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Estimation of Size Frequency Distribution, Sex Ratio and Length-weight Relationship of Hilsa (tenualosa Ilisha) in the Bangladesh Water

S. M. Nurul Amin
Institute of Bioscience, Lab. of Marine Science, University Putra Malaysia, 43400 Serdang, Malaysia.

A. Arshad
Institute of Bioscience, Lab. of Marine Science, University Putra Malaysia, 43400 Serdang, Malaysia.

G. C. Haldar
Fourth Fisheries Project, Sena Kalyan Bhaban (7 floor), 195 Motijheel C/A, Dhaka-1000, Bangladesh

S. Shohaimi
Department of Biology, University Putra Malaysia, 43400 Serdang, Selangor, Malaysia.

R. Ara
Department of Zoology, Jagannath University, Dhaka, Bangladesh

Abstract/ Executive Summary:

The study is an attempt to estimate the size-frequency distribution, sex ratio and length-weight relationship of hilsa (Tenualosa ilisha) by the SPSS programme from length-weight data collected from Bangladesh water. Annual mean length of male and female T. ilisha was estimated as 29.30 cm and 34.23 cm. The annual mean weight was 265.89 g and 520.38 g respectively. The standard deviation for length was 3.45 cm and 5.15 cm for male and female. Standard deviation for weight was 88.65 g and 276.28 g respectively. Females were on an average about 4.98 cm taller than males (p <0.05). The 95% confidence interval of the difference between two means was 5.35 to 4.60. The bigger size of female hilsa was observed during the month of June to November and mean length was between 35.36 cm and 34.81cm whereas mean weight was between 564.57g and 521.87g. A marked decline was observed in mean length and weight of male during the month of September. In case of females, mean length and as well as mean weight decreased from the month of October and it continued up to the month of January and subsequent recovery after this month. This may be the cause of peak spawning period of hilsa in the month of September. The value of regression coefficient and constant was 49.58 and –1173.091 respectively. The logarithmic form of the length-weight relationship of T. ilisha was Log W = -2.516 + 3.381*Log TL. The exponential form of the equation obtained for the length-weight relation was W = 0.00305 TL . The value of co-efficient of correlation (r) estimated for the species was 0.93 (P <0.01), * 3.381 which indicated that the relationship between length and weight of the fish was highly significant.

Keywords: Size frequency, length-weight relationship, Tenualosa ilisha, Bangladesh

Location: In Bangladesh

Start Date: 00-01-2003

End Date: 00-12-2003

Program Area: Socio-economic and Policy

Commodity: Hilsa

Objectives:

To determine the size-frequency distribution, sex ratio and length-weight relationship of T. ilisha were estimated to know the status of the hilsa fishery in Bangladesh, which could be helpful for the management of the fishery.

Methodology:

Statistical Package for Social Science (SPSS) software was used for the present study. For this purpose, length-weight data of male and female T. ilisha were collected monthly from the commercial catches at different landing sites (Chandpur, Barisal, Bhola and Kuakata) of Bangladesh from January to December for 1 year of 2003. To avoid gill net selectivity different landing sides were selected as different mesh of gill nets are used to catch the hilsa fish on the availability of different size group of fishes. Total length and weight of 4711 specimens where male was 774 and female was 3937 were measured in 'cm' and 'g' by a meter scale and a spring balance, respectively. The data from different landing sites were then pooled month-wise and subsequently grouped into length classes by 2 cm interval. Then the data were analyzed using the SPSS software. The length-weight relationship was established in the logarithmic form Log W = Loga + b*Log TL. The length and weight relationship was determined by the equation W = a*L^b given by Le Cren ^[5] , where ‘a’ was a constant and ‘b’ was exponent.

Source of Information: Research Journal of Agriculture and Biological Sciences 1(1): 61-66, 2005

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The results clearly indicated that the mean length of females was significantly higher than male T. ilisha. Disproportionate occurrence of the number of the two sexes of T. ilisha (males to females 1:5.09) was observed in the investigated area that should be hypothetically 1:1. The relationship between length and weight of the T. ilisha was highly significant.

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