Physico-chemical parameters and Ichthyofauna diversity of Arasalar estuary in southeast coast of India

C. Raju 0 1 G. Sridharan 0 1 P. Mariappan 0 1 G. Chelladurai 0 1 0 G. Chelladurai Department of Zoology, Kamaraj College , Tuticorin, Tamilnadu , India 1 C. Raju (&) G. Sridharan P. Mariappan PG and Research Department of Zoology, Rajash Serfoji Government College , Thanjavur, Tamilnadu , India The physico-chemical changes may have the tendency to accumulate in the various organs of estuarine organisms, especially fish which may in turn enter into the human metabolism through consumption causing serious hazards. Hence, the present study was carried out to determine the physico-chemical characteristics of water and Ichthyofauna in Arasalar estuary in southeast coast of India for the period of 1 year during September 2012August 2013. The environmental parameters such as, temperature, pH, salinity, DO, silicate, nitrate and phosphate were observed from Department of Zoology, Rajah Serfoji Goverment College, Thanjavur, Tamil Nadu, India. During the period of study, air temperature varied from 28.8 to 35 C. The surface water temperature also varied from 25 to 31.5 C. The monthly mean values of hydrogen ion concentration of water varied from 7.1 to 8.2. The salinity of water varied from 5.5 % to 34. Dissolved oxygen in Arasalar estuary was varied from 3.5 to 7.2 mg/l. The total phosphorus varied from 0.29 to 2.15 lg/1. The nitrate varied from 0.47 to 3.75 lg/l. The silicate content varied from 28.25 to 98.74 lg/l. Totally 866 fishes were collected belonging to 4 orders and 5 families. Mystus gulio was found to be the dominant species (25.40 %) in the study area. - Estuaries have very high potential for fishery development in the wild and, therefore, are considered as the potential source for feeding, spawning and nursery ground for most of the finfishes and shellfishes. The faunal distribution and productivity of estuary depend on various physico-chemical factors such as temperature, pH, salinity, DO and micro nutrients such as nitrate, phosphate and silicate. Several investigations have been carried out on the physicochemical features of southeast Indian estuaries and Uppanar estuary (Nedumaran et al. 2011). The fluctuation of physico-chemical characters in estuarine environment has a profound influence on the occurrence of the juveniles of fish stocks. The fish communities of the Australian estuary have been investigated by (Loneragon et al. 1986; Blaber et al. 1989; Morton 1989; Moyle et al. 1986). The Arasalar estuary is located on eastern, side 100 km away from Rajah Serfoji Government College, Thanjavur, Tamil Nadu, India. It is assumed that the combination of anthropogenic activities and the discharge of domestic sewage into the estuary might influence the biodiversity of the estuarine system. The water quality and biological diversity of this estuarine area are deteriorating, mainly due to rapid increase in human settlement, industrialization and sanitation (Ragothaman and Patil 1995). Few work has been published on the physico-chemical characteristics in relation to ichthyofaunal diversity in Arasalar estuary; hence, the present study was conducted to study the physicochemical parameters and distribution of ichthyofauna in the Arasalar estuary, southeast coast of India. Materials and methods Arasalar estuary is situated at Karaikal (Lat. 10 550N and Long.79 520E) of the Bay of Bengal, southeast coast of India (Fig. 1). In the present investigation, monthly samplings were carried out from September 2012 to August 2013. Analysis of physico-chemical parameters Water and air temperature was measured using a standard Celsius thermometer with the accuracy of 0.5 C. The pH of water was recorded in the field by using Elico pH meter (model-LI-120). The Mohr-Knudsen titration procedure and Winklers method was followed for salinity and dissolved oxygen quantification, respectively (Strickland and Parsons 1972). For analysis of nutrients, surface water samples were collected in clean polyethylene bottles and kept in an ice box and transported immediately to the laboratory. The water samples were filtered using a Millipore filtering system and analyzed for total phosphorus, nitrate and silicate by adopting the standard methods described by (Strickland and Parsons 1972). Collection and identification of fin fishes from Arasalar estuary To estimate the fishery potential, a cast net measuring 2.5 m length, with a mesh size varying from 7 mm at the base and 15 mm at the apex was employed for the collection of fish throughout the period of study. The net was Fig. 1 Study area map hauled ten times during every collection at each sampling site. The collected specimens were identified up to species level. The fin fishes were identified by using the description and key given by (Day 1889a, b; Nelson 2006). Physico-chemical parameters Monthly variation in meteorological and physico- chemical parameters viz., the correlation coefficient (r) values between the environmental parameters like air and surface water temperature, pH, salinity, dissolved oxygen, phosphate, nitrate and silicate content in Arasalar estuarine water were recorded for a period of 1 year from September 2012 to August 2013 (Table 1). The north east monsoon in Tamil Nadu brings very heavy rain during the October, November and December months. The pattern of rainfall facilitates the divisions of the year into post-monsoon (JanuaryMarch) summer (AprilJune) pre-monsoon (JulySeptember) and monsoon (OctoberDecember). During the study period, air temperature varied from 28.8 to 35 C, the minimum was recorded during monsoon season (December 2012) and maximum during the summer season (May 2013) Fig. 2. The surface water temperature varied from 25 to 31.5 C. The minimum surface water temperature was recorded during monsoon season (November 2012) and maximum was recorded during the summer season (May 2013) Fig. 3. The monthly mean values of hydrogen ion concentration of water varied from 7.1 to 8.2. Maximum values of pH were observed in the summer season (May 2013) and minimum values were 40 35 0C30 ree 25 hp20 so15 tm10 A 5 0 35 30 C25 0r 20 e ta15 W10 5 0 Table 1 Correlation coefficient (r) values between the environmental parameters Atmosphere Temperature Water Temperature Fig. 2 Monthly variations of atmospheric temperature during September 2012August 2013 Fig. 3 Monthly variations of water temperature during September 2012August 2013 recorded in the monsoon seasons (December 2012) Fig. 4. The Salinity in Arasalar estuary varied from 5.5 to 34 %. Minimum salinity (5.5 %) was recorded during monsoon (November 2012) and was slowly built up during postmonsoon, and attained maximum (34 %) during summer seasons (May 2013) Fig. 5. Dissolved oxygen in Arasalar estuary ranged from 3.5 to 7.2 ml/l, while the Minimum DO was recorded during the month of June, 2013; maximum occurred in the month of November, (2012) Fig. 6. For dissolved phosphorus, the monthly values recorded in Fig. 5 Monthly variations of salinity during Septembe (...truncated)