Assessment and Composition of Fish in the River District Maro Merauke

. Maro River is one of the major rivers in Merauke Regency that has a width of about 43-900 m and length of 300 km. The purpose of this study is to find out the type and composition of fish caught using gill net in Maro River, Merauke Regency. This study was conducted in Maro River, Merauke Regency from May to June 2014. It was conducted using survey method. The data analysis included: species composition, relative abundance, availability frequency, diversity index and dominance index. The results of showed 1,084 fish in 17 species with the following composition; 490 of Kurtus gulliveri species (37,01%), 212 of Eleutheronema tetradactylum species (20,33%), 170 of Polydactylus plebeius species (16,30%), 75 of crassilabris Cinetodus species (7,19%), 64 of Cinetodus froggatti species (6,14%), 37 of Argyrosomus amoyensis species (3,55%), 20 of Mugil cephalus species (1,92%), 15 of Megalops cyprinoides species (1,53% ), 15 of Thryssa scratchleyi species (1,4%), 12 of Lebtobrama sp species (1,15%), 9 of Lates calcarifer species (0,86%), 7 of Marilyna meraukensis species (0,67%), 7 of Scomberomorus commerson species (0,67% ), 5 of Nibea squamosal species (0,48%), 4 of Rhinoptera javanica species (0,38%), 3 of Harpadon microchir species (0,29%) and 1 of Datnioides campbelli species (0,10%). Based on the availability frequency, there are 37 species with a percentage of 100%, 37 species with 67% and 7 species with 33%. The diversity of fish has a moderate value of 1<H’<3. The obtained dominance index value is close to 0, then it is stated that there is no species found to be dominant.


INTRODUCTION
2. RESEARCH METHOD

Location and Time of Research
The research is conducted from May to July 2014 at the Maro River in Gudang Arang, Maro Village, Merauke Regency.

Tools and Materials
The tools used in this study were gill net (with a mesh size of 1 and 2 inch), boats, cool box, thermometer, pH meter, salinometer, analytical scales, hanging scales, plastic jars, plastic tray, tweezers, tissue, bucket , camera, stopwatch, fit bottle, raffia string, GPS, calculator, ruler, stationery, notebook and identification book. The materials used were ice cubes and types of caught fish.

Research Method
The method used in this research was survey method. Soehartono (1995) [6] suggests that the survey method is a method to obtain the existing data at the time of research conducted. This survey method can be a descriptive survey which aims to collect information a number of samples of people, object and others [7]. Such descriptive research uses survey method, while the data collection techniques used were as follows.

Observation
Sampling was conducted every Monday, Wednesday and Friday with 3 repetitions. The sampling technique used was purposive random sampling [8].

Interview
Interview is a data collection technique in survey methods that uses verbal questions to research subjects, which is conducted if the researcher needs communication to the respondents [6].

Research Procedures 2.4.1. Measurement of physical factors, water chemistry
Measuring the water temperature, flow velocity, salinity and water pH.

Collection of specimens or samples
Sampling was done every Monday, Wednesday and Friday with 3 repetitions. The sample of fish was taken at low tide at three locations or stations, namely station 1 located in Estuary which is ± 5 km away before the meeting point with location II in Floodgate which is ± 5 km away after the meeting point with location III which is on the Cape. Fish sampling at each location was done at three points, i.e., the right, middle, and left bank of the river. In the right and left bank, fish sampling was conducted by using the gill net with a mesh size of 1 inch and in the middle bank by using the gill net with a mesh size of 2 inches.
The samples were collected in mesh pockets at each of the three stations: station I (Estuary), station II (Floodgate) and station III (Cape).

Identification of Fish
The identification was conducted by using manual identification (Allen, 1989, and Allen 1991) [9,10] to determine the name of the collected species.

Data Analysis
The data analysis used descriptively is to process data obtained in field and compare with literature study. [16]

Type Composition
The type composition was obtained from the data of the size and number of nekton species obtained from each location with a predetermined station [12].

Relative Abundance
The calculation of relative abundance of each species was conducted by calculating the percentage of the number. The equation used was [13] Information : Kr = relative abundance ni = i-th individual species N = total number of individuals of all species

Availability Frequency
Availability Frequency was used for showing the spread of local distribution of certain species. This is evident from the frequency (%) of fish caught by using the following equation [14] Information : Fi = availability frequency of i-th caught species (%) ti = the number of stations in which the i-th species is caught T = the number of all stations

Diversity Index
In order to determine the diversity of fish, it used the Shannon-Wiener index [15]:

Determination of Criteria:
The ranges of diversity index value, according to Kreb (1989) are as follows: (1). H' < 1 : low diversity, narrow spread of individual species and low community stability. (2). 1<H'<3: moderate diversity, moderate spread of individual species and moderate community stability. (3) H'>3 : high diversity, high spread of individual species and high community stability.

Dominance Index
In order to determine whether the fish are available, the Simpson's dominance index was used, as follow (Odum, 1996): Legendre, (1983) states the value of dominance index ranges from 0-1; index 1 indicates very high dominance by one species (there is only one type in one station). While index 0 indicates that there is no dominance among the species found. Based on Table 1, there were 17 fish species caught in Maro River in Gudang Arang. Based on Table 1, there were 17 fish species found in station I, 7 species found in station II and 10 species found in station III.

Composition of Species
Based on the results of research conducted in Maro River, Gudang Arang, Maro Village, Merauke Regency, there were 17 species with total composition of fish caught can be seen in Table 2. Based on the results (Table 2)  Based on the results in Table 3, the highest relative abundance is found in Nurseryfish (Kurtus gulliveri) in Station III with a percentage of 39,61%. From the data in Table 3, the highest number of fish species caught is in station I with a total of 687 fish and the lowest is in station II with a total of 101 fish.

Availability Frequency
The Availability Frequency based on location of observation can be seen in Table 4. The results of Table 4 show the value of the availability frequency of the fish species in each station. The availability frequency value is related to the area of distribution. The greater the availability frequency value, the greater the area of distribution. The availability frequency value of fish species shows that there are 7 species with the percentage of 100% availability, means that the species have widespread distribution. Meanwhile, there are 3 species with a percentage of 67% availability, indicating moderate distribution and 7 species with a percentage of 33% availability, indicating the low distribution.

Diversity
The diversity based on the observation location can be seen in Table 5 below.  The diversity index value ( Table 5) of species of fish caught for three months in Maro River, Gudang Arang, is 1,8973. This result indicates moderate diversity, moderate distribution of individual number of each species, and moderate community stability.

Dominance
The dominance index based on the observation location can be seen in Table 6 below The value of dominance index (Table 6) of the type of fish caught for three months in the Maro River, Gudang Arang, is 0,21622669. This result shows that, among the species found, there is no dominance. Furthermore, based on the overall species of fish caught, the highest dominance index value, in general close to 0, is found in Kurtus gulliveri in Station 3 with a dominance value of 0,15689521.

Physical Parameters and Water Chemistry
The results of physical parameters, water chemistry, can be seen in Table 7 below: