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RESEARCH ARTICLE Indian Journal of Research, Volume Issue: ELEFAN Based Population Dynamics of Bombay Duck, nehereus Inhabiting the Marine Waters of the West Coast of India

D. Fofandi Mahendrakumar, Prathibha Rohit

ABSTRACT We studied ELEFAN based population parameters from length-frequency data for Harpadon nehereus collected from different landing centres along the west coast of India. We analyzed the size structure and estimated growth parameters, recruitment, mortality and -1 exploitation rate using FiSAT-II software. The asymptotic length (L = 366 mm), growth coefficient (K = 0.98 year ), total mortality (Z=3.32 year-1), natural mortality (M=1.6375 year-1), fishing mortality (F=1.6825 year-1), growth performance index (Ø = 3.12) and exploitation ratio (E = 0.51) were worked out for the species. The exploitation ratios were computed as Emax= 0.661, E10= 0.568, E50=

0.345. The length at first capture (Lc50) was estimated at 163.44 mm. The present value of E was found close to appropriate fishing pressure on the stock and a further increase of fishing pressure is not recommended.

Key words: Asymptotic Length, Bombay duck, Population dynamics, Recruitment Pattern, Y/R.

INTRODUCTION Central Marine Fisheries Research Institute, Veraval Regional Harpadon nehereus (Hamilton 1822) which is popularly Centre of ICAR-CMFRI, Matsyabhavan, Veraval 362 265, Gujarat, known as Bombay duck belongs to the family , India. class (Nurul, 2001; Froese and Pauly, 2018) Corresponding Author: D. Fofandi Mahendrakumar, Central and inhabiting the shallow inshore waters as well as Marine Fisheries Research Institute, Veraval Regional Centre of estuarine areas of Arabian Sea and the Bay of Bengal of ICAR-CMFRI, Matsyabhavan, Veraval 362 265, Gujarat, India, Indian Ocean. It is locally known as ‘Bumla’ or ‘Bombil’ and Email: [email protected] has a discontinuous distribution along the Western coastline How to cite this article: D. Fofandi Mahendrakumar and Prathibha of India. They forming an independent stock along the Rohit (2019). ELEFAN Based Population Dynamics of Bombay Saurashtra coast (Khan, 1983) within a narrow belt of 45 Duck, Harpadon nehereus Inhabiting the Marine Waters of the West km and depth range of 20 m to 70 m. The important landing Coast of India, Asian Journals of Dairy and Food Research. centres are nearly 92% of Bombay duck landed are by the Submitted: 26-06-2019 Accepted: 15-10-2019 Published: mechanized dol nets (CMFRI, 2016) and mainly made at Nawabunder, Rajpara and Jaffrabad. The size range of dol species. The outputs of the study would help recommend a net as 35 – 60 m length and with a mesh size of 20 mm cod- suitable management strategy for sustainable management end used to catch Bombay duck, operated entirely by the of Bombay duck. tidal forces along Gujarat and Maharashtra coasts (Ghosh et al., 2009). Bombay duck is an exceptionally delicate fish and MATERIALS AND METHODS because of its highly perishable body structure, most of the Study site and sample collection catch especially during the peak fishing season is sundried Random samples of Bombay duck were taken on weekly and a little quantity is sold in fresh form in the local markets. basis from major dol net landing centers (Nawabunder, The fishes are typically sunidried on constructed raising Rajpara and Jaffrabad) along the west coast (16° 57' 26'’ - bamboo stages and the dried fish are traded to nations like 23° 11' 33'’ N and 68° 36' 26'’ - 73° 13' 56'’ E) of India the Middle-East, U. K, Srilanka and Singapore (Nurul, 2001). throughout the period from September 2014 to November Various authors have studied the age and growth of this 2016 (Fig 1). A total of 1523 specimens comprising of 646 species from different location of the Indian and International males and 789 females were used for the study. Length waters (Biradar, 1989; Khan, 1989; Kurian and Kurup, 1992; frequency data were processed by the methodology of Mustafa et al., 1994, 1998; Fernandez and Devaraj, 1996; Gayanilo et al. (2005), using the FAO-ICLARM stock Pitcher et al., 1998; Nurul, 2001; Lin et al., 2006; Ghosh et assessment tool (FiSAT-II) package. Length frequency al., 2009; Li and Huang, 2009; Balli et al., 2011; Pan and records were grouped into 15 mm interval class and then Cheng, 2013; Laga et al., 2015; Liang and Pauly, 2017; pooled monthwise for all of the years. Sarker et al., 2018; He et al., 2018). Data processing and analysis The present study aimed to generate the population parameters for conventional stock assessment of the The growth parameters namely the asymptotic length (L), ELEFAN Based Population Dynamics of Bombay Duck, Harpadon nehereus Inhabiting the Marine Waters of the West Coast of India

growth coefficient (K) and t0 were estimated utilizing the Length-dependent virtual population analysis (VPA) is ELEFAN program. The Von Bertalanffy Growth Function used to acquire fishing mortalities in line with length class. (VBGF) depends on a bioenergetics articulation of fish Exploitation ratio (E) was estimated from the equations: growth and is used to depict the normal “length-at-age” E = [F / Z] (Cailliet et al., 2006) and the growth function is Exploitation rate (U) is characterized as the part of the communicated as Equation: fish present toward the beginning of a year that is discovered –k (t-to) Lt = L (1 – exp ) where; Lt = length at age t, and caught during the year (Beverton and Holt, 1957; Ricker, L = asymptotic length of the fish can 1975). Exploitation rate was evaluated by the formula theoretically attain, U = F/Z * (1-e-z) K = growth coefficient,

t = age of fish, The optimum length of exploitation (Lopt) was estimated empirically from the equation of Froese and Binohlan (2000) t0 = age of fish at zero-length. as The growth parameters were evaluated utilizing the L = 3*L /(3+M/K). ELEFAN 1 program in FISAT software (Gayanilo Jr. and opt ”

Pauly, 1997) and ’t0' estimated utilizing Pauly’s empirical The longevity (tmax) and growth performance index (Ø) formulae (Bailey, 2003). of the species were calculated using the method suggested by Pauly and Munro (1984). log (-t0) = [- 0.392 - 0.275 log L - 1.0381 K] t = 3/K Mortality coefficients incorporating total mortality (Z), max instantaneous natural mortality (M), fishing mortality (F) and Phi (Ø) = logK + 2 logL exploitation rate (E) were by taking the mean ocean surface The relative yield-per-recruit (Y’/ R) was estimated from temperature as 27C (Gayanilo Jr. and Pauly, 1997; Pauly, the analyzed growth parameters and probabilities of capture 2007). as suggested by Beverton and Holt, (1966) and Pauly and F = (Z – M) Soriano, (1986). The estimated exploitation rate (E)

Jones and Zalinge (1981) found a linear connection associated with the predictable values of Emax, E10 and E50 between catch and survivors. It depends on the existence (Sparre and Venema, 1992; Gayanilo Jr. and Pauly, 1997) of a linear relationship among the natural logarithms of the were also evaluated. cumulated frequency and the natural logarithm of (L - L). This relationship can be expressed as follows and used to RESULTS AND DISCUSSION estimate the total mortality rate. The maximum length recorded for Bombay duck during the present study was 351 mm, which is higher than the earlier {ln (CN) = a + (Z/K) ln (L - L)}  records of 270 mm from Hong Kong inshore waters (Pitcher Where: CN = Cumulated frequency, et al., 1998), 230 mm from neritic waters of (Nurul, 2001), 344 mm off Saurashtra coast (Ghosh et al., Z = Total mortality coefficient, (then Z = K* slope) 2009), 290 mm from coastal sea of China (Liang and Pauly, K = Growth coefficient 2017), 250 mm from Min River estuary of east China sea

Fig 1: Study area map for collection of samples.

2 Indian Journal of Animal Research ELEFAN Based Population Dynamics of Bombay Duck, Harpadon nehereus Inhabiting the Marine Waters of the West Coast of India

(He et al., 2018), but the present record of size from the In the present study, more 1,500 individuals of Bombay study region is lower than past reports from the same region duck were used and restructured length distribution shown (374.5 mm (1985) to 609.7 mm (1958) from N-W coast of in Fig 2. The analysis of length-frequency data to estimate India (Fernandez and Devaraj, 1996)). The differences in the growth parameters is not reliable if the sample size is maximum size records from the different regions can be small (Jones, 1981). The growth parameters estimated for -1 because of different stocks, whereas the decline in pooled samples were L = 366 mm, K = 0.98 yr and t0 = -0.0145. Many studies have documented the age and growth recorded Lmax during different periods may be attributed to the impact of changing climate and fishing pressure. of the Bombay duck, H. nehereus from Indian and These growth differences can also be attributed to international waters. The results of all the earlier studies made till date are provided in Table 1. The variations in the differences in environmental factors, particularly water age and growth parameters observed by researchers from temperature and food availability in rivers (Froese, 2006; different parts might be due to fluctuations in the environment Ahamed et al., 2012). and trophic conditions (Alrashada et al., 2019). According to Froese (2006), growth in fishes is not The maximum life span estimated by Pauly’s equation constant throughout their life; young fish proliferate and then in the present study was 3.06 years. Based on the findings growth decreases as the animal advances in age until there of ELEFAN-I, the growth function of the studied species is is no further growth. In the present study, Bombay duck -0.98(t+0.0145) presented as Lt =388 [1-exp ]. The assessed length attained a length of 230.51 mm at the end of the first year. at age is depicted in Fig 3. By the inverse von Bertalanffy The growth performance index Phi (Ø) was found to be 3.12. equation, the length attained after the completion of 1, 2 Mustafa et al. (1998) estimated the growth performance and 3 years were 230.51 mm, 325.15 mm and 346.91 mm index of this species from Bangladesh as 2.953, Ghosh respectively. A similar life span was recorded by Ghosh et al. et al. (2009) reported it as 3.032 along Saurashtra Coast. (2009) off Saurashtra Coast and estimated length at the Liang and Pauly (2017) estimated the value of 2.90 for end of at 1, 2 and 3 years for H. nehereus were 20.66 cm, collections made from coastal sea of China. 29.16 cm and 32.75 cm.

Table 1: Summery of L and K from Indian and International waters.

-1 Study Site L (cm) K (yr ) References Hooghly estuary system 73.02 0.176 (Krishnayya, 1968) Tropical waters 35.2 0.50 (Pauly, 1982) Off Maharashtra 39.1 0.53 (Biradar, 1987) Saurashtra coastline 42.52 0.76 (Khan, 1989) Off Saurashtra 41.0 0.749 (Khan et al., 1992) Off Maharashtra coast 42.6 0.519 (Kurian and Kurup, 1992) N-W coast of India 37.45 (1985) 0.77 (1985) (Fernandez and Devaraj, 1996) 60.97 (1958) 0.29 (1958) Bangladesh waters 24.48 1.50 (Mustafa et al., 1998) Hong Kong inshore waters 35.1 0.67 (Pitcher et al., 1998) Neritic waters of Bangladesh waters 24.48 1.50 (Nurul, 2001) Off Saurashtra coast 35.39 0.86 (Ghosh et al., 2009) Mumbai waters 43.4 0.81 (Balli et al., 2011) Bay of Bengal 45.05 1.30 (Sarker et al., 2018)

In this regards you may please reply of the reviewer comments mail.

Fig 2: Monthly restructured length-frequency distribution of Bombay duck with the estimated growth curves.

Volume Issue 3 ELEFAN Based Population Dynamics of Bombay Duck, Harpadon nehereus Inhabiting the Marine Waters of the West Coast of India

Fig 3: Length at the age of the pooled population of Bombay duck.

The total mortality (Z), natural mortality (M) and fishing mortality (F) were estimated as 3.32, 1.64 and 1.68 respectively (Fig 4). A slightly higher total mortality (Z) of 3.929 was recorded with Jones and van Zalinge method (Fig 5). This higher fishing mortality (1.68) over natural mortality (1.64) observed in the present study indicated that Bombay duck fished along the west coast of India is undergoing intense fishing pressure. Natural mortality is dependent on several biological and environmental factors; hence, the precise estimation of it is often tricky (Cushing, 1981; Pauly, 2007; Sajan et al., 2015). The estimated natural mortality rate of in the present study (M=1.64) is higher than Fig 4: Total mortality (Z) using by length converted catch curve the values estimated (1.20) by Pitcher et. al., (1998), 1.52 method. estimated by Ghosh et. al. (2009), 1.12 by Liang and Pauly (2017), 1.86 by Sarker et al. (2018) and 1.58 by He et al. (2018) but lower than that estimated (2.46) by Mustafa et al. (1998). Natural Mortality (M) is the mortality created by all other causes other than fishing. The direct estimation of ‘M’ is often impossible. The same species might have different rates of natural mortality in altered areas based on the predator’s density and competitors, whose abundance is generally influenced by fishing activities (Sparre and Venema, 1992). Mustafa et al. (1998) computed F and Z as 3.27 and 5.73 respectively for Bombay duck fished from Kumira, Chittagong area in the Bay of Bengal. Balli et al. Fig 5: Total mortality (Z) using by Jones and van Zalinge method. (2011) estimated M, F and Z as 1.30, 3.03 and 4.33 respectively for Bombay duck caught from Mumbai waters of the Indian coastline. Sarker et al. (2018) reported that the annual rate of fishing mortality (F) for Bombay duck was 2.58 from the Bay of Bengal along Bangladesh coastline. Various other authors have reported natural mortality for the species as 1.462 (Khan, 1986; Biradar, 1987), 1.572 (Khan, 1989), 0.8 (Kurian, 1989; Kurian and Kurup, 1992; Mustafa et al., 1994; Fernandez and Devaraj, 1996). The M/K ratio obtained in the present study was well within the normal range of 1 to 2.5, as suggested by Beverton and Holt (2008). The assumption made by Gulland (1971), stated that suitable yield is optimized and maximized when F=M and E more than 0.5, is indicative of overfishing. The

Fig 6: Relative isopleth (Y/R and B/R) of the pooled overexploitation of the same species was also found in the population of Bombay duck. coastal region of Bangladesh (Mustafa et al., 1994, 1998;

4 Indian Journal of Animal Research ELEFAN Based Population Dynamics of Bombay Duck, Harpadon nehereus Inhabiting the Marine Waters of the West Coast of India

Islam, 1995). Balli et al. (2011) detected the ratio of exploitation as 0.66 in Mumbai waters of India. The fishing mortality (1.68) and total mortality (3.32) of H. nehereus recorded was higher than that reported by Khan (1986,

Fig 10: Recruitment pattern of Bombay duck (pooled).

1989), Kurian (1989) and, Fernandez and Devaraj (1996); was an indication of intensive fishing of this species which was also revealed by a high exploitation rate (0.51). Similar Fig 7: Relative Y/R and B/R as per the Knife-edge se lection ratio of exploitation was reported for Bombay duck caught method (2-D Graph). off the coast of Maharashtra (Kurian, 1989), 0.57 (Mustafa et al., 1998), 0.512 (Ghosh et al., 2009) from Saurashtra coast of India, 0.52 estimated from coastal waters of China (Liang and Pauly, 2017) and 0.58 (Sarker et al., 2018). However, much lower ratios of exploitation (0.454 and 0.435) was found for the species from the same fishing grounds of Nawabunder, Rajpara and Jaffrabad (Khan, 1986, 1989). It is evident from there results that since the value of E was estimated to be close to appropriate fishing pressure on the stock and it is marginally higher than optimum. Hence any further increase in fishing pressure is not advisable. The Y/R examination result assessed as 0.038, which appeared in (Fig 6 and Fig 7). The relative yield per recruit and biomass per recruit for Bombay duck is depicted in Fig 8. In the present study, the relative yield per recruit (Y/R)

reached a maximum at an exploitation rate (Emax) of 0.661 and with an increase in the exploitation rate, Y/R decreased. Fig 8: Relative Yield per Recruit and Biomass per Recruit The Y/R model of knife-edge assumes that a selection of the pooled population of Bombay duck. procedure where the gear would not retain fishes below the length at first maturity. However, the dol net is a gear where the mesh sizes are continuously changed by the fishermen depending on the abundance of Bombay duck. Hence, this underlying assumption of knife-edge may not apply to this particular gear. The results of length based VPA demonstrated that fishing mortality (F) increased to a maximum of 1.755 at 210-224 mm size (Fig 9). It indicated that catches increase substantially from 105-119 mm and attained maximum at 195-209 mm size groups. Recruitment for the fishery takes place throughout the year. Nevertheless, two pulses are seen in the recruitment pattern every year (Fig, 10). The major one corresponds to May (15.67%) and a minor one during September (10.56%).

CONCLUSION From the results of the present study, the size at first capture Fig 9: Length based virtual population analysis of pooled population. (Lc) indicated that 50% of the population was caught when

Volume Issue 5 ELEFAN Based Population Dynamics of Bombay Duck, Harpadon nehereus Inhabiting the Marine Waters of the West Coast of India the fish attained a total length of 163.44mm. It may be Age and growth studies of chondrichthyan fishes: The concluded that the value of E is close to the optimum fishing need for consistency in terminology, verification, validation pressure and the stock is more or less under higher fishing and growth function fitting. Environmental Biology of pressure than desired warranting an immediate reduction Fishes. 77: 211–228. in fishing effort. The present study provides valuable baseline CMFRI. (2016). CMFRI Annual Report 2016-2017. Kochi. data on the age, growth and population of Bombay duck Cushing, D. (1981). Stock and Recruitment. In Fisheries Biology: that would be useful for fishery biologists to propose adequate a Study in Population Dynamics, pp. [Ed. by D. Cushing]. policies for the sustainable management of this important University of Wisconsin Press, Madison, Wisconsin. 142-171. fish species occurring along the West coast of India. Fernandez, I. and Devaraj, M. (1996). Dynamics of the Bombay duck (Harpodon nehereus) stock along the northwest ACKNOWLEDGMENT coast of India. Indian Journal of Fisheries. 43: 1–11. The authors are grateful to Dr. A. Gopalakrishnan, Director, Froese, R. and Binohlan, C. (2000). Empirical relationships to ICAR-CMFRI, Kochi for providing the necessary facilities, estimate asymptotic length, length at first maturity and support and for permission to carry out this study for a Ph.D. length at maximum yield per recruit in fishes, with a simple under the Department of Biosciences, Mangalore University. method to evaluate length frequency data. Journal of Fish The authors wish to express their sincere gratitude to SIC, Biology. 56: 758–773. Veraval Regional Centre of CMFRI, Veraval to facilitate the Froese, R. 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