FISH COMMUNITY STRUCTURE IN RELATION TO WATER QUALITY OF THE DOWN STREAM OF MUSI RIVER , SOUTH SUMATERA , INDONESIA

Musi River is a large riverwith its drainage area covers three provinces, South Sumatera, Lampung, and Bengkulu, and with multi uses of its resources. At the down stream of Musi River, most activities are dominated by industries with their wasle products go into the river which could harm its aquatic organism. Several assessment studies have been conducted in the Musi River, however they focused on physical and chemical aspects of the water. Aquatic organisms can reveal the real world effects of exceedences and consequent harm more precisely than can be predicted or measured on a chemical and or toxicity basis alone. Compared to other aquatic biota, fish are of particular interest for biological indicators. Species diversity and dominance are component of community structure that can be used to study several changes caused by the aquatic environment degradation The community structure of fish is frequently monitored to describe river conditions. Study in order to determine the fish community structure in relation to water quality of down stream of Musi River was conducted on April and June 2007. Sampling on physical and chemical parameters of the water and sediment, and fish sample were carried in each sampling site. Water sample was collected at a depth of 1.0 m from the water surface by using kemmererwater sampler. Some water quality parameters such as temperature, pH, and dissolved oxygen were directly analyzed in the field, while other water quality parameters such as total suspended solids, total dissolved solids, biochemical oxygen demand, nitrate, and phosphate were analyzed in laboratory. Fish sample was collected from the experiment fishing and from the fishermen. Two type of fishing gears, electrofishing, and gill net with 8 different mesh sizes were used. Fish sample from fishing experiment and from the fishermen were collected, sorted based on the species, labelled, measured for their weight and individual number, and then preserved with 10% off formaldehyde water quality parameters were analyzed using principle component analysis while fish relative abundances were analyzed with cluster. Fish community structure through simple diversity and dominance index, and proportionate abundance of species (relative abundance) were correlated with the quality of aquatic environment. The down stream of Musi River station starting from Gandus to PT. SAP station was in degradation prosses state indicated by diversity index in the range of 1to2 and high proportion of small fish than that the large fish.

Species diversity and dominance are component of community Structure that can be used to study several changes caused by the aquatic environment degradation (Odum affer Newman, 1994).The community structure of fish is frequently monitored to describe river conditions (Schiemer, 2000).ln addition, Ganasan & Hughes (1998) mentioned that the presence, absence, and proportionate abundance of species within fish assemblages indicate the quality of the physical, chemical, and biological condition in which they live.
The objective of this study was to determine the community structure of fish in relation to water quality of the down stream of Musi River, South Sumatera lndonesia.

MATERIALSAND METHODS
Field survey was conducted at the down stream of Musi River, South Sumatera Province of lndonesia onApriland June 2007.Seventeen sampling stations were set up based on the characteristic of microhabitat such as the condition of riparian vegetation, the tributary and industrial area (Figure 1).
:rftryii:-* '%.Sampling station for physical and chemical water quality parameters and fish sample at the down stream of Musi River, South Sumatera, lndonesia.

Fish Sampling
Fish samples were collected from the experiment fishing and from the fishermen.Two type of fishing gears, electrofish ing, and g ill net with experiment were used (Nakashizuka & Stork, 2002).Electrofishing is the single most effective gear for obtaining fish assemblages (Yoder & Smith, 1999).The specification of the electrofishing used was generator with power source of 2,500 W, amperage output of 4A, volts DC output of 500, and it was equipped with a scoop net.The gear was set up in the motor boat and operated to downstream direction at 0.5 km length during the daylight.ln each sampling station, electrofishing was operated at both side of the river.ln each side, the electrofishing was operated two times.
Gill net experiment was carried out in each sampling stations.A sets of gill net with B different opening mesh sizes, 0.75, 1.0, 1.25, 1.5, 1.75,2.0,2.25, and 2.5 inche was operated at each size of the river of each sampling stations with operation time approximately 4 hours.ln addition to the fishing experiment, fish sample was also collected from the fishermen using different fishing gears such as electrofishing, gill net, and barrierand fence.Fish sample from fishing experiment and from thefishermen were collected, sorted based on their species, labelled, measured for their weight and individual number, and then preserved with 10% of formaldehyde.ldentification of fish species was continued in the laboratory by using Kottelat et al. (1993);Weber & Beaufort (Vol. 1911-1940).

Data Analysis
Fish data was tabulated and anaiyzed further for their diversity and dominance indexs, and relative abundance by using the formula as follows: Relative abundance: Diversity indexs can be used to determine the status of aquatic environment degradation (Wilhm & Dorris, 1968afferMason, 1981).Avalue of H' greaterthan 3 indicated clean water, value in range 1 to 3 were characteiistic of moderately polluted condition and values less then 1 characterized heavily polluted conditions.
Simpson Dominance lndexs (Odum, 1971): Watef quality parameter and relative abundance of fish were tabulated and analyzed with multivariate analysis.Water quality parameters were analyzed with principal component analysis while relative abundance of the fish calculated with cluster analysis by using statisca version 6 software program.All data were checked for their normal distribution before analyzing -0.5 Figure 2. with these multivar.iateanalysis.Non normal distribution data were transformed with standard transformation formula as described by Krebs (1989).

Spasial Distribution of 'Physico Chemical
Parameter Principal component analysis on correlation matrix of physico chemical parameters of the down stream of Musi River on April and June indicated that the variance at the first, second, and third axis on April was 38.45, 17.89, and 14o/o respectively.The total variance of these three principal components was 70.34o/o,less than that the total variance recorded on J une which w as 7 8.02% (Figure 2 to 4).More variance that can be explained on June measurement may relate to the slow water current and water discharge during that time.Eventhough the water volume and water discharge were not measured in this study, it can be indicated by lower water depth and slower water current on June than that onApril (Figure 5).Principal component analysis showed that there were six groups of station both on April and June observations.The first group were consisted of station Pulokerto, Gandus, and Muara MusiKramasan.The second groupwas Musill, Muara Ogan, and Wilmar.
The third group were Pusri, Hoktong, and Kundur River.
The forth were PT.SAP, Borang, total suspended solids, and the fifth groups were Upang, Pre Cemara, r--r Depth Iune)

Sampling *ation
Water depth and current of the down stream of Musi River on April and June 2007.
dissolved solids and organic matter but high phenomenon since this two group closed by to the concentration of hardness and nitrate.ln June, itwas similar except for extreme high conductivity and total dissolved solids, while in April, the third group was characterized by low hardness and high in ammonia, while in June, the water quality was in moderate concentration.ln April the fourth group was characterized by low in total suspended solids and total dissolved solids, while in June .itwas characterized by high in ammonia.Analysis of diversity index revealed that in April, the diversity index in all station were less than 1 while on June it was in the range of 1 to 2 in most of stations, except at station Pusri and Teluk Buyut.Low diversity index on April could relate to the effectiveness of the fi sh ing gear due to hig h water depth and water current.The diversity index in the range 1 to 2 showed that aquatic environment was in the degradation process.According To Whilm & Dorris (1968) affer Mason (1981), the environment was in degradation process if the diversity index in the range of 1to3.A more clear picture on the condition of fish community structure can be extrated from dominance index (Figure 6).High Simpson lndex at station Pusri and Selat Cemara supported the statement earlier on the low diversity index in both stations.It can be summarized that fish community structure through simple diversity and dominance index, and proportionate abundance of species (relative abundance) can be used to determine the quality of aquatic environment.Musi River station Gandus to PT. SAP was in degradation process state indicated by diversity index in the range of 1 to 2 and high proportion ol small fish than that the large fish.

GONCLUSSIONS AND RECOM EN DATIONS
Fish community structure through simple diversity and dominance index, and proportionate abundance of species (relative abundance) can be used to determine the quality of aquatic environment.The down stream of Musi River starting from station Gandus to PT. SAP was in degradation process indicated by diversity index in the range of 1to2 and high proportion of small fish than that the large fish.lt recommend to find the alternative way to reduced total dissolved solids resulted from sand mining in Musi ll station, and ammonia and nitrite concentration of Pusri and Hoktong stations.
number pi = ni/Ni ni = individual number of species-i Ni = total individual number of species in station-i lndex ni = individual number of species-i Ni = total individual number of species in station-i
Figure 6.Dominance index of fish at the down stream of Musi River.
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The fifth and the six group had characteristic almost similar with high concentration of allwater quality parameters, except for low ammonia content of group six in April.The first station group was located at the upper part of other station.Most of activity in this area was rice field with some of two rubber factory and one soya ketchup industry.A better water quality in this stations than that other stations was indicated by low to moderate concentration of physico chemicalwater parameter.The second station group, which is closed by to the first group, the extreme increasing in conductivity and total dissolved solids concentration in June might relate to sand mining activity located to Musi ll stations.As already mention earlier that low water depth and slow water current was suitable for sand mining activities.ln the third group, high concentration of ammonia onAprilcould relate to the presence of in organic fertilizer industry.High concentration of most of water quality parameters in fifth and six group was mostly influence by the natural mouth of the Musi River.April the number species recorded was 55 species or 49.11o/o of totalspecies found, while in June itwas 105 species or 93.75o/o of the total species.High percentage of fish species found in June might relate to shallower water depth and slower water cu rrent than that in April.This condition make the chance of fish was captured by most of fishing g€ars; According to Hughes & Oberdoff (1998);Welcomme (2001), fishing activity in large river mostly affected by the water depth.Electrofishing was more effective operated in shallowwater than that in deep water. ln