Full title:Age analysis and growth patterns ofTenualosa ilishausing otolith examination and length-weight relationships from different regions of Bangladesh

Abstract

Conceptualization, A.K.S.A.; supervision, A.K.S.A.; methodology, M.B.U.A.; manuscript 18 editing, M.S.; sample collection, B.K.D; data arrangement, M.F.R; investigation, M.A.A.; 19 funding acquisition, A.B.; writing -original draft preparation, M.B.U.A.; writing -review and 20 editing, M.A.A.; project administration, Y.M. 2 21 Abstract 22The assessment of age and growth patterns provides crucial information on numerous 23 aspects of the population dynamics in fish, which can, in turn, be used to determine a 24 sustainable fishing rate and inform effective resource management practices. However, 25 studies on the age and growth pattern of Tenualosa ilisha (commonly referred to as hilsa) are 26 plagued by a lack of essential information; addressing this data gap is the aim of the present 27 study. Six diverse habitats across Bangladesh were chosen as sampling sites for hilsa 28 collection. For age determinations, the lunar rings in the otolith of the hilsa fish that are 29 periodically-deposited in accordance with the lunar cycle were used to reflect 14-day 30 increments of time. The length and weight of each fish were recorded prior to otolith 31 extraction. The resulting otoliths were polished to enable the visualization and quantification 32 of their lunar rings with a high-magnification microscope. Except for the Kali River and 33 Gaglajur Haor samples, the age of the fish correlated strongly with both their length and 34 weight (r > 0.95; p < 0.05). Again, aside from those from the Kali River and Gaglajur Haor, 35 all of the samples exhibited positive allometric growth patterns (b > 3) with the fish from the 36 Tetulia River being the most positive (b = 3.48). The causes these variations are not yet 37 clearly understood, however; the nutrient availability, environmental variation, and genetic-38 environmental interactions are likely contributors to the diversities displayed by the hilsa 39 from different regions of Bangladesh.40 41

Heavy Metals in the Fish Tenualosa ilisha Hamilton, 1822 in the Padma–Meghna River Confluence: Potential Risks to Public Health

“…In addition, a positive allometric growth (b > 3.0) was calculated in T. ilisha from the Meghna estuary, Padma River, Tetulia River, and Bay of Bengal (Bangladesh). However, an isometric (b = 3.0) and negative allometric (b < 3) growth were determined in the Kali River and Gajlajur Haor (Bangladesh), respectively [88].…”

“…CF > 1.0 indicates that all the T. ilisha were collected from a healthier population. However, the L-W relationships of T. ilisha also depend on the availability of foods, seasons, health, habitats, and sexes [70,[88][89][90]. For example, in Indian T. ilisha, an isometric growth was estimated during the monsoon, whereas negative allometric growth was measured during winter [89].…”