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ISSN 0032�9452, Journal of Ichthyology, 2013, Vol. 53, No. 5, pp. 365–371. © Pleiades Publishing, Ltd., 2013.

365

1 INTRODUCTION

A group of Clupeid fishes commonly known as shads comprising a number of species is found in Paki� stani waters. Among them hilsa shad, Tenualosa ilisha, migrating upstream is most valuable in Sindh Province (Fig. 1). While other species of shads remain in coastal waters or near estuarine areas. Kelee shad, H. kelee locally called as Palli in Sindh and Kolgar in Balouch� istan closely resembles the migratory hilsa shad. How� ever, in recent years, it was noted that kelee shad is get� ting more attention in the local markets and is avail� able in sufficient quantity. In Pakistan recently biological features and population statistics of hilsa shad, Tenualosa ilisha and kelee shad, Hilsa kelee are reported (Panhwar et al., 2011, 2012 and Panhwar and Liu, 2013).

Pelagic fishery in Pakistan is important for fish meal production. In 2003 about 2290 mt fishmeal was exported to Japan and a sum of about PKR.44.707 million was earned (Anon, 2006; FAO, 2009).

Length�frequency�based stock assessment tools are frequently chosen where age�structured data are limited especially in tropical fisheries. Notable works on length�based stock assessment have been published by various authors from different parts of the world (e.g. Guland 1959; Beverton and Holt 1959; Ricker

1 The article is published in the original.

1975; Pauly 1880a, 1980b; Moses 1988; Quinn and Deriso 1999). Unlike mineral resources, if the fishery resources or any other important biological resources are properly managed their duration will be practically limitless.

To date, no published information is available on the population parameters and stock assessment of kelee shad in the coastal waters of Pakistan. The objec� tive of this study was to analyze the key parameters of population dynamics of this valuable food fish species in the area. This study would help in understanding its sustainable exploitation in Pakistani waters.

MATERIAL AND METHODS

From January to December 2004, samples of Hilsa kelee were procured from the major commercial fish� eries landing sites at fish harbour Karachi. These fishes mainly caught near shore by monofilament gill nets, pelagic trawl and seines. Some 508 individuals were examined throughout the study period. The length� length relationship between TL, SL, and FL were esti� mated and the coefficient of determination R 2 are pre� sented in Table 1. All length�length relationships were highly significant with most of the coefficient of deter� mination values being >0.986.

Length–frequency data (fork length in cm used) analysis was done using FiSAT II (FAO, ICLARM stock assessment tool, Growt et al. 2003).

Growth, Mortality and Stock Assessment of Kelee Shad, Hilsa kelee (Fam: Clupeidae) in the Coastal Waters of Pakistan1

S. K. Panhwara, b, Q. Liub, and G. Siddiquia aCentre of Excellence in Marine Biology, University of Karachi, Sindh, 75270, Pakistan

bCollege of Fisheries, Ocean University of China, Qingdao�266003, China e�mail: [email protected]

Received September 24, 2012

Abstract—Growth of kelee shad, Hilsa kelee, in the coastal waters of Pakistan was estimated from the length� frequency samples. The von Bertalanffy growth equation was Lt = 23.10 (1 – exp (–0.94(t + 0.18))). Esti� mated parameters of total mortality (Z), natural mortality (M) and fishing mortality (F) were 2.08 year–1, 1.78 year–1, and 0.30 year–1 respectively. The length�at�first capture was Lc = 10.88 cm. Biomass per recruit� ment (B/R) and yield per recruitment (Y '/R) were 0.87 and 0.031 respectively. The annual exploitation rate was U = 0.12. The exploitation ratio for maximum yield per recruit Emax = 0.73 and fishing mortality for max� imum yield per recruit Fmax = 1.52; biological reference point Fopt = 0.89 year

–1 and Flimit = 1.18 year –1.

Present estimations showed that the natural mortality was higher than fishing mortality in Hilsa kelee, indi� cating that the state of the stock is sustainable and the fishery of kelee shad should not be increased beyond current levels in the coastal waters of Pakistan.

DOI: 10.1134/S0032945213030168

Keywords: Hilsa kelee; population biology; stock assessment; Pakistan

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PANHWAR et al.

Fish growth parameters were calculated by fitting von Bertalanffy growth function equation (VBGF) (Quinn and Deriso, 1999):

Lt = L∞(1 – exp(–k(t – t0))),

where L ∞

is asymptotic length (cm), k is growth coef� ficient (per year) and t0 is hypothetical age when length would be zero, calculated using the empirical equation (Pauly, 1980a):

Growth Performance Index (Φ')

The fish growth performance (Φ') was used to com� pare the growth parameters obtained in this study with

t0–( )10log 0.3922– 0.275 L10 ∞log–=

– 1.038 k.10log

BALOCHISTAN

SINDH

IRAN

Arabian Sea INDIA

Jiwani Gwadar Pasni

Ormara

Sonmiani Bay

Karachi

Chuma Island

Indos Delta

Astola Island

Desh t

N

64

24

Rann of Kutch

Sri Lanka

Ery of Eagal

Arabian Sea

India

Nepal

Tajikistan Turkmenistan

U.A.E.

Om an

MIDDLE EAST

Af gh

an ist

an

Pa kis

tan IranPertion

Guty

Fig. 1. Map showing major landing sites indicated (�) including provincial boundaries of Sindh and Balochistan provinces, Paki� stan.

Table 1. Length�length relationships between total length (TL), fork length (FL) and standard length (SL) combine sex for Hilsa kelee in Pakistan

n Equation a b 95%CI of a 95% CI of b R2

508 TL = a + b × SL 0.107 1.009 0.097–0.116 1.001–1.017 0.993

SL = a + b × FL –0.038 0.993 –0.050–0.025 0.982–1.003 0.989

FL = a + b × TL –0.048 0.981 –0.062–0.033 0.970–0.993 0.986

Note: n = sample size, a = intercept, b = slope, Cl = confidence intervals, R2 = coefficient of determination.

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GROWTH, MORTALITY AND STOCK ASSESSMENT 367

those reported on different fish species from different waters. It can be obtained by the equation of Munro and Pauly (1983):

Total Mortality Coefficient (Z), Natural Mortality (M) and Fishing Mortality (F)

Total mortality was estimated by the length�con� verted catch curve (Pauly, 1980a,b). The catch curve was acquired by pooling monthly length frequencies data, natural logarithm of the number of individuals in respect to age group (N) were plotted against their cor� responding relative age (t) (Pauly, 1985; Moses, 1988). Following the empirical formula by Pauly (1980a, b, 1983) instantaneous natural mortality was calculated as:

where T = the average annual sea surface temperature (SST) (=26°C) recorded in the coastal water of Paki� stan. Fishing mortality (F) was obtained by subtracting (M) from (Z) and exploitation ratio (E) was obtained from F/Z.

Following the procedure of Patterson (1992) and Taghavi Motlagh et al. (2009) the biological reference points were estimated as Fopt = 0.5 M and Flimit = 2/3 M.

The first exploitation rate is calculated with the for� mula by Beverton and Holt (1957):

U = F(1 – exp(–Z))/Z.

RESULTS

Length Frequency Distribution

In this study, 508 individuals were examined for length�frequency composition of the kelee shad in Pakistani waters. The size class 17.0–18.9 cm domi� nated the catch, with a minority of catch in the 23.0– 24.9 cm size class (Fig. 2). The length�at�first capture was Lc = 10.88 cm. The Length�length relationship as TL = 1.009 SL = 0.107 (R2 = 0.993), SL = 0.993 FL = –0.038 (R2 = 0.989) and FL = 0.891 TL = –0.048 (R2 = 0.986) for combine sexes.

Growth

The estimated von Bertalanffy growth parameters for the kelee shad estimated by ELEFAN 1 pro� gramme were L

∞ (FL) = 23.1 cm, growth coefficient

Φ' k( )10log 2* L∞( ).10log+=

M10log 0.0066 0.279 L10 ∞log–=

+ 0.6543 k10log 0.4634 T,10log+

k = 0.94 per year and t0 = –0.18 year (Fig. 3). The goodness of fit of model was Rn = 0.304 (Table 2).

Growth Performance Index (Φ')

Growth performance or phi prime denoted by (Φ') was estimated as 5.74 for kelee shad. By plotting raw data using ELEFAN I programme, it is clearly shown that the fishery of kelee shad operates on 3–4 popula� tion cohorts. Solid line in Fig. 3 shows the growth curve fitted to the raw data.

The common approach for estimating total mortality is catch curve analysis. Total mortality (Z), natural mor� tality, and fishing mortality were estimated at 2.08 yr–1, 1.78 yr–1, and 0.30 yr–1 respectively (Table 2, Fig. 4). The estimated values of relative yield per recruit Y '/R, relative biomass per recruit B '/R and exploitation rate in kelee shad are presented in Table 2.

The probabilities of capture were 25% (L25), 50% (L50) and 75% (L75) for sizes 13.05 cm, 14.58 cm and 16.16 cm, respectively.

Exploitation (E)

Exploitation ratio for maximum yield per recruit Emax = 0.73, fishing mortality for maximum yield per recruit Fmax = 1.52 yr

–1; the biological reference points are Fopt = 0.89 per year and Flimit = 1.18 per year. This

Fig. 2. Length frequency distribution of kelee shad in this study.

Table 2. Parameter estimate of mortality and yield of Hilsa kelee collected from coastal waters of Pakistan

Year Z F M E Y '/R B '/R U Φ' Lc, cm Rn

Jan�to�Dec 2004 208 0.30 1.78 0.14 0.031 0.87 0.12 5.74 10.88 0.304

30

35

25

20

15

10

5

0 23–24.921–22.919–20.911–18.915–16.913–14.99–0.9 11–12.9

Size classes

P er

ce n

ta ge

s

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PANHWAR et al.

indicates that the natural mortality was higher than the fishing mortality in Hilsa kelee fishery (Fig. 5).

DISCUSSION

The description of fish growth commonly used von Bertalanffy growth equation (von Bertalanffy, 1938), in this study the estimated fundamental growth parameters of kelee shad are asymptotic length L

∞ (FL) = 23.1 cm,

and growth k = 0.94 year–1 and t0 = –0.18 year. Sousa

and Gjøsaeter (1987) reported the biological parame� ters of kelee shad which are asymptotic length = 21.5 cm, growth k = 1.10 year–1 and t0 = –0.44 year from Maputo Bay, Mozambique. In Hilsa shad growth coef� ficient 0.82 was estimated in Bangladesh waters (Nurul Amin et al., 2002). Growth coefficient k = 0.77 for Hilsa shad was also reported (Roomiani and Jamili, 2011) from Iranian waters. The growth coeffi� cient of hilsa shad Tenualosa ilisha (Table 3) reported from Iranian and Bangladesh waters seems lower than

26

24

22

20

18

14

8

2

0 DecNovOctSepAugJan JulJunMayAprMarFeb

16

12

10

6

4

L en

gt h

, cm

Fig. 3. Length�frequency distribution data and the growth curves estimated for Hilsa kelee in coastal waters of Pakistan.

5.0

3.0

1.0

3.02.01.00

Realative age (years�t10)

In (

N /d

t)

Length�Converted Catch Curve

Fig. 4. A length�converted catch curve for Hilsa kelee, in Pakistani waters (L ∞

= 23.10 cm and k = 0.94 per year).

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GROWTH, MORTALITY AND STOCK ASSESSMENT 369

the growth (0.94) of kelee shad in Pakistan. The growth variations could differ in different species and environments. (Panhwar et al. 2010) studies age growth in ten fish species from different environments.

All length�length relationships were highly corre� lated, the coefficient of determination was (>0.986) and they were compared with the available literatures on shads. Such as on the Hilsa shad, Tenualosa ilisha (Panhwar et al. 2011) studied high correlation in length weight relationship. However, (Le Cren, 1951) suggested that the ecological conditions of the habits or variation in the physiology of animals, or both, are responsible in such variations.

In length frequency based stock assessment the estimation of phi prime (Φ') or growth performance index provides indices of growth performance between parametric values (L

∞ and K) and indicates the overall

growth performance of any fish species (Pauly and Munro 1984; Sparee and Venema 1998). In this study we obtained Phi prime = 5.74 which are compared with those reported in kelee shad and other species of shads (Table 3). The growth performance index in this study was higher than that in the studies of kelee shad reported earlier from Maputo Bay, Mozambique (Sousa and Gjøsaeter, 1987) which may indicate better

0.02

0.01

0.01

1.00.80.40

Exploitation ratio (E)

R el

at iv

e B

io m

as s/

R ec

ru it

( B

'/ R

)

0.60.2

0.03

0.03

0.04

R el

at iv

e Y

ie ld

/R ec

ru it

( Y

'/ R

) 00.50

0.25

0

0.75

1.00

Fig. 5. Relative yield per recruit and biomass per recruit plot of Hilsa kelee in Pakistani waters.

Table 3. Summary of the growth parameters in different species of shads from their distribution

Author and year Location and species L ∞

K t0 Φ

Nurul Amin et al., 2002 Bangladesh, hilsa shad 60.0 0.82 00 3.47

Roomiani and Jamili, 2011 Iran, hilsa shad 42.74 0.77 –0.21 3.14

Sousa and Gjøsaeter, 1987 Maputo bay, Mozambique, kelee shad 21.5 1.10 –0.44 2.71

Panhwar and Liu, 2013 Pakistan, hilsa shad 31.5 1.5 –0.10 2.13

Present study Pakistan, kelee shad 23.1 0.94 –0.18 5.74

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PANHWAR et al.

growth probably due to higher water temperature (21°C and 26°C).

The instantaneous total mortality in kelee shad was estimated Z = 2.08 year–1, whereas on other species of shads such as Hilsa shad, Tenualosa ilisha Z = 3.77 year–1

were estimated from Bangladesh waters (Nurul Amin et al., 2002). Furthermore he found high fishing mor� talities and suggested effective management measures to reduce fishing pressure. From Iranian waters total mortality of 2.55 year–1 in Hilsa shad was reported (Roomiani and Jamili, 2011). This study showed fish� ing mortality is smaller than natural mortality which indicates that Hilsa shad die more often due to the nat� ural death than the human exploitation.

The natural mortality and growth ratio (M/k) of 1.89 is ideal because Beverton and Holt (1959) sug� gested M/k ratio of 1.0–2.5 for fish. A continuous recruitment pattern was observed in kelee shad popu� lation round the year. Spawning in kelee shad (Pan� hwar et al. 2012) reported that the peak spawning occurs in April to June and August to October. Com� paring Fopt = 0.89 year

–1 and the current F = 0.30 year–1

we can infer that the stock of kelee shad is probably not being overexploited. Gulland (1971) reported that in an optimally exploited stock, natural and fishing mor� talities should be equal or E = F/Z = 0.5. In this study we used more conservative biological reference point of Eopt = 0.33 and Elimit = 0.40. Maximum exploitation ratio Emax for maximum yield per recruit was estimated 0.73 is greater than its current exploitation rate i.e. E = 0.144. Earlier studies such as (Nurul Amin et al., 2002; Roomiani and Jamili, 2011) reported exploitation rate E = 0.7 and E = 0.66 year–1 for hilsa shad, Tenualosa ilisha from Iranian and Bangladesh waters, which indicated over�exploitation of the stocks because they are higher than even the optimal biological reference point of E = 0.5.

In the light of above mentioned results, we propose that the fishery of kelee shad should not be increased beyond current levels in the coastal waters of Pakistan. Also increasing the length at first capture from 10.88 cm to size�at�maturity (15 cm SL) maturity size for kelee shad has been reported elsewhere by (Whitfield, 1998) and regular monitoring of the fishery would help the sustainability of this excellent food fish in the area.

ACKNOWLEDGMENTS

Authors are thankful to Dr. Shoukat Hayat Khan, Ex�Director, Centre of Excellence in Marine Biology (CEMB), University of Karachi, for the faculties pro� vided during the period of study and thank are due to Dr. Zarrien Ayub, Associate Professor of the CEMB for her assistance. The support of the special research fund of the Ocean University of China (201022001) is also acknowledged.

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