Tuna catch in a changing climate: Meet researcher Joshua Esman

Joshua Esman is a PhD student at the University of the Sunshine Coast sponsored by Tuna Australia under the National Industry Research Program. Tuna Australia spoke with Joshua to learn about what sparked his interest in fisheries and how his research will help fishers catch tuna in a changing climate.

What first sparked your interest in studying and researching fisheries?

I originally got into research with an interest in marine plankton, which is where all fish start life. My supervisors and I chose a project to compare the abundance of larval fish (the planktonic stage of the fish life cycle) with local zooplankton populations. I got heaps of exposure to topics in fisheries, as larval fish survival dictates the supply of adult fish to the population, and is key to long-term trends in fisheries sustainability. Once I got a taste of fisheries science, I was hooked and sought out a PhD project that would land me squarely in this awesome field.

In your 2024 honours research, you investigated Australian larval fish populations. What were the key findings?

To cut a long story short, it looks like larval fish are pickier eaters than we thought they were – or at least, the larvae that get specific food types are more likely to survive. We have a good idea of which zooplankton species may be critical for the abundance of larval fish generations, which could inform how we anticipate the right conditions for big increases in adult fish populations.

What is the focus of your PhD research, and what questions are you hoping to answer?

I’ll be trying to determine which oceanographic conditions are associated with higher catchability of tuna and billfishes using oceanographic modelling.

Fishers already have incredible experiential knowledge of these conditions, and I’ll be working to translate that knowledge – with the help of oceanographic and climatological data – into insights that may give fishers tools to operate more efficiently and maintain a profitable, sustainable fishery into the future.

I’d like to predict how catchability of tuna and billfish will change as the ocean warms, so our fishers and managers can work together to be two steps ahead of environmental change.

You’ll be working closely with industry through Tuna Australia, as well as researchers at the University of the Sunshine Coast. Why are these partnerships so important?

Fisheries science has no mandate without the involvement of fishers. Conversely, fisheries management needs qualified and informed scientists. There are still gaps to be bridged between these two camps, and partnerships like these are part of how we fix that. That means listening to and learning from those with experience on the water, and opening a dialogue on how we can continue to operate profitably and sustainably as conditions change.

How will your research help fishers catch tuna in a changing climate?

If we can know years in advance how catchability is likely to change, fishers can arm themselves against climate risk and anticipate how environmental change will affect their business. We’re still developing the specifics of the project, but I’d like to help create data tools that fishers want and are likely to use.

What’s your favourite way to enjoy tuna or swordfish—any go-to meal or recipe?

Nothing beats raw for fresh tuna. I don’t have the knife skills to do it myself, but I’ll take tuna sashimi any day of the week. I’m also partial to a poke bowl.

Thanks, Joshua.