Project Leader

Jens Hegg

Jens Hegg

Who I am

I am an aquatic ecologist interested in the importance of fish migrations to aquatic ecosystems and conservation. I grew up in the Palouse region in north-western USA, in a small, rural farming town nearly 300 miles (480 kilometres) from the coast. Despite this distance, my region is deeply tied to fish migration and the ocean. Salmon migrations in the nearby rivers stretch 500 miles (805 kilometres) into the Rocky Mountains and have been an important piece of the cultures of our region for millennia. Perhaps this helped influence my choice to return to the Palouse region to pursue fish migration as a career, though I was also enthralled by the chance to learn new chemical methods to understand how fish move. I earned my PhD at the University of Idaho, using the chemical records stored in salmon ear bones to retrace their migrations in the nearby Snake River, uncovering how these epic migrations are changing in response to man-made dams and environmental changes. But my journey into fish ecology really began with a visit to the Brazilian Amazon as an undergraduate student. I fell in love with the Amazon region, its complex ecology, welcoming culture and unique food traditions, and I have worked to build scientific collaborations in the region ever since. I continue to be fascinated by the incredible diversity of Amazonian fish and the complex interplay of land, river and ocean that drives incredible, but still poorly understood, fish migrations.

Where I work

I am an assistant professor of biology at Gonzaga University in the state of Washington in the USA. Much of my work, however, studies fish migration on the Brazilian Amazon coast and within the Amazon River. The Amazon conjures images of tough field work, oppressive humidity and small boats on huge expanses of water. While some of my work has involved field excursions – and these descriptions are apt – most of it entails hours in the lab hearing the whir of high-tech machinery. In fact, all our samples were collected from museums, as a way to gather information without disturbing living sawfish. I’m often found running a mass-spectrometer machine the size of a small car, using a laser smaller than a human hair to sample nanograms of fish tissue in order to determine isotopic ratios that are different by only thousands of atoms. It’s amazing what you can discover about a really big fish, which lives in a really big world, from an absolutely tiny sample. In this project we’re using these tiny samples to understand the movements of largetooth sawfish in the shallow freshwater and brackish environments along the Amazonian coast and within the lower Amazon River. This environment is complex and vast, with shifting salinity and water levels and numerous islands, bays and estuaries. The region’s size and complexity make studying sawfish difficult, but by using tiny samples of chemistry stored in sawfish rostral teeth (the teeth that stud the sides of their long nose) we can discover what they are up to without having to mount a field expedition in a difficult environment and without bothering living fish.

What I do

My scientific speciality is using high-tech isotopic and chemical tools to recover the records of fish movement that are stored inside their own bodies. Some hard parts in fish’s bodies grow throughout their life and store minuscule chemical records of the water in which they swam and the conditions they experienced. These structures act a lot like the flight data recorder of an aircraft, maintaining a detailed chemical record of the fish’s life. If we can recover and decode that chemical record, we can learn important things about the migration, ecology and behaviour of fish. The vertebrae of elasmobranchs (sharks and rays) store this information. But our research has shown that largetooth sawfish have another hard structure that stores this information: the teeth that stud the length of their long rostrum. Like vertebrae in other elasmobranchs, these rostral teeth grow continuously and their hard calcium phosphate construction stores chemical records in the same way. Using these high-tech isotopic tools, we are working to uncover the details of largetooth sawfish movement – details that may help to conserve them.

My project

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