KAJIAN TENTANG DAMPAK PERTUMBUHAN COMPENSATORY TERHADAP KUANTITAS DAN KUALITAS IKAN NILA MERAH (Oreochromis sp)

Abstract

Ikan nila merah (Oreachromis sp.) mempunyai keunggulan-keunggulan untuk dibudidayakan di laut. Masalah utama di dalam budidaya adalah semakin mahalnya barge palran, sedangkan 60% biaya operasional dari usaha budidaya adalah untuk penyediaan pakan ini. Memperbaiki feeding strategy dalam upaya efisiensi dan penghematan pakan, dengan mengaplikasikan pertumbuhan compensatory, merupalcan suatu kebutuhan tanpa mengorbankan kuantitas rnaupun laminas produk (basil budidaya). Tujuan dari penelitian ini (I). Mengevaluasi fenomena pertumbuhan compensatory, dan (2). Mengevaluasi kualitas produk (body composition), dari ikan nila merah yang dibudidayakan di air laut dengan mengukur kandungan protein, lemak, karbohidrat, dan kadar aimya. Penelilian skala laboratoriurn dilakukan dari awal Juni sampai awal Agustus 2003 di hatchery Ilmu Kelautan FPK Undip, Teluk Awur, Jepara. Benih limn nila merah (bent rata-rata 37,74 +SD 1,16 g) yang berasal dari balai benih ikan sebelumnya diaklimatisasikan pada kondisi taut dipelihara dalam bak-bak percobaan dengan kepadatan 5 ekor/m3. lvlasing-masing bak percobaan berisi 12 elcor don. Perlakuan pemuasaan diberikan dengan 3 kali pengulangan selama empat minggu percobaan, yaitu: ikan diberi pakan setiap hari (A/kontrol); ikan diberi pakan selama 6 kiln diikuti pemuasaan 1 hari (B); ikan diberi pakan selama 5 hari diikuti pemuasaan 2 hari (C); dan, ikan diberi pakan selama 5 hat' diikuti pemuasaan 3 hari (D). Pakan diberikan dua kali sehari sebanyak 5% dari biomassa. Pengamatan pertumbuhan (berat) dilakukan setiap minggu sekati. Analisa kualitas produk (body composition) dilakukan dengan mengukur kadar protein, kadar lemak, kadar karbohidrat dan kadar air (%). Analisa body composition dilakukan di Laboratorium Fisika dan Kimia Balai Budidaya Air Payau Jepara. Terhadap pertumbuhan (berat), analisa regresi dilakukan dimana koefisien regresi atau slope adidah menggambarkan tingkat atau kecepatan perttunbuhan (gram/minggu). Ancova (Analysis of Covariance) dilakukan untuk menguji apakah terjadi perbedaan dalam tingkat perturnbuhannya dari 4 perlakuart yang diadakan. Analisa sidik ragam (Anova) dilalculcan untulc mengetahui pengaruh perlakuan terhadap kadar protein, lemak, karbohidrat, clan kadar air. Baik terhadap tingled pertumbuhan maupun body composition daging ikan apabila perlakuan memberikan pengaruh yang berbeda sangat nyata atau berbeda nyata, maim dilanjutican dengan uji BNT (Beds Nyata Terkeeil) Tukeys untuk mengetahui perbedaan pengaruh antar perlakuan (Sudjana, 1996). Basil penelitian menunjuldcan bahwa ikan pada semua perlalcuan mengalami pertumbuhan, yaitu 7,42 gr/minggu (A); 7,18 gr/minggu (B); 3,44 gr/minggu (C); dan, 5,34 miminggu (D). Meskipun tinglcat pertumbuhan berbeda, tetapi secara statistik tidal( ada perbedaan dalam tingkat pertumbuhannya. Basil ini menunjuldtan telah terjadi pertumbuhan compensatory. Kualitas procluk yang chhasilkan juga tidal( menunjukkan adanya perbedaan dalam kadar protein, lemak, karbohidrat, dan air. Kadar protein secara umum >18%, dart ini berarti tnasih dakun kadar yang normal untulc nila merah. Dili hat dari !radar lemak di mana berkisar antara 1,50-1,80%, menunjtddcan bahwa lcadamya rendaft, yaitu hampir seperdua dari lomdungan lentak tnalcanan ikan yang diberikan (3-5%). Rendalmya kadar lemak diikuti dengan kadar air yang tinggi (>70%). Tingginya kadar air akan menyebablcan tekstur daging lebih lunak. Untuk karbohidrat, sangat sulit untulc memberilcan penilaian dengan kadar karbohidrat yang ada (2,7-4,8%). Karbohidrat mempunyai peranan panting dalam mertentukan karakteristik bahan makanan seperti rasa, wama, tekstur dan lain-lain. Red tilapia (Oreochromis sp.) has considerable attention as a marine culture fish because of their high quality performance. Main problem on the culture is due to the high price of food; and, about 60% of culture's operational expense is for the need of the food. Proper feeding strategy is crucial to work under an efficient basis and save the food, by application the compensatory growth, without lowering both quantity and quality of the fish. The aims of this study were (1) to evaluate compensatory growth occurred, and, (2) to evaluate red tilapia's body composition consisting the contents of protein, fat, carbohydrate, and water (percentage). The experiment was commenced from beginning June to beginning August 2003 at the hatchery of Marine Science, Undip, in Teluk Awur-Jepara, under the laboratory condition. Red tilapias of mean weight of 37.74 g + SD 1.16 obtained from the fish hatchery were acclimated in seawater conditions. The fish were cultured in the tank with a density of five fish/m3 (12 fish/tank), The treatments were feeding daily (A/control); fish fed 6 days—a day unfed (B); fish fed 5 days-2 days unfed; and fish fed 4 days-3 days unfed (D). Feeding frequency was twice a day with 5% of the biomass, Growth was measured weekly. For fish quality analysis (body composition), it was done in Physical-Chemical laboratory, Balai Budidaya Air Payau Jepara by measuring the contents of protein, fat, carbohydrate, and water (%). In the relation to growth, regression analysis was performed, in which the regression coefficient or slope was to represent the growth rate (g/week). Ancova (Analysis of Covariance) was also performed to investigate if there were differences among the four treatments. Four Anova tests were to test the influence of the treatments (each for protein, fat, carbohydrate, and water, respectively). If the treatments resulted in significantly different or very significantly different result, then it was followed by Tukey Test to know the differences between the treatments. The resulted showed that all of fish at the difference treatments tended to grow; and, the growth rates were 7.42 g/week (A), 7.18 g/week (B), 3.44 g/week(C), and 5.34 g/week (D). Statistically, however there was no significant difference of the growth rate among the fish (Ancova). The result also suggested that the compensatory growth occurred. There was no difference for protein contents, also for fat contents, carbohydrate contents, and water contents. In general, the protein content was above 18%, and it was the normal condition for red tilapia. The fat contents in the range of 1.50 to 1.80 % was to indicate that the value was low because nearly a half of fat content given as food (3-5%). The low fat contents was followed by the high water contents (>70%). The high water content made the flesh texture became soft. In case of carbohydrate, it was difficult to justify with the available contents (2.74 to 4.8%). Carbohydrate has important roles to influence the food characteristics such as taste, colour, texture, etc.