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Land-mark Based Morphometric and Meristic Variations in Two Congeneric Hilsha Population, Tenualosa Ilisha and Tenualosa Toli from Bangladesh Water Bodies

Mithun Das
Department of Fish Biology and Biotechnology, Faculty of Fisheries, Chattogram Veterinary and Animal Sciences University, Chattogram-4225, Bangladesh

Md. Mahiuddin Zahangir
Department of Fish Biology and Biotechnology, Faculty of Fisheries, Chattogram Veterinary and Animal Sciences University, Chattogram-4225, Bangladesh

Fatema Akhter
Department of Fish Biology and Biotechnology, Faculty of Fisheries, Chattogram Veterinary and Animal Sciences University, Chattogram-4225, Bangladesh

Md. Main Uddin Mamun
Department of Fish Biology and Biotechnology, Faculty of Fisheries, Chattogram Veterinary and Animal Sciences University, Chattogram-4225, Bangladesh

Md. Moudud Islam
Corresponding author
Department of Fish Biology and Biotechnology, Faculty of Fisheries, Chattogram Veterinary and Animal Sciences University, Chattogram-4225, Bangladesh

Abstract/ Executive Summary:

The morphometric characters are effectively used for better differentiation among the fish population and sustainable management. The appraisal of the natural population stock and morphological variation within and between two hilsha species (Tenualosa ilisha and Tenualosa toli) from three different habitats (Coastal, riverine and marine) of Bangladesh, were investigated by applying the land mark based morphometric and meristic variation measurement methods. All data were adjusted and Univariate ANOVA, where discriminant function analysis (DFA) and principal component analysis (PCA) exhibited the divergences in eight morphometric measurements and eight truss network measurements among the three stocks of T. ilisha. The 1st DFA accounted for 89.8% & 87.4% and the second DFA resolved 10.2% and 12.6%, respectively in morphometric characteristics variation among the group studied. Scattered plotting from PCA and dendrogram from cluster analysis (CA) revealed that, the river habitats were morphologically different from the coastal and marine population. Twelve of fifteen morphometric measurements and thirteen of fourteen truss network measurements showed significant differences between T. ilisha and T. toil with significant variation in meristic characters. PCA revealed 89.23% and 88.29% in case of morphometric and truss measurement respectively confirmed high degree of variations in morphological characteristics between two species. Overall, our results based on morphometrics with truss measurements together provide useful information about the morphological differentiation which will be helpful for sustainable exploration and effective management for these two species.

Keywords: Land-mark, Morphometrics, Truss-network, population structure, Tenualosa spp.

Location: Chattogram Veterinary and Animal Sciences University, Chattagram, Bangladesh

Start Date:

End Date:

Program Area: Variety and Species

Commodity: Hilsa

Objectives:

To determine the morphological differences between Hilsha populations using Land-Mark-based analysis.

Methodology:

Ethics approval and consent to participate:
This experiment was conducted by following the “animal care and use committee guideline” of Chattogram Veterinary and Animal Sciences University. The ethics issue is not required for the described study in Bangladesh. Samples are collected not from the privately owned or from protected areas and these species are not endangered or protected one.

Sample collection:
T. ilisha and T. toil were collected from the three different habitats (Coastal, riverine and marine) and preserved in icebox with the quick succession of time and brought to the laboratory of Fish Biology and Biotechnology, Faculty of Fisheries, Chattogram Veterinary and Animal Sciences University, Chattogram for morphometric, meristic and landmark studies. Fish samples were collected from all three locations within 3 days considering their capture date and migration time. A total of 16 fresh and healthy fish samples from each group were chosen for further analysis.

Measurement of morphometric and meristic characteristics:
Sixteen (16) general morphometric characters were measured from each sample fish by applying the conventional method described by Hubbs and Lagler (1958). The morphometric measurement was conducted with an accuracy of 0.05 mm with the help of Vernier calipers and metric scale. The measured morphometric characters used in this experiment for morphological analysis with their descriptions are presented in Table 2. Meristic characters like Dorsal fin rays (DFR), Anal fin rays (AFR), Caudal fin rays (CFR), Pectoral fin rays (PcFR), Pelvic fin rays (PvFR), number of branchiostegal rays and scales on lateral line of each sample were counted from each fish and used for comparative analysis using magnifying glass.

Measurement of Land-mark distances:
Eight landmarks outlining with 14 distances were measured on the body of Tenualosa sp (Figure 1B). The selection of landmark points were done to bring the coverage homogeneity of the total body plan in between two species based on the Strauss and Bookstein (1982). Each landmark was obtained by placing the fish sample on a graph paper and the detection of the landmark points were done with colored pointers for enabling accurate and consistent measurements. Finally, the distances found on the graph paper were determined by using centimeter scale.

Data adjustment:
The elimination of the size effects from the data set was done before the analytical studies. An allometric formula given by Elliott et al. (1995) with slight modification was used to remove the size effect from the data set.
M_adj= M (Ls/Lo)^b
Where,
M adj: size adjusted measurement,
M: original measurement,
Ls: overall mean of standard length for all fish from all samples in each analysis
Lo: total length of fish
Parameter „b? was estimated for each character from the observed data as the slope of the regression of log M on log Lo, using all fish in all groups. The efficiency of the size adjusted values was then correlated with the TL and the transformed values.

Statistical analysis:
In the first level of analysis, we compare among the collected samples of T. ilisha to show the morphological differences among habitats. In the second steps, we then compare between the T. ilisha and T. toil to observe the morphological distances in these two species. Univariate analysis of variance (ANOVA) was conducted to test the significance of morphological differences (p<0.01) on the basis of size-adjusted morphological and landmark distance data. Meristic characters among fish groups were compared using the non-parametric Kruskal-Wallis test. In addition, all size-adjusted morphological and landmark distance data were standardized and submitted to a Discriminant Functional Analysis (DFA) and Principal Component Analysis (PCA). All statistical analysis was carried out using Statistical Packages for Social Sciences (SPSS version 16.0) and Microsoft office Excel, 2010.

Source of Information: Asian J. Med. Biol. Res. 2020, 6 (2), 265-282; doi: 10.3329/ajmbr.v6i2.48072; ISSN 2411-4472 (Print) 2412-5571 (Online)

Article Link (Online Journal): www.ebupress.com/journal/ajmbr

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Fish plays a central role in dietary patterns, livelihoods and culture in Bangladesh. Fish is by far, the most consumed animal-source food across all population groups around the globe. But this sector is facing an enormous threat due to overfishing, habitat degradation, pollution, indiscriminate use of agrochemicals, the introduction of exotic species, lack of suitable habitat, decreased fecundity and so on. The Hilsha fish, called 'Ilish' in Bengali, is of national importance to us. But increased request due to its taste and nutritional profile has led to pressure on the fish species. To fulfill the demand of its increasing pressure sustainable and efficient stock management is necessary. So, we have to save this species from being threatened or extinct. This study has provided important morphological information that can be used to differentiate Tenualosa sp. with more accuracy among groups and species and affords elementary information about the variation of Tenualosa populations in different water habitats of Bangladesh. The outcomes of the study would serve as primary information of the stock management and enable efficient management strategies for the distinct stocks of Tenualosa sp. populations in order to develop sustainable fishery and appropriate conservation plans in near future. The authors hope that the information obtained from the present study will be helpful for fisheries, biologists, and taxonomist concerned with these two fascinating fishes.

Knowledge Management: Journal