Reproductive potential and histological profiling of the wild female anadromous shad (Tenualosa ilisha) in lower Meghna Estuary, Bangladesh

Abstract

Hilsha shad (Tenualosa ilisha, Hamilton 1822) is the most commercially important and national fish of Bangladesh, belongs to the family of Clupeidae of the Clupeiformes. The study was conducted to identify the seasonal gonadal cycles through histological study and the peak breeding season combining histological and Gonado Somatic Index (GSI). One hundred and twenty fish samples with an average weight of 756.75±6.25 g was collected from the Tentulia river for the study throughout the year. Monthly mean GSI values of females ranged from 6.36±0.69 to 15.02±1.33. The lowest mean GSI value was found in December and the highest GSI value was in October. From the histological observation of the ovary, early perinucleolar stage, late perinucleolar stage, yolk vesicle stage, yolk granule stage, pre-mature and mature stages were identified. The highest percentage (75%) of mature oocytes and peak breeding season were observed in October and the breeding season continues from October to November. These results will be helpful for fishery managers to impose adequate regulations for sustainable fishery management in Bangladesh.

Seasonal Variation in the Epibenthic Feeding Habits of Hilsa Shad (Tenualosa ilisha) in the Upper Meghna River Estuary, Bangladesh

“…Diatoms and copepods, the most preferred food items for young hilsa in the Meghna River Estuary could be consistent with prior studies [7,39] conducted in the lower Meghna Estuary. Five genera of tychoplanktonic diatoms (Aulacoseira sp., Tricratium sp., Nitzschia sp., Synedra sp., and Coscinodiscus sp.)…”

Molecular characterization and expression profile of estrogen receptor subtypes in female hilsa (Tenualosa ilisha)

“…The nucleus occupies the greater part of the cell during the formation of chromatin nucleolus, transformed into the perinucleolus stage; the appearance of cortical alveolus is the marker of oocyte development at the beginning of primary vitellogenesis, the formation of single and double germinal disk during secondary vitellogenesis, and breakdown of the eccentric germinal disk showing post-ovulatory changes during tertiary vitellogenesis. These findings were also observed by Akhter et al (2022), in the same species as hilsa. Similar findings had been shown in Dicentrarchus labrax and Danio rerio (Çakici and Ücüncü, 2007).…”

“…The developmental stages of the gonad, oocyte size, presence of follicular layer, and number of nucleoli and cytoplasmic inclusions were detected and used to categorize the oogenesis process following the method developed by Akhter et al (2022).…”