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Some Aspects of Reproduction in Amblypharyngodon Mola from Sylhet, Northeast Bangladesh

Mohammad Amzad Hossain
Department of Fish Biology and Genetics, Sylhet Agricultural University, Bangladesh

Abstract/ Executive Summary:

The mola carplet, Amblypharyngodon mola (Hamilton, 1822) is the most common small indigenous freshwater fish species in Bangladesh. The precise information addressing the reproduction in this species including breeding peak, ovarian histology, morphometry, and sex ratio in nature is still insufficient. A one yearlong field survey and different laboratory assays have been directed to disclose some key features of reproduction in female A. mola from wetland reservoirs in the greater Sylhet region in Bangladesh. The total length and the bodyweight have shown a strong correlation with gonad weight, occupying statistical r² values of 0.89 and 0.91, respectively. However, a Chi-square test at P<0.05 reported no significant deviation in the sex ratio of the wetland’s stock. The maximum fecundity has been reported during the month of May as 12569+620 while the lowest is during the month of July as 9377+455. The highest values for gonadosomatic index have been reported in May while the lowest is in January with another peak in November. The histological study of ovarian cells resulted in the characterization of oocytes, previtellogenic oocytes, vitellogenic oocytes, perinuclear oocytes, and mature cells with yolk mass.

Keywords: Amblypharyngodon mola, Sex ration, GSI, Fecundity, Morphometric regression analysis, Gonadal histology

Location: The Greater Sylhet region of Bangladesh

Start Date: 00-00-2019

End Date: 00-00-2020

Program Area: Resource Development and Management

Commodity: Mola/Dhela/Dankina

Objectives:

To disclose some key features of reproduction in female A. mola from wetland reservoirs in the greater Sylhet region in Bangladesh.

Methodology:

Study area and duration: Fresh and live random samples of A. mola have been collected from different fisher landing stations and local markets of the Greater Sylhet region of Bangladesh. They were transported in insulated ice boxes or in oval fiberglass tanks to bring into the Fish Biology and Genetics laboratory of Sylhet Agricultural University, Bangladesh. This research continued for a full-length year from July 2019 to June 2020. Recording morphometric data: Shortly after bringing them back to the laboratory, all the fish were washed well with rinsing freshwater and placed on thick tissue towels to reduce the access of water and mucous content within them. Then, the total length and weight of each fish was calculated by using scale (a mm stainless-steel scale attached on a specially designed wooden structure) and electric balance (Ohaus corp. Pine Brook, NJ USA), respectively. Sexual recognition of each fish was confirmed by following the dissection of their gonad, which was weighted and recorded immediately. Measurement of gonadosomatic index (GSI) and Fecundity: The value of gonadosomatic index for each fish was calculated by using the below formula (Brooks et al., 1997) gonadosomatic index (GSI) = (Weight of gonad (g)/ Total body weight (g)) ×100 Fishes collected during the early to late monsoon season was subjected to the calculation of fecundity. Gravid female fish were selected for fecundity, and Gilson’s fluid was used to lessen the oocytes. Finally, absolute fecundity was calculated by using the description of Rahman & Samat, (2020). The fecundity, F = n × G/ g, where “n” denoted the average number of eggs counted in sub-sample, “G” is net weight of the gonads, and “g” is the weight of the sub-sample. Histology of gonad: The samples from the ovaries were chopped into small pieces and preserved in neutral buffered formalin. The standard protocol for gonad histology described by Van-Dyk & Pieterse, (2008) was followed for the preparation of histology slides. Tissues were embedded and infiltrated in Paraffin, and the resulting blocks were formatted into 3-micrometer slides. Finally, hematoxylin-Eosin staining accompanied the samples to view the cell with a Zeiss microscope (software version 3.0 pro). Data analysis: The raw data were recorded on excel sheet before further analysis. Data were analyzed by using IBM SPSS Statistics v26 and a one-way ANOVA was tested at P<0.05 to measure the difference between mean values.

Source of Information: Aquat Sci Eng 2021; 36(3): 140-5

Article Link (Online Journal): DOI: https://doi.org/10.26650/ASE2020858534

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

This research has disclosed a set of necessary information regarding the reproductive aspects of A. mola from the natural wetlands of the Greater Sylhet region of Bangladesh. The above information might be used in aquaculture development, wild stock management, and conservation of this fish in Bangladesh. However, broad studies with the collection of samples from different areas within the country would reflect actual trends of the reproduction in this fish.

Knowledge Management: Journal