BEBAN KERJA OSMOTIK DAN SIFAT PERTUMBUHAN IKAN BANDENG (Chanos chanos Forskal) YANG DIBUDIDAYA PADA TAMBAK TRADISIONAL DI DESA MOROSARI DAN DESA TAMBAKBULUSAN KABUPATEN DEMAK

Abstract

Kabupaten Demak merupakan salah satu wilayah di Jawa Tengah sebagai penghasil ikan Bandeng. Ikan Bandeng (Chanos chanos Forskal) memiliki beberapa keunggulan yaitu tahan terhadap perubahan lingkungan, dapat dibudidayakan di air payau, laut dan air tawar. Penelitian bertujuan untuk mengkaji nilai tingkat kerja osmotik (TKO), pola osmoregulasi serta sifat pertumbuhan dan faktor kondisi ikan Bandeng. Penelitian menggunakan metode studi kasus yang bersifat deskriptif dengan teknik sampling purposive sampling. Pengambilan sampel dilakukan setiap satu minggu sekali selama 4 minggu. Pengambilan sampel osmolaritas (media dan darah) dilakukan pada minggu pertama dan minggu keempat. Sampel ikan yang digunakan sebanyak 100 ekor untuk analisis hubungan panjang berat dan 3 ekor untuk mengetahui osmolaritas (media dan darah). Uji independent-Samples t test digunakan untuk mengetahui perbedaan TKO antara kedua tambak. Hasil yang diperoleh menunjukkan rata-rata TKO ikan Bandeng di desa Morosari dengan rata – rata salinitas 28 ^o/_oo sebesar 235,26 mOsm/l H₂O dan di desa Tambakbulusan dengan rata – rata salinitas 14 – 20 ^o/_oo sebesar 173,875 mOsm/l H₂O. Terdapat perbedaan TKO yang sangat signifikan (p< 0,01)  antara ikan Bandeng pada tambak tradisional di desa Morosari dengan desa Tambakbulusan. Ikan Bandeng di Morosari memiliki pola osmoregulasi hipoosmotik dan hiperosmotik di Tambakbulusan. Pertumbuhan ikan Bandeng pada tambak tradisional di desa Morosari dan desa Tambakbulusan bersifat allometrik positif dengan nilai b pada masing – masing tambak sebesar 3,232 dan 3,562. Faktor kondisi (Kn) ikan Bandeng pada tambak tradisional di desa Morosari sebesar 1,02 dan desa Tambakbulusan sebesar  1,06 yang berarti bahwa badan ikan kurus atau kurang montok.

Demak regency is one region in Central Java as a producer of Milkfish. Milkfish (Chanos chanos Forskal) had speciality consists of resistant to environmental changes, can be cultivated in brackish water, marine and freshwater. This research was purposed to examine value of  the osmotic work levels, osmoregulation pattern, growth characteristic, and the factor of Milkfish condition that is cultivated in the traditional brackishwater ponds at Morosari village and Tambakbulusan Village. The research methods of descriptive case studies and sampling method with purposive sampling. Taking sample is conducted every once week for four week. Taking media osmolarity and sample of blood osmolarity is conducted in the first week and fourth week. Fish sample that was used as much as 100 heads for analyzing the relationship between lenght-weight and 3 heads to know the value of media osmolarity and sample of blood osmolarity. The study of independent-Samples t test is used to know the differences of the osmotic work level  between both fishponds. The result that is got shows the average of the osmotic work level at Morosari with range salinity 28 ^o/_oo as much as  235,26 mOsm/l H₂O and at Tambakbulusan with range salinity 14 – 20 ^o/_oo as much as 173,875 mOsm/l H₂O. There were differences of the osmotic work level that was so significance (p<0,01) between fishpond at Morosari and Tambakbulusan Villages. Milkfish at Morosari has osmoregulation hypoosmotic pattern and hyperosmotic at Tambakbulusan. The growth of Milkfish in fishpond at Morosari and Tambakbulusan Villages had the characteristic of positive allometric with b value in each fishponds as much as 3,232 and 3,562. The condition factor of Milkfish in fishpond at Morosari village as much as 1,02 and at Tambakbulusan village as much as 1,06 that was means the body of thin fish or less-fat.