Navigating Challenges and Embracing Rewards – Doing Fieldwork in Tonga 😊

Author: Siosina Katoa

Taula Island - Tonga, located in the far south of the Vava'u Group in the north of the country.

Tonga is a small island nation in the South Pacific Ocean, and if it’s hard to picture where it’s situated, it’s above New Zealand, across Australia, next to Fiji. It has 169 islands where residents inhabit 45. The country is divided into four main island groups: 1: Tongatapu group is the main island and the most populous out of the four; 2; Ha’apai group, a cluster of low-lying islands with stunning beaches; 3; Vava’u group, the second most populated island and famous for whale watching and a tourist’s favorite place to visit. The last is the Niuas group, the northernmost island that is a 2-hour flight away from Tongatapu.  

My research involves collecting environmental DNA from isolated islands in Vava’u to assess biodiversity. Years ago, rats were eradicated from 3 of these islands. Unfortunately, financial constraints limited follow-up efforts. Here is where I step in.  

The adventure begins with a 1-hour flight from Tongatapu to Vava’u in a quaint 12-seat plane almost the same age as me. The real expedition begins after touching down at the nearest airport (the only airport in Vava’u) to the sites. Every morning at 8 a.m., we board a medium-sized steel boat bound for the islands. The timing was crucial as high tide is our window of opportunity. If we miss it, low tide will trap us on the reefs, making the journey to our sampling sites nearly impossible. It took us 45 minutes to 1 hour to get to our destination and back every day.   

We collected samples from 6 isolated islands and did sampling at three sites per island, with six 1L replicates per site. So, if we collect samples from 1 island daily, we’d take back 180L of seawater in an ice-cube-filled eski to be filtered. If we try to cover two islands daily, that’s double the weight to carry plus the eski of ice, and you do the math. Our small boat could only take a limited weight capacity, and we were already heavy enough to be on board.  Some days, we’d take only two people to help, plus the captain of the boat, and other days, just one to do the sampling. We removed the seawater and filtered these in a designated small space in our accommodation as we don’t have laboratories on the island. Over 13 days, we collected and filtered 1080 Liters of seawater (using a 50ml syringe), packed them, and sent them off for analysis.  

Filtering eDNA samples, with the help of caulking guns!

The challenge lay in the logistics of reaching and navigating these remote islands and having limited resources to aid us in the process. Yet, the reward came from uncovering what exists (a load of species) on these islands and the satisfaction of completing this task. Fieldwork in Tonga is not for the faint-hearted, but the combination of challenges and opportunities makes it a remarkable experience. For those willing to embrace the journey, the rewards offer a profound reminder of the wonders beyond the beaten path. 

Siosina with a water sample.