Cross-species gene enrichment revealed a single population of Hilsa shad (Tenualosa ilisha) with low genetic variation in Bangladesh waters

Abstract

Tenualosa ilisha is a popular anadromous and significant trans-boundary fish. For sustainable management and conservation of this fish, drawing an appropriate picture reflecting population status of this species is very essential based on their all-strategic habitats in Bangladesh. In this study, 139 samples from 18 sites were collected and cross-species gene enrichment method was applied. Like most of the Clupeiforms, nucleotide diversity of this shad was very low (0.001245–0.006612). Population differences between most of the locations were low and not significant (P > 0.05). However, P values of a few locations were significant (P < 0.05) but their pairwise FST values were very poor (0.0042–0.0993), which is inadequate to recognize any local populations. Our study revealed that the presence of a single population in the Bangladesh waters with some admixtured individuals, which may contain partial genes from other populations. Most of the individuals were admixed without showing any precise grouping in the ML IQtree and Network, which might due to their highly migratory nature. Fishes from haors and small coastal rivers were not unique and no genetic differences between migratory cohorts. The hilsa shad fishery should be managed considering it as a single panmictic population in Bangladesh with low genetic diversity.

Environmental Factors and Genetic Diversity as Drivers of Early Gonadal Maturation: A Gonadosomatic Index Based Investigation on Indian Shad, Tenualosa ilisha Population of Bangladesh

“…After maturation for spawning purpose Hilsa shad follow two types of migration pattern-(1) fluvial potamodromous (fish remain in freshwater habitats and breed therein) and (2) marine ecotype (fish migrate to salt water for breeding purposes) in Bangladesh (Raja, 1985). Based on these, different levels of genetic variations and diversities have been recognized by previous studies (Majumder and Alam, 2009;Asaduzzaman et al, 2019Asaduzzaman et al, , 2020Sarker et al, 2021). However, interpretation on whether these variations are caused by different migratory patterns or is the cause of reciprocal migration is not yet understood.…”

“…For breeding purposes (with a further intention of nursing the juvenile), Hilsa follow their main migration route [Meghna river (lower part)-Meghna river (upper stream)-Padma (lower stream of the Ganges)-Jamuna (New Brahmaputra River)] to reach in upper stream rivers, which facilitate them with an uncompromising favorable environment in purpose of their breeding success. Apart from this main migration route, there is also evidence that Hilsa takes entry in freshwater through some other unpopular and secondary coastal migration route (Pashur River-Madhumati River-Gorai River-Padma River; reviewed in Sarker et al, 2021). With an unknown number of mysterious issues about the migration intention of Hilsa, the fish have also been found to use unfocused water bodies, including marshy wetland ecosystems known as Haor and hill stream rivers (e.g., Someshwari River) bordering the northeastern part of Bangladesh as their travel route (Sarker et al, 2021).…”

“…Apart from this main migration route, there is also evidence that Hilsa takes entry in freshwater through some other unpopular and secondary coastal migration route (Pashur River-Madhumati River-Gorai River-Padma River; reviewed in Sarker et al, 2021). With an unknown number of mysterious issues about the migration intention of Hilsa, the fish have also been found to use unfocused water bodies, including marshy wetland ecosystems known as Haor and hill stream rivers (e.g., Someshwari River) bordering the northeastern part of Bangladesh as their travel route (Sarker et al, 2021).…”

Confirmation of hilsa shad (Tenualosa ilisha) in Vietnamese waters: a morphological and genetic analysis

“…On the other hand, G. chapra , the outgroup species, appears to be distantly related to T. ilisha , and shows significant genetic divergence (Egana et al ., 2018; Milec et al ., 2022). This genetic distance helps to clarify the evolutionary lineage of T. ilisha and its separation from the outgroup species (Sarker et al ., 2021; Sultana et al ., 2022).…”

“…The low genetic diversity and the presence of admixed individuals without precise grouping could further contribute to the morphological confusion (Jorde and Wooding, 2004; Slovák et al ., 2012; Holm et al ., 2018; Garmendia et al ., 2022). Recent studies highlighted the low genetic variation within T. ilisha populations, suggesting a single panmictic population with admixture from other populations (Sarker et al ., 2021). Moreover, the genetic population structure of T. ilisha is influenced by its highly migratory nature (Mohindra et al ., 2019; Habib et al ., 2022; Sultana et al ., 2022).…”