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Temporal Variations of Sex Ratio, Length-weight Relationships and Condition Factor of Cabdio Morar(cyprinidae) in the Jamuna (brahmaputra River Distributary) River, Northern Bangladesh

Md. Yeamin Hossain
Department of Fisheries, Faculty of Agriculture, University of Rajshahi, Rajshahi 6205, Bangladesh

Md. Mosaddequr Rahman
Faculty of Fisheries, Kagoshima University, 4-50-20 Shimoarata, Kagoshima 890-0056,Japan

Ali H. Bahkali
Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, Saudi Arabia

Khairun Yahya
School of Biological Sciences andCentre for Marine and Coastal Studies, Universiti Sains Malaysia, Penang 11800, Malaysia

Mst. Somaiya Arefin
Department of Fisheries, Faculty of Agriculture, University of Rajshahi, Rajshahi 6205, Bangladesh

Md. Istiaque Hossain
Department of Fisheries, Faculty of Agriculture, University of Rajshahi, Rajshahi 6205, Bangladesh

Abdallah M. Elgorban
Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, Saudi Arabia

Md. Alomgir Hossen
Department of Fisheries, Faculty of Agriculture, University of Rajshahi, Rajshahi 6205, Bangladesh

Md. Mahmudul Islam
Department of Genetic Engineering and Biotechnology, University of Rajshahi, Rajshahi, Bangladesh

Zubia Masood
Department of Zoology,University of Karachi, Karachi-75270, Pakistan

Abstract/ Executive Summary:

The fish Cabdio morar (Hamilton, 1822) is a member of the family Cyprinidae, commonly known as morari in Bangladesh and Aspidoparia in India. This fish was previously known as Aspidoparia morarandis widely distributed in Bangladesh, India,Myanmar, Nepal, Pakistan, and Thailand. The present study describes the temporal variations of sex ratio(SR), length-frequency distributions (LFDs), length-weight relationship (LWRs),and Fulton’s condition factor (KF) of the C. morar.A total of 1200 specimens (male = 552, female = 648) ranging from 4.06-12.84 cm TL and 0.53-16.75 g BW were analyzed. The overall SR showed significant differences from the expected value of 1:1 (male: female) (χ2= 7.68,P > 0.01), and there was also a significant difference in LFD between the sexes (P < 0.05). The allometric co-efficient (b)for the overall LWR indicated positive allometric growth (> 3.00) in males and isometric growth in females (~ 3.00). Hence, LWRs were significantly different between males and females (ANCOVA,P < 0.001). KF showed significant variation (P< 0.01) between the sexes, with better performance by females (0.88 ± 0.14) than for males (0.86 ± 0.15).In addition, our study uniquely discovered the spawning season based on lower values of allometric co-efficient (b) for C. morar during December to March in the Jamuna River.These results will help further studies on population assessment and stock management of C. morarin the Jamuna River ecosystem.

Keywords: Temporal variations, Sex ratio, Length-weight relationship, Condition factor, Cabdio morar.

Location: Sirajganj, Bangladesh

Start Date: 00-07-2010

End Date: 00-06-2011

Program Area: Conservation and Biodiversity

Commodity: Fish

Objectives:

This study is the first report on the temporal variations of the sex ratio(SR), length frequency distributions (LFDs), length-weight relationships (LWRs) and Fulton′s condition factor (KF) of C. morar using monthly data over one year in the Jamuna River, northern Bangladesh

Methodology:

Study site and sampling The present study was conducted in the Jamuna River (Latitude: 24°30' E and Longitude: 89°44' N),a distributary of Brahmaputra River, Sirajganj, Bangladesh. Monthly samples of C. morar were collected from the fisherman catch landed at the Sirajganj Mote Shaber Ghat, Sirajganj during July 2010 to June 2011. This fish is usually caught by means of the traditional fishing gear jhaki jal (cast net). Samples were instantly preserved with ice upon capture, then stored in 10% buffered formalin in the laboratory. Fish measurement Fish were sexed by microscopic observation of the gonads. For each individual, total length (TL) was measured to the nearest 0.01 cm by digital slide calipers (Mitutoyo, CD-15PS; Mitutoyo Corporation, Tokyo, Japan). Whole body weight (BW) was taken using a digital balance (Shimadzu, EB-430DW; Shimadzu Seisakusho, Tokyo, Japan) with 0.01 g accuracy. Length-weight relationships The LWR was calculated using the expression: BW= a*(TL)b.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 r2were estimated. Based on Froese (2006), all extreme outliers were excluded from the analyses. A t-test was applied to determine significant differences from the isometric value of b= 3 (Sokal and Rohlf,1987) to declare the growth pattern either isometric or (+/-) allometric. The differences of growth pattern in LWRs between two phases (Phase-1: Immature to maturing; Phase-II: Mature to ripe) was conducted by ANCOVA (Analysis of co-variance), where the size at first sexual maturity was derived from Hossain et al. (2013a). In addition,monthly variations of gonadosomatic index (GSI) and allometric co-efficient (b) were observed. Condition factor The Fulton′s condition factor (KF) was calculated according to Fulton (1904) as KF=100× (BW/TL3). The scale factor of 100 was used to bring the KF close to the unit factor (Hossain et al., 2012b). The monthly variations of KF and b were also observed. Furthermore, the relationship between TL vs.KFwas conducted in female population of C. morar. Statistical analysis Statistical analysis were performed using GRAPHPAD PRISM5 software (GraphPad Software, Inc., San Diego, CA). The chi-square test was used to examine sex-ratio divergence from the expected value of 1:1 (male:female). Homogeneity and normality of data were checked.The Mann-Whitney U-test was used to compare the mean values between sexes as a non-parametruc test. The Kruskal-Wallis test was applied to check the homogeneity of the KF among months. ANCOVA was used to check the differences of growth pattern between the overall sexes and for two phases (I) immature to maturing and (II) mature to ripe. All statistical analyses were considered significant at 5% (P < 0.05).

Source of Information: Pakistan J. Zool., vol. 48(4), pp. 1099-1107, 2016

Article Link (Online Journal):

Funding Source:

1.

Budget:

Total Budget (Tk.) :

Achievement/Findings:

In conclusion, this study has provided basic information on the sex ratio, LFD, LWR, and KF, which are relevant to via stock assessment and sustainable fishery management in the Jamuna River. We introduced a new method for estimating the spawning season, based on lower seasonal values of b for C. morar.Also, this research has established a strong base for monitoring the biological changes (allometric co-efficient, conditions, GSI) of this important species due to high fishing pressure, climate changes, and other factors within the Brahmaputra River basin. Finally, this study will form an important baseline for future studies here and for surrounding South Asian ecosystems.

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