Bridging knowledge gaps for the conservation and management of a 'Data Deficient', diadromous fish: the Indo-Pacific tarpon, Megalops cyprinoides.

Context: The Indo-Pacific tarpon (Megalops cyprinoides) is a diadromous species, for which limited information is available regarding demographics and exploitation levels. Aim: We aimed to fill critical knowledge gaps on population dynamics and exploitation levels of M. cyprinoides along the south-western coast of India. Methods: Structured length frequency-based population dynamics models were used to determine the growth, mortality and exploitation levels of the species. Key results: Habitat-related variations in growth patterns were found, with positive allometric growth in the marine (b = 3.208), and negative allometric growth in freshwater (2.759) and estuarine (2.876) habitats. Different estimates of natural mortality suggested high fishing pressure, potentially threatening the long-term sustainability of local M. cyprinoides populations. Conclusions: This study provides the first comprehensive estimates of demographic parameters of M. cyprinoides , and contributes significantly to our knowledge required for the management of Indo-Pacific tarpon fisheries. The critical need to address overfishing and habitat degradation to ensure long-term sustainability of local populations is highlighted. Implications: Knowledge generated through this study will help inform improved conservation assessments of this 'Data Deficient' species, in addition to informing the development and implementation of conservation and management plans. The first study on exploitation levels and population dynamics of a poorly known migratory fish (Megalops cyprinoides) based on samples collected from the south-western coast of India showed habitat-related (marine, estuarine and freshwater) variations in growth patterns. Fishing mortality was the greatest in the length range of 25–30 cm, indicating a higher fishing pressure on immature individuals. [ABSTRACT FROM AUTHOR]