DISTRIBUSI DAN KELIMPAHAN LARVA IKAN DI PERAIRAN SELAT DAN ESTUARIA BENGKALIS BERDASARKAN FASE BULAN GELAP DAN BULAN TERANG

Abstract

Stadia awal dari kehidupan ikan berupa larva ikan (fish larvae) setelah telurnya menetas. Fase larva merupakan tahap awal kehidupan ikan yang sangat menentukan regenerasi populasi ikan secara alami. Tujuan penelitian adalah untuk mendapatkan informasi tentang distribusi dan kelimpahan larva ikan di perairan sekitar Pulau Bengkalis, Kabupaten Bengkalis, Provinsi Riau. Pengambilan sampel larva dilakukan selama 8 bulan pada 2015 yaitu mulai April, Mei, Juni, Agustus, September, Oktober, dan November. Stasiun pengambilan sampel ditentukan sebanyak 16 dengan stasiun 1-5 mewakili perairan laut, stasiun 6 – 10 mewakili muara sedangkan 11 – 16 mewakili sungai. Waktu sampling disesuaikan dengan fase bulan saat mana April, Mei, Agustus, dan September adalah mewakili bulan gelap sedangkan Juni dan Oktober mewakili bulan terang. November mewakili keadaan netral. Selain larva ikan, juga dilakukan pengamatan variabel oseanografi seperti kecerahan, arus, suhu, salinitas, plankton, pH, dan kadar oksigen. Hasil penelitian menunjukkan kelimpahan larva ikan di perairan Pulau Bengkalis cukup bervariasi. Kelimpahan berkisar antara 702 – 2761 ind/1.000 m³. Kelimpahan tertinggi ditemukan pada September dan terendah pada Agustus. Sebaran larva berpindah pindah lokasi menurut perubahan waktu, pada April kelimpahan tertinggi terjadi di Sungai Siak; pada Mei beralih ke Selat Bengkalis, Juni terjadi di sungai Pakning, Agustus berpindah ke Sungai Siak, selanjutnya September dan Oktober terjadi di Selat Bengkalis, pada November tercatat kelimpahan tertinggi larva ikan kembali di Sungai Siak. 

Fish larvae is part of meroplankton, early life stage of fish after the egg hatched. The objective of this study was to obtain information on fish larvae distribution and abundance in waters around Bengkalis Island, Kabupaten Bengkalis, Riau Province. Samples were collected during 8 months (April, May, June, August, September, October and November) in 2015. There were 16 stations which represented different oceanographical situation : station 1 – 5 represent coastal water, 6 – 10 represent estuarine waters and 11 – 16 represent river. Term of sample collection was adjusted to the moon phase, where April, May, August and September represented dark moon while June and October respresent new moon. November represent neutrality. Along with fish larvae, some oceanographic variables such as current, temperature, salinity, plankton, pH and dissolved oxygen was also collected. Results showed that fish larvae abundance varied between months. Abundance ranged between 702 – 2761 ind/1.000 m³ with the highest abundance in September and the lowest in August 2015. Fish larvae distribution also varied between months and location. The highest abundance in April was in Siak River, on May it was in Bengkalis strait, June in Pakning River, August in Siak River, September and October was in Bengkalis strait, while in November in Siak River.