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July 6, 2023

Anissa Volanandiana, PhD student, discusses the progress of her thesis research on the fish diversity in Ranobe Bay

I am a PhD student at the University of Toliara, with a grant from the  IRD (Institut de la Recherche pour le Développement)  (ARTS). I'm part of the "fish diversity" component of the ARMS Restore project, and I'm working on "analysis of real and perceived ichthyological diversity in southwest Madagascar using an ethno-ichthyological approach to coral ecosystems".

In 2022, I focused on collecting data for the first two chapters of my thesis. The collection of fin tissues and photos of fish caught by fishermen in Ranobe Bay, which I made with the fisheries component of the ARMS Restore project, aims to determine the ichthyological diversity exploited in the area. The sampling of environmental DNA left by the fish, in different habitats (mangrove, sand, seagrass, natural reef) in the bay aims to determine the diversity of fish available according to habitat type. A total of 4076 fish tissues and 7422 photos were collected, of which 1000 fish tissues were exported for DNA barcoding analysis. While 108 filtrates were sent to the ADNID laboratory in Montpellier for metabarcoding.

In March 2023, I began the second semester of my first-year thesis with laboratory work on DNA barcoding analysis of collected tissue at the University of Montpellier, where my supervisor is based. The analysis begins with the extraction of genomic DNA from fin tissue. After purification, this matrix is used to amplify a fragment of the mitochondrial gene cytochrome oxidase 1. This fragment is then sequenced and is automatically compared with those present in the Barcod Of Life Datasystems (BOLD) database. I'm also working on the amplification of a representative of each BIN (Barcode Index Number) from Madagascar fish to create a usable reference base for environmental DNA. I have barcoded about 521 tissues.

Presently, I plan to complete my work in the laboratory June 2023, so that I can proceed with the analysis and processing of the data for my first paper on the diversity exploited by the various fishing gears in Ranobe and Toliara bays. The environmental DNA data was sent by ADNID in May, and I will start cleaning the data in July. At the same time, I'm starting to organize data collection for my third chapter, based on a survey of fishers' perceptions of fish diversity. I will begin drawing up the survey protocol and planning this summer, and the fieldwork will take place from September to November 2023.