Summary

The aquatic communities and more specifically fish communities are very good indicators of disturbances, and since these communities play prominent role in the aquatic food chain, their study can effectively depict the comphrehensive account of aquatic ecosystemstructure and function. The present study of fish diversity in the Linganamakki Reservoir of the upper catchment has recorded 64 species from 32 genera and 16 families. From the lower catchment, 51 freshwater fish species have been recorded. The Sharavathi estuary has a total of 44 species of fishes. The annual fish yield of both the native and introduced fishes of the Sharavathi reservoir is estimated to be 200 ton. The decline in native fish stock necessitates the stocking of indigenous and endemic fishes of Western Ghats. Prevention of over-fishing, migrant fishermen and breeding season fishing can contribute to sustainable fishery in the reservoir. Strict practice of restricted mesh size utility can minimize the death of non-target fishes. Educating local fishermen and activating the inactive cooperative society can lead to sustainable fishery in Sharavathi River basin.

Introduction

Fishes are poikilothermic aquatic vertebrates, breathe through pharyngeal gills, propelling and balancing themselves by means of fins. Presently over 28,500 fish species are known throughout the world (Nelson, 1996); of these 40% are inhabitants of fresh and inland waters. A majority of these fishes are found in the tropical waters. For instance, it has been estimated that the river Amazon and its tributaries together harbour about 3000 or more species. Likewise, it is estimated that about 2500 fish species are found in India, of which 930 species are freshwater fishes, belonging to 20 orders, 100 families and 300 genera (Daniels, 2000).

Fish diversity investigations in rivers of southern India (Chandrashekhariah, 2000) show that in Krishna River basin, 101 fish species belonging to 19 Families and 5 Orders were recorded along with Indian gangetic carps and exotic fishes. Majority of the fish species in this riverine system are endemic and 20 species are under the threat of extinction. The Cauvery river basin has 96 fish species under 23 Families and 8 Orders. Studies show that 15 fish species are on the verge of total elimination and the carps such as Puntius carnaticus, Hypselobarbus dubius and the non-predatory catfish – Pangasius pangasius were not recorded in recent investigations in Cauvery riverine zone of the state. Sixty fish species belonging to 13 Families and 4 Orders were recorded in Godavari basin. Of these, Thynnichthys sandkhol has become extinct; in addition 15 more species are under the threat of elimination.

The west-flowing rivers of Karnataka (Kali, Bedthi, Aghnashini, Sharavathi and Netravathi, etc.) have recorded 83 species belonging to 19 Families and 7 Orders. Hypselobarbus thomassi, Labeo nigerscens and Clarias dussumieri have become extinct while 9 more species are on the verge of extinction.

A study of freshwater fish diversity in Aralam Wildlife Sanctuary of Kerala (Shaji et al., 1995) found 33 species belonging to 15 families. The study found Garra mullya, Barilius bakeri and Danio aequipinnatus were the commonest and uniformly distributed species. Whereas, river Periyar of Periyar Tiger Reserve has 35 species belonging to 21 genera and 11 families. Similar studies carried out in Kalakad – Mundanthurai Tiger Reserve, and rivers in Western Ghats of Kerala (Johnsingh, 2001) reported 33 species belonging to 9 families. During the 1993 – 95 survey of freshwater fishes in two east flowing and three west flowing rivers in Kerala part of the Nilgiri Biosphere Reserve 92 species were recorded. Individually, Kabini River has 59 species, followed by River Chaliyar with 50 species and Kunthi River with 11 species. The interesting observation made in this study is the east flowing rivers were more diverse than the west flowing rivers. But almost all the species found in west flowing rivers were endemic to Kerala.

The catchment of the Sharavathi river has bountiful natural resources and houses rich biodiversity as well as enormous hydro potential. The river receives many tributaries. The major tributaries are Haridravathi near Pattarguppe and Yenneholé near Bharangi. Along with them, the minor tributaries like Nagodiholé, Nandiholé, Mavinaholé, Hurliholé and Birerholé also join this river. The water from Chakra and Savehaklu reservoirs of Chakra River has been diverted to this reservoir. Present study has been undertaken in the upper catchment of Sharavathi River with the aim of documenting the ichthyo-diversity of the basin and to study the existing pattern of commercial fishery.

Materials and Methods

Fish sampling was carried out in the Linganamakki catchment area from January 2002 to August 2004. Collections were made using Gill nets, Cast nets, Drag nets and Hooks and Lines of varying dimensions. Stratified random sampling method was adopted to locate the 29 sampling sites. In these sites, 261 samplings were made with approximately 40 samplings per season (summer, winter and monsoon). The sampling sites are shown in Figure 2. Within each site, all microhabitats of aquatic habitat (riffle zone, pools, cascade, falls, embayment, run, plunge and backwater) were also sampled using various types of nets. Fish specimens collected were fixed initially in 30-35% formaldehyde and later transferred to 4% formaldehyde. Standard keys of Jayaram (1999), Talwar and Jhingran (1991) and Day (1889) were followed for species identification. Some specimens were identified with the help of experts at the Southern Regional Station, Zoological Survey of India, Chennai.

Figure 2. Classified image (supervised classification based on maximum likelihood classifier) of the study area with major sub-basins and sampling points

Gill nets of varying mesh sizes (2 x 1”, 2 x 2”, and 1 x 5” nets) were chosen and laid in an approximate area of 200´200 m. The lengths of the nets were maintained at 100 metres. The nets were put in the evenings and removed early in the morning. The total duration of netting was 12 – 14 hours.

In case of cast net sampling, transects with an approximate length of 100 meters along the banks were laid. In each location totally 20 castings were made. Dragnets were towed to a length of about 5 meters at each towing except at inaccessible localities. Finally, benthic habitats were sampled using hooks.

Historical Information

Systematic historical data regarding fish species of the reservoir were not available. However, experienced local fishermen with fishing history of more than 30 years helped us in this regard.. The knowledge of fishery in terms of historical and present status was evident from their continuous association with the fishing activities over a long period. Most of the fishermen participated enthusiastically in discussions and shared their views and experiences in fishing and social aspects. Market information such as location, channels, seasonal demand, etc., was collected from the fish merchants. The Fisheries Department provided all available statistical data regarding seeding methods, annual income to the department, licensing pattern, etc.

Results and Discussion

Fish diversity

In the present study 64 species from 38 genera and 17 families were recorded from the Linganamakki catchment of Sharavathi river basin. Annexure 1 details the species recorded from the region with their IUCN status. The total species collected from these basin alone accounts for 6.88 % of Indian fresh water fish (930 species) and 22.2 % of Western Ghats species (288).  Based on the IUCN categories of the fish species, of the 51 species, 35.3 % (18 species) are endemic to Western Ghats, about 43.1 % (22 species) are threatened species and the remaining 19.6 % (10 species) are data deficient. This analysis excludes introduced and unidentified species.

Species composition, distribution and abundance

Considering the species richness at the family level, Cyprinidae dominated with 30 species, followed by Balitoridae and Bagridae with 7 and 6 species respectively. Among the genera, Puntius recorded 7 species followed by Schistura with 5 species. There are four introduced species and distribution of five species is unknown.

Reservoir fish composition

The native fishes like Gonoproktopterus kolus, Cirhina fulungee, Ompok bimaculatus, Mystus cavesius, Mystus malabaricus, Mastacembelus armatus, Channa marulius, etc, are largely found all over the reservoir. During the non-monsoon season these fishes form bulk of the catch in commercial fishery. Similarly, some of the catfishes like Wallago attu, Heteropneustes fossilis and Clarias batrachus are rare in the reservoir. Recently described species, Batasio sharavatiensis, from the downstream region (Bhat, 2004) of the Linganamakki dam has been collected from the upper catchment. Interestingly, the distribution of Batasio sharavatiensis is restricted to Sharavathi river basin and its occurrence seems to be occasional.

Among the four introduced species, three species (Common carp) were introduced into the reservoir. Oreochromis mossambica, a prolific breeder introduced accidentally is abundantly found in the central parts of the reservoir. During last few years, O. mossambica has spread all over the catchment including the hill streams. The translocated species like Labeo rohita, Cirhina mrigala and Catla catla contribute substantially towards fish yield especially from central parts of the reservoir only during the monsoon season.

Out of the 64 species, within the catchment, about 39 species are found in the reservoir. Of this, 25% (10 species) are endemic to Western Ghats and about 7.5% (3 species) are restricted to peninsular India. The introduced species in the reservoir accounts for 17.5% (7 species). Nearly 43.2 % (17 species) are non-endemics having distribution all over India. 

Stream fish composition

The stream habitats of the river are very diverse and account for greater endemism. The perennial streams are associated with Puntius fasciatus, P. arulius, P. sahyadriensis, P. filamentosus, Nemacheilus denisonii, Lepidocephalus thermalis, Garra gotyla stenorhynchus, etc, many of which are restricted to the Western Ghats. The species of Balitoridae are commonly found in the Sharavathi River, the Nagodi tributary and the Yennehole tributary. Schistura nilgiriensis has been reported for the first time from Karnataka from this region (Sameer Ali, personal communication). The common species of the streams include Rasbora daniconius, Danio aequipinnatus, Puntius filamentosus, P. sophore and Garra gotyla stenothynchus. These species have wider distribution including in the reservoir. The glass fishes (Parambassis ranga and Chanda nama) are very common during the early monsoon season.

The streams of the study area have 33 species of which 42.4 % (12 species) are endemic to Western Ghats. About 21.2% (7 species) of the total species are restricted to peninsular India and 36.3% (11 species) has distribution all over India. The only introduced species in the streams is Oreochromis mossambica.
Comparison between the reservoir and stream fishes composition

The comparison between the ecological parameters between these two major habitats is given in Table 63. Species richness is more in reservoir (39 species), attributed mainly to the introduced and generally distributed species, than stream habitats (33 species). However, endemism and restrictedly distributed species are more in streams compared to reservoir.

Table 63:  Ecological status of fish species in two major habitats of the catchment

Ecological Status	Reservoir	Streams
Species richness	39	33
Endemic species (%)	25.0	42.4
Restricted to peninsular India (%)	7.5	21.2
Distributed throughout India (%)	47.5	36.3
Introduced species (%)	17.5	3.0

Influence of Riparian Vegetation on Fish Distribution

During the field visits it is observed that riparian vegetation plays a determinant role in species composition. As the summer arrives there will be a great variation in day and night temperature. The rainwater dependent streams especially in the eastern part of the study area show considerable reduction in the flow. The less flow makes them sensitive to any variation in atmospheric temperature. The sparse riparian vegetations further worsen the condition by directly exposing the stream to sunlight. When this condition comes, most of the habitats for most of the fishes become unsuitable and they move to those places where there is considerable vegetation along the bank, which will maintain the stream temperature. The summer sampling in these hill streams confirmed these facts as no fishes other than Danio aequipinnatus and Aplocheilus lineatus were found in open areas. Where there is canopy cover, higher concentration of fishes both in terms of species and individuals were noticed. However, this effect was comparatively less in western part of the area as there is uniform canopy cover (throughout the year due to evergreen and semi evergreen vegetation) and more flow coupled with lower temperature (Table 64).

Table 64. Cast net summer sampling in eastern streams.

Locality	Species	Description with respect to Vegetation in sampling sites
Nandiholé	Oreochromis mossambica, Danio aequipinnatus, Salmostoma boopis, Aplocheilus lineatus	The sampled locality had absolutely no vegetation on both sides.
Haridravathi	Danio aequipinnatus, Aplocheilus lineatus	On one side paddy fields with two trees. On the other side small Acacia plantation.
Mavinaholé	Aplocheilus lineatus, Mystus malabaricus, Puntius dorsalis, Garra gotyla stenorhynchus, Chanda nama, Cirhina Sp., Danio aequipinnatus	Lophopetalum wightianum, Hopea wightianum and other trees covered over the river.
Sharavathi River	Danio aequipinnatus, Aplocheilus lineatus, Garra gotyla stenorhynchus, Chanda nama, Salmostoma boopis	No vegetation other than bamboo. But significant water flows in the river.
Hilkunji River	Danio aequipinnatus, Aplocheilus lineatus, Rasbora daniconius, Salmostoma boopis, Chanda nama, Cirhina species	Hopea wightianum and Bambusa Sp. on one side and paddy fields on other side. But significant water flows in the river.

People and Fishery

About 120 fishermen families reside in the reservoir catchment area with distinct social and cultural aspects. Among these, 70 families are permanent residents while remaining 50 families migrate from neighbouring southern states during monsoon. These families are restricted to these localities and are isolated from other localities and trade with merchants who visit this area. Generally these communities are very poor and uneducated. Their kids spend 3 – 4 years for basic education and then get into fishing.

Fishermen Communities

The communities such as Killakhyatha, Mada and migrated fishermen are engaged in fishing activities in these localities. Tamil fishermen from Tamilnadu state who were fishing in Mettur Dam of River Kaveri have migrated to Koluru area. The drawbacks in the licensing system (like one person gets the license for fishing in a family and no one else is allowed for fishing) at Mettur were one of the reasons for migration. Thus, about 20 families of fishermen have migrated about 30 years back and most of them are settled in the region.

‘Killekyatha’ or ‘Burudebestha’ communities with 50 families are found near Suttha Village of Hosanagara taluk. Some of these families migrated from the Anjanapura reservoir catchment of Shikaripura taluk. Even though these families have permanent houses in their village Suttha and reside there during festivals and other family occasions, most of the time they travel from place to place for fishing. There are five families of ‘Mada’ community engaged in fishing as seen near Malali village of Hosanagara taluk.

Management Structure

Three government agencies manage the water body based on its spatial extent. Water bodies with an area between 1 ha and 10 ha are under the control of Fish Farm Development Agency. This agency trains interested persons with a daily stipend of 25 rupees and gives the lake on a lease for 6 years. The trained person gets 50% subsidy on seeds, manure, restoration and other requirements for one year with compulsion to buy the seeds from the department and insurance; 

Water bodies with area between 10 ha and 100 ha are regulated by the Zilla Panchayaths and are given for lease on cost basis; and The Deputy Director of Fisheries regulates water bodies with more than 100 ha. Linganamakki Reservoir falls under this category.

License Pattern

Obtaining yearly license is compulsory to all the fishermen for fishing in the reservoir.  The fee structure for gill net with a length of 500 meters is Rs. 1000/- per year, cast net Rs. 300/- per year and hooks Rs. 100/- per year. The Fisheries Department data shows that at present there are about 200 license holders fishing in the reservoir area. Thus, the department is getting 1.65 lakh rupees of revenue annually from this source.

Facilities provided by the Department to the Fishermen

Fisheries Department provides housing to the fishermen at various places. Koluru village has fishermen colony of 20 houses. Under the department scheme, construction of 13 houses near Chikmathur village and 7 houses near Kippadi Village is in progress. In addition to this, iceboxes, measuring equipment, nets and bicycles to these families are provided free of cost.

Seeding Pattern

Seeds are introduced after the monsoon season in order to avoid overflow and washing, even though the seeds are to be introduced during the beginning of monsoon as per stipulations. Table 64 lists seeding pattern for the last 20 years and the quantity of seeds introduced depending on availability. The department gives least preference to the reservoir for seeding. It is seen that during the last two years, seeding quantity has reduced to a minimum.

Table 64. Yearly data on seeds introduced into the reservoir.

Year	Seeds in Lakhs (0.1 million)
	Catla	Rohu	Mrigal	Common Carp
1983 – 1984	1.643	0	0	2.21
1984 – 1985	1.278	0	0	1.62
1985 – 1986	6.8	0	0	7.42
1986 – 1987	6.81	0	0	2.48
1987 – 1988	7.87	0	0	0
1988 – 1989	4.754	0	0	0
1989 – 1990	2.95	0	0	3.55
1990 – 1991	0.85	2.783	0.312	8.41
1991 – 1992	0	0	0	4.6
1992 – 1993	0	0.42	0	5.4
1993 – 1994	1.2	5.75	0	15.058
1994 – 1995	5.3345	7.0685	0	11.418
1995 – 1996	7.266	11.07	0.35	10.605
1996 – 1997	0	26.362	0.72	9.86
1997 – 1998	3	21.885	6.03	1.25
1998 – 1999	2.448	19.016	1.12	1.4
1999 – 2000	12.115	14.374	0	0
2000 – 2001	0	0	0	5
2001 – 2002	0	0	0	3

Fishermen Co-operative Society

Fishermen co-operative society, which is located in Sagar, has presently 412 members (fishermen and fish merchants) with their share being Rs. 13,895/- and Government’s share being Rs. 10,000/-. But the fishing activities in the reservoir are more or less under the control of merchants. The Society’s efforts to market through society without any middlemen is in vain as most fishermen sell fishes to merchants due to mutual dependence of fishermen and merchants with flexible credit and services. As the fish catch is highly fluctuating over the season, fishermen borrow loans from the merchants for their livelihood and reimburse in the form of fish. The loans are as huge as Rs. 60,000/-. Due to financial constraints the society is not in a position to help needy fishermen.

Marketing

Fresh-water fish decay earlier than marine fish necessitating transportation, proper storage mechanism and marketing network. The reservoir fish is marketed in Sagar and Hosanagara Taluks and parts of Soraba, Shikaripura, Shiralakoppa and Shimoga taluks. Besides, small open market outlets at various places are established to market the fishes, including door-to-door selling on two wheelers.

Harvesting Pattern

Craft: Most commonlyused fishing craft is coracle (locally called Ukkada), constructed with bamboo thatches and covered by nylon sheets. The outer surface is pasted with tar to prevent water seeping into the coracle. 

Usually gill nets with length varying from 300 m to 500 m and with different mesh sizes (depending on the type and size of fish) are used. Net placement at different levels is also a deciding factor in harvesting types of fishes. Usually Gill nets are used for covering large area while cast nets are used for a small area. The Department has banned the use of dragnets, but certain fishermen still use dragnets for capturing large quantity of fish with less effort, which results in capturing juvenile fish that ultimately affects the fish stock. The department with meagre resources and manpower is unable to monitor and control such unauthorized activities. Fishing with hooks and lines is a hobby to many people who are residing near the reservoir.

Seasonal Fluctuation in Demand and Supply

The regional supply fluctuates between freshwater and marine fish. Marine fish is imported extensively during non-monsoon seasons from the nearby coastal districts. During this period, the availability of freshwater fish is considerably less. During monsoon season, the supply of sea fish decreases with increased availability of freshwater fish. As such the region receives continuous supply of fish throughout the year either from marine or freshwater depending on seasons.

Reservoir Yield

A systematically managed database is highly useful in assessing the yield of any reservoir, which is not available either at the fisheries department or with any other government agencies. In the absence of any historical information from any sources, an attempt could be made through fish landing sources. However, unorganized market channels in this region have complicated the data collection. Yield of the reservoir is assessed based on sampling at five localities - Lingadakai, Hasaramakki, Muppane, Holebagilu and Madenur. Landing data was collected and quantified with the help of the fishermen without interfering in their routine way of collection. Multiple sampling in the same locality was carried out considering day-to-day variations (Table 65).

Table 65. Fish-catch (kg/person/day) during the year 2001-02.

Locality	During non-monsoon season	During monsoon season
Lingadakai	1.3	No fishermen
Hasaramakki	1.75	4.3
Muppane	2.8	5.25
Holebagilu	2.1	8.4
Madenur	1.6	5.6

Table 66. Estimation of total fish yield of the reservoir.

Monsoon yield Total authorized fishermen during monsoon season   Considering 10 % extra as unauthorized fishermen, the total number of fishermen engaged in fishing are  The product of total number of fishermen and average individual fish catch gives the total monsoon fish catch per day (220´5.8875) Considering 3.5 months as monsoon period, total fish catch over this period becomes	200 220 1,295.25 kg 1,36,001.25 kg
Non-monsoon yield Assuming 60 % of the total fishermen remain engaged in fishing activities and only 5 % of the total unauthorized fishermen remain for non-monsoon season, total fishermen engaged are Total non-monsoon fish catch per day is (170´1.91) Total non-monsoon fish catch (Total non-monsoon period is 8.5 months from which 2 month are deducted for non-fishing days) is	165 324.7 kg 63,316.5 kg
Total yearly fish catch from the reservoir is	1,99,317.75 kg

This data represent the fishing using gill nets and hooks as majority of the fish catch is carried out in this manner. Monsoon data collection was done considering higher sample size (10 % extra fishermen). During the field visits it is observed that migratory fishermen are always in a group of 10 or more and few of them had fishing licenses. Illegal fishing is accounted as 10 % in yield computation. After monsoon, most of these migratory fishermen move to other reservoirs, which considerably reduces unauthorized fishing.  This is summarised in Table 66 and the total yearly catch is 1,99,317.75 kg.
 
Fishermen get Rs. 22 per kg of fish from merchants (who buy at shore) and the total gross income works out to Rs. 43,84,990.5 per year. Thus, a permanent fisherman earns annually about Rs. 22,042. 

Based on the yield computations (Table 66), the reservoir fish yield per sq. km is 610.76 kg. at full reservoir level. About 68.23 % of the total fish-catch takes place during monsoon and this quantum includes breeding season. The increased catch is due to movement of bottom dwellers to the upper strata and higher yield of introduced fish and also due to turbidity. It is noticed that some fishermen practice destructive fishing by harvesting at breeding grounds. Fishermen shift to shallow areas as the water level rises during monsoon season and these are normally the breeding ground for fishes.

Localitywise and Seasonwise Species Distribution

During the field visits, it was observed that western river Yenneholé is mainly dominated with the native species. Fishes like Cirhina reba and Labeo fimbriatus dominate the fish catch along with other species like Ompok bimaculatus, and Mystus species. The Tor species were found in Hallibylu region of this river system. Thus, the season-wise species composition remains more or less same in this locality. Further, the southwestern part shows similar trends of Yenneholé. But here Tor species was not recorded. In both the cases, natural terrain is undulating with hills and valleys. Valleys being shallow areas are excellent localities for indigenous monsoon breeders.

Figure 2. Sensitive fish breeding regions

The deeper regions of the reservoir like Holébagilu, Hasaramakki and Madenur have major fish catch of introduced species during monsoon season. As the monsoon season recedes the catch of indigenous species increases compared to introduced species and this condition prevails until there is water inflow into the reservoir.

Discussions

Large number of Western Ghat endemics (18 species) in the region highlights the uniqueness of the region. About 55 % (28 species) of the fishes are found only in peninsular India. Similar comparisons were made with respect to the status of each species. The only critically endangered species, Tor mussullah is found in the western parts of the reservoir. Ten species are endangered and require immediate conservation measures, while 12 are vulnerable, 19 are with lower risk and remaining 10 are data deficient. This clearly emphasises the richness and ecological value of the region.

Comparison between the reservoir and streams shows that the species composition of the reservoir is dominated with non-endemic and introduced species. The reason for the flourishing of non-endemics/introduced species is due to development of commercial fishery in the Linganamakki reservoir, since 1969. On the other hand the streams have more number of endemics having narrow range of distribution, emphasizing the importance of streams as natural habitats for endemics. This in turn, accounts for high conservation value of the region. 

The data on seeding (refer Table 64) reveals that no scientific approach was adopted. Without determining the carrying capacity and productivity of the reservoir enormous amounts of seeds were introduced during early 90s. The present condition reveals that the approach adopted in seeding has negatively affected the total fish fauna.

Introduction of Tilapia (Oreochromis mosambica): Tilapia is a hardy, territorial and a powerful competitor in nature, and is has started dominating in Linganamakki reservoir. As per the local fishermen, the fish catch of Tilapia is increasing over years. The catch starts at the post monsoon period and during November, it dominates in the entire catch. Due to the least demand for this fish in local markets, fishermen treat this fish as unwanted catch. Ecologically these fishes have adverse effects on the native fish diversity. As per the fishermen, the maximum weight that this fish can attain is 0.5 kg in this reservoir.

Endangered Mahseers: Tor khudree and Tor mussullah are the two endangered species present in the reservoir. These fishes breed during post monsoon period and their habitat is rocky pools. Their commercial value and habitat destruction might be the factors contributing to their decline. In Linganamakki Reservoir, mahseers were recorded in Hallibylu of Sharavathi Wildlife Sanctuary area. In other areas also these fishes are found rarely. At present, the silt deposition at the bottom is slowly disturbing their habitat along with fishing pressure.

Cyprinus carpio (Common Carp) Fishery: During monsoon period, Common carp is the major fish catch in deeper areas like Holébagilu, Madenur and Hasaramakki areas. During other seasons, this fish catch is almost nil. Since Common carp is a bottom dweller, high transparency of the reservoir makes it to move to the bottom surface. During monsoon season, transparency reduces and Common carp comes to the surface. Cyprinus carpio is regarded as one of the major competitors to the native species of fishes for food and habitat. In the present case, the fish may affect benthic fishes like Wallago attu, Ompok bimaculatus and Channa striatus indirectly. Since Cyprinus carpio is an herbivorous fish, and its growth is quite fast, it consumes lower level organisms like phytoplankton, zooplankton and other aquatic insects andmay in turn affect the food requirement of carnivorous fishes and result in decreasing their population.

Role of Predatory Fish in Total Fish Catch: Depending upon the fish catch composition it can be concluded that, predatory fishes like Wallago attu and Channa striatus are least in number. Only Ompok bimaculatus catch is quite encouraging. This could be due to excessive introduction of Gangetic carps like Cyprinus carpio during the last decade, which has led to competition among the bottom dwellers. Yenneholé tributary is the only place with considerable catch of predatory fishes with no introduced species. In this locality, 13 hooks were placed and out of six, 4 Wallago attu and 2 Channa striatus were caught. This indicates the presence of predatory fishes in this area.  

Diseases - Epizootic Ulcerative Syndrome (EUS): The fishermen recall the widespread outbreak of a disease about 5 years back, featured by the severe ulcerative skin lesions over the body, which ultimately caused the death of the fish. Reports on the outbreak of EUS in Shimoga District show that during Dec 1993 – Jan 1994 the disease had caused mortality in the major and minor irrigation tanks. Even though initially the disease affected the bottom dwellers like Channa species slowly it spread to catfish and minor carps. Interestingly it has not affected the Indian major carps like Catla, Rohu, Mrigal and common carp in Karnataka (Mohan and Shankar, 1994). This disease might be one of the main reasons for extinction of many species. According to the local fishermen, fish species like Wallago attu, Heteropneustes fossilis and Channa striatus were severely affected by this disease and there was a remarkable decline in their population. Presently there are no such episodes of disease in the reservoir. Still one of the sampling at Lingadakai found a Garra gotyla stenorhynchus with lesions on the body.

Parasitic infection to Mastacembelus armatus: Recently parasitic infection to the species Mastacembelus armatus was observed in areas like Hasaramakki. The infection showed numerous lesions within the abdomen with approximately 1 – 2 cm diameter. After the death of the fish during fishing, nearly 2” long thread like worms (helminthes) were coming out of the abdomen. The infection was at its peak during summer season and affected almost all the fishes of the species. During this period, the commercial use of this fish had almost stopped in this area. However, the question of the suitability of the fish as food and the reason for the first time occurrence of this disease during June 2002 remains unanswered.

Destruction at the breeding ground: Species of Garra, Puntius, Labeo, Cirhinus, Mystus, and Pseudeutropius etc. are regarded as resident species. These fishes breed within the reservoir or migrate to smaller distances in search of shallow weedy areas for breeding. Most of the people residing along the bank go for fishing and capture them during monsoon season. Residents here adopt traditional techniques to capture these fishes. These are the localities where large congregations of the spawning fishes are caught and destroyed. Some fishermen even move to shallow upstream areas during monsoon to exploit the breeding grounds. Probably this is a prime factor that retards the population of these migratory fishes. Most of the streams along the western side are observed to be excellent breeding grounds for the native fishes.

Over exploitation and improper fishing system: The over exploitation of the reservoir plays a major role in extinction of the species. The department issues licenses to any number of fishermen. Many fishermen from Tungabhadra dam migrate to this area during rainy season and catch huge quantity of fish. This has adversely affected the livelihood of permanent local fishermen. Over exploitation of the reservoir for fishing has resulted in excessive mortality and reduction in effective population size of the fish. Monsoon is the breeding season for most of the fishes and the fishing activity is at its peak during this season.

The commercial fish catch of the reservoir is dominated by species belonging to Cyprinidae family (54%). The other major families are Bagridae (23%) and the Siluridae (15%). When biomass is considered, the fast growing Indo-gangetic carps, popularly known as Indian major carps, occupy a prominent place. Mainly Catla catla (21%), Labeo rohita (8.4%) and Cirhina mrigala (6.32%). These fishes are introduced to fulfill the commercial fish requirement along with the exotic species (Cyprinus carpio 21%). The native fishes with significant biomass are Gonoproktopterus kolus (11.5%), Ompok bimaculatus (10%) and Wallago attu (9%).

Table 67. Fish-catch observed at different locations during the year 2003-04

Locality	Catch per unit effort (Kg/boat/day)
	Non-monsoon season	Monsoon season
Holebagilu	1.34	39.4
Muppane	7.93	16.5
Konjavalli	6.2	16.5
Melmanji	6.8	24.2
Kogar	8.2	28.5

Data on fish catch of the selected seven localities show that at the center of the reservoir (Holebagilu) the yield variation is very high compared to other regions (Table 67). During monsoon season, the central region yields the introduced species in bulk. In the peripheral localities (Muppane, Konjavalli, Melmanji and Kogar) variation in catch during two seasons is less.

Table 68. Percentage catch composition of various species during non-monsoon season

Species name	Percentage biomass
	Holebagilu	Muppane	Konjavalli	Melmanji	Kogar
Introduced
Catla catla	0.0	0.0	0.0	0.0	0.0
Labeo rohita	0.0	0.0	0.0	0.0	0.0
Cyprinus carpio	0.0	0.0	0.0	0.0	0.0
Native
Gonoproktopterus kolus	0.0	28.4	28.9	13.3	11.0
Cirhina fulungee	5.6	8.5	8.4	2.2	4.6
Garra gotyla stenorhynchus	0.0	1.5	0.6	0.0	0.0
Mastacembelus armatus	0.0	25.2	19.3	17.8	19.5
Mystus cavecius	16.8	3.8	6.0	8.9	14.6
Mystus malabaricus	22.4	5.7	7.2	7.8	10.1
Ompok bimaculatus	32.8	8.3	14.1	39.1	29.5
Ompok pabo	0.0	13.9	10.6	9.8	10.7
Oreochromis mossambica	0.0	1.0	2.4	1.1	0.0
Puntius arulius	0.1	0.0	0.0	0.0	0.0
Puntius filamentosus	17.9	0.0	0.0	0.0	0.0
Tor khudree	0.0	3.8	2.4	0.0	0.0
Xenentodon cancilla	4.5	0.0	0.0	0.0	0.0

During summer season there is no role of introduced species in enhancing the fish catch of the reservoir (Table 68). The catch is mainly represented by Mystus cavecius, Mystus malabaricus and Mastacembelus armatus in almost all the localities. At the peripheral localities Gonoproktopterus kolus shows significant catch whereas its catch is negligible at the central region.

Table 69. Percentage catch composition of various species during monsoon season

Species name	Percentage biomass
	Holebagilu	Muppane	Konjavalli	Melmanji	Kogar
Catla catla	25.4	0.0	0.0	0.0	0.0
Cyprinus carpio	12.7	0.0	0.0	0.0	0.0
Labeo rohita	10.1	0.0	0.0	0.0	0.0
Cirhina mrigala	7.6	0.0	0.0	0.0	0.0
Cirhina fulungee	0.0	12.7	5.4	2.5	3.2
Gonoproktopterus kolus	0.0	39.0	43.4	38.9	43.2
Mastacembelus armatus	8.1	9.7	12.1	4.9	8.4
Mystus bleekeri	0.0	0.3	0.0	0.0	0.0
Mystus cavecius	9.1	7.2	1.4	0.6	0.5
Mystus malabaricus	1.7	2.7	1.4	0.6	2.1
Ompok bimaculatus	24.0	23.9	15.9	8.1	37.1
Ompok pabo	0.0	1.3	2.6	0.9	1.5
Osteocheilus nashi	0.0	0.9	0.0	0.0	0.0
Pseudeutropius atherinoides	0.0	0.2	0.3	0.1	0.2
Puntius filamentosus	0.0	1.1	1.4	1.5	3.8
Tor khudree	0.0	0.9	0.0	0.0	0.0
Tor mussullah	0.0	0.0	0.9	0.6	0.0
Wallago attu	0.0	0.0	15.1	41.2	0.0
Xenentodon cancilla	1.2	0.0	0.0	0.0	0.0

During monsoon season, the fish biomass composition (Table 69) in the central region is dominated by introduced (Holebagilu - 55.8 %). Of the indigenous population, only Ompok bimaculatus has shown significant biomass in these localities. Whereas in other localities where there is no introduction, their catch is totally absent and substituted by indigenous commercial fishes like Gonoproktopterus kolus, Wallago attu, Mastacembelus armatus and Ompok bimaculatus. Apart from G. kolus, the market value for all other indigenous fishes is higher than the introduced species.

Variable fishing pressure: Monsoon is the peak fishing period and there will be 3.4 times increase in fish catch per person per day during this period compared to non-monsoon period. Even though the monsoon period being shorter than non-monsoon period, about 86.7 % of the total fish-catch takes place during monsoon. Nearly 63.5 % of the original fishermen population arrives here during the initial monsoon season from various parts of peninsular India. As the density of fishermen increases 2.75 times, the fishing pressure also increases. During the initial monsoon season, the reservoir attains the minimum water spread area. It is observed that most of the fishermen get concentrated in the central regions like Holebagilu in order to harvest huge catch. Obviously this results in overexploitation of resource. This is evident from the low fish catches of summer season from this region.

Loss at the breeding grounds: Monsoon is the breeding season for most of the fishes and the fishing activity is at its peak during this season. Muppane, Konjavalli, Melmanji and Kogar represent the peripheral localities of the western region. The biomass composition of this region shows that in these localities, the catch is formed by the native species. These are the flood plains where majority of the fish species breed during monsoon season. Huge quantities of fish catch in these localities during monsoon season poses huge threat to their population. It is evident that the catch per unit effort increases at the periphery than the other localities. Almost all the fishermen move to the extreme ends of the tributaries thereby destructing the breeding fish population.

Fish translocation from other basins: Details on the pattern of introduction clearly reveal that no scientific approach has been adopted before determining the quantity of introduction. Seeds have been introduced depending on the availability. This unscientific approach has resulted in an artificial system of fishing wherein the indigenous fishing population has to rely on an external source to increase the fishing stock. Declined native fish population is inefficient to cope up their livelihood. The low catches during non-monsoon season totally affects the permanent fishermen of the region who are totally relying on this resource for their livelihood. The biomass composition of this region also reveals that other than catfishes, no other native species has succeeded to form a stable population. Thus the fishermen are dependent on an artificial system in the form of introduction and harvest. It is implicative that the original fauna has been changed and hardy fish species has taken advantage of the vacant niches. Thus transplantation of fishes from other basins has led to radical changes in the species set up.

Conclusion

The present study of fish diversity in the Linganamakki Reservoir recorded 52 species from 32 genera and 16 families, where as lower catchment area harbours 51 freshwater species and Sharavathi estuary has 44 species. Altogether, entire basin has 112 species. For the first time a monotypic genus Phylloneura westermanni was recorded from a Myristica swamp of Kathalekan in Siddapur. The only earlier report on this species was from Nilgiris, Coorg and Wayanad in 1933 by Fraser. The presence of Philorus in the Vatehalla stream indicates its pristine nature and presence of primeval forests around. Some pollution sensitive genera have also been found in Kathalekan indicating the beginning of human disturbances.

The annual fish yield of the reservoir is estimated to be 200 ton with both native and introduced fishes. The decline in native fish stock necessitates the stocking of indigenous and endemic fishes of Western Ghats. Prevention of over-fishing, migrant fishermen and breeding season fishing can contribute to sustainable fishery in the reservoir. Strict practice of restricted mesh size utility can minimize the death of non-target fishes. Eliminating predatorial exotics and omnivores like tilapia and common carp is required to minimize the negative effects. Educating the local fishermen and activating the inactive co-operative society can lead to sustainable fishery in Linganamakki reservoir.

Management Approaches

Conserving the breeding areas: As discussed earlier, shallow and stream joining areas are the breeding grounds of most of the fish species. In this connection, fishing activities should be totally restricted in shallow areas during June to September. The breeding area should be demarcated and these areas should be kept under continuous monitoring. Monsoon fishing should be allowed only at the central part and limited to harvest transplanted species by operating large mesh sized gill nets.

Permanently stopping the fishermen migration: The Fisheries Department should reconsider its revenue-oriented approach in issuing the licenses to the fishermen. Licenses should be issued to the permanent fishermen residing near the reservoir, who are solely dependent on this reservoir for their livelihood. In order to reduce the fishing pressure, it is advisable to avoid migratory fishermen from fishing. Since their fishing period is monsoon, large quantities of breeding fishes are destroyed by over fishing. These fishermen are highly mobile in nature, which complicates the authorities in monitoring. This provides sufficiently large fishing ground to the permanent fishermen thereby considerably retarding the stress on the aquatic system.

Strengthening the indigenous fish population: Culture techniques for endangered species should be developed to protect and rehabilitate the endangered species taking into account the critical need to conserve genetic diversity. The native commercial fishes like Tor khudree, Tor mussullah, Labeo kontius, etc., have tremendous potential in commercial fishery and their population need to be strengthened by external input. Specifically in the central part of the reservoir most of the cyprinids have poor population indicating the immediate requirement of their culture. 

Proper introduction: Presently it is necessary to translocate the gangetic carps to share the fishing stress on the native fishes. However there is a great ecological concern over the introduction of exotic species. In this regard, carrying capacity of aquatic environments should be well studied and the quantification of introduction should be made in order to eliminate the adverse effect on native fish fauna.

Strict supervision: Presently the department is lacking trained staff to strictly and properly supervise the fishing activity. They should be strengthened through increasing their number and proper training. This can enlighten the scientific approach in them towards fisheries management.

Activating the Cooperative society: It is another major necessity to activate the Cooperative Society, which is presently passive. All fishing activities should be carried out through the society. Frequent meetings among the fishermen, merchants and the departmental staff can strengthen the society. Here once again banning the temporary fishermen can simplify the task of activating the Cooperative society.

Properly managed data: There is no scientific information available about fisheries in of Sharavathi Wildlife Sanctuary.  This severely affects the decision-making. Without any statistical data, it is impossible to maintain the fishery activity in healthy condition. Thus it is the prime importance to maintain at least the data pertaining to total yield statistics, species-wise yield, physicochemical analysis of reservoir water representing the entire water body, disease episodes which is very useful during any planning stage. 

Educating the local fishermen: Fishermen should be properly educated about the importance of fish diversity and the associated interconnections between different species. This can considerably decrease improper fishing practices by understanding their negative impacts on fish resources.

REFERENCES

1. Bhat, A. 2002. A study of the diversity and ecology of the freshwater fishes of four river systems of Uttara Kannada District, Karnataka, India. Ph. D Thesis. Centre for Ecological Sciences, Indian Institute of Science.
2. Canter, L. 1999. Cumulative Effects Assessment. Handbook of Environmental Impact Assessment - Vol. 1, Ed. Judith Pets, pp. 405 – 440.
3. Chandrashekhariah, H.N. 2000. Status of Fin Fishes in Karnataka, Workshop on Karnataka Bio-diversity Information System.
4. Daniels, R.J.R. 2000. Project Lifescape 6. Freshwater Fishes: Catfishes. Resonance Journal of Science Education, 5(4):95 – 107. 
5. Daniels, R.J.R. and R. Abraham, 1995. Role of faunal bioindicators. In: Bioindicators – Identification and use in assessing environmental disturbances (Eds. M.S.S. Mohan, S. Nair and R.J.R. Daniels). M. S. Swaminathan Research Foundation. Chennai, India.
6. Easa, P.S. and Shaji, C.P. 1997. Freshwater fish diversity in Kerala part of Nilgiri Biosphere Reserve. Current Science, 73(2): 180 – 182.
7. Jayaram, K.C. 1981. The Freshwater Fishes of India, Pakistan, Bangladesh, Burma and Sri Lanka – A Handbook. The Director, Zoological Survey of India.
8. Jayaram, K.C. 1996. Manual for Field Identification – Common Freshwater Fishes of Karnataka. World Wide  Fund for Nature – India, Biodiversity Conservation Prioritization Project – India (BCPP).
9. Jhingran, V.G. 1982. Fish and Fisheries of India. Hindustan Publishing Corporation (India), Delhi, pp 3-666.
10. Johnsingh, A.J.T. 2001. The Kalakad – Mundanthurai Tiger Reserve: A global heritage of biological diversity. Current Science, 80 (3): 378 – 388.
11. Leveque, C. 1997. Biodiversity dynamics and conservation – the freshwater fish of tropical Africa. Cambridge University Press. pp. 95 (438). 
12. Nelson, J.S. 1996. Fishes of the world, 3rd edition. John Wiley and Sons, New York.
13. Shaji, C.P., Easa., P.S. and Basha, S.C. 1995. Freshwater Fish Diversity in Aralam Wildlife Sanctuary, Kerala, South India. Journal of the Bombay Natural History Society, 92 (3):360-363.
14. Talwar, P. K. and Jhingran, A.G. 1991. Inland Fishes of India and Adjacent Countries – Vol. 1 & Vol. 2. Oxford & IBH Publishing Co. Pvt. Ltd.

APPENDIX I

Annexure I: Fresh water fishes of Linganamakki catchment area with their distribution and IUCN status.

Species	IUCN status	Stream	Reservoir
ENDEMIC SPECIES
Family: Cyprinidae
Barilius bakeri	VU	+	-
Barilius canarensis	DD	+	-
Barilius gatensis	DD	+	-
Salmostoma boopis	LR	+	+
Osteocheilichthys nashii	VU	+	+
Gonoproktopterus dubius ?	EN	+	-
Gonoproktopterus kolus	EN	-	+
Puntius arulius	EN	+	+
Puntius sahyadriensis	DD	+	-
Labeo kontius	LR	-	+
Garra gotyla stenorhynchus	EN	+	+
Tor mussullah	CR	-	+
Family: Balitoridae		-	-
Nemacheilus anguilla	LR	+	-
Schistura nilgiriensis	EN	+	-
Schistura semiarmatus	VU	+	-
Family: Bagridae		-	-
Batasio sharavatiensis	DD	-	+
Mystus malabaricus	EN	-	+
Family: Sisoridae
Glyptothorax lonah	LR	-	+
NON-ENDEMIC SPECIES
Family: Cyprinidae
Barilius bendelisis	LR	-	+
Amblypharyngodon mellettinus	LR	+	-
Danio aequipinnatus	LR	+	-
Brachydanio rerio	LR	+
Rasbora daniconius	LR	+	-
Tor khudree	VU	-	+
Oreichthys cosuatis	DD	+	-
Puntius chola	VU	+	+
Puntius sophore	LR	+	-
Puntius ticto	LR	+	-
Puntius fasciatus	EN	+	-
Puntius filamentosus	DD	+	+
Cirrhinus fulungee	LR	-	+
Family: Balitoridae		-
Schistura denisonii denisonii	VU	+	-
Acanthocobitis botia	LR	+	-
Family: Cobitidae
Lepidocephalus thermalis	LR	+	-
Family: Bagridae
Mystus keletius	DD	-	+
Mystus bleekeri	VU	-	+
Mystus cavesius	LR	-	+
Family: Siluridae
Ompok bimaculatus	EN	-	+
Ompok pabo?	DD	-	+
Wallago attu	LR	-	+
Family: Schilbeidae
Pseudeutropius atherinoides	EN	-	+
Family: Claridae
Clarias batrachus	VU	-	+
Clarias dussumieri dussumieri	VU	-	+
Family: Heteropneustidae
Heteropneustis fossilis	VU	-	+
Family: Belonidae
Xenentodon cancilla	LR	-	+
Family: Aplocheilidae
Aplocheilus lineatus	LR	+	-
Family: Chandidae
Chanda nama	VU	+	+
Parambassis ranga	DD	+	+
Family: Gobiidae
Glossogobius giuris	LR	+	+
Family: Belontidae
Pseudophromenus cupanus	DD	+	-
Family: Channidae
Channa orientalis	VU	+	-
Channa marulius	LR	-	+
Family: Mastacembelidae
Mastacembelus armatus	LR	-	+
TRANSLOCATED SPECIES
Family: Cyprinidae
Cyprinus carpio communis		-	+
Cyprinus carpio sp.		-	+
Cyprinus carpio specularis		-	+
Catla catla		-	+
Cirhinus mrigala		-	+
Labeo rohita		-	+
Family: Cichlidae
Oreochromis mossambica		+	+
SPECIES WITH STATUS UNKNOWN
Family: Balitoridae
Schistura sp1		-	-
Schistura sp2		+	-
Schistura sp3		+	-
Family: Bagridae
Aorichthys sp.		-	+

APPENDIX - II

Checklist of Fish species recorded in Sharavathi River Basin

Linganamakki Dam up to Estuary  (Bhat, 2002)	Sharavathi estuary (Nakadia)
Aplocheilus lineatus	Ambassis commersoni
Arius caelatus	Arius arius
Barilius canarensis	Arius platystomus
Brachydanio rerio	Arius subrostratus
Caranx carangus	Austrobatrachus dussumieri
Caranx ignobilis	Belone cancilla
Chanda nama	Bothus pantherinus
Cirrhinus fulungi	Carangoides malbaricus
Danio aequipinnatus	Chrysophrys berda
Eleotris canarensis	Cyanoglossus sp.
Garra gotyla stenorhynchus	Drepane punctata
Gerres (setifer) spp.	Etroplus suratensis
Gerres setifer	Euryglossa pantherinus
Gerres spp	Gerres filamentosus
Glossogobius giuris	Gerres lucidus
Gonoproktopterus dubius	Gobius giuris
Gonoproktopterus kolus	Gobius ornatus
Hyporhampus limbatus	Hemiramphus xanthopterus
Labeo boggut	Johnius glaucus
Labeo fimbriatus	Lates calcarifer
Labeo kawrus	Leiognathus daura
Labeo potail ?	Leiognathus equulus
Mastacembalus armatus	Liza macrolepis
Mystus cavesius	Liza parsia
Mystus malabaricus	Lutjanus argentimaculatus
Nemacheilus anguilla	Lutjanus johni
Nemacheilus botia	Mugil cephalus
Osteocheilus nashii	Mugil poicilus
Parabatasio sharavatiensis	Nematolosa nasus
Parambassis dayii	Platycephalus indicus
Parambassis thomassi	Platycephalus scaber
Periophthalmus weberi	Pristipoma hasta
Pristolepis marginata	Scatophagus argus
Puntius amphibius	Sillago sihama
Puntius bimaculatus	Sphyraena jello
Puntius dorsalis	Stolephorus cummersonii
Puntius fasciatus	Stolephorus indicus
Puntius filamentosis	Strongylura strongylura
Puntius jerdoni	Terapon jarbua
Puntius narayani	Teuthis vermiculata
Puntius sahyadrensis	Teuthris oramin
Puntius sarana sarana	Thryssa hamiltonii
Puntius sophore	Trachynotus ovatus
Puntius ticto
Rasbora daniconius
Salmostoma boopis
Salmostoma clupioides
Tor khudree
Xenontodon cancilla

Conclusions

The biological examination of the stream and reservoir ecosystems of Sharavathi River basin showed a rich and diverse aquatic fauna. The physicochemical and biological analysis of water samples in the upper catchment of the river and the phytoplankton sampling revealed that the river is in oligotrophic condition and there is no high organic pollution load. This could be due to least domestic and industrial pollutants in this region. Also the annual rainfall in the range of 2000 – 6000 mm contributes to the dilution of pollutants that enter into the river basin resulting in flushing effect of the pollutants. The freshwater zooplankton fauna of Sharavathi River is rich and highly diversified. They were showing a typical tropical assemblage. Large zooplankton species were absent in this river system, probably due to high predatory pressure. However these studies were unable to reflect the cumulative impacts resulted in the river basin. This could be mainly due to the fact that these communities along with physico-chemical analysis are the indicators of localized and short-term environmental changes. Fishes are good indicators of long-term effects and broad habitat conditions.  

The study of freshwater fishes of the Sharavathi Upper catchment revealed that there are large numbers of Western Ghats endemics (18 species) in the region. The only critically endangered species, Tor mussullah is found in the western parts of the reservoir. Ten species are endangered and require immediate conservation measures, while 12 are vulnerable, 19 are with lower risk and remaining 10 are data deficient. This clearly emphasises the richness and ecological value of the region. The distribution pattern of fishes revealed that reservoir has supported the non-endemic and introduced species. On the other hand the streams have more number of endemics having narrow range of distribution, emphasizing the importance of streams as natural habitats for endemics. This in turn, accounts for high conservation value of the region. The study also found that the promotion of commercial fishery into the Linganamakki Reservoir has resulted in rapid depletion of native fish fauna.

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