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Age and Growth of Hilsa Shad, Tenualosa Ilisha (hamilton, 1822) of the River Tentulia in Bangladesh

Rajaul Karim
Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh

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

Purobi Rani Roy
Department of Fisheries, The People’s Republic of Bangladesh

Krishna Chandra Roy
Department of Fisheries Management, Hajee Mohammad Danesh Science and Technology University, Dinajpur

Abstract/ Executive Summary:

This study was carried out on age and growth of hilsa shad, Tenualosa ilisha in river Tentulia in Bhola district using monthly samples from January to December 2009 by checking annual rings or growth checks on hard parts. Age and growth of T. ilisha got progressed by direct fit of length frequency data both to standard and to modified von Bertalanffy growth models with ELEFAN procedure where the predicted maximum total length were (TL∞) 41.88 cm for male and 52.40 cm for female. Powell-Wetherall procedure gave an initial asymptotic total length (TL∞) for both male and female 40.42 cm, 50.61 cm respectively. The values of Z/K were 3.362 for male and 2.626 for female. The growth co-efficient (K) was obtained as 1.40 year^-1for male and 1.00 year^-1 for female. The von Bertalanffy growth equations in terms of body weight (BW) for both male and female were BWt=799.26[1-exp{-1.40(t+0.002)}]³ and BWt=1717.82[1-exp{-0.99(t+0.013)}]³ respectively. The length-weight relationship for both sexes were BW=0.0101 TL ^3.02 for male and BW=0.0086 TL ^3.08 for female. The value of coefficient of determination (R2) was estimated for both male and female species were 0.969 and 0.968.

Keywords: Hilsa shad, Tenualosa ilisha, Von Bertalanffy growth, Asymptotic length, Growth co-efficient

Location: Bhola district, Barisal.

Start Date: 00-01-2009

End Date: 00-12-2009

Program Area: Animal Health and Management

Commodity: Hilsa

Objectives:

To find out the age of both male and female hilsa in the river Tentulia,
To scrutinize body weight relationship;

Methodology:

Sampling spot: The experiment was conducted in Tentulia River of Bhola district in Barisal division. The river Tentulia is a flow of the Lower Meghna river and originates from the Meghna at north of Bhola district. Sampling of fish: Length-frequency data of T. ilisha were composed monthly from the commercial catches at dissimilar landing sites from January to December, 2009 in randomly selected transect of the river Tentulia. A total of 1200 specimens (607 males and 593 females) of hilsa were utilized for length-frequency study and only 15 specimens of different sizes were used for otolith study. At each sampling, emphasis was given on the fact that at least 100 specimens were collected. After ending of sampling of each month, fish samples were conserved with crushed ice in fish boxes at the same time as early as possible to keep away from decomposition of fish which would degrade otolith and gonad quality. Then the formalin conserved samples were transferred to the laboratory for research purposes. Total length (TL) and body weight (BW) of the specimens were measured in ‘cm’ and ‘g’ using a meter scale and a specific electronic weight balance, respectively and the size ranging from 15.90-50.50 cm in total length and 33.20-1600.00 gin body weight. Data collection of length and weight: Fishes were washed with running tap water to remove dirt and surplus water was removed with blotting paper. Then fish was left in room temperature for about half an hour for leasing the moisture completely. Finally the total body length and total body weight of each fish were measured by using a measuring scale to the nearest centimeter and the body weight in gram by an electronic digital balance. Total length (TL) was measured from the tip of the snout (mouth closed) to the end of upper caudal fin. Collection of gonad and determination of sex: By cutting the ventral portion of fishes with the help of scissors and forceps gonads were extracted with more awareness and their weights recorded to the nearest 0.001 g. Female gonads were preserved into small vial along with 10% formalin solution to avoid any damage. If it was not possible to ascertain whether the gonad was an ovary or testis then the sex of each fish was determined macroscopically. Individuals that could not be sexed were recorded as juveniles. In subsequent analysis, juveniles were randomly assigned to either male or female. Age group analysis: The monthly collected samples were constructed on the basis of total length frequency distributions by sex with 1 cm interval. A series of component normal distributions were fitted to the frequency distribution for each sample by sex using a computer analysis (FiSAT). Each component nominal distribution is assumed to represent an age group in the population. This analysis provided the mean TL, standard deviation and proportion of each age group explained by each component normal distribution. Collection and preparation of otoliths and scales: To examine annual growth formed on scales and otoliths of hilsa otolith and scale of 15 specimens were detached randomly for investigation. Scales were observed by microscope fitted with reflected light with the magnification of 30 to 50x and fitted with transmitted light with the magnification of 100 to 1000x. Among the three pairs of otoliths, the right otoliths (sagittae) were used for age determination; the left sagittae were used if the right sagittae were damaged when extracted from the fish or during the sectioning process. The dried otoliths were then transported to the laboratory. Otoliths length were measured under microscope and weighed with a balance. Measured otoliths are embedded in epoxy resin, a mixture Dodencenyl Succinic Anhydride (DDSA), Epok 812, Methyl Nadic Anhydride (MNA), Dimethyl Ameminomethyl Phenol (DMP). Embedded otoliths were cut with a micro cutter and polished using a grinder in order to make transverse sections crossing the focus, leaving a thin slice of approximately 0.2 mm thick and mounted on a glass slide and coated with nail enamel. Multiple samples length- frequency analysis: In multiple samples, the number of size cohorts in the length frequency histograms for each sequential month was estimated by visual inspection to fit a normal curve to the size distribution of each cohort in each length-frequency histogram. Direct fit of length-frequency data of hilsa shad, Tenualosa ilisha. Electronic Frequency Analysis I (ELEFAN I): ELEFAN I is a routine that can be used to identify the (seasonally oscillating) growth curve that "best" fits a set of length frequency data, using the value of Rn as a criterion. FiSAT II provides three options to the user to identify that "best" growth curve: (1) curve fitting by eye (2) scan of Kvalues, and (3) response surface analysis. Powell-Wetherall plot: The value of TL∞ and Z/K are estimated independently by the use of Powell-Wetherall plot, by pooling a series of length-frequency data collected at small time intervals. From the regression line, the value of Z/K is estimated from the slope, b, as: Z/K = - (1+b) / b. A useful result of the analysis is that L may be estimated from the intercept, a, with the X-axis as: L = -a /b. Analysis pathway: Total length frequency distribution by sex with 1 cm interval was constructed for each monthly sample and graphed as histograms to represent an age group in the population. This analysis provided the mean TL, standard deviation and proportion of each mode explained by each component normal distribution. The growth patterns of both male and female T.ilisha were established by fitting the von Bertalanffy growth equation to the mean body weights at ages. Body weights and ages were calculated from a few corresponding total lengths of both by means of respective length-weight relationships approximated by the allometric equation. The growth parameters in terms of BW for both male and female were obtained by non-linear methods based on a direct search for the parameters that best fitted to body weight at age data using a routine that performs a Gaussian elimination by Delta Graph 4.5 software.

Source of Information: J Fish 3(1): 227-232, Apr 2015

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The predicted maximum total length were (TL∞) 41.88 cm for male and 52.40 cm for female.
The values of Z/K were 3.362 for male and 2.626 for female.
The growth co-efficient (K) was obtained as 1.40 year^-1 for male and 1.00 year^-1 for female.
Body weight (BW) for both male and female were BWt=799.26[1-exp{-1.40(t+0.002)}]³ and BWt=1717.82 [1-exp{-0.99(t+0.013)}]³ respectively.
The length-weight relationship for both sexes were BW=0.0101 TL ^3.02 for male and BW=0.0086 TL ^3.08 for female.
The value of coefficient of determination (R2) was estimated for both male and female species were 0.969 and 0.968.

Knowledge Management: Journal