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Propagation Of Mahseer In The Himalayan Waters Of Nepal

T.K. Shrestha

Department of Zoology, Tribhuvan University

Kathmandu, Nepal

Abstract

The number of migratory mahseer (for putitora) is dwindling because of overexploitation, environmental pollution, habitat modification, and power dams. Conservation and management of this superior game fish requires special propagation practices. Spawning runs of the mahseer start in early September, terminate in late October, and occur at night in gravel-bottomed creeks, pools, and rapids. Eggs from the spawning beds were collected and successfully cultured in egg trays. The complete incubation period (fertilized egg to free swimming fry) was about 25 days at mean temperature of 35°C. Sexually mature migratory spawners were also caught for artificial breeding experiments. Spawners injected with hormones were stripped and the fertilized eggs were incubated in trays and aquaria. Fry were reared in several rearing ponds within 60 days and 50 % survived. Early 8-day-old sac fry were also reared in ponds, but they did not survive well. Fry were successfully raised in cloth bags (happa) by providing artificial food (egg yolk). Critical stages of fertilized spawn were monitored in the laboratory and field and a life table for the mahseer was constructed for use in transplantation of mahseers into new habitats.

Introduction

In recent years, various investigators have given considerable attention to the propagation of the seriously endangered mahseer in Himalayan waters (Badola and Singh 1984, Shrestha 1986, Nautiyal and Lal 1984, Das 1990). They have been prompted by several considerations: (1) loss of natural habitat, endangering the breeding population; (2) overfishing in natural waters and pollution, which is destroying the spawning grounds and broodfish; (3) scarcity of healthy broodfish for artificial breeding by hormone injection; (4) recognition by cold water fish culturists of the need for propagating mahseer in lakes and reservoirs to boost recreational fisheries; and (5) the realization that the mahseer can be farmed and that wild populations can be restored in natural waters.

In developed countries, particularly in the United States, methods have been developed for the successful propagation of fish (McFarland 1960, Collins and Hulsey 1964, Anderson 1968, Webster et al. 1978, Mauri et al. 1979).

TABLE 1. Observations on the Spawning of Mahseer in Gadkhar Creek

Date

Weather

Temperature

Interstream Migratory

Downstream Movement

Spawning Dens

Spawning

Lunar

   

Movement

   

Assembly

Cycle

 
   

(°C)

         

8/19/86

Sun and clouds.

25

Vigorous movement started

Spawners moved

Gravel, sand

Possibly 3

Two

 

Rain for whole day.

 

around 1 a.m. at creek

downstream at 1 a.m.

bar,intergravel

males, 1

days

 

Barometric pressure 385.

 

confluence and upstream in

Fifty (38 males, 12

shallow water

female.Low

before

 

net across confl.

 

creek. Preliminary courtship

females) captured in gill

current speed to

turbidity

full

   

acts and false spawning in the

0.5 m/sec

gravel beds

moon

   
     

Temp. 31°C

clearly vis.

     
       

Spawners moved

SSpawners moved

   

9/2/86

Cloudy, heavy rain

28

Mass movement of mahseer at

downstream at 5 p.m.

Gravel,

Possibly 53

Full

 

(for about 6 hr.)

 

about 12 p.m. Spawners

Six females, six males

sandbar,

males,18

moon relatively clear

 

and wind. Sky

 

travelled lOO meters upstream

were captured in gill

intergravel

females. High

first at day. night. Full moon

     

from confluence site. Male

nets.

water with

turbidity,

 
     

chased the female, brief

 

depth 0.5 to 1

gravel beds not

 
 

visible. Barometric

 

courtship took place.

 

m. Current

visible.

 
 

pressure 360.

 

Spermatic fluid released over

 

velocity 0.5 to

   
     

the eggs deposited in the

 

2 m/sec. Temp

   
     

gravel. Creek water at certain

32°C.

     
     

spots appeared milky.

       
       

Spawners moved

     

10/5/86

Cloudy, drizzling

28.5

Movement of mahseer at the

downstream. Two

 

About 500

Full moon. with wind

 

Full

 

creek. Jumping, courtship and

females, two males

 

spawners

 
 

moon. Barometric

 

spawning.

captured in gill nets.All

Edge of deep

congregated,

 
 

pressure 380.

   

had running eggs or

pool, with

peak spawning

 
       

sperm.

mixed stones,

period reached

 
       

pebbles and

Gravel bed

   
         

and current

turbidity low.

 
       

Spent spawners moved

velocity as

   

11/15/86

Cloudy, drizzling.

25.5

Usual spawning movement

downstream. Twenty

above. Temp.

Number of

New

 

New moon.

 

followed by courtship action

females and sixty males

35°C.

spawners

moon..

 

Barometric pressure

 

No eggs or sperm released.

captured in gill net. All

 

decreasing

 
 

456.

 

False spawning occurred.

were in spent condition.

Spawners very

sleeply. Few

 
         

active. No

   
         

ovulation or

   
         

sperm

   
         

observed

   
         

Temp. 28°C

   

 

As a contribution to this problem, studies were initiated in 1985 on the propagation of the mahseer, Tor putitora (Hamilton). Although experiments are still in progress, sufficient data have been obtained to warrant the publication of results for the four-year period 1985-1989.

A few accounts of induced breeding of the species of mahseer have been published (Tripathi 1978, Ogale and Kulkarni 1987). Methods for artificial propagation have yet to be described in detail (Shrestha 1985). This is the first attempt at large-scale breeding and propagation of mahseer species in the ponds, lakes, and reservoirs of Nepal.

Materials and Methods

For the study of natural spawning and behavior, both direct-sensing and remote-sensing methods were used. Direct sensing of the mahseer habitat and behavior was made visually. Spawners were dazzled with light to facilitate the study of spawning performance. Florescent-tube lamps were also used as a light source in remote and inaccessible places. Occasionally, underwater torch lights were used to observe spawning activity and to sample freshly deposited spawn or fertilized eggs. Plankton nets of various sizes were used to collect the spawn. The physico-chemical features of the spawning grounds were recorded in situ (Tables 1 and 2). Remote sensing of the habitat was done with binoculars and a camera fitted with a telephoto lense and a video recorder. The shape and size of the spawning ground and other physical characteristics were recorded. Freshly deposited eggs were removed from the spawning beds and successfully incubated in hatchery eggs trays. Both early and advanced fry were reared in trays or cloth bags suspended in pond water. For stocking purposes, fry of different stages were transported to different places.

For artificial breeding, adult fish (Figure 1) were collected from the spawning creeks by using gill and trammel nets. Captured fish were tranquilized using tricaine methanesulfonate (MS-222). All adults were tagged with Floy tags on 15-16 September 1987. Mahseer were transported to the laboratory by truck and jeep. At the laboratory they were acclimatized, by sex, in separate plastic pools or cloth bags suspended in river water. The conditioned fishes in the plastic pools were fed with soybean and rice bran in a 1:1 proportion. Spawning was induced by injecting extracts of pituitary glands from carp, the dosage was four glands per kg body weight of fish. Females spawned after 18 hr with only one intramuscular injection. Artificial fertilization was accomplished by stripping the male and female brood fish by conventional wet and dry methods. Early fry produced as a result of artificial breeding were reared in incubation trays. Advanced fry were reared in cloth bags suspended in pond water. The developmental stages of fry were monitored for three years (1986-1989) and a life table was constructed.

To study the survival of mahseer in new habitats, experimental releases were made in Trisuli reservoir and Kulekhani reservoir (Indrasarovar). About 1,044 semi-adult fish were released in the Trisuli and Tadi river confluence site. One year later, 580 of these fish were recovered.

 

TABLE 2. Physical and chemical Parameters of the Tisuli River Water (1986)

Month

Mean

Discharge

Temp.

Depth

Color

Odor

Tur-

pH

Dis-

Free

Total

Spec.

 

Current

Mean cu

(0°C)

(m)

   

bidity

 

solved

CO2

Alkalinity

Conductivity Velocity

 

m/sec

Mean

Average

   

(cm)

 

O2

(ppm)

   

m/sec

           

(ppm)

           

January

0.6

60.00

10.0

2.5

Clear green

Fishy

180

7.6

18

28.0

160

61

February 0.5

46.00

14.0

2.0

Clear green

Fishy,

150

7.8

16

20.0

160

52

 
         

methane

             

March

0.5

43.00

16.0

2.5

Unstable

Methane

130

7.8

15

18.0

185

55

     

green

                 

April

1.2

85.00

18.0

2.8

Silty brown

Fishy,

30

7.9

15

16.0

186

65

           

methane

           

May

1.5

103.00

18.0

3.0

Silty brown

Strong,

20

7.4

10

18.0

192

76

 

       

methane

           

June

3.0

440.00

24.0

4.0

Red silty

Methane

8

6.5

12

12.0

194

130

       

brown

               

July

2.7

1080.00

25.0

6.0

Reddish silty

Weak

4

7.6

9

14.0

195

115

         

brown

methane

           

August

2.9

1226.00

26.0

6.5

Red brown,

Weak

5

7.8

8

4.0

245

128

         

silty

methane

           

September 3.0

870.00

27.0

4.0

Red silty

Fishy,

13

7.9

10

10.5

250

70

 
         

brown

methane

           

October

1.3

375.00

15.0

3.0

Dark green

Fishy,

19

7.4

12

15.2

310

62

           

methane

           

November 0.8

164 00

12.0

2.5

Clear green

Fishy

85

7.5

18

20.0

320

65

 

December 0.7

61.00

9.0

2.0

Clear green

Fishy

100

7.6

20

30.0

340

60

 

 

Results

Natural Spawning and Physical Features of Spawning Sites

Gadkhar Creek is located in Chokedovan, near His Majesty's Government (HMG) Fish Farm (Figure 2). The creek becomes flooded during early May and dries to a trickle during February and March. Its bed consists of gravel, pebbles, cobbles, and boulders. There is a wide area where the creek enters the Tadi River. Three spawning beds, A, B, and C, were identified in the creek. Bed A, consisting of pebbles less than 10 cm in diameter, is the cleanest among the three. Bed B consists of rocks 15-40 cm in diameter, and Bed C consists of rocks from 50 to more than 80 cm in diameter. Water quality of the spawning ground is given in Table 2.

At midnight, mature mahseers came to the creek-river confluence a few at a time. They gathered into a group numbering 10-30. While swimming together, several males would actively pursue the females, nuzzling and biting. After midnight, during the full moon period, courtship behavior was intensified and suddenly the mahseers swam rapidly in shallow zones of the creek near the bank, where they vigorously flopped and trembled. Eggs and sperm were released and fertilization took place. The fertilized eggs came to rest on, and adhering firmly to, stones and pebbles. After an interval of two hours, ejection of eggs and sperm were again noticeable when the water of the outgoing current turned milky. The majority of eggs 2.5-3.5 mm in diameter were washed away gradually by the current and the number of eggs adhering to the pebbles was very small. Hydrological and biological observations of the mahseer and its spawning habitat are given in Table 1.

Observations of mahseer spawning activity commenced in August 1986, and active spawning was observed from August to September 1986. As evident in Table 1, there is a strong correlation between spawning days and weather conditions. Both daytime and nighttime observations were made. During the breeding season (September to October), spawning took place every evening on billowy days or stormy days with heavy rainfall. Commencement of spawning behavior also seemed to be related to the hours of high flood in the parent river and medium flood in the feeder creek. Spawning took place from midnight to early dawn. There also was a significant relationship between the hours of onset of spawning and the weather (high rainfall and low barometric pressure). Spawners selected rocks, stones, pebble, gravel, sand, and log debris as spawning substrata (Table 1). Spawning was not noticed among algae or discarded plastic bags that had drifted to the creek bank.

Spawning of mahseer was initially observed on five evenings, during the period September 2 to October 5 (full moon September 2 and October 5). Spawning was noted to be related to flood conditions and usually began within 30 minutes after heavy flooding. The time of first spawning occurred after midnight on September 2, when there was a full moon. On November 15 no spawning was seen. During this last period, there was no moon, flood intensity was too low, and the water was relatively clear (Table 1). Mass spawning during and after floods showed that flood levels may provide a mechanism whereby fertilized eggs (Figure 3) are transported to the river bank to find suitable shallow nursery habitat to settle and develop into fry.

High temperature accelerated hatching time when eggs were reared in incubation trays and aquaria, but caused a decrease in oxygen content. This situation was rectified in aquaria by supplying fresh river water and maintaining aeration. Laboratory observations revealed that a continuous freshwater supply, proper aeration, right start food, and regular removal of dead eggs and waste material are the best ways to reduce mortality and shorten the time required for hatching. The mahseer sac fry undergo latency for a period of two days until the yolk is fully absorbed; this phase was considered suitable for long distance transfer (Figure 4).

Collecting Naturally Spawned Egg Fry

The collection net (3-7 m long) devised for this purpose was conical or funnel shaped and made of coarse cloth to allow easy filtering (Figure 5). The tapered end, fitted with a ring 9-12 inches in diameter, was made of reeds. A small pocket net (0.5 m long and 2.5 cm deep) that looked like a monk's hood was attached to the tapering end. Water flow through the net was often enhanced by adding two wings at the mouth.

The net was stretched with the mouth facing upstream in shallow bends of the creek where the flow is gentle, 1.2-2.5 m/sec. The downstream portion of the net would drift in the direction of the current and was tied in this position to poles just below the surface. The upper edge of the mouth of the net and the upper edge of the tail piece was just above the water. The collected spawn and fry were acclimatized separately in cloth bags (Figure 6) and were reared to fingerling stage. Fully grown fingerlings were released later in adult fish ponds at the Gadkhar Fish Farm (Figure 7). Hatchery bred and naturally spawned fry were transplanted to different water bodies.

Artificial Spawning

Induced spawning experiments during 1986-1989 utilized injected extracts of pituitary from carp, with the dosage being four glands per kg body weight of the target fish. The pituitary extracts were injected (with 0.3% saline water as carrier) into male and female breeders. Normally, they spawned after 18 hours with only one intramuscular injection. No death was caused by a higher dosage.

Artificial fertilization, by stripping the male and female breeders, was done by both conventional dry and wet methods. These brood fish ranged from 80 to 160 cm in length and weighed 2,500-3,800 grams. The dry method was far more successful than the wet one.

The larvae obtained by induced breeding as well as the artificial stripping process resulted in 80,000 fry. They were reared in incubation trays and aquaria for a fortnight. About 40% mortality was recorded. Dead fry were immediately preserved for development and life history studies, and live ones were reared to adulthood in the Gadkhar Fish Ponds over a three-year period (Table 3). Various stages such as sac fry, swim-up fry, and fingerlings were transferred from the Gadkhar Fish Farm to the Balaju Fish Pond, Gokarna Fish Ponds and the Kulekhani Reservoir, where the survival of young fish in new habitats was monitored.

During the embryonic development of T. putitora, a characteristic latency period was noticed in which the sac fry became quite inactive, with only feeble motion, and congregated in dark corners of the incubator. This period lasted about 8-12 hours. The hatching period appeared to depend on temperature, with temperatures of 32-34°C accelerating the hatching process. In these experiments, hatching occurred when oxygen concentrations were 8-15 ppm. Although warm, overcast rainy days triggered spawning in T. putitora, hot and sunny days were harmful for the survival of hatchlings.

TABLE 3 Biometric Data on Stages of the Mahseer during a Three-Year Period

Life History Stage

Time

Weight

Length

   

(gm)

(mm)

Egg or spawn

0 hrs

0.15

3.5

Fertilized egg

30 minutes

0.18

4.5

Hatchlings

55 hours

0.20

8.0

Sac fry

72 hours

0.25

12.0

Swim-up fry

110 hours

0.45

20.0

Jumping fry

180 hours

0.50

30.0

Fingerlings

3 months

1.90

80.0

Young fish

6 months

5.00

150.0

Young fish

1 year1

35.00

221.0

Adolescent fish

1.5 years

450.00

250.0

Maturing fish

2 years

2,000.00

600.0

Mature fish

2.5 years

3,500.00

800.0

Spawning fish

3 years

5,000.00

900.9

 

Transfer of Hatchery Bred Fry

During the 1986 studies it was found that 4- to 8-day-old sac fry could be handled safely and transported long distances. On 21 September of that year, 10,000 sac fry (volumetric measurement, 150 fry per cm³) were carried for a distance of 76 km without significant loss. This successful operation was repeated again on September 15, 1987, at which time 50,000 fry were moved the same distance. Each of these trips required about three-and-a-half hours to complete and the water was not changed en route. The sac fry were not advanced enough for free-swimming and settled to the bottom when placed in cans where they remained during transit. The sac fry were raised to fingerling stage in the cloth bags suspended in pond water.

Some transfers of advanced fry (free swimming for 60 days) were made from the Gadkhar Fish Ponds to ponds at Balaju. These fry were collected by net from incubators and transported in fish cans. A total of 22,000 fry of this age were transported by truck in 10-gallon cans for a distance of 70 km without significant loss. It was concluded from these results that advanced fry can survive handling and transportation over long distances.

Stocking of Advanced Fry

There is little information on the relationship between the rate of stocking and the age of stocked fry, and equally little information on the rate of survival and growth. Two of the Gadkhar Fish Ponds were used for stocking 60-day-old fry in 1986. One year later, in September 1987, these two ponds were drained and the fish removed with representative samples collected and recorded. After a 360-day growing period, the fish had attained an average length of 25 cm and weight of 135 gm (Table 3).

Two ponds in Gadkhar were also stocked with 30-day-old fry, which after 360 days had a much lower rate of survival than the two ponds originally stocked with 60-day-old fry. After 360 days, the fish originally stocked as 30-day-old fry had attained an average length of 18-22 cm and a weight of 120-130 am.

Tagging Mahseer

To study the migration and dispersion of mahseer, 1,044 fully grown mahseer and 2,500 young mahseer were tagged (Figure 8). Thirty percent of adults and 10% of young mahseer were recaptured. The young fish were often captured 5-10 km from the release site, but adult fish were usually captured 70-200 km downstream from the release site. This clearly showed that adult fish moved slowly to warm water feeding zones. The younger fish also converged in feeding zones downstream. The release sites in parent creeks often dried up as soon as normal floods were over. Therefore, most of the fish stayed in lower reaches where there was sufficient water for them to survive dry spells. In any case, the mahseer are very mobile. As noted, long distance movement was previously thought to be spawning migration. It is now established that mahseer need fast and relatively warm rainfed creek water for spawning, so they migrate to headwater streams like the Trisuli and Tadi for spawning. Soon after spawning is over, exhausted spawners move downstream as the floodwaters in creeks start to recede until they reach slow water in downstream reaches of the Narayani River. They repeat such migratory cycles year after year. The spawning and feeding areas are geographically separated between mountains and often range over great distances. Mahseer tags were recovered at different points of the Trisuli, Tadi, and Narayani rivers. The tags were returned voluntarily by fishermen, for which they received an award of a mahseer T-shirt. Most of the tags were returned during the spawning season. Tagging studies are still in progress.

Transfer Of Adults

Adult mahseer frequently suffer heavy mortality during transportation. This was counteracted, to some extent, when salt was added to the transport water and, in some species, by adding an anesthetic. The present study was conducted to determine the methods, concentrations, and kinds of anesthetics appropriate for use in the successful transport of mahseer for as long as 10 hours. The 20 adult males used in these experiments had mean total lengths of 50-60 cm and weights of 8-10 kg and the fingerlings were 18-20 cm in length and weighed 45-50 am.

Tricaine methanesulfonate (MS-222) was used as the experimental anesthetic. The anesthetized fish were subjected to a series of tests to evaluate this anesthetic at various concentrations; the stocking density was 2 fish/10 l of water. Concentrations of MS-222 were tested at 5 mg/l with increases up to 35 mg/l. At concentrations up to 15 mg/l the fish exhibited loss of equilibrium. Those exposed to 20-25 mg/l were lightly anesthetized and those exposed to 30-35 mg/l exhibited deep anesthesia. All fish quickly revived. Water quality was better at higher levels of MS-222. The deep anesthesia at 30-35 mg/l indicated the approach of lethal concentrations. Fish were also held without an anesthetic (control) in transport water containing salt at concentrations of 0.05 or 10%. The tests were made in double-lined plastic bags (Figure 9) held in boxes. Air was forced out by deflating the bags to water level; oxygen was then added and the bags were sealed and covered. Boxes were left unattended for 10 hours, after which the bags were opened and fish behavior (Table 4) evaluated by the criteria described by McFarland (1960), with modifications. Fish were acclimatized to 21-28°C and then released together in troughs for observation 10 hours later to evaluate their behavior after being anesthetized (Table 4).

TABLE 4 Classification of the Behavioral Changes of Mahseer under Anesthesia

Stage

Anesthesia

Fish Behavior

 

Classification

 

0

Normal or natural

Highly excited, frantic reaction to external stimuli when caught from riverine habitat

1

Drugged

Decreased reaction to external stimuli, but swimming ability retained

2

Loss of equilibrium

Able to stay afloat, but unable to maintain body equilibrium

3

Light anesthesia

Total loss of swimming power, but able to move on the bottom (with tail movement)

4

Deep anesthesia

No movement on bottom, gill movement greatly reduced

5

Death

Gill movement ceased, fish float belly upwards

Hauling Mahseer By Truck

Three additional tests were conducted to determine the best method for hauling the mahseer in trucks. Anesthetized fish were put into a rectangular tank containing 5,0Q0 1 of water with the anesthetic and salt. Oxygen (3-51/min) was added through a porous pipe. Fish were hauled in the tank for 10 hours, then removed to a holding trough for a 10-hour observation period.

Hauling Mahseer By Jeep

The transportation of mahseer to Kathmandu in a jeep was also evaluated, using MS-222. Two fish were put into each bag containing water (25°C; 10% salinity) and anesthetic, (25 mg/l). Bags were inflated with oxygen and ice was added to the styrofoam boxes. Seventeen boxes of fish were brought to Kathmandu. Fish were acclimatized by floating the bags in a pond at the Balaju Fish Pond following the trip. Water temperature in the bags was about 18°C, whereas in the pond it was 16°C. When the fish were released into the pond they appeared to be in good condition. After one month, two mortalities were noted.

The effectiveness of MS-222 in different species of fish is variable. The threadfin shad (Dorosoma petenese) and gizzard shad (D. copedianum) were hauled successfully in 22 mg/l of MS-222 (Collins and Hulsey 1964, Anderson 1968), whereas the American shad (Alosa sapidissima) was intolerant of a 10-mg/1 dose of MS-222 (Mauri et al. 1979).

Adult mahseer were also transported in big earthen pots filled with water. Natural red clay rich in hematite and collected from river banks was added at the rate of 200 gm in 40 1 of water. Common salt concentration was maintained at 0.5%. Three changes of water were made during the transit, with each change made after a one-hour interval. Fresh red soil and salt were also added at each interval. The dissolved oxygen in the water was found sufficient for the transported fish. Splashing water provided good aeration while the fish were being carried in the earthen pots. This method is useful in places where manpower is cheap and access by road is poor.

Further studies may show that stocking densities in both bags and tanks could be increased. Results of these present tests, however, confirm that every effort should be made to reduce stress and scale loss during the handling and transport of mahseer.

The present work demonstrates the possibility of stocking mahseer in the tailwaters of dams and reservoirs in Nepal to rebuild the declining populations of this valuable fish. Only fingerlings of mahseer are recommended for transplanting and restocking using anesthetics and therapeutic oxygen-inflated bags. In this study, it was possible to transport and release mahseer over a long distance (more than 180 km), from the Trisuli River to the Kulelchani Reservoir.

Discussion

The ranges of mahseer within Nepalese drainage are primarily restricted to the headwaters. Poor habitat caused by man-induced disturbances have eliminated or reduced mahseer and benthic macroinvertebrate communities. The main disturbance in river and creek drainages has been surface stone-mining and siltation. Abandoned stone mines and eroded gullies in stream banks have also contributed to the overall decline in environmental quality. Other factors reported to have an impact on fish communities in these drainage systems include agricultural runoff, drilling runoff, domestic and industrial pollution, and low water discharge during dry periods. All these factors are reported to be of greater magnitude in river tributary watersheds (Shrestha 1988, 1990a,b).

Increased environmental degradation in these drainages in the future could eliminate other allied mahseer species such as Acrossocheilus hexagonolepis, Barbus chillinoids, and B. dukai,

especially those with rigid habitat requirements. Reduced fish communities in tributaries already heavily polluted indicate that this is a serious problem. Additional man-induced disturbances can only escalate the likelihood of the extinction of pristine golden mahseer habitat. Entire watershed control or management and faster propagation may be essential if endangered mahseer populations with limited spawning habitats are to survive. The present study provides some clues for the long-term preservation of Tor putitora by adopting ranching practices or modifying existing fish farming practices.

It was noted that the spawning of mahseer in the Tadi River was always associated with lunar periodicity, water level, flood cycle and heavy monsoon rain, thunderstorms, some physico-chemical features, and undetected biological factors. Majumdar (1940) noted the influence of thunderstorms, rains, and cloudy weather on the spawning of carp. Patra and Azadi (1984, 1985) noted the dates of spawning in the Halda River and found that spawning occurred about the time of the full moon or new moon. The lunar periodicity in T. putitora Is similar to that of many fishes (Ross 1983).

Bandola and Singh (1984) observed that floodwaters and the current of running water act as stimulating factors for carp spawning. It appears from the present study that the water current provided aeration, dispersion, and defense from pathogenic infections of the developing eggs.

The function of flood in the reproductive activities of fish is not clearly known (Shrestha 1986). The turbid waters of flooded streams are apparently not a deterrent to spawning, although great turbulence due to rapid flooding, as in July and August, is unfavorable and mahseer breed with decreasing intensity at high flood periods. It appears that well-oxygenated, gently advancing floodwater over the gravel beds provides the necessary rheotactic stimulus, evoking sexual play in T. putitora. A newly inundated streambed is less likely to be inhabited by enemies and predators such as fry-eating insects and amphibians, and there is less chance of fungal and bacterial infections of the developing egg and fry. Therefore, mahseer leave their parent river for spawning grounds in feeder streams to breed. After the onset of the flood is over, they move downriver to rejoin the main river channel.

It may be concluded from this study that the pattern of spawning behavior of the cold water game fish T. putitora appears to be adapted to reproduction in shallow water creeks and streams. The most distinctive feature is the spawning run, which serves to disperse the pelagic eggs across the current, which are then carried downstream.

Management Consideration

Because mahseer travel extensively, management-oriented ranching research must be conducted. The management of mahseer in relatively closed systems of ponds and reservoirs in Nepal requires very specific strategies. However, research in open water ranching and release systems must also be conducted on a long-term basis. In open river systems, a well-coordinated research effort needs to be directed toward assessing the status of mahseer populations and determining the geographic areas over which uniform management can be exerted.

Acknowledgments

This study (grant number 3.E30) was supported and financed by the U.S. Agency for International Development, Washington, D.C. I am grateful to Mr. B.B. Shah, Deputy Secretary,Department of Wildlife Conservation, Royal Palace, Kathmandu, for his cooperation. I am also grateful to Mr. R.B. Thapa, Additional Secretary, Ministry of Agriculture, for encouragement and support. My thanks also to Professor Douglas A. James and Mr. Robert Jenkins, University of Arkansas, for reading of the manuscript and for providing valuable suggestions. I also want to thank the Office of Research, USAID, for funding the network meeting and publication of this paper.

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