ASPEK PERTUMBUHAN DAN REPRODUKSI IKAN NILEM (Osteochilus hasselti) DI PERAIRAN RAWA PENING KECAMATAN TUNTANG KABUPATEN SEMARANG

Abstract

Rawa Pening merupakan perairan umum yang potensial di Jawa Tengah dan tempat mata pencaharian utama bagi nelayan sekitar. Ikan Nilem (Osteochilus hasselti) adalah salah satu ikan air tawar asli perairan umum Indonesia yang dapat ditemukan di Rawa Pening. Saat ini ikan Nilem dieksploitasi tidak hanya untuk dikonsumsi dagingnya saja tetapi juga telurnya. Oleh karena itu perlu dilakukan pengelolaan agar stok ikan di alam tetap terjaga dengan  mengkaji dari aspek pertumbuhan dan reproduksi. Penelitian ini bertujuan untuk mengetahui beberapa aspek pertumbuhan dan reproduksi ikan Nilem serta strategi pengelolaan yang baik. Penelitian ini dilaksanakan pada bulan Januari 2014– Maret 2014 di Rawa Pening Kecamatan Tuntang. Metode penelitian yang digunakan adalah metode survey yang bersifat deskriptif, dengan teknik pengambilan sampel simple sensus sampling. Data yang digunakan yaitu data primer. Pengambilan sampel dilakukan setiap 2 minggu sekali. Selama penelitian didapatkan 78 ekor sampel. Hasil penelitian menunjukan bahwa sifat pertumbuhan ikan Nilem adalah alometrik negatif, dengan nilai b sebesar 2,8392. Faktor kondisi ikan Nilem sebesar 1,144 yaitu kurang pipih (bertubuh kurus). Ukuran rata – rata pertama kali tertangkap ikan Nilem 135 mm dan ukuran pertama kali matang gonad 102,93 mm, menunjukkan ukuran tersebut layak tangkap. Tingkat Kematangan Gonad didominasi TKG IV dan V yaitu dalam keadaan matang gonad. Nilai Indeks Kematangan Gonad tertinggi ikan betina diperoleh 45,32%  sedangkan IKG tertinggi pada ikan Nilem jantan sebesar 23,07%. Fekunditas tertinggi sebanyak 156.695 butir sedangkan nilai fekunditas terendah sebanyak 2966 butir. Perbandingan jantan dan betina 1:1,29. Strategi pengelolaan yang dapat dilakukan adalah dengan cara mempertahankan ukuran mata jaring, mengurangi intensitas penangkapan dan penegakan hukum.

Rawa Pening is a water source which is potential in Central Java and the main livelihood for fishermen living around. Nilem fish (Osteochilus hasselti) is one of the native freshwater fish in Indonesia, and can be found in Rawa Pening. Currently, Nilem is exploited not only for its meat but also its eggs to be consumed. Therefore, it is necessary that conserving fish in nature should be examined based on the aspects of growth and reproduction. The research was intended to determine some aspects of reproduction and growth, as well as good management strategy. The research was done from January 2014 – March 2014 in Rawa Pening, District Tuntang. The research method used was descriptive survey using simple sampling method to collect the data. Primary data was used in the research and the sample was done once in two weeks. During the study 78 samples obtained. The results of the research has shown that Nilem has negative alometric growth showing b value as much as 2,8392. The condition factor of Nilem has indicated that the fish was flat (thin) based on value 1,144. The average first caught Nilem has the size 135 mm and the first measurement of gonad maturity was 102,93 mm, showing that the fish was suitable catching. The gonad maturity was dominated by level TKG IV and V, showing that the fish were mature. The highest index of gonad maturity in female fish was 45,32%, while in male fish was 23,07%. The highest fecundity was 156.695 while the lowest was 2.966. The ratio of male and female fish was 1 : 1,29. The management strategy that can be use were maintain the mesh size, minimize the intensity of catch and law enforcement.