasil karakterisasi menunjukkan bahwa terdapat 2 kelompok utama pada varietas-varietas ikan nila yaitu ikan nila GMT Sukabumi, GIFT Sukamandi, BEST Bogor, dan red NIFI bergabung menjadi satu kelompok sedangkan ikan nila Nirwana Wanayasa membentuk kelompok tersendiri. Di dalam kelompok pertama, ikan nila red NIFI mempunyai bentuk yang berbeda dari 3 populasi lainnya.

Intraspecific crossing of giant gouramy was done to get better hybrid population. This study was conducted to evaluate the hybrid vigour or heterotic value of the hybrids line, especially for growth rate character. Besides that, we want to know the effect of hybridization on performance of phenotypic variability. Two days post hatching age larvae of four populations i.e. Bastar and Blue-saphire strain, F-1 hybrid and F-1 hybrid reciprocal, were used in this experiment. All fish were reared in aquaria for 30 days period in indoor hatchery. The fish were fed with live food such as Moina and Daphnia for the first ten days, followed by Tubifex for the second ten days and finally, commercial feed were given until the end of the study. The collected data were total length, standard length, and body weight of each population. The results showed that the phenotypic variability of the hybrid population was higher than that of inbred population. Hybrid population from female of Bastar and male of Blue-saphire has better growth than both of its parents. Heterotic values of total length, standard length, and body weight of the hybrid population was 9.5%, 2.9%, and 15.6% respectively. Maternal effect was detected in hybrid population.

One of the most popular techniques in mass production of all or nearly all male tilapia population is through sex reversal. However, cross mating of YY super male with regular brood-stock is gaining popularity and has been practiced by aqua-culturists. This study was conducted to evaluate the performance of 2 populations of sex reversed tilapia (sex reversed with dietary application of 17-α methyl testosterone, SRT-1, and sex reversed with dietary administration of imidazole, SRT-2) and 1 population of genetically male tilapia (GMT) derived from YY super male until the end of fingerling rearing period. Mixed sex tilapia (MST) derived from normal mating was used as the control population. The results showed that the daily growth rates of SRT-1, SRT-2, GMT, and MST were 0.12, 0.11, 0.20, and 0.07 g/day, with survival rates were 57.83%, 64.67%, 39.67%, and 68.78%, respectively. The GMT has higher harvest yield than the other populations; SRT-1 (+15.73%), SRT-2 (+6.37%), and MST (+20.82%).