RELATIONSHIP OF WATER QUALITY PARAMETERS TO ICHTHYOFAUNA COMMUNITY STRUCTURES IN THE INLAND WATERS OF SIBERUT ISLAND. The study is aimed to determine water quality parameters that have the greatest influence upon species composition, species diversity index and ichthyofauna biomasa in the inland waters of Siberut island. Sampling was conducted using a cash-net of I cm meshsize which was operated ten times at each station. Water samples were preserved and analyzed following the methods as described in Standard Methods (Rand et al. 1975).
Fish samplings have been conducted at 49 stations for two years (1993 - 1994) and the results showed that only at 27 stations (55. 1%) were fish samples obtained, which contained 19 species. These 19 species belong to eleven families. One species of Cvprinidae, Puntius binotatus, was found dominating the fish populations in the tributaries, which showed a patchy horizontal distribution pattern.
The existing fact showed that a relatively low fish biomass (1.45 0.89 g/m
2 or 14.2 kg/ ha) and a low index of species diversity (0.377 +/- 0.178) were found in Siberut island waters. Fish species diversity was significantly correlated to temperature only (r* = 0.53; P = 0.05; n = 27), whilst fish biomass was very significantly correlated multiply to both ammonia and conductivity (r* multiple = 0.69; P = 0.01; n = 27). Other limnological parameters, i.e., pH, N-nitrate, dissolved oxygen, total ortophosphate P (P0
4), conductivity (uS/cm) and current velocity were also multiply correlated to fish biomass. How the water quality parameters influence the fish biomass and the fish species diversity is discussed.