Longitudinal Patterns of Population Structure for Fishes Inhabiting River Tawi in Jammu region ( J & K )

The present study, was carried out to investigate the diversity and assemblage structure of ichthyofauna of both upstream and downstream section of river Tawi from four different sections i.e. Station I (Chenani), Station II (Jhajjar kotli), Station III (Nagrota), and Station IV (Gujjar Nagar). The sampling was done from January 2016 to December 2016. The results of present investigation revealed the occurrence of twenty one fish species in all the study stations belonging to five orders viz. Cypriniformes, Mastacembeliformes, Synbranchiformes, Perciformes & Siluriformes and 6 families i.e. Cyprinidae, Nemachilidae, Mastacembelidae, Chinnidae, Sisuridae and Bagaridae. In all the study stations Cyprinidae was found to be dominant (62%) followed by family Nemacheilidae, (9%) Mastacembelidae, (9%) Channidae, (10%) Sisuridae and Bagaridae showed least contribution of 5% each. The fish diversity indices i.e. Shannon weiner (H) and Evenness (e) at all the stations were 1.286 & 0.7234, 1.662 & 0.753, 1.959 & 0.5454 and 1.978 & 0.4252 at station I, II, III and IV respectively.

Fishes are the major component of an aquatic ecosystem, as they provide the nutritious and delicious food for mankind.They are indicator of aquatic health, and also play significant role in ecosystem preservation.They play major role in enhancing the economy of nation.India is one of the mega bio-diversity countries in the world, and occupies 9 th position in term of fresh water diversity.In India there are 2,500 species of fishes of which 930 live in fresh water and 1,570 are marine (Kar et al, 2003).
The share of riverine fisheries in total inland fish production may not be significant, but being the prime source of original fish germplasm, their role becomes crucial for conservation of fish diversity.Moreover, millions of fisherman and their families depend on rivers for their livelihood.Rivers, the life line of our country are a vast repository of unmatched biological wealth.With catchment areas of 3.12 million sq.kms, 14 large (covering 18.3% of drainage area) and 44 medium and minor river system are characterized by highly diverse aquatic communities.
Biological communities reflect the pattern of habitats.In smaller headwater areas and small specialized habitat features, the variety of species may be small.As the size and complexity of habitats incease so too the potential size and variability of fish community.Within the river system, the number and types of species will fluctuate with the variability of habitats.Modification of river system can have serious implications for the sustainability of communities.Dams, water withdrawal, canalization, pollution, modifications of erosion and deposition patterns, and other features contribute to an alteration in the pattern and quality of habitat.J&K region is endowed with potentially rich and varied aquatic resources amendable for fisheries.Most of the area encompasses hill regions from where the rivers, streams and its tributaries meandered in plains and valleys.Moreover, these hill streams are in more precarious conditions as regard to their ecological status because of their metastable eco-geography.
Since most of lotic water bodies in upper reaches of Jammu region have not thoroughly being explored, with hardly any information regarding the fish composition, distribution and population dynamics, primarily on account of inaccessibility to these regions due to presence of deep gorges, narrow valleys and due to meager transport facilities.
Thus, regular documentation and management of fresh water fishery of these sensitive lotic water bodies requires immediate attention to access the ecosystem health, fish community structure, and distribution patterns and to develop management and conservation strategies.Therefore, the present research work has been designed to raise first-hand information on various aspects of population structure in the various sections of river Tawi.

Collection and identification
During present study fishes were monthly captured from January to December 2016 by using different types of nets i.e. cast net, drag net, hand/ dip net.Collected fish samples were preserved in 10 % formalin for detailed examination.The collected specimens were sorted at species level and all the species obtained were counted.Species identification and confirmation were carried out using available literature (Day, 1958;Talwar and Jhingran, 1991;Jayaram 1999).

Population studies
Information on structure of fish assemblage was extracted by using different univariate indices, namely Shannon diversity index, Simpson index, Margalef Index and Evenness Index.

Shannon's Diversity index (H) H=-Spi In pi
Pi=ni/N Ni=Number of individuals of each species in the Sample.N=Total number of individuals of all species in the sample ii. Simpson's index (D) D=S (n-1)/N (N-1) n=the total number of organisms of a particular Fig. 1-4.Showing contribution of fish species at all the study stations i.e.I, II, III, & IV species.N=the total number of organisms of all species.iii.Margalef's Index Margalef's index was used as a simple measure of species richness (Margalef, 1958).Margalef's index = (S -1) S = total number of species N = total number of individuals in the sample In = natural logarithm iv Pielou's Eveness For calculating the evenness of species, the Pielou's Evenness Index (e) was used (Pielou, 1966).e = H / In S H = Shannon -Weaver diversity index S = total number of species in the sample.

RESULTS AND DISCUSSION
During the present investigation, for a period of one year (January 2016 to December 2016) a total of 21 fish species belonging to five orders viz.Cypriniformes, Mastacembeliformes, Synbranchiformes, Perciformes and Siluriformes and 6 families i.e.Cyprinidae, Nemachilidae, Mastacembelidae, Chinnidae, Sisuridae and Bagaridae including variety of fishes were present i.e.Cold water, warm water, food fishes and ornamental fishes etc.In all the study stations Cyprinidae was found to be dominant (62%) followed by family Nemacheilidae, (9%) Mastacembelidae, (9%) Channidae, (10%) Moreover, a comparative study of various stations revealed that there was more abundance of cold water fishes in upstream sections (Station 1) whereas downstream section (station IV) showed more abundance of hardy warm water fishes.Similar abundance pattern of both cold and warm water fishes was also advocated by Sharma and Dutta (2010), while studying the ichthyofaunal diversity of river Basantar, an important tributary of river Ravi.Andotra (2014) in river Tawi and Gandotra and Poonam (2015) who also reported that there was more abundance of cold water fishes in upstream sections of Rajouri district whereas downstream sections showed more abundance of warm water and hardy fishes.
Further, during the present study fish diversity indices i.e.  5).The result thus, clearly shows that maximum number of abundance and species diversity was found at station IV (downstream) and minimum at station I i.e. (upstream).The diversity indices of all the four longitudinal sections of river Tawi during present investigations shows inconsistency at all the study stations these variations may be due to variation in habitat and different conditions of selected sites such as food availability, primary production of plants and alga, bottom type depth, marginal vegetation, water current, substrate and temperature etc. Present findings are in line with other workers who also correlate rich diversity in downstream rivers with better food availability, breeding sites and water depth (Marais, 1988;Welcomme, 1985;Hina, 2010;Khajuria et al., 2013;Andotra, 2014;Samal et al,. 2016).

CONCLUSION
The present study on diversity and abundance of Ichthyofauna at four different longitudinal sections of river Tawi, clearly discloses that all the study stations has ample number of fish species and variety which shows that habitat of river Tawi is conducive and can be used for aquaculture.The data also revealed that all the stream sections harbour food fishes and majority of them with some ornamental values.In order to conserve these valuable resources, a holistic approach integrating the concept of sustainable development and conservation measures should be adopted which will not only increase the economy but also provide employment to the rural folk.

Table 1 .
Showing fish abundance and percentage at station I (Chenani).For the year January to December 2016.(Upstream)

Table 2 .
Showing fish abundance and percentage at station II (Jhajjar kotali).For the year January to December 2016

Table 3 .
Showing Fish abundance and percentage at station III (Nagrota).forthe year January

Table 4 .
Showing Fish abundance and percentage at station IV (Gujjar Nagar).for the year January 2016-December 2016 (Downstream)

Table 5 .
Showing Fish species Richness, Abundance and diversity indices of four longitudinal sections of river Tawi Fig. 5. Graph showing various diversity indices at four different longitudinal sections of river Tawi Shannon weiner (H) and Evenness (e) revealed that value of H and e was 1.286 & 0.7234, 1.662 & 0.753, 1.959 & 0.5454 and 1.978 & 0.4252 at stations I, II, III and IV respectively (Table 5 & fig,