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Indian Journal of Geo Marine Sciences Vol. 48 (12), December 2019, pp. 1870-1880

Life History and Population Dynamics of Tenualosa ilisha of Sundarban Estuary in Bay of Bengal, India for Sustainable Fishery Management

Sachinandan Dutta1*, Kunal Chakraborty2, and Sugata Hazra1 1School of Oceanographic Studies, Jadavpur University, Kolkata, West Bengal, India. 2Indian National Centre for Ocean Information Services, Hyderabad, Andhra Pradesh, India. *[E-mail: [email protected]]

Received 25 April 2018; revised 24 July 2018

The population structure of Hilsa Shad (Tenualosa ilisha), a choicest table fish, in the estuaries of India, Bangladesh and Myanmar of Bay of Bengal has been studied by different methods and each provided complementary data on population structure. Considering the present scenario of climate change, increasing pollutant load in Indo–Bangladesh estuarine region and its effect on reproduction and maturation of anadromous Hilsa Shad, a thorough and detailed understanding of the life history of Hilsa is a pre requisite criterion. Results of such studies would be important for sustainable management of this highly economic biological resource. The present paper deals with the aspects of life history and population dynamics of Hilsa Shad in Sundarban estuaries. The data collection was done during the period of June 2011 to March 2012 at Frasergunje Fishing Harbour and offshore of northern Bay of Bengal. The length and weight of total 617 Hilsa fish were measured under this study. Monthly variations of length and weight, length frequency distribution, monthly variation of the allometry coefficient, movement pattern, and catch per unit effort were estimated. The exploitation rate of Hilsa species was found to be 0.78 and the maximum sustainable yield was 11700.18 tonnes whereas the annual catch was 18126.00 tonnes. Highest weight of adult Hilsa was recorded during the monsoon i.e. the months of June, July and August. The result of relative yield per recruitment indicated that the mortality due to current fishing period and pressure were high. Widespread fishing of juvenile and growing Hilsa (< 500 g) declined the Hilsa population considerably losing the economic advantage. The present paper dealt with life history parameters like, growth, exploitation, mortality, stock assessment for sustainable management of Hilsa population. In our study we have observed that Hilsa fish, especially Jatka (<500 gms and <230 mm) is over harvest, from West Bengal coastal areas.

[Keywords: Bay of Bengal; Exploitation rate; Hilsa; Life history; Sustainable management]

Introduction Kuwait and Iran5. Large fish schools of Hilsa Shad have Five species of tropical shads (Tenualosa ilisha, been reported throughout its geographical range, by T. toil, T. macrura, T. reevesii, T. thibaudeaui from fishermen at various times of the year in coastal waters, the Clupeidae family) live in the estuaries and coastal but, the origin and movement of these fish have never waters of tropical Asia1. Among the above-mentioned been investigated6. The growth, mortality estimates five species, Hilsa Shad (Tenualosa ilisha) is the most derivations have suggested that Tenualosa ilisha economically important species and its habitat is has a high resilience to exploitation7. This fish is marine water, freshwater and brackish water. The generally categorized based on its distribution, nature of Hilsa species is pelagic-neritic and abundance, habitat, life history characteristics and the anadromous. Hilsa spends most of its life in the amount of harvest. inshore areas of the sea and undertakes extensive In order to study the population response or, in migrations ascending the estuaries and rivers for the general, the life history pattern of an economically purpose of breeding2. In India, Hilsa migrate upto important species, it is necessary to consider both Allahabad before Farakka barrage contraction and the human impact and the environmental forcing8. reduction in Hilsa catch recorded at upstream of Life history theory offers a promising framework Farakka barrage3,4. The distribution of the species is for building bridges between demography and very high in GBM (Ganges-Brahmaputra-Meghna) fundamental aspects of species biology9. basin of northern Bay of Bengal, it is also found in The life history of Tenualosa macrura has been Mayanmar, Vietnam, West coast of India, Pakistan, studied for the purpose of its management1,10. Growth 1871 DUTTA et al.: LIFE HISTORY OF TENUALOSA ILISHA

and life history studies were conducted on Hilsa in Materials and Methods Hooghly Estuarine System11, in the waters off the coast The present study was conducted during June, 2011 of Bangladesh12,13in India14and in Sindh, Pakistan15. to March, 2012 (Fishing ban is observed during In this paper, we have studied the length weight 15th April to 31st May on the east coast of India) at relationship along with the month wise length weight Frasergunje Fishing Harbour and northern Bay of variation, length frequency distribution, weight Bengal (NBOB) of West Bengal (WB) (Fig. 1). The frequency distribution, allometry coefficient. length and weight of 617 Hilsa fish were measured Moreover, Catch per Unit Effort (CPUE) of Hilsa and under this study. In order to study the migration migration pattern along with catch structure in Bay of pattern of Hilsa, we have used the fish catch and Bengal, West Bengal was examined. The basic effort data obtained from fishermen in NBOB, WB. objective of this paper was to study the life history Length-weight data of T. ilisha were measured by pattern of Hilsa species to utilise it in sustainable metric scale and a digital weighing machine of usage and conservation. In this light, the management Wensar (TTB-3), (providing a maximum measuring of Hilsa species was taken into consideration. capacity of 3 kilograms and an accuracy of 0.1 gram). The managerial recommendations were provided The harvest data was collected from the gillnetters with the help of the obtained results for the most fishermen of northern Bay of Bengal. We measured uncertain climatic zone of northern Bay of Bengal total length of each fish. Total length means the (Sundarban Estuary). Mandal et al.16 nicely described measurement of the fish from the lower jaw to the tip the fish diversity of Sundarban estuary in their review of the tail by laying it normally i.e., without any work, but the present study is conducted in marine stretching17. The on-board sea surface temperature part of Sundarban estuary. (SST) was measured in  C unit. The salinity was

Fig. 1 — Map of the northern part of the Bay of Bengal with bathymetry and Frasergunje Fishing Harbour. INDIAN J. MAR. SCI., VOL. 48, NO. 12, DECEMBER 2019 1872

measuredin ppt (parts per thousand) unit. The SST The natural mortality (M) of Hilsa Shad was and salinity were measured by the fishermen regularly calculated using Pauly’s M-empirical equation20 as with the help of a hand held digital thermometer follows: (H-9269) ranged between  50 ° C and 200  C and Erma Hand Refractometer ranged between 0-100 ppt. Log10M=.0066 – 0.279Log10L8 + 0.6543Log10K + The month wise catch and effort data were obtained 0.4634Log10T, SD (logM)=0.245 from the fishermen of Frasergunje Fishing Harbour. CPUE was calculated in kg/hour unit. where, the mean habitat temperature (T) is considered All computations were carried out using Microsoft as 27.8 °C. Office 2010 and MINITAB 13.31 software package. The fishing mortality rate (F) was calculated as The Pearson co-relation was used for all statistical F = Z  M and the rate of exploitation (E)was calculations. calculated using the quotient between fishing and total 21 The frequency distribution of length and weight mortality: E = F / Z . was calculated. We have used the following non- The length of Hilsa depending on age was linear form of the length-weight relationship: estimated from the von Bertalanffy growth equation:

b W = aL , L = L ( 1  e  K(t  t 0 ) ) , t  where, W is the weight of the fish, L is the total length where, L =Length at age t, L = Asymptotic length, of the fish, b is the exponent describing the rate of t  change of weight with respect to length and a K= Growth coefficient, t0 = Age at length zero and denotes the weight at unit length. The ‘ a ’ and ‘b ’ t0 was calculated from the following expression: b were calculated from the W = aL equation. Fulton’s condition factor was calculated using the following Log(  t ) = 0.392  0.275 Log(L )  1.038 K . formula: 0 

C = 10 5 W / L 3 , Again, the weight of Hilsa depending on age was estimated from the von Bertalanffy growth equation: where, W = the weight of the fish in grams; L = the (  K(t  t0 ) 3 standard length of the fish in millimeters. W t = W  ( 1  e ) , Ford18 – Walford19 equation was used to estimate the von Beralanffy growth parameters; asymptotic where, Wt =Weight at age t , = Asymptotic weight, length (L) and VBGF growth constant (K). K = Growth coefficient and t = Age at weight zero. The equation is: 0

The age at maturity (Tm ) was estimated according  K  K 22 L t  1 = L  (1  e )  e L t to Richter and Efanor . where, L and L are the total length at age t and t+1 1.52 t t+1 T = respectively. By plotting L against L , the resulting m 1 t t+1 ( )(M + 0.16 ) slope b  e K ) and the intercept a  L  (1  e  K ) 0.72

Total mortality (Z) could be estimated using The lifespan (Ls) of Hilsa was calculated from parameters of the von Bertalanffy Growth Function (VBGF) as follows: 3 L = + t . s K 0 L   L Z = K  , L  L' The recruitment pattern was figured out by the backward projection of the length-frequency data, where, K is the VBGF growth constant, L is the using the von Bertalanffy growth equation and the 23 asymptotic length, L is the mean length of the fish estimated growth parameters ( L and K ) . population and L' represents the mean length at entry The total annual stock size, average standing stock into the fishery. size and MSY of T. ilisha was estimated. In this

1873 DUTTA et al.: LIFE HISTORY OF TENUALOSA ILISHA

regard, the initial exploitation rate (U) was estimated Relative biomass-per-recruit (B ' / R) was estimated 24,25 using the following equation : from the following equation:

Z U = F / Z( 1  e ) . B ' / R = (Y ' / R) / F .

In order to estimate the annual catch (Y) of Hilsa, The Hilsa movement pattern was traced out by the landing data was collected from the Department of utilising the fisherman catch data as well as by using Fisheries, Govt. of WB. The total annual stock and Geographic Information System (GIS) and Remote standing stock were calculated usingU , F andY . Sensing in this study. An attempt was made to map Finally, the approximate MSY was calculated using the position of the major stock of Hilsa. The the following relationship, proposed by Gulland26, geographical positions of high (>150 kg per haul) Hilsa catch zone was incorporated in a geo-referenced image of BOB in order to create an output map for MSY = Z t  0.5  B t , clear understanding of the Hilsa migration pattern. where, Z is the instantaneous total mortality in the Moreover, during the study period, we recognized the t movement of Hilsa stock in the marine and lower year and is the standing stock size in the year t. t Bt estuarine part of Hugli-Matla estuary of Sundarban The relative yield-per-recruit and biomass-per- Biosphere Reserve. recruit were estimated based on the Beverton and 27 Holt model. Relative yield-per-recruit (Y ' / R) was Results computed from: Length and weight frequency distribution The minimum and the maximum length of Hilsa of ' M / K Y / R = EU our sample were 208 mm and 504 mm respectively. 1  3U / ( 1 + m) + 3U 2 / ( 1 + 2m )  U 3 / ( 1 + 3m ) , For presenting a length frequency distribution the seven length classes of 50 mm width was considered with uniform step length 50. The class 258–308 mm where,U = 1  (L / L ) and L is the mean length of c  c comprises the majority of specimen throughout the fish at first capture. In standard case is taken as , Lc L50 year (Fig. 2). The weight frequency distribution of T. ilisha was m = (1  E) /(M / K) = (K / Z) divided into fifteen classes with minimum weight and E = F / Z . 94.10 g and maximum weight 1382.20 g with uniform

Fig. 2 — Monthly length frequency distributions of Hilsa between June-2011 and March-2012 with an interval of 50 mm and minimum length class 208 mm and maximum length class 508 mm. INDIAN J. MAR. SCI., VOL. 48, NO. 12, DECEMBER 2019 1874

class width 100 g. The weight class 195 – 295 g was highest during the monsoon i.e. the months of comprises the majority of Hilsa fish throughout the June, July and August. The weight of Hilsa was year and consequently, it was obvious that maximum approximately 450 g during monsoon whereas during Hilsa fish belong to this class (Table 1). The weight the rest of the year the weight observed was 300 g. decreased during post monsoon season. Allometry coefficient Length weight relationship The allometric coefficient of Hilsa was increased The length-weight relationship of T. ilisha was during monsoon season (June-August, Fig. 4). At the statistically significant (p<0.0001) and estimated as end of the monsoon, it started decreasing, and subsequently, during the post monsoon season, it 2.86 2 W = 0.00002×L , R =0.92 (Fig. 3). remained almost uniform. It was also observed that allometric coefficient again starts increasing during The month wise variation of length-weight the pre-monsoon season. relationship was clearly depicted in Figure 4. It was to be noted that the length of Hilsa did not Condition factor vary significantly throughout the year (Fig. 5). The The condition factor varied between 0.9 and 1.2. average length was measured 301.18 ± 44.72 S.D. mm. During June to October, the condition factor of It was clearly observed that the weight of adult Hilsa Hilsa was increased from 1.0 to 1.2, which clearly indicates that the fish were in good condition indicating a favorable and healthy habitat for living. However, it decreased during December to March. The condition factor of Hilsa increased with decreasing salinity and increasing temperature (Fig. 6). The habitat mean temperature and salinity were 27.765 ± 0.147 S .E . and 21.938 ± 0.363 S .E . , respectively.

Catch per Unit Effort The values of CPUE were varying significantly during monsoon, pre-monsoon and post monsoon season. During the monsoon period, CPUE increased steadily. It started from June and continued till Fig. 3 — Total length weight relationship of Tenualosailisha October, but in the post-monsoon season CPUE in 2011-12. decreased drastically (Fig. 7). This implies that the

Table 1 —Weight frequency distribution of Tenualosailishain June, 2011 to March, 12 of West Bengal coast, weight is divided into 15 class of 100 g interval with lower limit of weight class of 95 g and higher limit of weight class of 1395 g Gram June July August September October November December January February March 95 g 1 195 g 3 3 13 21 9 8 20 6 3 13 295 g 3 13 2 23 38 26 59 22 44 40 395 g 2 29 4 15 5 3 26 17 17 15 495 g 1 15 3 8 5 2 7 2 1 5 595 g 3 5 6 5 2 2 695 g 1 6 4 2 1 1 795 g 2 4 1 2 3 895 g 2 2 3 1 1 995 g 1 2 1095 g 2 1 1195 g 1295 g 1395 g 1

1875 DUTTA et al.: LIFE HISTORY OF TENUALOSA ILISHA

Fig. 4 — Monthly length-weight relationships of Tenualosa ilishain 2011-12. abundance of the Hilsa Shad was low in the fishing excessively low, which indicates a low mean zone during November to March, possibly due to an concentration in the fishing area. The Hilsa CPUE offshore migration of the fish population i.e. into was positively correlated with SST areas outside of the scope of fishing zone. The mean R 2 = 0.692 , p = 0.027 and negatively correlated with CPUE was 3.455 ± 0.354S.E.kg/hour, which was salinity R 2 =  0.772 , p = 0.009 .

INDIAN J. MAR. SCI., VOL. 48, NO. 12, DECEMBER 2019 1876

Mortality and exploitation The total mortality (Z) of the Hilsa population was 3.15, using von Bertalanffy Growth Function (VBGF), in West Bengal coast. The natural mortality (M) is 0.71, (95% CI: 0.24-2.1) obtained from Pauly’s M-empirical equation, where the mean habitat temperature was considered as 27.8 °C. The fishing mortality (F) was thus 2.44, with a 95% CI of 2.9- 1.05, when assuming a correct Z- value. Using the expected values, fishing mortality appears to be substantially higher than the natural mortality, which indicates that the population was highly overexploited with an exploitation rate (E) of Hilsa was 0.78.

However, the estimate of natural mortality includes a Fig. 5 — Monthly variation of mean length and weight of Hilsa large uncertainty and so does the exploitation rate with error bar from Frasergunje fishing harbour of West Bengal (95% CI: 0.3-0.9). coast from June, 2011 to March, 2012. Length and weight at age We had estimated the length and weight of Hilsa depending on its age at WB coast (Table 2). The mean length of a one-year-old Hilsa was 300 mm, and that of a 1.5 year old was 379 mm (Fig. 8). It was also observed that, at the age of five years, Hilsa could

Table 2—The length and weight at different age of Hilsa. Age in year Weight (g) Length (mm) 0 0 0 0.5 61.51 181.17 1 281.55 300.81 1.5 566.73 379.81 2 833.80 431.98 2.5 1049.61 466.43

Fig. 6 — Monthly variation of the condition factor with SST 3 1210.78 489.18 and salinity. 3.5 1325.78 504.20 4 1405.58 514.12 4.5 1459.99 520.67 5 1496.68 524.99

Fig. 7—Monthly CPUE of Hilsa in the gill net fishing boat of Frasergunje Fishing Harbour, in 2011-12, compared to SST Fig. 8—Length and weight at age of Hilsa from West Bengal and Salinity. coast.

1877 DUTTA et al.: LIFE HISTORY OF TENUALOSA ILISHA

grow up to 524 mm in West Bengal coast. However, collected market sale data of Diamond Harbour fish the mature Hilsa was available at the age of 1.26 year market, West Bengal. with a length up to 345.96 mm. The one-year-old Hilsa weighs 281 g and by the age of 2.5 years, it Relative yield and relative biomass per recruit grows up to 1 kg (Fig. 8). It was observed that we The relative yield and relative biomass per recruit could get a five-year-old Hilsa weighing up to were plotted with respect to exploitation rate (E) 1496.68 gm in WB coast. (Fig. 11). It was obvious that the relative yield increased with increasing rate of exploitation. The Recruitment pattern result of relative yield per recruitment indicated that The recruitment pattern of Hilsa was only one the current fishing mortality was high and most of the pulse and it was during the monsoon season from juvenile Hilsa were caught by the fishermen, which June to August (Fig. 9). The maximum percentage of decline the fish population and also losing the Hilsa recruitment was 17.72 and was found in the economic advantage. month of July. Estimation of MSY Catch structure The estimation of total annual stock, standing stock Hilsa is an anadromous fish, which means that it and maximum sustainable yield (MSY) was calculated migrates from ocean to fresh water river during using annual data of catch collected from Department monsoon season. If we look at the seasonal catch of of Fisheries, Government of West Bengal. The Hilsa, it was clear that during monsoon season the total annual catch of Hilsa from West Bengal was amount of catch increases (Fig. 10). In order to 18126 tonnes during 2011 fishing year. Based on the estimate the seasonal fluctuation of Hilsa catch we estimated F- and Z- values the annual stock and standing stock were expected to be in the order of 24000 tonnes and 7400 tonnes respectively. Finally, the MSY(11700tonnes) is in accordance with the Gull and sequation however it is also in accordance with the conservative suggestion of Beddington and Cook. These data include high uncertainties, mainly due to the uncertain M- estimate, which requires confirmation.

Movement pattern The pattern of Hilsa movement was studied with the help of fishermen catch data. Most of the Hilsa catch was concentrated in NBOB and near the

Fig. 9—Recruitment pattern of Hilsa Shad from West Bengal coast with one pick during June to August, 2011.

Fig. 11 — Beverton and Holts Relative Yield per recruit Fig. 10 — Hilsa sold from Diamond Harbour Fish market and Biomass per recruit of Hilsa from West Bengal during on 2011-12. 2011 to 2012. INDIAN J. MAR. SCI., VOL. 48, NO. 12, DECEMBER 2019 1878

28 Sundarban estuary. We collected Hilsa fish catch data and Jamili pointed out b = 2.97 of Hilsa growth in from the ten (10) gill net fishing trawlers of Iran, whether in Bangladesh water the growth Fresergunje Fishing Harbour. We had plotted the allometry was positive (b=3.38)13. Considering the fishing catch data of Hilsa from June to October, 2011 monthly variation in the condition factor, it was in order to identify the areas of Hilsa fishing in BOB indicated that during the monsoon months, Hilsa was (Fig. 12). From the fishermen catch data; we had found to be well fed, whereas during pre and post mapped the monsoon Hilsa fishing zone. During the monsoon periods, Hilsa was slim and slender in form. months of June and July, Hilsa was observed to If the value of E is more than 0.50, we can conclude migrate towards maximum freshwater input pathway that the fish is overharvested from a particular area driven by the monsoons i.e., near to the coastline. At during some specific period29. In our study, we had the end of the monsoon, i.e. October onwards, the fish found that the exploitation rate (E) of Hilsa was 0.78. population was found to be scattered in more offshore Though this value was still highly uncertain and required in the deep water, which marks the beginning of the confirmation, the studied population was potentially retreating migration towards open sea. largely overexploited. Hashemi et al.7 estimated the rate of exploitation (E) of Hilsa as 0.72 in Coastal Waters of Discussion Iran and Nurul Amin et al.30 found the exploitation (E) The present paper deals with Hilsa life history of Hilsa as 0.66 in Bangladesh water, indicating over parameters like, growth, exploitation, mortality, and exploitation of these population. Dutta et al.14 projected stock for its management. The growth allometry of a threat of overexploitation of Hilsa resources of Hilsa is negative as the value of ‘b’ is 2.86. Roomian northern Bay of Bengal in near future.

Fig. 12 — High catch zone of Hilsa between June and October 2011 to understand their movement pattern.

1879 DUTTA et al.: LIFE HISTORY OF TENUALOSA ILISHA

The effort is increasing day by day and the catch notification for total allowable annual catch is an getting decline. As a result, the mean The Catch per essential task. Prohibition of catch beyond a Unit Effort (CPUE) of Hilsa was very low31. The permissible limit should be formulated to enhance estimated mean CPUE was 45.7 kg/boat/day during the overall annual stock. the peak period (September-October).CPUE III Declaring ‘Sanctuary’ for Hilsa with proper hypothesis was influenced by diverse factors other identification of spawning and breeding grounds than abundance like environmental conditions, as the Sundarban estuary, work as a nursing fishing methods, fishing equipment, fisher behavior, ground of the fish. Hilsa sanctuary should be management and economic factors32. In the present declared considering the areas of high importance study, the low CPUE was influenced by fishing taking breeding and spawning as a main factor. methods, as bottom trawling in shallow water was IV The mean CPUE is very low, so we should increased enormously by management practices, that confine the fishing effort. result the destroy of Hilsa habitat in shallow water. V The Hilsa population is overharvested during Rahman and Cows33 observed two pulses of the this study period, so intensive fishing should recruitment pattern of Hilsa in Bangladesh water, one be penalised. major pulse during March-May and one minor pulse 34 On such suggestions, recently in 2013 the during November and January. Nurul Amin et al. Government of West Bengal has enforced new fishing reported more or less continuous recruitment with one regulations36 exclusively for Hilsa. Treating Hilsa as a major peak from June to September. The results flagship species, the entire estuarine–marine obtained by us indicate only one pulse of Hilsa in WB ecosystem of northern Bay of Bengal can be during June to August. managed sustainably in a long run. The MSY estimated for the Hilsa population in this study was as uncertain as the estimated exploitation Acknowledgement rate; however, it may show the order of magnitude the The authors are also greatly indebted to the Indian annual catch should be reduced for a sustainable National Center for Ocean Information Services fishery. The results obtained by us indicate that unless (INCOIS) for funding the Potential Fishing Zone proper stock assessment and improved fishery validation project, which led to systematic data management techniques were employed, the collection. The second author is also grateful to the livelihoods of about 380 thousand Hilsa fishermen Director, INCOIS for his encouragement and would come under threat. unconditional help. We also extend our gratitude to

Management the field staffs and marine fishermen of West Bengal The successful management of a system is often for their help during data collection under adverse identified with its successful interaction with condition. biological, economic, social, and political objectives35. The Hilsa fishery is the most significant fishery from References the socio-cultural and economic point of view in West 1 Blaber, S. J. M., Brewer D. T., Milton D. A., Merta G.S., Bengal. Therefore, a proper management leading to a Efizon D., Fry, G., & Velde T. The Life History of the Protandrous Tropical Shad Tenualosa macrura (Alosinae: sustainable utilization of this vulnerable biological Clupeidae): Fishery Implications. Estuarine, Coastal Shelf resource is extremely essential. The management Sci., 49: (2019) 689-701. options of the Hilsa fishery are as follows: 2 Reuben, S., Dan, S.S., Somaraju, M.V., Philipose, V., & I The mean length and weight of the caught hilsa Sathianandan, T.V. The resources of Hilsa Shad, Hilsa ilisha population is very low, which is due to use of (Hamilton), along the northeast coast of India. Indian J. Fish., 39: (1992), 169-181. small mesh sized net. Therefore, banning catch of 3 Sinha, M. Farakka Barrage and its Impact on the the small fishes called “Jatka” (<500 gms and Hydrology and Fishery of Hooghly Estuary. The Ganges <230 mm.) and enforcement of fishing regulation Water Diversion: Environmental Effects and Implications. restricting mesh size (>90mm) of fishing net and Water Sci. Technol. Libr., 49: (2005) 103-124. DOI 10.1007/1-4020-2480-0_6. type of fishing gear in shallow depth (<50m) 4 Bhaumik, U., & Sharma, A.P. Present status of Hilsa should be considered. in Hooghly-Bhagirathi River. Central Inland Fishery II The annual stock is being declined as we harvest Research Institute. Barrackpore, Kolkata- 700120. more than the MSY. Proper stock assessment with Bulletineno. 179. (2012). INDIAN J. MAR. SCI., VOL. 48, NO. 12, DECEMBER 2019 1880

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