66

Souvenir , 21st All India Congress of Zoology and National Seminar on Biodiversity Conservation with

reference to fisheries management for food , livelihood and environment security held at CIFRI,Barrackpore

, December 21-23, 2010: 66-81.

Status of the fishery of Indian Shad (Tenualosa ilisha) with special reference to

Hooghly river system.

Utpal Bhaumik

Central Inland Fisheries Research Institute, Barrackpore, Kolkata-700120.

The Indian shad, Tenualosa ilisha (Hamilton) popularly known as hilsa belongs to the sub-family

Alosinae of Family Clupeidae. There is no denying fact that hilsa has established itself as one of the most

important commercial fishes of the Indo-Pacific region. It has a wide range of distribution and occurs in marine,

estuarine and riverine environments. The fish is found in the Persian Gulf, Red Sea, Arabian Sea, Bay of

Bengal, Vietnam Sea and China Sea. The riverine habitat covers the Satil Arab, and the Tigris and Euphrates of

Iran and Iraq, the Indus of Pakistan, the rivers of eastern and Western India namely the Ganga, Hooghly,

Rupnarayan, Brahmaputra, Godavari, Narmada and other coastal rivers, the Irrawaddy of Myanmar, and the

Padma, Jamuna, Meghna, Karnafully and other coastal rivers of Bangladesh. The major portion of hilsa (about

95%) is caught by Bangladesh, India and Myanmar.

Presently five species under the Genus Tenualosa viz., Tenualosa ilisha (Hamilton-Buchanan, 1822), T.

toli (Valenciennes, 1847), T. macrura (Bleekar, 1852), T. reevesii (Richardson, 1846) and T. thibaudeaui

(Durand, 1840) have been recognized from the estuaries and coastal waters of tropical Asia. The normal habitat,

trend of migratory habit, maximum age and growth differ from species to species. Since, all these species are

commercially important, they are subject to heavy fishing pressure and its irresponsible exploitation resulted in

decline in catch. Among these five species, only T. ilisha and to a certain extent T. toli are available in Indian

waters.

Scenario of the hilsa fisheries in the Hooghly estuary

Hilsa is the major component of fishery in the Hooghly estuary accounting about 15-20% of the total

fish landing. The annual fish catch of hilsa from the Hooghly estuary are highly fluctuating over the years

(Fig.1). During pre-Farakka barrage period (1957-74), the annual landings of this species varied between 114

and 6573 t with an average of 1,427.6 t. But, increased level of yield was observed during post-barrage period.

The average annual harvest of hilsa was recorded as 2,471 t and 6,370.1 t during 1975-76 to 1990-91 and 1991-

92 to 1998-99 respectively (Annual reports, CIFRI). Hilsa landings in the Hooghly estuarine system during

1998-99 to 2002-03 varied between 6448.2 and 15,799.0 t with an average of 10,382.9 t. Maximum harvest

(15,799 t) was recorded during 2000-01 (De,2001). Hydrological changes with higher freshwater discharge

caused by water diversion at Farakka barrage through Hooghly river might have attracted more hilsa towards

Hooghly estuary. Tremendous increase in effort from nineties with enormous improvement of mechanization to

catch this higher congregation of hilsa in the estuary mouth also contributed to this 4-fold increase of hilsa

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landing. In general, about 80-90 percent of the hilsa is captured during monsoon months (July to October).

Based on the investigation conducted at the Institute during 2010 it can stated that commercial hilsa fishery

exists with the mean length of the catch depicting largest in the range of 300 mm to 480 mm during June-

August, in the middle range of 300 mm to 480 mm during September-November and in the lower range of 300

mm to 400 mm during January to March . Impact of Farakka barrage on hilsa fisheries was very much vivid in

upstream of the barrage where in all the landing centres, contribution of hilsa is almost negligible in total catch.

Fig. 1, Hilsa catch of Hooghly-Matlah estuary

The contribution of hilsa in total catch of the Hooghly estuary were estimated at 15.4%, 11.5% and 7.4 %

thus indicating a decreasing trend during the successive years of 1966-75, 1976-78 and 1984-94 respectively

(Fig. 2). During 1995-2004 the percent contribution has almost touched the record of 1966 - 75. The annual

yield of hilsa increased from 1 457.1 t (1966-75) to 9726.0 t (1995-2004) in comparison to total fish yield

ranging from 9,481.5 to 64,840.8 t from the system during the corresponding period.

Fig. 2. Year wise total and hilsa catch in the Hooghly estuary.

0 10000 20000 30000 40000 50000 60000 70000 80000 90000

Catch (t)

1995-96 1996-97 1997-98 1998-99 1999-00

2000-01 2001-02

2002-03 2003-04 2004-05

Year

Year-wise Total Catch & Hilsa Catch from Hooghly Estuary during 1995-2005

Total catch T.ilisha

0.0

2000.0

4000.0

6000.0

8000.0

10000.0

12000.0

14000.0

16000.0

Catch (t)

Year

Hilsa Catch( t ) of Hooghly -Matlah Estuary

* Bumper catch year (1971-72) * Bumper catch year (1990-91) * Bumper catch year (1981-82) * 1978-79 to 1980-81 no catch available

Post-Farakka Average = 5327.4 t Range = 1101-15799 t Pre- Farakka

Average = 1754.9 t Range = 678-6573 t

Raise of 203.6 %

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Mukherjee and Chakraborty, (2010) while expressing the productions of West Bengal indicated hilsa catch

from inland waters (Hooghly) as 13,172 t, 7156 t, 3310 t, and 4256 t during 2004-5, 2005-6, 2006-7, 2007-8

and 2008-9 respectively whereas from estuarine waters of marine zone it was 27,252 t, 13,172 t, 19061 t,

18,072 t, 9,431 t and 11,744 t respectively in the years as stated.

Age and growth

Table 1: Age and growth of hilsa.

Hooghly estuary (Pillay,

1958)

Hooghly estuary (De 1986;

De & Datta 1990)

North east of india of

Hooghly estuary

(Reuben et al., 1992)

Brahmaputra river

(Choudhury et al.,

1990)

Age

group

Length

(cm)

Age

group

Length

(cm)

Age

group

Length

(cm)

Age

group

Length

(cm)

1.5 24.7-26.5 1 18.9 1 23.8 1 23.0

2.5 34.5-39.1 2 27.7 2 37.2 2 33.0

3.5 39.3-43.6 3 35.1 3 45.6 3 41.0

4 41.3 4 50.8 4 47.0

Godavari estuary, (Pillay &

Rao, 1960)

Chilka Lake (Jhingran &

Natarajan, 1969)

Chilka Lake (Jhingran

& Natarajan, 1969)

Chilka Lake

(Ramkrishnaiah,

1972)

Age

group(yr

)

Length

(cm)

Age

group

(yr)

Length

(cm)

Age

group

(yr)

Length

(cm)

Age

group

(yr)

Lengt

h

(cm)

+1 35.5 1 0-21.0 1 21.7 0 16.2

+2 41.5 2 18.5-31.0 2 35.7 1 23.7

+3 45.5 3 29.4-41.2 2 38.7

+4 48.5 4 39.5-49.3

+5 50.5 5 48.8-56.0

+6 52.5 6 56.0-61.0

The age and growth of hilsa in differet stages was studied by Prashad et al., (1940); Jones & Menon

(1951); Raj(1951) and Pillay(1958) .The growth of juvenile hilsa collected from Hooghly estuary has been

studied by Sujansingani(1957) and De(1986 and 2001). The average growth of young hilsa, observed by them,

after hatching was 28 mm to 32 mm, 48 mm to 63 mm, 64 mm to 73 mm , 74 mm to 83 mm, 84 mm to 93 mm

and 94 mm to 102 mm at the end of one month, two month, three month , four month, five month and six month

respectively. The age and growth of adult hilsa from various water bodies were observed dissimilar. Although,

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it is well known that rate of growth of fish population may vary from one environment to other, or in the same

environment from year to year due to changes in ecology including changes in food availability, density

dependent growth factors etc. (Table-1). The maximum size recorded so far is 600 mm where females are larger

than males. A fair degree of agreement was observed between lengths and at ages obtained by Pillay (1958) and

De(1986) & De & Datta(1990).

Maturity

Table 2: The size at maturity attained by hilsa.

Minimum size

at maturity

Water body Investigator

Male(mm) Female(mm)

280 382 Godavari river Chacko & Krishnamurthy(1950)

300 356 Godavari river Chacko & Ganapati(1949)

216-254 267-305 Hooghly, Chilka & Mhanadi Jones & Menon(1951)

160-170 190-200 Hooghly estuary Pillay(1958)

---- 266 Narmada river Karamchandani(1961)

256 370 Godavari Pillay & Rao(1962)

---- 341 Hooghly estuary De, (1980; 1986)

200 350 Ganga river Mathur ( 1964 )

---- 330 Ganga at Allahabad Mathur ( 1964 )

---- 310 Ganga at Varanasi Mathur ( 1964 )

175-300 200-300 Chilka lake Jhingran& Natrajan (1966)

172 186 Chilka lake Ramakrishnaiah (1972)

360 420-430 Godavari Rajyalakshmi (1973)

210 320 Meghna (Bangladesh waters) Shafi, Quddus & Islam (1978)

400 400 Bangladesh waters Dunn (1982)

---- 415 Kuwait waters Al-Baz (1993)

250 330 Shatt Al-Arab river (Iraq) Mussain et al., (MS)

Minimal size of fish at its first maturity was studied by many investigators (Table 2) whereas stages of maturity

of female gonads have been studied by only few workers namely Pillay & Rao(1962); Mathur(1994) and

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De(1980 & 1986). Perusal of the Table 2, depicts that females below 300 mm size groups are rarely observed to

be taking part in spawning activity. The smallest mature females observed in Hooghly estuary (De, 1980 &

1986)) are around 341 mm (av. wt. 550g) which are comparable to the hilsa of the Ganga where the smallest

mature females observed at Allahabad, Varanasi (Mathur, 1964) and Godavari (Pillay & Rao, 1962) were330,

310 and 370 mm respectively. In almost all cases the age resembles at 2+ or 3+ years of maturity. In the

Hooghly the maximum values of Gonado-somatic Index (GSI) of hilsa were observed during September to

March with a peak in October (15.8470) with an average of 10.2447 indicating its gonadal maturity and

breeding season (De, 1986 & 2001).

Fecundity

Table 3. Fecundity of hilsa from various water bodies.

Water body Fish size Fecundity (nos.) Investigator

Hooghly estuary 253 mm-481 mm 250,000-1,600,000 Pillay(1958)

Hooghly estuary 343 mm-522 mm

3,73,120-1,475,676 De,(1986)

Ganga & Yamuna

(near Allahabad)

315 mm-506 mm 289,000-1,168,622 Swarup(1961)

Ganga(near Allahabad

& Varanasi)

310 mm-436 mm 316,316-1,840,179 Mathur(1964)

Chilka lake 353 mm-515 mm

390,379-1,120,304 Ramkrishnaiah(1972)

Godavari estuary 401 mm-548 mm 400,000-1,300,000 Pillay & Rao (1962)

Narmada 2100 g 1,864,000 Kulkarni (1950)

Padma and Meghna 275mm-483 mm 90,000-2,000,000 Quereshi (1968)

Padma 273 mm-420 mm

348,318-1,465,969 Doha and Hye (1971)

Meghna 380 mm-520 mm 380,000-1,820,000 Shafi et al., (1977)

Padma and Meghna 330 mm-510 mm

320 mm-490 mm

600,000-1,500,000

400,000-670,000

Quddus (1982)

Padma and Meghna 342mm-520 mm

260 mm-470 mm

660,000-1,547,000

399,000-670,000

Quddus et al., (1984)

Meghna 267 mm-523 mm

226,000-1,390,000 Moula (1992)

A wide range of variation is observed in the fecundity in hilsa. Fecundity of the species from various

water bodies estimated by different workers has been presented in Table 3.

The unfertilized mature eggs are almost spherical in shape and demersal in nature. The diameter of eggs

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ranged from 0.70 mm to 0.89mm. Kulkarni (1950) observed that in the Narmada river freshly laid eggs were 1.3

mm to1.5mm in diameter. Jones and Menon(1951), Pillay (1958) and De(1986) observed that the egg diameter

ranged from 0.70 to 0.75mm, 0.89mm and 0.76 to 0.87mm respectively in the Hooghly river. The diameter of

fully ripe egg was recorded as 0.85mm by Pillay and Rao(1962), .76 to 0.86mm by Mathur (1964), 0.70mm by

Quereshi (1968) and 0.73mm by Shafi et al., (1977) from the river Godavari, the Ganga and Bangladesh waters

respectively. The yolk is segmented and has numerous oil globules of varying sizes. The number of ova

increased with the age of the fish and egg diameter was found to increase with increasing fecundity of the fish.

Migration and behaviour

The normal habitat of the fish is the lower region of the estuaries and the foreshore areas of the sea.

Hilsa prefers to reside in this region due to the presence of sub-surface oxygen, relatively low salinity, strong

tidal action, high turbidity, heavy siltation and rich growth of plankton (Pillay and Rosa, 1963). It is well known

that hilsa ascends the rivers for spawning (Hora, 1938; Pillay, 1958; De, 1986) and the spent fish as well as their

progeny migrate down the river towards lower estuaries and coastal areas (Pillay, 1958).Most of the stocks of

hilsa are anadromous, breeding much above tidal limits (Naidu, 1939). Some stocks have also been reported to

remain permanently in the freshwater stretch of rivers (Hora, 1938, Hora & Nair, 1940) and some spawn in tidal

areas. There is no doubt that hilsa is very salinity tolerant and inhabits freshwater, estuarine and coastal waters

in the Bay of Bengal.

Migration and behavioural aspects of the fish are yet to be studied more in detail. Hilsa move on the

surface in the foreshore region whereas in the river they move in deeper zones near the bottom of rivers. The

species move in shoals. The peak upstream migration of hilsa in most of the rivers of the country is generally

with the advent of south-west monsoon i.e., July and August and continues up to October or November

(Kulkarni, 1951; Jones & Menon, 1951; Pillay & Rosa, 1963). While in the Hooghly estuary, the period of

migration is found to be prolonged and extended up to winter (De, 1986; De & Saigal, 1989; De et al., 1994). A

wide range of upstream migration of the fish in various river systems of the country has been reported.

Hamilton (1822) recorded the presence of hilsa near Kanpur and Agra. Day (1877) found hilsa to ascend as high

as delhi. The long range migration of the fish also reported from other principal river systems of the country

viz., Brahmaputra (pillay & Ghosh, 1958; Pillay & Rosa, 1963), Mahanadi (pillay & Rosa, 1963), Godavari

(Chacko, 1949a, b), Krishna (Chacko, 1954), Cauvery (Chacko, 1954), Narmada (Kulkarni, 1954) and Chilka

lake (Jones & Sujansingani, 1951) are well known. Presently the migration of the fish is adversely affected in

these rivers by the construction of dams, weirs, anicuts and barrages (Nair, 1954; Gupta & Jhingran, 1982;

panickar, et al., 1985) and this fish is unable to reach its natural breeding grounds.

Regarding the migration of hilsa into the Hooghly estuary, the fish ascend only for spawning and their

progeny generally after attainment of a size range from 80-110 mm, start their downstream migration towards

its coastal region which commences from February and continues up to June (De, 1986; De & Saigal, 1989 &

De et al., 1994). The young hilsa after leaving the rivers do not go far into the sea but move about on shoals in

the estuary and foreshore regions (Raj, 1937). While in the river Brahmaputra, the peak migratory season of the

species is observed from May to July due to early monsoon.

The upstream migration has been found associated mainly with the state of sexual maturity as well as

volume of freshwater discharge from the estuary during monsoon onwards. However, the other factors like

rainfall, current velocity and temperature, low salinity, turbidity, primary productivity and availability of

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planktonic food cannot be ignored.

The migratory movement of hilsa into and from the river was studied recently in the Hooghly river at

Diamond Harbour and marine zone of the estuary off Frazerganj . The mode of fishing of hilsa in the gill net

was observed during January to March and June to November, 2010. The direction of entangling of the fish i.e.

towards river or sea, and the position of entangling in the net i.e. at the top, centre or the bottom of the net were

recorded. The sex, maturity and length of the fish caught during the days of investigation on board fishing

vessel were recorded. It was observed that a large number of hilsa were entangled in the gill net at the top and

central portion during high tide especially in the evening hours during their migration process into the river.

However, during low tide migrating spent fishes from the river into the sea were invariably gilled at the bottom

of the net indicating the habitat of the spent fish. The experimental fishing to follow the movements of hilsa was

conducted during peak periods of migration in monsoon, post monsoon and winter. As compared to the higher

catch of hilsa obtained in the coastal areas and the lower estuary, the poor catch was recorded in the river which

indicates that hilsa does not move in the river in shoals.

Based on the study of extensive samples of fish for length frequency as well as sex ratio and maturity

condition of the migrants it was observed that there are two well-marked migration of hilsa into the Hooghly

during monsoon (May - October) and the other during the winter (January-February). In the riverine area the

large size groups of fish are abundant roughly between May and October. After October this group declined to a

minimum by December. The catch rates for the Hooghly revealed two peaks, one in May another in August, but

the Gonado-Somatic index (GSI) value was found to peak in October. The medium- sized group was available

all through the year. From November to March, medium- sized groups showed dominance over the large- sized

group. Fishermen during this time also fished with smaller- meshed nets, because of the predominance of

smaller to medium sized hilsa. The catch rate and GSI value were found to be higher during March. The catch

rate of this medium sized fish in winter indicates a lesser degree of migration into the river. Two size groups of

300-430 mm and 460-490 mm, former being the most dominant, participate in spring migration. The monsoon

run of hilsa comprises two groups varying between 300-370 mm and 400-500 mm, the later being most

dominant occurring very much in the river catches. Smaller size fish of less than 300 mm also enter the river

sporadically in very small numbers along with the bigger size groups of spring as well as monsoon runs of hilsa

. The spring spawners that enter the river for spawning in January - March return to the sea during July- August

when these are caught in good numbers. The monsoon spawners that enter the river during September- October

return to the sea after spawning and these spent fishes are caught in good numbers during January- March.

Similarly, the offspring of spring spawners journey to the from the river during November- January, whereas

the offspring of monsoon spawners return to the sea from the river during July- September. The return of the

broods of spring and monsoon spawners to the sea is not as precise as the river- ward migrations of hilsa. Full

recruitment of juveniles into the marine fishery is observed for 4 to 5 months in a year i.e. between July and

January with a peak in October. Although the minimum size at recruitment into the sea is at 160 mm to 180 mm

whereas the juveniles are fully recruited into the fishery at a length of 260 mm to 270 mm approximately at an

age of one year. But the maximum exploitation of this stock is effected when they congregate in the near shore

areas and lower estuaries at lengths of 350-390 mm at the age of about 2 years approximately. This also

coincides with the size at first maturity of hilsa .

In the Sunderbans, the commercial fishery is supported by the medium sized group ranged between 300 mm

and 390 mm. In the river Yamuna, Ghosh (1967) observed that distribution of dominant size group fell into the

category of small to medium sized fish ranged between 230 mm and 380 mm, while the success of the fishery

depended upon additional contributions from the larger fish group , size of which ranged between 380 mm and

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500 mm. This is very similar to the situation obtained in the previous study also. In Chilka lake, it was the small

and medium-sized fish group whose size ranged between 240 mm and 400 mm, supported the fishery (Thingson

and Natarajan, 1969; Ramakrishnaiah, 1972). The upstream migration of winter spawners and the downstream

migration of summer spawners as spent fish are likely to intermingle at various positions in one or other

environment. Such intermingling cannot be ignored owing to the use of different mesh sizes in the fishing

operations.

Spawning

Investigations made by many workers on the reproductive biology of hilsa indicated that the spawning

of this species is seasonal. In almost all major river systems and lagoon viz., Hooghly, Ganga, Chilka, Tapti,

Indus and Padma and Meghna the spawning season of hilsa has remarkably been noticed during the period

between August and October. Rao and Pathak(1972) observed the peak spawning of hilsa in the river

Brahmaputra from May to July. It is also noticed that mature hilsa immigrate to Iraqi rivers for spawning during

March to July.

Some school is in opinion that the fish spawn throughout the year in the Hooghly whereas Pillay (1958)

opined that hilsa spawn intermittently in the Hooghly and the fish have two distinct breeding seasons where the

same fish do not spawn twice during the year. The occurrence of two spawning has also been reported from the

Ganga river (Nair, 1958; Mathur, (1964) and Chilka lake (Kotwal, 1967).

The existing knowledge on early growth rate species in the Hooghly estuary as estimated by

Sujansingani (1957), De (1986), De and Saigal (1989), and De et al ,1994) indicated prolonged spawning

season of the species i.e. during August - March with peak in October- November and February-March.

Based on the study conducted at the institute in 2010 towards availability of hilsa seed along the entire

stretch of the Hooghly indicates the available sizes of the juveniles as 40 mm to 92 mm in December, 50 mm to

90 mm in January, 56 mm to 112 mm in February, 70 mm to 115 mm in March and 75 mm to 149 mm in April.

It clearly indicates that major spawning takes place during October–November and minor spawning during

May–July and January–March. This is in conformity with the study of Bhanot (1973) who confirmed through

collection of the hilsa juveniles in the Hooghly estuary that the species breeds throughout the year with peak

activity in February-March , July-August and October-November.

Artificial Fecundation of Hilsa

During late seventies Malhotra et al., (1969 & 1970) successfully bred hilsa by ‘wet stripping’ in the

Ganga river about 50 Km downstream of Allahabad during 1968 to 1972. Panicker et al., (1985) also achieved

success in propagating the fish at Vallabasagar(Ukai) reservoir in Gujarat. After that De (1986), De &

Sinha(1987) and Sen et al., (1990) also successfully bred the fish by wet stripping the marine stock of hisa

collected from the lower stretch of Ganga, downstream of Farakka barrage and they were able to rear the

hatchlings for a considerable period.

Hilsa juveniles

During the commencement of the south-west monsoon and consequent flooding of all the rivers, hilsa

starts its spawning migration upstream. A mature hilsa lays eggs, the eggs are deposited in fresh water where

hatching takes place in about 23 to 26 hours at an average temperature of 23oC. The newly hatched larvae is

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recorded as 2.3 mm in size and the larvae and juveniles make their way downstream to the sea during a period

of several months, feeding and growing on the way. At this stage of their life cycle , the juveniles of hilsa

having the size range of 40 mm to 150 mm are widely available during February to May in the foreshore and

riverine water of Hooghly and other deltaic rivers of Sunderbans.

Usually, these juveniles graze for five to six months of age in fresh water before they migrate to

seawater. They are caught in large amount using current nets of small mesh size during their grazing period in

rivers as well as in sea shore by artisanal fishermen to sell them in local markets, calling them "Khoira (Gudusia

chapra)" and thus, taking part in wanton killing of these tiny fishes .

Method of exploitation

Hilsa is available throughout the year in the Hooghly estuary with peak (about 70%) in monsoon months of

July to September. Fishermen deploy various fishing gear to harvest this prized fish mostly by engaging drift

gill nets (locally known as Chhandi jal, dholi jal, kona jal, etc.). Besides the gill nets, purse nets (locally known

as Sangla jal) and set-gill nets (locally known as Nangar jal) are also among the selective gear exclusively used

for catching hilsa. Inventory of crafts and gears and effort computations are available dating back to 1956-58 in

respect of Hooghly-Matlah estuarine system. Mitra et al. (2001) have computed past information on fishing

gears of Hooghly estuary which pertains to year 1982-83 and compared with their earlier availability, two and

half decades back. Conspicuous decrease in seines, purse nets, lift and long lines have been recorded by them

but there has been observed significant increase (from 36966 during 56-58 to 98083 during 82-83) in drift gill

nets (265.33%) and other nets used for exploiting Hilsa, over the years from 1956-58 to 1982-83. Switching

over from purse nets to drift gill nets for catching Hilsa is attributed to higher CPUE of the later so that the

increased demand of this fish may be met. Crafts and gears used for exploitation of Hilsa during the period

1999-2000 revealed an overwhelming increase in numbers of drift gill nets to the tune of 441510 (size range –

40’x18’ to 60’x30’). Regarding crafts, 1572 numbers of mechanized boats with capacity varying from 15 to 105

HP and 22992 numbers of non-mechanized boats were recorded operating for exploitation of Hilsa during the

period 1999-2000. Such a tremendous increase in numbers of gears very precisely indicated over-exploitation of

this resource negating the sustainable development of Hilsa fishery.

Remesan, Pravin and Meenakumari (2009) have dealt upon the non-selective gears and sustainability

issues relevant to the Hooghly-Matlah estuary and inferred that gears viz. Behunti Jal, a stationary bag net with

a wide mouth of 27 m and with very small cod end of mesh size (about 2 mm), Char-pata Jal, a screen barrier

having very small mesh operated for harvesting juveniles and Sitki Jal, a skimming net made up of polyethylene

netting of mesh size of about 2 mm for collecting fry and fingerlings, are non-selective and highly hostile for

sustaining the fisheries. They have also offered certain suggestions for improvement in context of code of

conduct for responsible fisheries (CCRF).

Status of Stocks Mitra et al. (2001) have undertaken the trend analysis of time series data of Hooghly-Matlah estuarine

system for the period 1961-62 to 1995-96 and have concluded that the total yield has already touched the MSY

and the system will attain overexploitation by 2000-01. Nath, Misra and Karamkar, 2004 have computed the

maximum catchable potential yield Cmax being 67855.1 t by using time series data for the period 1998-99 to

2002-03 in absence of effort data based on calibration of gears. A peep into the average catch for the

corresponding period revealed that the estuary is being exploited very near to Cmax and further increase in

efforts will make the system unsustainable. MSY in respect of Hilsa was computed to be 3507.5 t which

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indicated an over-exploited state of Hilsa fishery in Hooghly-Maltah system. The emerged state of Hilsa stock

in Hooghly-Matlah system and other resources indicate that no yard-stick has been prescribed for Harvest

Management Decision. No assessment is available regarding how many numbers of Hilsa migrate to fresh water

habitat and how many returns to marine habitat. The Harvest Management scenario is very foggy. For

conservation and sustainable development of Hilsa fishery in this region, there is exigent need to identify the

tools for reaching to harvest management decisions, a pre-requisite for sustainable development. This is equally

essential to verify the suitability of existing methodology to assess the stocks. Hilsa migrates from marine

habitat to fresh water habitat through estuarine habitat, as such; this anadromy has made Hilsa vulnerable to

varied set of environmental conditions prevailing in these habitats and the stocks will have the impact of such

conditions. This warrants studies pertaining to the impact of natural and anthropogenic factors on Hilsa stock.

Exploitation vis a vis Conservation

As per protocol fisheries are a state subject and practically control on modes of fishing is totally rested on them.

Mono-filamentous fishing gears having 80 to 85 mm and below mesh size are being used to exploit undersized

hilsa below 500g at Fraserganj, in proximity to mouth of Hooghly estuary. This denies the fishes to breed and

the very purpose of developing sustainable hilsa fisheries is greatly defeated. Observations in the fish catch of a

few mechanized boats operating from Frazerganj fishing harbour revealed that hilsa contributed to 56.3% of

total catch of 3.2 t and most of the fishes (66%) were female and 59.8% of fishes have attained 4th stage of

maturity. A concern for bottom trawling by foreign vessels has also been raised, since besides exploiting hilsa,

these are also ruining the breeding grounds of a number of fin and shell fishes. Bag net fishing is rampant and

this is denying the hilsa juveniles to contribute towards fishery .These approaches cover high risk under the

prevailing set of negative harvesting measures. There is practically no control on fishing efforts and compliance

of observing closed season is limited and there is hardly any gear restrictions due to open access, lack of social

awareness, poor control and surveillance.

Desired measures towards responsible fishery

Technical measures for effecting improvisation in harvesting methods and employing conservational

measures are main concern at state as well as central level. An official fishing ban in marine fisheries sector

exists from 15th April to 15

th June in West Bengal which does not coincide with the period as real migration of

brood fishes which takes place beyond this period. There is a need enforce the laws more realistic and user-

friendly. Fine meshed gears are employed which are non-selective and cause comprehensive loss due to non-

compliance of Code of Conduct of Responsible Fisheries (CCRF). As a matter of fact the compliance of

measures towards conservation is very poor.

Monitoring, Control and Surveillance (MCS)

Monitoring, Control and Surveillance are state subject. The State Fisheries Department estimates catch

based on sample survey and compute total fish catch of different fisheries resources of the state. But this data

does not provide adequate base for trend analysis. There is hardly any control over the exploitation systems

being practised by fishers in the estuary. This is like an open access to every one although licensing codes

imposed the state are existing . There seems to be inadequate resource management policies where the

enforcement agency expresses their helplessness due to limited man power and other infrastructure facilities.

The fishers and other user groups due to poor socio-economic status find it very difficult to comply with the

rules and regulations. As such, the surveillance towards responsible fishing is very poor resulting in destructive

fishing not only by the fishers of national arena but also from the foreign intruders.

Possible modification of management measures

Possible modifications in prevailing management practices may be exercised by bringing in holistic eco-

system based approach of management since institutional management arrangements vested with various

stakeholders do not adequately address the challenges, which the hilsa fishery faces today. A score of factors

viz. over-harvesting, negative habitat modifications, climate change etc. have contributed to the decline of hilsa

76

fisheries but we need to give due impetus to human activities overridingly effecting the management of hilsa

fisheries. Habitat improvement following stock assessment, harvest management decisions including closed

season declaration, closed area provision and ban on negative fishing methods and a strong monitoring

machinery is the need of the hour.

Threat perceptions

i) Siltation in estuary mouth

The mouth of estuary is gradually affected by siltation resulting in serious hindrance of hilsa migration

into the estuary.

ii) Impact of barrages, dams etc

Construction of dams, barrages, anicuts etc over the rivers has created an obstruction in migration of

hilsa resulting in sharp decline of its fisheries. The barrages or dams also deprived of water flow required for

spawning and migration of hilsa. Hilsa used to migrate even up to Delhi through river Ganga and also it was

recorded from Agra and Kanpur. After commissioning of Farakka barrage over the river Ganga in 1975, hilsa

fisheries at upstream of the barrage was almost extinct in most of the fish landing centres. An average of 92%

reduction in hilsa catch at upstream of Farakka barrage was estimated by CIFRI due to construction of the

barrage. Even at Allahabad, where hilsa used to occupy a significant share in total fish catch, now it forms a

meager percentage in total fish catch. Due to Farakka barrage, hilsa is forced to shift its natural breeding ground

at the long stretch of Allahabad to Munger. Change in hydrological regime and obstruction at Farakka barrage

forced hilsa to breed downstream of the barrage.

iii) Juvenile fishing Present study reveals that hilsa breeds through a prolonged breeding season as evidenced by availability

of hilsa seed from August to May. This suggests that spawning is not strictly simultaneous for all ascending

individual. The small juveniles are often caught in small meshed bagnet and scoop net during their migration

towards sea especially during November to May and sometimes up to July. The recent investigation in 2010

recorded a very alarming situation when a single bagnet catch of 10 kg at Godakhali near Budge Budge had a

share of 2.8 kg very small hilsa juveniles with 5-20 g in weight. Similarly, the catch of scoop net (locally called

vetijal) operated between Sodepur and Budge Budge during March mostly consisted of hilsa juveniles (>90%

by numbers in total fish caught).

The estimated catch of these juveniles fluctuated between 41.1 t and 151.01 t with an average of 85 t per

year during 1998-2003. Their size ranged between 62 mm and 155 mm in length and 2 to 28 g in weight. An

extrapolated estimation reveals that 50% reduction of the juvenile killing has the potentiality to increase the

adult production by about 10%. Another estimate reports that if even 1% of this could be saved, then the

production of hilsa would be increased by 4000 t/year.

iv) Exploitation of brood fishes

the present study reveals the fishermen harvest gravid female hilsa during their upstream breeding

migration especially at estuary mouth during monsoon. This has a tremendous adverse impact on declining of

hilsa fisheries. The undersized hilsa below 500g are being caught in plenty using monofilament fishing nets at

Frazerganj-Namkhana area in Hooghly estuary defeating the very cause of stock sustenance and facilitating

decline of hilsa fishery in the Hooghly estuary. Hilsa is reported to attain its first maturity for spawning after

attainment of 340 mm (av.wt 550 g). Fish catch recorded from five mechanized boats at the Frazerganj fishing

harbour was 5.6 t where the contribution of hilsa alone was 3.2 t (56.3%) and 66% were female fish.

Observations on the maturity conditions revealed that 59.8% of the fishes were in 4th

stage of maturity followed

by 26.3% in 3rd

stage, 7.5% in 2nd

stage and 6.4% in 5th stage.

v) Lack of mesh size regulation

Presently fishing with small mesh sized (< 60 mm) gill nets are mainly responsible for reducing the size

of hilsa in the coastal as well as in the inland waters of West Bengal. In order to maintain sustainable yield and

77

also to increase fish production, regulation of selective fishing through control of mesh size of the fishing

gears are warranted.

vi) Over-fishing

The trend of fish catch in Hooghly indicated significant increase during the post Farakka Barrage,

primarily due to manifold increase in Hilsa catch. In recent years, between 1998-99 and 2002-03, the average

per annum catch of hilsa has been estimated at 10,382.9 t with an impressive increase of 63.3% from the

corresponding five years (6279.6 t). Over the years, however, the mean length of hilsa has declined, from 356

mm (1960s) to 325 mm or even less (2000s) - a manifest of increased efforts, indicating over-fishing.

vii) Ineffective fish pass

Fish pass constructed in some of the weirs and barrages across most of the river systems of India also

totally failed to facilitate upstream migration and vice-versa. Same situation is observed at Farakka barrage also.

Tagging experiments conducted CIFRI revealed that hilsa from Bhagirathi / Hooghly cannot move across the

barrage due to obstruction at feeder canal outlet. However, hilsa can negotiate Farakka run barrage to a small

extent during monsoon from Padma side and observed to bred upstream barrage.

viii) Loss of habitat

Increased water abstraction for irrigation as well as use in industrial purpose resulted in reduction of

water volume in parts of upper Hooghly estuary which has caused loss of required habitat for migration and

spawning. Siltation in rivers created shallow water depth unsuitable for hilsa migration and it is reported that

hilsa prefers migration at a depth >3 m. The loss in habitat is directly related to the recruitment potential of

hilsa fishery.

ix) Pollution

Ecological parameters due to presence of industrial and domestic effluents in most of the river systems

also inhibit the upstream migration. Hooghly-Matlah estuarine system flows through highly industrialized area

like Haldia complex and Calcutta metropolis and gets domestic refuse from thickly populated city areas, as

such, the estuary has become the repository of municipal sewage and industrial effluents. This exerts great

stress to migratory fishes like hilsa.

Suggested interventions towards conservation of the hilsa fisher in the Hooghly estuary

The major breeding migration of hilsa starts during July, which extends up to winter. The official fishing

ban in force in the marine fisheries sector along the West Bengal coast is from April 15 to June 30. Thus,

beyond the prevailing period of the closed season there is need to strictly adhere to the mesh size (100 mm)

regulation especially at estuary mouth for exploitation of hilsa above 550 g to protect the precious hilsa

brooders and give them chance to breed at least once in a life cycle.

It is recommended that there should be a strict ban on catching of juveniles to conserve hilsa fishery. Strict

vigil is required by the law enforcing authority. As most of the juveniles start downstream migration during

March-May after attainment of the size of 80-150 mm, regulation towards the use of bag net or scoop net

during these three months will facilitate the juveniles to migrate to the sea and maintain the original stock.

It is expected that most of the migrating hilsa breed near Farakka barrage once obstructed. Fishing may be

prohibited within five kilometers of the barrage to facilitate brooders for spawning.

Improvement of aquatic habitat with more emphasis in dredging the estuary mouth may encourage more

spawner to migrate upstream.

Surveillance by the Territorial Coastal Guard is very much desired to stop operation foreign vessels in the

fishing areas of marine zones of the estuary.

Conclusion:

In view of the present national interest for sustaining hilsa fishery in the country, there is an urgent need

towards conservation of the species. Intensive fishing in all the water bodies is to be controlled without further

78

lapse of time. In order to maintain sustainable yield and also increase production, regulation of selective fishing

by adjusting mesh size of the gears should be encouraged. This will ensure the fish, having a length and weight

up to 340 mm and 550 g respectively when it attains first maturity, to have a chance to escape for breeding. To

fulfill this, minimum mesh size of the gill net should be 100 mm. Hence, strict conservation measures are

warranted for improvement of hilsa fisheries in the Hooghly river system.

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