Fishery Biology of Gangetic Whiting Sillaginopsis Panijus (Hamilton, 1822) Endemic to Ganges Delta, Bangladesh
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Egyptian Journal of Aquatic Research (2015) 41, 307–313 HOSTED BY National Institute of Oceanography and Fisheries Egyptian Journal of Aquatic Research http://ees.elsevier.com/ejar www.sciencedirect.com FULL LENGTH ARTICLE Fishery biology of gangetic whiting Sillaginopsis panijus (Hamilton, 1822) endemic to Ganges delta, Bangladesh Muhammad Abu Bakar Siddik a,*, Md Abu Hanif a, Md Reaz Chaklader a, Ashfaqun Nahar b, Sultan Mahmud c a Department of Fisheries Biology and Genetics, Patuakhali Science and Technology University, Patuakhali 8602, Bangladesh b Department of Marine Fisheries and Oceanography, Patuakhali Science and Technology University, Patuakhali 8602, Bangladesh c Department of Aquaculture, Patuakhali Science and Technology University, Patuakhali 8602, Bangladesh Available online 12 January 2016 KEYWORDS Abstract The aim of the present study was to establish the baseline data on fishery biology of Allometric growth; Sillaginopsis panijus which is very endemic in the southern coastal waters of Bangladesh. Altogether Length–weight; 300 individuals of S. panijus were sampled from five catchment areas within the Ganges delta in Condition factors; which males represent 46% and females 54% of the total sampled population. The overall sex ratio Form factor; in the populations agrees with the expected value of 1:1 in normal population. The values of allo- Ganges delta metric coefficient (b) of the LWRs indicated positive allometric growth (b > 3) in female and com- bined sexes, while male showed a negative allometric growth (b < 3). All the relationships among length parameters (SL–TL, SL–FL and TL–FL) of the species were found significant with all (r2) values being >0.900. The mean values of CFs for males were higher than those of females in all different length classes. The study would expedite future studies on population assessment and sus- tainable conservation of the fish species along the southern coastal region of Bangladesh. Ó 2015 National Institute of Oceanography and Fisheries. Hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Introduction considerable commercial importance in the coastal region of Bangladesh due to its deliciousness, white flesh and few bones Gangetic whiting Sillaginopsis panijus (Hamilton, 1822) a (Islam et al., 2012). There are, however, very few information member of Sillaginidae, is an inshore marine and estuarine fish on the life history traits of the species except for a document on species found on the southern Asian coast including the their classification and description by Froese and Pauly (2014). Ganges delta in Bangladesh, India, Myanmar, Malaysia and The Ganges delta is a major spawning and growing area of occasionally as far south as the Indonesian archipelago fishes which supports a diverse fish fauna in the southern (Krishnayya, 1963; McKay, 1992). This species has coastal waters of Bangladesh (Islam, 2003; Sharker et al., 2015; Chaklader et al., 2015). Many catadromous, anadro- * Corresponding author. Tel.: +880 1768584609. mous and diadromous fishes use the Ganges delta seasonally E-mail address: [email protected] (M.A.B. Siddik). as a major breeding, feeding and migratory route with Bay Peer review under responsibility of National Institute of Oceanography of Bengal (Islam, 2003; Siddik et al., 2013). However, over and Fisheries. http://dx.doi.org/10.1016/j.ejar.2015.11.001 1687-4285 Ó 2015 National Institute of Oceanography and Fisheries. Hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). 308 M.A.B. Siddik et al. the last century, the riverine ecosystems within this delta have has been done dealing with fishery biology of S. panijus around changed considerably due to human intervention, intense tour- the world. Thus the present study aimed to provide baseline ism, illegal logging, pollution and even global change conse- data of the endemic fishes, S. panijus in the Ganges delta. It quences which have altered water quality and quantity is considered to be the first to provide clear information (IUCN, 2000; Chaklader et al., 2014; Nahar et al., 2015; on some aspects of the biology of this fish species in this Sharker et al., 2015). These factors also rendered body mor- region and will thus further contribute to the development of phology and growth rate of fishes (Froese, 2006; Rypel and inclusive baseline data and the effective management plans Richter, 2008; Akel and Philips, 2014). Therefore, studies on for fishes not only in this region but also its whole geographical various aspects of fishery biology are crucial for sustainable distribution. conservation and management of the stock within the delta. As a biology parameter, LWR is considered the significant Materials and methods biological tool that generates overall growth and condition of fish (Wanner and Klumb, 2009; Philips, 2014; Sabrah, 2015). It A total of 300 individuals of S. panijus were captured with the is also useful for morphological comparisons between sexes of help of fishermen during day time using trawl nets from 5 population and life history study of fishes from different loca- rivers within the Ganges delta in the southern coastal region tions (El-Drawany, 2013; Akel and Philips, 2014; Sabrah, 0 of Bangladesh namely, the Karnafuli River (S1:91°85 N and 2015). In line with LWRs, the condition factors (CFs) of a spe- 0 0 22°32 E: 50 individual), the Meghna river (S2:90°66 N 0 0 cies are important to assess the overall health condition of and 22°79 E: 50 individual), the Tentulia River (S3:90°61 N 0 0 fishes, its productivity and physiology as well (Torres et al., and 22°27 E: 50 individual), the Baleshwar river (S4:89°89 0 2012; Ragheb, 2014). The form factor (a3.0) of a particular spe- N and 22°19 E: 50 individual) and the Marjata river (S5: cies can be applied to demonstrate whether the phenotypes of 89°590 N and 22°110 E: 50 individual) for a period of one year an individual are significantly different from others (Froese, from March 2014to February 2015 (Fig. 1). After collection, 2006; Ahmed et al., 2014). samples were preserved with ice and transported to the Information concerning the fishery biology and characteris- research laboratory. Total length (TL), fork length (FL) and tics are well stated in many fishes; however, to date no research standard length (SL) for every specimen were measured by Figure 1 Map showing five sampling sites in Ganges delta, southern Bangladesh. Fishery biology of gangetic whiting Sillaginopsis panijus 309 slide calipers (Mitutoyo, CD-15PS, Japan) and weight (W) was Version 15.0 was used for all statistical procedures at 5% taken on a digital electronic balance (Shimadzu, EB-430DW, (p < 0.05). Japan) for each fish. The sex was identified by visual inspection of morphometric characteristics (Liang et al., 2005) and Results and discussion. gonads (Mahmood et al., 2011). The length and weight relationship of S. panijus was deter- Length composition and sex ratio mined according to Ricker (1975): W = aLb where, (a) and (b) are constant indicating the body form and the fish growth type. The total length of 300 species of S. panijus obtained for the However, the length–length relationships have been done using study ranged from 14.60 to 29.30 cm for males and 14.70 to the linear regression between TL, FL and SL for males, 28.70 cm for females. The number of sample, minimum and females, and pool samples separately. The 95% confidence 2 maximum lengths and body weights, 95% confidence limit levels of (b) and the coefficient of determination (r ) were cal- (CL) for male, female and pool sample are presented in Table 1. culated. In order to confirm whether (b) values obtained in the The length frequency analysis showed that the distribution of linear regressions were significantly different from the isomet- males and females of S. panijus was not normal according to ric value (b = 3), a t-test was applied, expressed by the equa- Kolmogorov–Smirnov test (p < 0.001) in the Ganges delta À tion: ts =(b 3)/sb, where ts is the t-test value, b the slope (Table 2 and Fig. 2) but Mann–Whitney U-test (p < 0.001) and sb the standard error of the slope (b). showed significant differences in the length-frequency distribu- There are three condition factors that have been performed tions of S. panijus between males and females. to generalize the health condition of S. panijus in the present Among the specimens, the number of males was 138 indi- study as follows: viduals which constitute 46% of the studied samples, whereas the female samples were 162 individuals representing 54% of Fulton’s condition factor (Fulton, 1904): total population. These make a sex ratio of about 1:1.17  3 (KF) = 100 (W/L) . between sexes not showing significant (df =1, v2 = 1.92, Relative condition factor (Le Cren, 1951): b p < 0.05) variation from the expected ratio of 1:1 excluding (KR)=W/a  L . b the length class 21.00–21.99 where significant variation was Allometric condition factor (Tesch, 1971): (KA)=W/L . observed (Table 2). However, there is no previous study deal- ing with the length composition and sex ratio available in the where W is the weight, L is the total length and a and b are the literature comparing these findings. LWR parameters. Finally, the form factor (a3.0) for S. panijus was determined using the equation given by Froese (2006): log a À S(b À 3) Length–length relationships (LLRs) a3.0 =10 where, a and b are regression parame- ters, S is the regression slope, and S = À1.358 considered mean slope.