Journal Article

Stable isotope on hilsa shad (Tenualosa ilisha) otoliths revealed migratory behavior of a population found in Hooghly River, West Bengal, India

Sakthivel, Thamizharasan, Banerjee, Yogaraj, Nath, Ashim Kumar, Nazir, Aafaq, Ghosh, Prosenjit, Rajawat, Veerendra Singh

2022

Overview

Anadromous fishes like hilsa shad are found near the delta region of Ganges River which are exotic and carry economic potential. The river offers a tidal environment connecting with marine and freshwater ecosystem providing nutrient-rich seasonal water for their growth and development. The complex migratory pattern of these fishes is a major concern in fisheries research. The present study is based on a large collection of isotopic data from otolith specimens of varying sizes covering population of varying age. Here we examined their stable isotopic signature and relate it with their age and locations in the stream length. Otolith δ18O showed significant relationships with fish sizes (length and weight) and distance from the river mouth and can provide a new tool to distinguish their habitats. Small size individuals show affinity for freshwater, while bigger individuals originates from Bay area. The ANOVA and discriminant function analysis (DFA) is used to check whether the fish inhabiting upstream and downstream can be categorized by their δ18O values and to define the composition of the end member. Further, a numerical model of two component mixing is introduced to prescribe the integrated time interval, equated with their size to define specific habitat. The significant variations in otolith δ18O values are found between upstream and downstream of the Hooghly River, and the DFA showed the overall 81% of individuals were assigned to the upstream or downstream of the Diamond Harbour, while the remaining individuals of 1–2 years age represent mobile population, probably participating in the successful spawning and feeding activities. This method allowed understanding the migration tendency of adult individual (fraction of time spend in the freshwater) and clearly identified the habitat based on isotopic ratios in otolith specimens. This study will serve as template for understanding the aquaculture potential and scientific management policies for hilsa shad in the West Bengal region.

• Publisher: Springer Nature B.V
• Subject: Age / Anadromous fishes / Anadromous species / Aquaculture / Aquatic ecosystems / Connecting / Creeks & streams / Diamonds / Discriminant analysis / Downstream / Fish / Fisheries / Fisheries research / Fishing zones / Freshwater / Freshwater ecosystems / Freshwater fishes / Function analysis / Habitats / Harbors / Harbours / Inland water environment / Intertidal environment / Isotope ratios / Isotopes / Length-weight relationships / Marine ecosystems / Mathematical models / Migrations / Numerical models / Otoliths / Polyculture (aquaculture) / River mouth / River mouths / Rivers / Spawning / Stable isotopes / Tenualosa ilisha / Upstream / Variance analysis