# Life History Traits of the Flying Barb Esomus danricus (Hamilton, 1822) (Cyprinidae) in the Ganges River, Northwestern Bangladesh.

Byline: Md. Yeamin Hossain, S. M. Abu Naser, Ali H. Bahkali, Khairun
Yahya, Md. Alomgir Hossen, Abdallah M. Elgorban, Md. Mahmudul Islam and
Md. Mosaddequr Rahman

ABSTRACT

The present study describe the first life-history traits of threatened fish Esomus danricus from the Ganges River, northwestern Bangladesh. This study also calculates the form factor, size at first sexual maturity and natural mortality of E. danricus from world-wide different water bodies using available literature. Sampling was done, using traditional fishing gears including cast net, square lift net and conical trap during January to December 2014. A total of 309 individuals ranging from 2.94-6.10 cm total length and 0.25-1.38 g body weight were analyzed in this study. The length frequency distributions showed that the 4.00-4.99 cm total length size group was numerically dominant and constituted 50.00% of the total population. The allometric coefficient (b) of the length-weight relationship indicates negative allometric growth (b less than 3.0) for E. danricus in the Ganges River. The results also indicate that the length-length relationships were highly correlated (r2 [greater than or equal to] 0.974).

The allometric condition factor varied from 0.015 to 0.018 and Fulton's condition factor varied from 0.607-0.985. Also the relative condition factor ranges from 0.923 to 1.127 and minimum and maximum values of relative weight were 92.185-112.727 in the Ganges River. The Fulton's condition factor is the best index for a ssessing the wellbeing of E. danricus in the Ganges River. According to Wilcoxon signed test the relative weight did not show any significant difference from 100 (p = 0.295), indicating the balance habitat for E. danricus. The form factor was calculated as 0.0033 and the size at first sexual maturity for combined sexes of E. danricus was estimated as 3.98 (~ 4.00) cm total length in the Ganges River, northwestern Bangladesh. In addition, the mean natural mortality was estimated as 2.31 year-1. These results will be useful for sustainable conservation of this threatened fish in the Ganges River and surrounding ecosystem.

Key words

Esomus danricus, length-weight relationship, relative weight, form factor, size at first sexual maturity.

INTRODUCTION

The flying barb, Esomus danricus (Hamilton, 1822) belongs to the family Cyprinidae, is a small indigenous fish species (SIS) of Bangladesh. This fish is known as Darkina, Darki, Darkya in Bangladesh (Rahman, 2005). In India it is known as Darkina, Dadhikha, Danrika, Jongia, Chilwa, Jhai, Astapakke, Messaparavi and Meesa-parava (Talwar and Jhingran, 1991). This species is widely distributed throughout the Indian sub-continent including Bangladesh, India, Nepal, Pakistan, Sri-Lanka and some other countries of the world such as Afghanistan and Thailand (Froese and Pauly, 2015). The flying barb, E. danricus inhabits ponds, weedy ditches, streams, beels and inundated fields (Rahman, 1989; Talwar and Jhingran, 1991). It is an important target species for small-scale fishers (Shafi and Quddus, 1982).

Nonetheless, the untamed population of this species is waning due to reckless fishing, habitat destruction and other ecological changes to their surroundings (Hossen et al., 2015; Hossain et al., 2015a, b) and afterward categorized as least concern in Red list (Devi and Boguskaya, 2009). This fish is a major source of animal protein and macronutrients in the diet of rural poor people in fresh and dried condition (Bijen et al., 1990; Lilabati and Vishwanath, 2000). E. danricus also used as ornamental fish (Froese and Pauly, 2015).

Length-weight relationships (LWRs) are very helpful in fishery for predicting length distributions into weights for estimation of biomass (Gerritsen and McGrath, 2007). Additionally, LWRs parameters are important to evaluate fish-stock condition (Gonzalez Acosta et al., 2004). Furthermore, condition factors are functional parameters that can be used for determining the possible differences among different stocks of the same species (King, 2007; Soomro et al., 2012). Moreover, relative weight (WR) is one of the most popular indices to know the condition of fishes in the USA since last two decades (Rypel and Richter, 2008) and recently it has been used in Bangladesh for determining the condition of freshwater fishes (Hossain et al., 2012a, 2015c).

A number of studies including length-frequency distributions (Hossain et al., 2008; Rahman et al., 2012), length-length and LWRs (Hossain, 2010a; Hossain et al., 2006a,b; 2009a), condition-and form-factors (Hossain, 2010b; Hossain et al., 2010, 2012b) of several fish species have been conducted, but the research on the life history traits of E. danricus are evidently lacking from Bangladesh or else. Therefore, this study reports the first complete and comprehensive description on life-history traits of E. danricus in the Ganges River, northwestern Bangladesh using a large number of specimens from small to large body sizes.

MATERIALS AND METHODS

Study site

The current study was conducted in the Ganges River (known as Padma in Bangladesh) (24.35' N; 88.64' E) northwestern (NW) Bangladesh. It is one of the longest rivers and believed to be an important spawning and feeding ground for riverine fishes (Hossain et al., 2010; Rahman et al., 2012).

Sampling and measurement

The samples of E. danricus were collected during daytime from the fishermen at different parts (Charghat; 2415' N, 88 44' E; Godagari; 24 26' N, 88 19' E and Saheb bazar; 24 20' N, 88 34' E) of the Ganges River in Rajshahi region during January 2014 to December 2014. The fishes were caught using cast net, square lift net and box trap. The fresh samples were immediately chilled in ice on site and fixed with 10% buffered formalin upon arrival in the laboratory. For each individual, total length (TL), fork length (FL) and standard length (SL) were measured to the nearest 0.01 cm using digital slide calipers (Mitutoyo, CD-15PS; Mitutoyo Corporation, Tokyo, Japan) and whole body weight (BW) was taken by a digital balance (Shimadzu, EB-430DW; Shimadzu Seisakusho, Tokyo, Japan) with 0.01 g accuracy.

Length-frequency distribution (LFDs)

The LFDs for the E. danricus were constructed using 1 cm intervals of TL. The normal distribution was fitted to the TL frequency distribution of E. danricus using a computer analysis Microsoft Excell-add-in-solver) based on Hasselblad's maximum-likelihood method (Hasselblad, 1966).

Length-weight and length-length relationships (LWRs and LLRs)

The LWRs were calculated using the equation: W= a*Lb, where the W is the body weight (g) and L is the length (cm). The parameters a and b were estimated by linear regression analysis based on natural logarithms: ln(W) = ln(a) + b ln(L). Additionally, 95% confidence limits of a and b and the coefficient of determination r2 were estimated. In order to confirm whether b values obtained in the linear regressions were significantly different from the isometric value (b = 3), a t-test Sokal and Rohlf (1987): ts = (b-3) / sb, where ts is the t-test value, b the slope and sb the standard error of the slope (b) was applied. Additionally, the data of E. danricus from India by Mustafa (1978) and Mercy et al. (2008) were used to compare the LWRs with present study s through analysis of co-variance (ANCOVA). Furthermore, the LLRs including TL vs. FL; TL vs. SL and FL vs. SL were estimated by linear regression analysis (Hossain et al., 2006b).

Condition factors (CF)

The allometric condition factor (KA) was calculated using the equation of Tesch (1968): W/Lb, where W is the body weight (BW in g) and L is the total length (TL in cm), and b is the LWR parameter. In addition, the Fulton's condition factor (KF) was calculated using the equation of Fulton (1904): KF =100x (W/L3), where W is the BW in g and L is the TL in cm. The scaling factor of 100 was used to bring the KF close to unit. Furthermore, the relative condition factor (KR) was calculated following the equation of Le Cren (1951): KR = W/(axLb), where W is the (BW in g) L is the (TL in cm) and a and b are LWRs parameter.

Relative weight (WR)

For assessing WR the equation of Froese (2006): WR = (W / Ws) x 100, were used, where W is the weight of a particular individual and Ws is the predicted standard weight for the same individual as calculated by Ws = a*Lb (a and b values obtained from the composite of LWRs).

Form factor (a3.0)

The a3.0 of E. danricus was calculated using the equation of Froese (2006) as: a3.0 = 10 log a - s (b-3), where a and b are regression parameters of LWRs and s is the regression slope of ln a vs. b. In this study, a mean slope S = -1.358, was used for estimating the form factor because information on LWRs is not available for this species for estimation of the regression (S) of ln a vs. b.

Size at first sexual maturity (Lm)

The Lm of E. danricus was calculated using the empirical equation, log (Lm) = -0.1189 + 0.9157 * log (Lmax), where Lmax is the maximum observed length (Binohlan and Froese, 2009).

Natural mortality (MW)

The MW of E. danricus was calculated using the model, MW=1.92 year-1 *(W)-0.25 (Peterson and Wroblewski, 1984), where, MW = Natural mortality at mass W; and W = a*Lb, a and b are regression parameters of LWR.

Statistical analysis

For statistical analysis Microsoft(r) Excel-add-in-DDXL and GraphPad Prism 6.5 (GraphPad Software, Inc., San Diego, CA) were used. Tests for normality was conducted by visual assessment of histograms and box plots, and confirmed using the Kolmogorov-Smirnov test. Where test for normality assumption was not met, then the non-parametric Wilcoxon rank test was used to compare the mean WR of a population with 100 (Anderson and Neumann, 1996). In addition, the Spearman rank test was used to correlate body measurements (e.g., TL, FL, SL, and BW) with condition factors (KA, KF, KR). Furthermore, the LWRs between waters were compared by the ANCOVA. All statistical analyses were considered significant at 5% (pless than 0.05).

RESULTS

Length-frequency distribution

A total number of 309 individuals of E. danricus were collected from the Ganges River. Table I illustrates the descriptive statistics on the length (cm), weight (g) measurements and 95% confidence limit (CL) of the E. danricus. The LFDs of E. danricus showed that the smallest and largest individuals were 2.94 cm and 6.10 cm TL, respectively, whereas the BW ranges from 0.25-1.38 g. The 4.00-4.99 cm TL size group was numerically dominant and constituted 50.00% of the total population (Fig. 1). According to Shapiro-Wilk normality test, the LFDs were normally distributed (p = 0.018 for TL and p less than 0.001 for BW) in the Ganges River.

Length-weight relationships

The sample size (n), regression parameters of the LWRs, 95% CL of a and b, the coefficient of determination (r2) and growth type of E. danricus are given in Table II and Figure 2. The calculated allometric coefficient (b) of TL vs. BW indicate negative allometric growth type in the combined sexes of E. danricus (bless than 3.00, pless than 0.01). In addition, the FL-BW and SL-BW relationships showed similar pattern of growth (Table II) in the Ganges River, NW Bangladesh. All LWRs relationships were highly significant (pless than 0.01), with all r2 values being >0.966. The ANCOVA revealed significant differences on the LWRs of E. danricus between Bangladesh and Indian waters (pless than 0.001) (Table III, Fig.3).

Table I.- Length (cm) and weight (g) measurements with 95% confidence limit of combined sexes of Esomus danricus (Hamilton, 1822) (n=309) from the Ganges River (24.35' N; 88.64' E), northwestern Bangladesh.

Characteristics###Range (cm)###Mean SD###Mode###95% CL

Total length###2.94-6.10###4.40 0.67###3.09###4.33 - 4.48

Fork length###2.68-5.53###3.95 0.60###2.87###3.88 - 4.02

Standard length###2.43-4.79###3.44 0.50###2.59###3.38 - 3.49

Body weight###0.25-1.38###0.67 0.26###0.47###0.64 - 0.70

Table. II.- Descriptive statistics and estimated parameters on the length-weight relationships (BW = axTLb) of Esomus danricus (Hamilton, 1822) from the Ganges River (24.35' N; 88.64' E), northwestern Bangladesh.

Equation###Regression parameters###95% CL###r2###GT

###a###b###a###b

Combined sex (n=309)

BW=a x TLb###0.0158###2.502###0.015 - 0.016###2.476 - 2.529###0.991###-A

BW=a x FLb###0.0205###2.509###0.019 - 0.022###2.461 - 2.557###0.972###-A

BW=a x SLb###0.0253###2.619###0.024 - 0.027###2.563 - 2.674###0.966###-A

Table III.- Comparison on length-weight relationships of Esomus danricus (Hamilton, 1822) between the Ganges River (24.35' N; 88.64' E), northwestern Bangladesh and the Indian waters through analysis of co-variance (ANCOVA)

Water-body###Channel of flowing water,###Freshwater fish pond, Aligarh,###Western Ghat, india

###Aligarh, India###India

Ganges River,###***###***###***

NW Bangladesh###F = 2883.23, df = 614,###F = 84.64, df = 614,###F = 218, df = 614

###p less than 0.001###p less than 0.001###p less than 0.001

Table IV.- The estimated parameters on the length-length relationships (Y = a +b x X) of Esomus danricus (Hamilton, 1822) from the Ganges River (24.35' N; 88.64' E), northwestern Bangladesh.

Equation###n###Regression parameters###95% CL###r2

###a###b###a###b

FL = a + b xTL###0.0762###0.880###0.0118 - 0.1460###0.866 - 0.895###0.979

SL = a + b x TL###309###0.2013###0.735###0.1411 - 0.2616###0.721 - 0.748###0.974

SL = a + b x FL###0.1730###0.826###0.1119 - 0.2341###0.811 - 0.841###0.974

Length-length relationships

The relationships between TL, FL and SL of E. danricus including 309 specimens along with the estimated parameters of the LLRs and the coefficient of determination (r2) are presented in Table IV and Figure 4. All LLRs were highly significant (pless than 0.001) and most of the coefficients of determination values being [greater than or equal to]0.974.

Condition factors

Allometric condition factor

The KA varied from 0.015-0.018 (meanSD = 0.0160.001) (Table V). According to Spearman rank correlation test there was no significant relationship among the TL vs. KA (spearman, r = 0.063, p = 0.270), FL vs. KA (spearman, r = 0.060, p = 0.296), SL vs. KA (spearman, r = 0.067, p = 0.240) but significant relationship exist between BW vs. KA (spearman, r = 0.129, p = 0.003) (Table VI).

Fulton's condition factor

In our study KF ranged from 0.607 to 0.985 (mean SD = 0.762 0.065) (Table V). Spearman rank correlation test revealed that there was strong correlation among the TL vs. KF (spearman, r = -0.854, pless than 0.001), FL vs. KF (spearman, r = -0.846, pless than 0.001), SL vs. KF (spearman, r = -0.842, pless than 0.001) and BW vs. KF (spearman, r = -0.814, pless than 0.001) (Table VI). Based on the spearman rank correlation test, the KF is the best condition factor for assessing the well-being of E. danricus during the study.

Relative condition factor

In the present study the KR ranged from 0.923-1.127 (meanSD = 0.9980.038) (Table V). Spearman rank correlation test indicated that there was no significant relationship among the TL vs. KR (spearman, r = 0.063, p=0.269), FL vs. KR (spearman, r = 0.060, p=0.296), SL vs. KR (spearman, r = 0.067, p=0.240). But there exist significant correlation between BW vs. KR (spearman, r = 0.129, p=0.023) (Table VI).

Relative weight

The calculated minimum and maximum WR were 92.184 and 112.727, with a mean values of 99.8083.755 (Table V) which was not significantly different from 100 (Wilcoxon signed rank test, p=0.295) indicating a balance population in presence of prey and predators for E. danricus in the Ganges River. According to spearman rank correlation test there was no significant relationship between TL and WR (spearman, r = 0.063, p=0.269). Also the spearman rank correlation test specify that there was significant association between BW vs. WR (spearman, r= 0.129, p=0.023) for E. danricus in the Ganges River. The relationship between TL vs. WR was also shown in the Figure 5.

Form factor

The a3.0 was calculated as 0.0033 for combined sexes of E. danricus from the Ganges River, NW Bangladesh and also our study calculate the a3.0 of E. danricus from world-wide different water bodies using available literature (Table VII).

Table V.- Condition factors of combined sexes of Esomus danricus (Hamilton, 1822) (n=309) from the Ganges River (24.35' N; 88.64' E), northwestern Bangladesh.

Condition factor###Range###Mean SD###95% CL

KA###0.015-0.018###0.016 0.001###0.0157 - 0.0158

KF###0.607-0.985###0.762 0.065###0.7542 - 0.7688

KR###0.923-1.127###0.998 0.038###0.9939 - 1.0023

WR###92.184-112.727###99.808 3.755###99.389 - 100.228

Table VI.- Estimation of correlation for Allometric (KA), Fulton's (KF) and Relative (KR) condition factor with total length (TL, cm), fork length (FL, cm), standard length (SL, cm) and body weight (BW, g) of Esomus danricus (Hamilton, 1822) from the Ganges River (24.35' N; 88.64' E), northwestern Bangladesh

Condition factor###rS value###95% CL of rS###P value###Degree of significance

Allometric condition factor

TL vs. KA###0.063###-0.052 to 0.176###P = 0.269###ns

FL vs. KA###0.060###-0.056 to 0.173###P = 0.296###ns

SL vs. KA###0.067###-0.048 to 0.180###P = 0.240###ns

BW vs. KA###0.129###0.015 to 0.240###P = 0.023###*

Fulton's condition factor

TL vs. KF###-0.854###-0.882 to -0.820###P less than 0.001###***

FL vs. KF###-0.846###-0.876 to -0.810###P less than 0.001###***

SL vs. KF###-0.842###-0.872 to -0.805###P less than 0.001###***

BW vs. KF###-0.814###-0.849 to -0.771###P less than 0.001###***

Relative condition factor

TL vs. KR###0.063###-0.052 to 0.176###P = 0.269###ns

FL vs. KR###0.060###-0.056 to 0.173###P = 0.296###ns

SL vs. KR###0.067###-0.048 to 0.180###P = 0.240###ns

BW vs. KR###0.129###0.015 to 0.240###P = 0.023###*

Table VII.- The calculated form factor (a3.0), size at first sexual maturity (Lm) and natural mortality (MW) of Esomus danricus in world-wide different water-bodies

Water-bodies###a###b###Maximum###Reference###a3.0###Lm cm###MW

###TL###year-1

Western Ghats of India###0.0441###2.294###7.2 cm###Mercy et al. (2008)###0.0048###4.64###1.91

Ponds, India###0.0663###2.632###Mustafa (1978)###0.0210###1.51

Water channel, India###0.0051###3.245###Mustafa (1978)###0.0110###2.42

Nageshwari water,###0.0505###2.812###6.8 cm###Ferdaushy and Alam (2015)###0.0281###4.40###1.48

Bangladesh

Ganges River, Bangladesh###0.0158###2.502###6.1 cm###Present study###0.0033###3.98###2.31

Size at first sexual maturity

The size at first sexual maturity (Lm) for the E. danricus was estimated as 3.98 (~ 4.00) cm TL (95% CL = 3.30 - 4.86 cm TL) in the Ganges River, NW Bangladesh. In addition, our study calculates the Lm of E. danricus from world-wide different water bodies using available literature (Table VII).

Natural mortality

The mean natural mortality was estimated as 2.31 year-1 for the E. danricus in the Ganges River, NW Bangladesh.

DISCUSSION

Information on life-history traits of E. danricus from Bangladesh is not available in the literature, but some studies on LWRs were conducted by Hossain et al. (2009b, 2015d); Sani et al. (2010); Naeem et al. (2012) from Indian sub-continent. However, this study collected a total number of 309 individuals with various body sizes using traditional fishing gears from the Ganges River, NW Bangladesh. This study focuses on LWRs, LLRs, CF (KA, KF, KR), WR, a3.0 and Lm and MW of E. danricus from the Ganges River. Also comparison on LWRs between two water-bodies, which would be effective for further study and sustainable conservation of this species in different geographical locations.

In our study, it was not possible to collect the E. danricus smaller than 2.94 cm, which can be attributed that, the fishermen did not go where the smaller size exist or selectivity of fishing gears (Hossain et al., 2012 c, d). The maximum length of E. danricus found in the present study 6.10 cm in TL which is lower than the maximum recorded value of 7.2 cm TL in the Western Ghats of India, Mercy et al. (2008). In addition, maximum BW of E. danricus found in the present study was 1.38 g, which is lower than by Mercy et al. (2008) as 1.72 g in the Western Ghats. Information on maximum length is necessary to estimate the asymptotic length and growth coefficient of fishes (Hossain, 2010c), which is vital for fisheries resource planning and management (Ahmed et al., 2012; Hossain et al., 2012e).

The present study r evealed that the calculated b values lies between 2.5 to 2.6 for differ ent LWRs of E. danricus from the Ganges River. However, the b values ranging fr om 2.5 to 3.5 ar e mor e common (Carlander, 1969; Froese, 2006). In general b val u es close to 3, indicating that fish grow isometrically and different from 3.0 indicate allometric growth (>3 positive allometric and less than 3 negative allometric) (Tesch, 1971). In the present study, b values ranges from 2.5-2.6 that indicate negative allometric growth for E. danricus in the Ganges River, NW Bangladesh. In a recent study by Mercy et al. (2008) recorded the isometric growth for E. danricus from the Western Ghats, India. In addition, Mustafa (1978) described the growth of this flying barb as negatively allometric in two freshwaters including a pond and a running channel, Aligarh, India, which is accordance with the present study.

However, ANCOVA revealed significant differences on the LWRs between Bangladesh and Indian waters (pless than 0.001). Such differences may be ascribed due to observed length ranges of the specimen caught, preservation techniques, health of the stocks, seasonal effect or geographic condition (Hossain et al., 2010).

All the LLRs for the combined sexes of E. danricus were highly correlated with all r2 values [greater than or equal to] 0.974. Since the current study is the first assessment on LLRs of E. danricus, so lack of references dealing with LLRs restrains the comparison of the present results with early literature on the same population/ species.

Although most of the studies deal with single condition factor, however we have worked on four condition factors (allometric, KA; Fulton's, KF; (2004) relative, KR and relative weight, WR) to assess the health and habitat condition of E. danricus in the Ganges River. Spearman rank correlation test stated that the KF was more significantly correlated with TL, FL, SL and BW than other factors. Therefore, it can be postulated that, the Fulton's condition factor (KF) is the best biometric index for assessing the well-being of this E. danricus in the Ganges River and surrounding ecosystem.

Additionally, the Wilcoxon signed rank test indicates WR was not significantly different from 100 (p=0.295) indicating a balance population with the availability of food and lower predators for E. danricus in the Ganges River ecosystem. Moreover, the WR can use to evaluate the overall health and fitness as well as population-level responses to ecosystem disturbance (Rypel and Richter, 2008). However, there is no available information in literature dealing with the WR of this species restrains the comparison with our present findings.

The calculated form factor (a3.0) was 0.0033 for E. danricus in the Ganges River. The a3.0 can be used to verify whether the body shape of individuals in a given population or species is significantly different from others (Froese, 2006). There is no reference regarding the form factor of this species in the literature and this is the first study for the estimation of a3.0 for E. danricus in different water-bodies which will provide the foundation for future studies.

The size at first sexual maturity (Lm) for E. danricus was 3.98 (~ 4.00) cm in TL. Studies on Lm for the fishes of Bangladeshi waters are very rare (except Hossain et al., 2010; 2012f). This study presents the first attempt to determine the size at first sexual maturity and natural mortality for E. danricus from different waters of Indian sub-continent. Therefore, this study presented the basis for more detailed studies to provide combination of factors affecting the size at first sexual maturity and natural mortality in different populations of E. danricus in the Indian sub-continent.

CONCLUSIONS

The present findings describe the life history traits of E. danricus including, length-frequency distribution, growth pattern based on LWRs, best fitted condition factor, relative weight, form factor, size at first sexual maturity and natural mortality. The results of this study would be an effective tool for fishery managers, fish biologists and conservationists to initiate early management strategies and regulations for the sustainable conservation of the remaining stocks of this species in the Ganges River and surrounding ecosystem. Therefore, the results of this study provide invaluable information for the online FishBase database, as well as providing an important baseline for future studies within the Ganges River and neighboring countries.

ACKNOWLEDGEMENTS

The authors would like to extend their sincere appreciation to the Deanship of Scientific Research at King Saud University for its funding this Research group NO (RG-1436-025).

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ABSTRACT

The present study describe the first life-history traits of threatened fish Esomus danricus from the Ganges River, northwestern Bangladesh. This study also calculates the form factor, size at first sexual maturity and natural mortality of E. danricus from world-wide different water bodies using available literature. Sampling was done, using traditional fishing gears including cast net, square lift net and conical trap during January to December 2014. A total of 309 individuals ranging from 2.94-6.10 cm total length and 0.25-1.38 g body weight were analyzed in this study. The length frequency distributions showed that the 4.00-4.99 cm total length size group was numerically dominant and constituted 50.00% of the total population. The allometric coefficient (b) of the length-weight relationship indicates negative allometric growth (b less than 3.0) for E. danricus in the Ganges River. The results also indicate that the length-length relationships were highly correlated (r2 [greater than or equal to] 0.974).

The allometric condition factor varied from 0.015 to 0.018 and Fulton's condition factor varied from 0.607-0.985. Also the relative condition factor ranges from 0.923 to 1.127 and minimum and maximum values of relative weight were 92.185-112.727 in the Ganges River. The Fulton's condition factor is the best index for a ssessing the wellbeing of E. danricus in the Ganges River. According to Wilcoxon signed test the relative weight did not show any significant difference from 100 (p = 0.295), indicating the balance habitat for E. danricus. The form factor was calculated as 0.0033 and the size at first sexual maturity for combined sexes of E. danricus was estimated as 3.98 (~ 4.00) cm total length in the Ganges River, northwestern Bangladesh. In addition, the mean natural mortality was estimated as 2.31 year-1. These results will be useful for sustainable conservation of this threatened fish in the Ganges River and surrounding ecosystem.

Key words

Esomus danricus, length-weight relationship, relative weight, form factor, size at first sexual maturity.

INTRODUCTION

The flying barb, Esomus danricus (Hamilton, 1822) belongs to the family Cyprinidae, is a small indigenous fish species (SIS) of Bangladesh. This fish is known as Darkina, Darki, Darkya in Bangladesh (Rahman, 2005). In India it is known as Darkina, Dadhikha, Danrika, Jongia, Chilwa, Jhai, Astapakke, Messaparavi and Meesa-parava (Talwar and Jhingran, 1991). This species is widely distributed throughout the Indian sub-continent including Bangladesh, India, Nepal, Pakistan, Sri-Lanka and some other countries of the world such as Afghanistan and Thailand (Froese and Pauly, 2015). The flying barb, E. danricus inhabits ponds, weedy ditches, streams, beels and inundated fields (Rahman, 1989; Talwar and Jhingran, 1991). It is an important target species for small-scale fishers (Shafi and Quddus, 1982).

Nonetheless, the untamed population of this species is waning due to reckless fishing, habitat destruction and other ecological changes to their surroundings (Hossen et al., 2015; Hossain et al., 2015a, b) and afterward categorized as least concern in Red list (Devi and Boguskaya, 2009). This fish is a major source of animal protein and macronutrients in the diet of rural poor people in fresh and dried condition (Bijen et al., 1990; Lilabati and Vishwanath, 2000). E. danricus also used as ornamental fish (Froese and Pauly, 2015).

Length-weight relationships (LWRs) are very helpful in fishery for predicting length distributions into weights for estimation of biomass (Gerritsen and McGrath, 2007). Additionally, LWRs parameters are important to evaluate fish-stock condition (Gonzalez Acosta et al., 2004). Furthermore, condition factors are functional parameters that can be used for determining the possible differences among different stocks of the same species (King, 2007; Soomro et al., 2012). Moreover, relative weight (WR) is one of the most popular indices to know the condition of fishes in the USA since last two decades (Rypel and Richter, 2008) and recently it has been used in Bangladesh for determining the condition of freshwater fishes (Hossain et al., 2012a, 2015c).

A number of studies including length-frequency distributions (Hossain et al., 2008; Rahman et al., 2012), length-length and LWRs (Hossain, 2010a; Hossain et al., 2006a,b; 2009a), condition-and form-factors (Hossain, 2010b; Hossain et al., 2010, 2012b) of several fish species have been conducted, but the research on the life history traits of E. danricus are evidently lacking from Bangladesh or else. Therefore, this study reports the first complete and comprehensive description on life-history traits of E. danricus in the Ganges River, northwestern Bangladesh using a large number of specimens from small to large body sizes.

MATERIALS AND METHODS

Study site

The current study was conducted in the Ganges River (known as Padma in Bangladesh) (24.35' N; 88.64' E) northwestern (NW) Bangladesh. It is one of the longest rivers and believed to be an important spawning and feeding ground for riverine fishes (Hossain et al., 2010; Rahman et al., 2012).

Sampling and measurement

The samples of E. danricus were collected during daytime from the fishermen at different parts (Charghat; 2415' N, 88 44' E; Godagari; 24 26' N, 88 19' E and Saheb bazar; 24 20' N, 88 34' E) of the Ganges River in Rajshahi region during January 2014 to December 2014. The fishes were caught using cast net, square lift net and box trap. The fresh samples were immediately chilled in ice on site and fixed with 10% buffered formalin upon arrival in the laboratory. For each individual, total length (TL), fork length (FL) and standard length (SL) were measured to the nearest 0.01 cm using digital slide calipers (Mitutoyo, CD-15PS; Mitutoyo Corporation, Tokyo, Japan) and whole body weight (BW) was taken by a digital balance (Shimadzu, EB-430DW; Shimadzu Seisakusho, Tokyo, Japan) with 0.01 g accuracy.

Length-frequency distribution (LFDs)

The LFDs for the E. danricus were constructed using 1 cm intervals of TL. The normal distribution was fitted to the TL frequency distribution of E. danricus using a computer analysis Microsoft Excell-add-in-solver) based on Hasselblad's maximum-likelihood method (Hasselblad, 1966).

Length-weight and length-length relationships (LWRs and LLRs)

The LWRs were calculated using the equation: W= a*Lb, where the W is the body weight (g) and L is the length (cm). The parameters a and b were estimated by linear regression analysis based on natural logarithms: ln(W) = ln(a) + b ln(L). Additionally, 95% confidence limits of a and b and the coefficient of determination r2 were estimated. In order to confirm whether b values obtained in the linear regressions were significantly different from the isometric value (b = 3), a t-test Sokal and Rohlf (1987): ts = (b-3) / sb, where ts is the t-test value, b the slope and sb the standard error of the slope (b) was applied. Additionally, the data of E. danricus from India by Mustafa (1978) and Mercy et al. (2008) were used to compare the LWRs with present study s through analysis of co-variance (ANCOVA). Furthermore, the LLRs including TL vs. FL; TL vs. SL and FL vs. SL were estimated by linear regression analysis (Hossain et al., 2006b).

Condition factors (CF)

The allometric condition factor (KA) was calculated using the equation of Tesch (1968): W/Lb, where W is the body weight (BW in g) and L is the total length (TL in cm), and b is the LWR parameter. In addition, the Fulton's condition factor (KF) was calculated using the equation of Fulton (1904): KF =100x (W/L3), where W is the BW in g and L is the TL in cm. The scaling factor of 100 was used to bring the KF close to unit. Furthermore, the relative condition factor (KR) was calculated following the equation of Le Cren (1951): KR = W/(axLb), where W is the (BW in g) L is the (TL in cm) and a and b are LWRs parameter.

Relative weight (WR)

For assessing WR the equation of Froese (2006): WR = (W / Ws) x 100, were used, where W is the weight of a particular individual and Ws is the predicted standard weight for the same individual as calculated by Ws = a*Lb (a and b values obtained from the composite of LWRs).

Form factor (a3.0)

The a3.0 of E. danricus was calculated using the equation of Froese (2006) as: a3.0 = 10 log a - s (b-3), where a and b are regression parameters of LWRs and s is the regression slope of ln a vs. b. In this study, a mean slope S = -1.358, was used for estimating the form factor because information on LWRs is not available for this species for estimation of the regression (S) of ln a vs. b.

Size at first sexual maturity (Lm)

The Lm of E. danricus was calculated using the empirical equation, log (Lm) = -0.1189 + 0.9157 * log (Lmax), where Lmax is the maximum observed length (Binohlan and Froese, 2009).

Natural mortality (MW)

The MW of E. danricus was calculated using the model, MW=1.92 year-1 *(W)-0.25 (Peterson and Wroblewski, 1984), where, MW = Natural mortality at mass W; and W = a*Lb, a and b are regression parameters of LWR.

Statistical analysis

For statistical analysis Microsoft(r) Excel-add-in-DDXL and GraphPad Prism 6.5 (GraphPad Software, Inc., San Diego, CA) were used. Tests for normality was conducted by visual assessment of histograms and box plots, and confirmed using the Kolmogorov-Smirnov test. Where test for normality assumption was not met, then the non-parametric Wilcoxon rank test was used to compare the mean WR of a population with 100 (Anderson and Neumann, 1996). In addition, the Spearman rank test was used to correlate body measurements (e.g., TL, FL, SL, and BW) with condition factors (KA, KF, KR). Furthermore, the LWRs between waters were compared by the ANCOVA. All statistical analyses were considered significant at 5% (pless than 0.05).

RESULTS

Length-frequency distribution

A total number of 309 individuals of E. danricus were collected from the Ganges River. Table I illustrates the descriptive statistics on the length (cm), weight (g) measurements and 95% confidence limit (CL) of the E. danricus. The LFDs of E. danricus showed that the smallest and largest individuals were 2.94 cm and 6.10 cm TL, respectively, whereas the BW ranges from 0.25-1.38 g. The 4.00-4.99 cm TL size group was numerically dominant and constituted 50.00% of the total population (Fig. 1). According to Shapiro-Wilk normality test, the LFDs were normally distributed (p = 0.018 for TL and p less than 0.001 for BW) in the Ganges River.

Length-weight relationships

The sample size (n), regression parameters of the LWRs, 95% CL of a and b, the coefficient of determination (r2) and growth type of E. danricus are given in Table II and Figure 2. The calculated allometric coefficient (b) of TL vs. BW indicate negative allometric growth type in the combined sexes of E. danricus (bless than 3.00, pless than 0.01). In addition, the FL-BW and SL-BW relationships showed similar pattern of growth (Table II) in the Ganges River, NW Bangladesh. All LWRs relationships were highly significant (pless than 0.01), with all r2 values being >0.966. The ANCOVA revealed significant differences on the LWRs of E. danricus between Bangladesh and Indian waters (pless than 0.001) (Table III, Fig.3).

Table I.- Length (cm) and weight (g) measurements with 95% confidence limit of combined sexes of Esomus danricus (Hamilton, 1822) (n=309) from the Ganges River (24.35' N; 88.64' E), northwestern Bangladesh.

Characteristics###Range (cm)###Mean SD###Mode###95% CL

Total length###2.94-6.10###4.40 0.67###3.09###4.33 - 4.48

Fork length###2.68-5.53###3.95 0.60###2.87###3.88 - 4.02

Standard length###2.43-4.79###3.44 0.50###2.59###3.38 - 3.49

Body weight###0.25-1.38###0.67 0.26###0.47###0.64 - 0.70

Table. II.- Descriptive statistics and estimated parameters on the length-weight relationships (BW = axTLb) of Esomus danricus (Hamilton, 1822) from the Ganges River (24.35' N; 88.64' E), northwestern Bangladesh.

Equation###Regression parameters###95% CL###r2###GT

###a###b###a###b

Combined sex (n=309)

BW=a x TLb###0.0158###2.502###0.015 - 0.016###2.476 - 2.529###0.991###-A

BW=a x FLb###0.0205###2.509###0.019 - 0.022###2.461 - 2.557###0.972###-A

BW=a x SLb###0.0253###2.619###0.024 - 0.027###2.563 - 2.674###0.966###-A

Table III.- Comparison on length-weight relationships of Esomus danricus (Hamilton, 1822) between the Ganges River (24.35' N; 88.64' E), northwestern Bangladesh and the Indian waters through analysis of co-variance (ANCOVA)

Water-body###Channel of flowing water,###Freshwater fish pond, Aligarh,###Western Ghat, india

###Aligarh, India###India

Ganges River,###***###***###***

NW Bangladesh###F = 2883.23, df = 614,###F = 84.64, df = 614,###F = 218, df = 614

###p less than 0.001###p less than 0.001###p less than 0.001

Table IV.- The estimated parameters on the length-length relationships (Y = a +b x X) of Esomus danricus (Hamilton, 1822) from the Ganges River (24.35' N; 88.64' E), northwestern Bangladesh.

Equation###n###Regression parameters###95% CL###r2

###a###b###a###b

FL = a + b xTL###0.0762###0.880###0.0118 - 0.1460###0.866 - 0.895###0.979

SL = a + b x TL###309###0.2013###0.735###0.1411 - 0.2616###0.721 - 0.748###0.974

SL = a + b x FL###0.1730###0.826###0.1119 - 0.2341###0.811 - 0.841###0.974

Length-length relationships

The relationships between TL, FL and SL of E. danricus including 309 specimens along with the estimated parameters of the LLRs and the coefficient of determination (r2) are presented in Table IV and Figure 4. All LLRs were highly significant (pless than 0.001) and most of the coefficients of determination values being [greater than or equal to]0.974.

Condition factors

Allometric condition factor

The KA varied from 0.015-0.018 (meanSD = 0.0160.001) (Table V). According to Spearman rank correlation test there was no significant relationship among the TL vs. KA (spearman, r = 0.063, p = 0.270), FL vs. KA (spearman, r = 0.060, p = 0.296), SL vs. KA (spearman, r = 0.067, p = 0.240) but significant relationship exist between BW vs. KA (spearman, r = 0.129, p = 0.003) (Table VI).

Fulton's condition factor

In our study KF ranged from 0.607 to 0.985 (mean SD = 0.762 0.065) (Table V). Spearman rank correlation test revealed that there was strong correlation among the TL vs. KF (spearman, r = -0.854, pless than 0.001), FL vs. KF (spearman, r = -0.846, pless than 0.001), SL vs. KF (spearman, r = -0.842, pless than 0.001) and BW vs. KF (spearman, r = -0.814, pless than 0.001) (Table VI). Based on the spearman rank correlation test, the KF is the best condition factor for assessing the well-being of E. danricus during the study.

Relative condition factor

In the present study the KR ranged from 0.923-1.127 (meanSD = 0.9980.038) (Table V). Spearman rank correlation test indicated that there was no significant relationship among the TL vs. KR (spearman, r = 0.063, p=0.269), FL vs. KR (spearman, r = 0.060, p=0.296), SL vs. KR (spearman, r = 0.067, p=0.240). But there exist significant correlation between BW vs. KR (spearman, r = 0.129, p=0.023) (Table VI).

Relative weight

The calculated minimum and maximum WR were 92.184 and 112.727, with a mean values of 99.8083.755 (Table V) which was not significantly different from 100 (Wilcoxon signed rank test, p=0.295) indicating a balance population in presence of prey and predators for E. danricus in the Ganges River. According to spearman rank correlation test there was no significant relationship between TL and WR (spearman, r = 0.063, p=0.269). Also the spearman rank correlation test specify that there was significant association between BW vs. WR (spearman, r= 0.129, p=0.023) for E. danricus in the Ganges River. The relationship between TL vs. WR was also shown in the Figure 5.

Form factor

The a3.0 was calculated as 0.0033 for combined sexes of E. danricus from the Ganges River, NW Bangladesh and also our study calculate the a3.0 of E. danricus from world-wide different water bodies using available literature (Table VII).

Table V.- Condition factors of combined sexes of Esomus danricus (Hamilton, 1822) (n=309) from the Ganges River (24.35' N; 88.64' E), northwestern Bangladesh.

Condition factor###Range###Mean SD###95% CL

KA###0.015-0.018###0.016 0.001###0.0157 - 0.0158

KF###0.607-0.985###0.762 0.065###0.7542 - 0.7688

KR###0.923-1.127###0.998 0.038###0.9939 - 1.0023

WR###92.184-112.727###99.808 3.755###99.389 - 100.228

Table VI.- Estimation of correlation for Allometric (KA), Fulton's (KF) and Relative (KR) condition factor with total length (TL, cm), fork length (FL, cm), standard length (SL, cm) and body weight (BW, g) of Esomus danricus (Hamilton, 1822) from the Ganges River (24.35' N; 88.64' E), northwestern Bangladesh

Condition factor###rS value###95% CL of rS###P value###Degree of significance

Allometric condition factor

TL vs. KA###0.063###-0.052 to 0.176###P = 0.269###ns

FL vs. KA###0.060###-0.056 to 0.173###P = 0.296###ns

SL vs. KA###0.067###-0.048 to 0.180###P = 0.240###ns

BW vs. KA###0.129###0.015 to 0.240###P = 0.023###*

Fulton's condition factor

TL vs. KF###-0.854###-0.882 to -0.820###P less than 0.001###***

FL vs. KF###-0.846###-0.876 to -0.810###P less than 0.001###***

SL vs. KF###-0.842###-0.872 to -0.805###P less than 0.001###***

BW vs. KF###-0.814###-0.849 to -0.771###P less than 0.001###***

Relative condition factor

TL vs. KR###0.063###-0.052 to 0.176###P = 0.269###ns

FL vs. KR###0.060###-0.056 to 0.173###P = 0.296###ns

SL vs. KR###0.067###-0.048 to 0.180###P = 0.240###ns

BW vs. KR###0.129###0.015 to 0.240###P = 0.023###*

Table VII.- The calculated form factor (a3.0), size at first sexual maturity (Lm) and natural mortality (MW) of Esomus danricus in world-wide different water-bodies

Water-bodies###a###b###Maximum###Reference###a3.0###Lm cm###MW

###TL###year-1

Western Ghats of India###0.0441###2.294###7.2 cm###Mercy et al. (2008)###0.0048###4.64###1.91

Ponds, India###0.0663###2.632###Mustafa (1978)###0.0210###1.51

Water channel, India###0.0051###3.245###Mustafa (1978)###0.0110###2.42

Nageshwari water,###0.0505###2.812###6.8 cm###Ferdaushy and Alam (2015)###0.0281###4.40###1.48

Bangladesh

Ganges River, Bangladesh###0.0158###2.502###6.1 cm###Present study###0.0033###3.98###2.31

Size at first sexual maturity

The size at first sexual maturity (Lm) for the E. danricus was estimated as 3.98 (~ 4.00) cm TL (95% CL = 3.30 - 4.86 cm TL) in the Ganges River, NW Bangladesh. In addition, our study calculates the Lm of E. danricus from world-wide different water bodies using available literature (Table VII).

Natural mortality

The mean natural mortality was estimated as 2.31 year-1 for the E. danricus in the Ganges River, NW Bangladesh.

DISCUSSION

Information on life-history traits of E. danricus from Bangladesh is not available in the literature, but some studies on LWRs were conducted by Hossain et al. (2009b, 2015d); Sani et al. (2010); Naeem et al. (2012) from Indian sub-continent. However, this study collected a total number of 309 individuals with various body sizes using traditional fishing gears from the Ganges River, NW Bangladesh. This study focuses on LWRs, LLRs, CF (KA, KF, KR), WR, a3.0 and Lm and MW of E. danricus from the Ganges River. Also comparison on LWRs between two water-bodies, which would be effective for further study and sustainable conservation of this species in different geographical locations.

In our study, it was not possible to collect the E. danricus smaller than 2.94 cm, which can be attributed that, the fishermen did not go where the smaller size exist or selectivity of fishing gears (Hossain et al., 2012 c, d). The maximum length of E. danricus found in the present study 6.10 cm in TL which is lower than the maximum recorded value of 7.2 cm TL in the Western Ghats of India, Mercy et al. (2008). In addition, maximum BW of E. danricus found in the present study was 1.38 g, which is lower than by Mercy et al. (2008) as 1.72 g in the Western Ghats. Information on maximum length is necessary to estimate the asymptotic length and growth coefficient of fishes (Hossain, 2010c), which is vital for fisheries resource planning and management (Ahmed et al., 2012; Hossain et al., 2012e).

The present study r evealed that the calculated b values lies between 2.5 to 2.6 for differ ent LWRs of E. danricus from the Ganges River. However, the b values ranging fr om 2.5 to 3.5 ar e mor e common (Carlander, 1969; Froese, 2006). In general b val u es close to 3, indicating that fish grow isometrically and different from 3.0 indicate allometric growth (>3 positive allometric and less than 3 negative allometric) (Tesch, 1971). In the present study, b values ranges from 2.5-2.6 that indicate negative allometric growth for E. danricus in the Ganges River, NW Bangladesh. In a recent study by Mercy et al. (2008) recorded the isometric growth for E. danricus from the Western Ghats, India. In addition, Mustafa (1978) described the growth of this flying barb as negatively allometric in two freshwaters including a pond and a running channel, Aligarh, India, which is accordance with the present study.

However, ANCOVA revealed significant differences on the LWRs between Bangladesh and Indian waters (pless than 0.001). Such differences may be ascribed due to observed length ranges of the specimen caught, preservation techniques, health of the stocks, seasonal effect or geographic condition (Hossain et al., 2010).

All the LLRs for the combined sexes of E. danricus were highly correlated with all r2 values [greater than or equal to] 0.974. Since the current study is the first assessment on LLRs of E. danricus, so lack of references dealing with LLRs restrains the comparison of the present results with early literature on the same population/ species.

Although most of the studies deal with single condition factor, however we have worked on four condition factors (allometric, KA; Fulton's, KF; (2004) relative, KR and relative weight, WR) to assess the health and habitat condition of E. danricus in the Ganges River. Spearman rank correlation test stated that the KF was more significantly correlated with TL, FL, SL and BW than other factors. Therefore, it can be postulated that, the Fulton's condition factor (KF) is the best biometric index for assessing the well-being of this E. danricus in the Ganges River and surrounding ecosystem.

Additionally, the Wilcoxon signed rank test indicates WR was not significantly different from 100 (p=0.295) indicating a balance population with the availability of food and lower predators for E. danricus in the Ganges River ecosystem. Moreover, the WR can use to evaluate the overall health and fitness as well as population-level responses to ecosystem disturbance (Rypel and Richter, 2008). However, there is no available information in literature dealing with the WR of this species restrains the comparison with our present findings.

The calculated form factor (a3.0) was 0.0033 for E. danricus in the Ganges River. The a3.0 can be used to verify whether the body shape of individuals in a given population or species is significantly different from others (Froese, 2006). There is no reference regarding the form factor of this species in the literature and this is the first study for the estimation of a3.0 for E. danricus in different water-bodies which will provide the foundation for future studies.

The size at first sexual maturity (Lm) for E. danricus was 3.98 (~ 4.00) cm in TL. Studies on Lm for the fishes of Bangladeshi waters are very rare (except Hossain et al., 2010; 2012f). This study presents the first attempt to determine the size at first sexual maturity and natural mortality for E. danricus from different waters of Indian sub-continent. Therefore, this study presented the basis for more detailed studies to provide combination of factors affecting the size at first sexual maturity and natural mortality in different populations of E. danricus in the Indian sub-continent.

CONCLUSIONS

The present findings describe the life history traits of E. danricus including, length-frequency distribution, growth pattern based on LWRs, best fitted condition factor, relative weight, form factor, size at first sexual maturity and natural mortality. The results of this study would be an effective tool for fishery managers, fish biologists and conservationists to initiate early management strategies and regulations for the sustainable conservation of the remaining stocks of this species in the Ganges River and surrounding ecosystem. Therefore, the results of this study provide invaluable information for the online FishBase database, as well as providing an important baseline for future studies within the Ganges River and neighboring countries.

ACKNOWLEDGEMENTS

The authors would like to extend their sincere appreciation to the Deanship of Scientific Research at King Saud University for its funding this Research group NO (RG-1436-025).

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Author: | Hossain, Md. Yeamin; Naser, S. M. Abu; Bahkali, Ali H.; Yahya, Khairun; Hossen, Md. Alomgir; Elgorba |
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Publication: | Pakistan Journal of Zoology |

Article Type: | Report |

Geographic Code: | 9BANG |

Date: | Apr 30, 2016 |

Words: | 6333 |

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