Heterogeneity habitat of three threatened freshwater catfishes

the day (7 H to 13 H). The nets (75×1.3 m, 50×1m, and 30×1m) were weighted

bottom sets with varied mesh sizes ranging from 2.5 to 7cm. All fish specimens

were identified following Jayaram (1999), Talwar and Jhingran (1991).

Pysicochemical Characterization

Environmental variables were measured each time in the same site where fishes

were sampled. Eleven environmental variables were used to interpret the variation

in species composition (Table 1). The physical and chemical variables followed

were temperature (°C), turbidity (NTU), water flow (cms), depth (m), conductivity

(µmhoscm), total dissolve solid (TDS) (ppm), dissolve oxygen (DO) (mg.l) and pH.

Water temperature, conductivity, pH, TDS and DO were measured by Cyber Scan

Waterproof PC 300 multiparameter at the sampling locations. The total percentage

of each substrate class was calculated using transects within each sampling

site. The dominant substrate material for each sampling site was determined by

inspection and striking the river bottom with a bamboo pole. Substrate classes

included sand (0.06–2mm), gravel (2–64mm) and cobble (64–250 mm) according

to Bain and Stevension (1999) with some modifications.

Table 1. Environmental variables mean (standard deviation in parenthesis) and ranges

from the 40 sampling sites in different rivers

Variables

Mean

Range

Water flow (cm/sec)

22.6 (10.5)

11.21-39.70

Depth (m)

3.38 (1.7)

1.10-6.47

Temperature (ºC)

22.98 (3.6)

16.22-26.8

Dissolved Oxygen (mg/L)

5.4 (1.1)

3.3-7.20

pH

7.14 (.4720)

7.0-8.4

Turbidity (NTU)

17.88 (13.3)

6.21-80.2

Conductivity (µS/cm)

414.16 (207)

165-667

Total Dissolved Solids (ppm)

223.4 (127.1)

110-589

Fine Substrate (%)

46.75 (32.4)

0.01-86.2

Fine Gravel (%)

22.2 (16.2)

0.01-65.2

Coarse Gravel (%)

16.37 (17.7)

0.01-69.3

International Journal of Bioinformatics and Biological Sciences : v.2 n.3&4. Dec. 2014

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