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Sex Ratio, Length-weight, and Length-length Relationships of Amblypharyngodon Mola (cyprinidae) in the Payra River, Southern Bangladesh

Ferdous Ahamed
Department of Fisheries Management, Patuakhali Science and Technology University, Patuakhali, Bangladesh

Newton Saha
Department of Fisheries Management, Patuakhali Science and Technology University, Patuakhali, Bangladesh

Md. Rasel
Department of Fisheries Management, Patuakhali Science and Technology University, Patuakhali, Bangladesh

Zoarder Faruque Ahmed
Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh, Bangladesh

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

Abstract/ Executive Summary:

Sex ratio, length-weight and length-length relationships of Amblypharyngodon mola were studied in the Payra River during February 2016-January 2017. Monthly samples were collected from the small-scale fishers of set bagnet fishery in the Payra River. All specimens were sexed out and standard length (SL), total length (TL), fork length (FL) and body weight (BW) were measured. The overall sex ratio showed no significant difference between sexes. However, the monthly sex ratio was 1:1 for almost all the year, except in June when females were significantly more abundant than males. With regard to the size class, the sex ratio was found to be non-significant up to 4.0 cm TL, however; at 5.0 cm TL the number of male was significantly higher than female and after that the number of female increased significantly than male till the maximum size class. The allometric coefficient ‘b’ of the LWRs between SL vs. BW and FL vs. BW indicated negative allometric growth and isometric growth respectively for both sexes. While TL vs. BW indicated positive allometric growth in males and isometric growth in females. On the other hand, the LWRs for pooled data indicated negative allometric growth, positive allometric growth and isometric growth for SL vs. BW, TL vs. BW and FL vs. BW respectively. The allometric coefficient ‘b’ of the LLRs between SL vs. TL, SL vs. FL and TL vs. FL indicated positive allometric growth, isometric growth and negative allometric growth respectively for both sexes. However, the pooled data shows positive allometric growth between SL vs. TL, negative allometric growth between SL vs. FL and between TL vs. FL. It was concluded that the data generated from the study will form a baseline tool for effective fisheries management and sustainable exploitation of A. mola in the Payra River as well as surrounding waters of Bangladesh.

Keywords: Amblypharyngodon mola, Sex ratio, Length–weight relationships, Length–length relationships, Payra River

Location: In the Payra River, Southern Bangladesh

Start Date: 00-02-2016

End Date: 00-01-2017

Program Area: Animal Health and Management

Commodity: Mola/Dhela/Dankina

Objectives:

However, there is no information on the sex ratio, LWRs and LLRs of from the Payra River, hampering the formulation of sound management strategies for this important fishery. Hence, the aim of the present study was to carry out the comprehensive description of the sex ratio, LWRs and LLRs of A. mola from the Payra River, southern Bangladesh which will be useful for the fishery and stock enhancement of this species.

Methodology:

The present study was conducted in the Payra River, a southern coastal river of Bangladesh situated in the Patuakhali district (straddling 22º 35´ N and 90º 26´ E). Samples were collected monthly from the small-scale set bag net fishers of the Payra River during February 2016-January 2017. After collection the samples were preserved in 10% formalin and transferred to the laboratory for further analysis. Standard length (SL), total length (TL) and fork length (FL) for all individuals was measured to the nearest 0.01 cm using a measuring scale, while the body weight (BW) was recorded using a digital balance (AND, FSH, Korea) to 0.01 g accuracy. Sex was determined by incision of the abdomen of each individual and visual inspection of the gonad by naked eye.

The length-weight relationship (LWR) was estimated by the log-transformed linear regression: ln (W) = ln (a) + b ln (L), where the W is the body weight (BW g) and L the standard length (SL cm), total length (TL cm), fork length (FL cm). In addition, 95% confidence limits of a and b, and the coefficient of determination r2 were estimated. All extreme outliers were excluded from the analyses according to Froese. Furthermore, SL vs. TL, SL vs. FL and TL vs. FL relationships were estimated by linear regression separately for both sexes. T-test was used to determine the significant differences of b value from the isometric value (b = 3.0 for length-weight relationship and b = 1.0 for length-length relationship). Deviation of the b value from the theoretical isometric value indicates either positive (b > isometric value) or negative (b < isometric value) allometric growth. Analysis of covariance (ANCOVA) [21] was used to test for significant differences in slopes and intercepts among the relationships. Sex ratio (female/ male+female) was calculated in terms of monthly basis and size (TL in cm) class and the results were analyzed by using χ2 test (1:1; p<0.05).

Source of Information: International Journal of Fisheries and Aquatic Studies 2017; 5(4): 359-362

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

This study has provided basic information on the sex ratio, LWRs and LLRs of A. mola that would be useful for fishery biologists/managers to impose adequate regulations for sustainable fishery management in the Payra River (southern Bangladesh) and nearby areas of Bangladesh. However, further and more detailed research are necessary for future assessment.

Knowledge Management: Journal