ABSTRAK Sungai Siak merupakan sungai yang penting keberadaannya di Propinsi Riau, Sumatera, karena mengingat sungai tersebut biasa digunakan untuk berbagai keperluan masyarakat yang hidup di sepanjang sungai ini. Air sungai ini antara lain digunakan sebagai sumber air minum, mandi, mencuci perkakas dapur dalam rumah tangga, habitat ikan, sumber bahan baku industri dan transportasi. Akan tetapi dengan serbagunanya sungai Siak ini, berbagai tekanan terhadapnya makin besar yaitu pencemaran limbah

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... ndustri, erosi tanah dan sedimentasi, abrasi pinggiran sungai/pelebaran sungai dan menurunnya jumlah jenis dan jumlah populasi sumberdaya ikan yang biasa dimanfaatkan oleh masyarakat sekitar sungai. Oleh karena itu perlu dilakukan penelitian untuk mengkaji jenis-jenis ikan dan gambaran populasinya yang masih ada di Sungai Siak, selain mengukur beberapa parameter kualitas air di Sungai Siak yang mempempengaruhi kehidupan jenis-jenis ikan di sungai tersebut. Dua metoda utama digunakan dalam penelitian ini, yaitu wawancara dengan responen dan pengukuran langsung beberapa parameter kualitas air di lapangan, serta analisis sampel air di laboratorium. Hasil penelitian menunjukkan bahwa telah tercatat 36 jenis ikan di Sungai Siak. Beberapa jenis ikan masih relatif banyak ditemukan di sungai Siak yaitu baung, juara dan selais, dan yang jarang adalah patin, belido, gabus dan udang air tawar. Keanekaan jenis ikan di sungai Siak apabila dibandingkan dengan sungai-sungai yang ada di Kawasan Propinsi Riau cenderung relatif rendah, mengingat hasil penelitian di sungai di sekitar Bukit Tigapuluh, Siberida tercatat 97 jenis. Berdasarkan pengukuran di lapangan dan analisis laboratorium beberapa parameter kualitas air, hasilnya menunjukkan bahwa telah melampaui baku mutu kualitas air berdasarkan PP 20/1990 yaitu TSS, pH, BOD, COD, serta logam Zn, Fe, Mn dan F. Kata kunci: jenis ikan, populasi ikan, kualitas air, sungai Siak, Riau, Sumatera. FISH SPECIES DIVERSITY IN SIAK RIVER, RIAU ABSTRACT Siak river has been considered to have an important role in Province of Riau, Sumatra, because the Siak river has been variously used by local communities who reside along this river. For instance, water river are used as a source of drinking water, bathing, washing, fish habitat, source of industry and for water trans fortation. However, due to multifunction of the Siak river, some environmental stresses on this river have been increasing over time, such as industrial polutions, soil erosion and sedimentation, river bank abrasion/widening of river, and decreasing fish species and population which are commonly used by local communities. Therefore, study on fish species and its population in the Siak river, and measurement of some parameters of water quality that can determine fish life in this river have been conducted. Two main methods were used in this study, namely the structure interview with the respondents and direct measurment of water quality parameters in the field and water sample analysis in the laboratory. Results of the study showed that 12 fish species were recorded in Siak River. Some fish species were relatively predominantlly recorded in Siak river, namely baung, juara and selais, meanwhile, fish species were rarely recorded, such as patin, belido, gabus and fresh water shrimps. Species diversity in Siak River compared with that in other rivers in the Riau Province has been considered to be low, since based on fish study in Bukit Tigapuluh, Siberida, 97 species were recorded. Based on direct measurement in the field and analysis of several water quality parameters in the laboratory, its result showed that several parameters, such as TSS, pH, BOD, COD, Zn, Fe, Mn, and F were recorded over water quality standard based on regulation of PP 20/1990.