Bringing guitarfish back from the brink in Bangladesh
Bangladeshi fishers in the Bay of Bengal, a biodiversity hotspot in the Indian Ocean, have reported declines in guitarfish over the past decades. But without sufficient information about their life history, instituting adequate management is just guesswork. No biological information is available for three Critically Endangered guitarfish species, which are a regular part of the bycatch in coastal Bangladesh: the sharpnose guitarfish, the Bangladeshi guitarfish and the widenose guitarfish. Nahla wants to change this by determining guitarfish ages using their vertebrae, filling in knowledge gaps and preparing recommendations to inform policies.
Nahla Khan
Having been born and raised in Dhaka, an overpopulated megacity, I have always felt the lack of nature exploration in my life, although my love for nature was kindled when my tiny hands learned to grasp the tiny blades of grass in the urban dust. This lost connection with nature was regained during my undergraduate studies in zoology at the University of Dhaka. Initially I worked with threatened species, mostly birds, and studied how protected areas can help in their conservation. While doing so, I started working on another project that focused on assessments of the protected areas...
Demystifying Vertebral Secrets: Life History traits of Three Critically Endangered Guitarfish Species from Bangladesh
The objective is to get detailed, species-specific biological information on three Critically Endangered guitarfish by studying their vertebral cartilage. These data will help us to understand their population and biology in the Bay of Bengal, Bangladesh, and can easily be incorporated into robust marine megafauna management plans.
The Bay of Bengal falls within one of the Indian Ocean’s marine hotspots for chondrichthyans, especially guitarfish. The lack of data on guitarfish in this region hampers their conservation and management. This project will reveal life-history details about the populations of three threatened guitarfish species by studying their vertebral cartilage.
The guitarfish are one of the most threatened groups of elasmobranchs worldwide as they are susceptible to misidentification, unregulated fishing, overfishing and trade. A study in 2018 showed that fishers from Bangladesh described how the guitarfish populations have dwindled in the past few decades. To prevent the populations from declining further, the government of Bangladesh has included guitarfish in the only wildlife protection act in Bangladesh in 2021. However, to protect and manage any threatened species, it is crucial to have a thorough understanding of their biology and population. No biological information is available for the sharpnose guitarfish, Bangladeshi guitarfish and widenose guitarfish, which are regularly taken as bycatch in the coastal areas of Bangladesh. A comprehensive project to reveal their life-history traits in this region is therefore necessary.
Determining age is a fundamental step when learning about biology and population dynamics. Fishery biologists use many methods to determine age, one of the most popular of which is interpreting annual rings or growth bands on calcified structures. It is challenging to do this for elasmobranchs, as they lack bony structures in their body. The age determination process for these species therefore relies mostly on growth bands on vertebral cartilage. Every year the vertebra gets two new bands, one during summer growth and one during winter growth. Interpreting these bands enables researchers to estimate the age from the vertebral cartilage, and this is later used to build growth models.
This study aims to decode the vertebral cartilage of three Critically Endangered guitarfish species to reveal their biology and provide detailed baseline data at population level. These data will inform decision-makers, enabling them to create effective and appropriate management tools to protect guitarfish in Bangladesh’s waters.
- To determine the age of guitarfish from their vertebral cartilage and build growth trajectories.
- To reduce the knowledge gap in this region and provide species-specific biological and life-history data of the sharpnose guitarfish, Bangladeshi guitarfish and widenose guitarfish.
- To uncover their reproductive biology.
- To prepare recommendations from the findings to inform policy-makers and other associated stakeholders, with the aim of improving guitarfish conservation in the Bay of Bengal, Bangladesh.