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Big Fish a Long Way from Home: Using ear bones and teeth to unravel migration in Amazonian fish

Backed by Nancy Hegg, Lea Anne, Theodore Hegg, Mark Q Wright, Charles Cooper, Alex Flecker, Jerry McCollum, Nicole Flansburg, John D. West, Sunrise Swanson Williams, and 136 other backers
University of Idaho
Moscow, Idaho
DOI: 10.18258/6836
Grant: Fish Challenge
Funded on 5/11/16
Successfully Funded
  • $5,664
  • 214%
  • Funded
    on 5/11/16

About This Project

Amazonian catfish make the longest freshwater migration in the world (5,000km). Dams being built could block this migration before we can even understand it completely. Similarly, largetooth sawfish make upriver movements from the Atlantic ocean but we do not know why. We have published one paper using isotopic tracers from fish earbones to reconstruct details of catfish migration and propose to expand our work and to include sawfish, another endangered megafish, in our isotopic migration study.

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What is the context of this research?

Amazonian goliath catfish make one of the longest migrations on earth, from the Amazon estuary to the Andes foothills. This is as long as a road trip from Seattle to Miami, via Chicago, yet we know very little about how they make this trip. Dams are being built in the headwaters of many Amazon tributaries that could block this migration, and the species are already overfished.

Sawfish, related to sharks and rays, are listed as Critically Endangered worldwide. In the lower Amazon River, sawfish are often caught accidentally in fishing nets. Aside from their decline, very little is known about the ecology of these species.

Like megafishes worldwide, the long distance movements of both goliath catfish and sawfish make them particularly vulnerable yet we know very little about them.

What is the significance of this project?

Understanding the details of catfish and sawfish migrations are vitally important for Amazon conservation and its fishing economy. We need only look to the story of salmon to see how dams and overfishing might affect these catfish. Sawfish, despite being critically endangered, lack almost all understanding of their movements.

Luckily, modern chemistry has given ecologists incredible tools to understand these types of migrations. Using the chemistry trapped in the hard parts of fish (sawfish teeth or catfish ear bones) we can reconstruct with incredible precision the movements of individual fish. This data can help direct conservation strategies.

We have proven this is possible in the Amazon and further research will help us to understand how best to conserve these migrations in the future.

What are the goals of the project?

The best conservation strategies take into account the natural variation in migration within the population We currently have very little understanding of this for either species. Chemical analysis of the movements of many fish help us build an understanding of the whole population.

To complete this project we will collect sawfish rostral teeth and catfish ear bones from fish captured by fisherman. For sawfish, 6 individual samples are already collected and we hope to collect more during my trip. For catfish we will focus our efforts on a single tributary, likely the Madeira.

Our samples will be analyzed in the United States for age, as well as for strontium isotopes and trace elements using cutting-edge techniques. Travel will occur on of after January of 2017 and analysis soon thereafter.


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Although we have conducted one preliminary study which resulted in a paper published in PLOS ONE, we have never actually met in person. The best research happens when scientists can discuss the details of the work face-to-face and observe the location and logistics of the study site during field work. As we move into the next phase of our study it is vitally important that we have the opportunity and time to plan a comprehensive study design and get into the field to collect additional data.

The largest portion of the budget is to pay for an airline flight to Belém, Brazil where Tommaso is based. In addition the budget includes the cost of food and lodging in Belém for a two week trip, as well as the gasoline required to complete sawfish and catfish sampling.

Stretch Goal: Now that we have funded the first sampling, we need to do the analysis. $1,300 will give us enough time on the machine to tweak the method to analyze rostral teeth and finish ~30 samples.

Endorsed by

Jens has been taking the work in our lab in 3 important directions: 1) providing spatially explicit predictions about isotope variation across the landscape, 2) improving techniques for applying it to otolith microchemistry, and 3) developing robust ways of quality-controlling and analyzing the large amounts of data that is generated from scans for multiple elements across thousands of fish. Jens, enabled with the state-of-the-art equipment that we manage at UI and collaboratively with WSU, can do the proposed work with Amazon fish populations.
I have know Jens since he conducted research with me as an undergraduate at Macalester College. Jens came back a few years ago to give a seminar on his otolith research. It was great! I know that Jens has the background and drive to complete this exciting project.
Migratory fishes are aquatic marvels but what if Earth’s waters had none? Figuring out where these fishes move is a job Jens is qualified to get done! Jens is a thoughtful and effective communicator and communication of this work will be key. To peers, the public and policy makers, Jens has the skillset to reach all three!
From the Andes to the sea, the Amazon River is a natural wonder of the world. The plants, animals, indigenous human populations are all interconnected. Dams drive a wedge in those connections. This research, conducted by leading scientists who know how to share information with the world, will help us better understand the importance of connected habitats for some of the most important fish species in the river.
Jens has done some groundbreaking work in the Amazon River basin, tracking fishes with isotopic tracers. His new project will break further ground, and will help to address the burning issue of the importance of connectivity of habitats for these highly migratory fishes. This work is important because it will shed light on the potential impacts of new hydropower dams.
The impacts of dams on fish migration is a global issue, yet critically understudied in the Southern Hemisphere. This project will provide vital information about the migratory patterns of this species, and develop a productive international collaboration. Jens is fully qualified to complete this project, and is skilled in the application of geochemical methods for unraveling fish migration. I can't wait to see the results of this study!
Using cutting edge methods, Jens's work will help illuminate patterns of migration and life-history for species that we know little about. His work is critical for furthering the knowledge needed to conserve these great species.
Jens is a dedicated and brilliant colleague who is passionate about using cutting edge tools to examine important but understudied issues. Using the microchemistry of hard structures to follow the migration of fish is valuable not just for the conservation of the species but also for the advancement of the technique, and to highlight the incredible biology of the sawfish and catfish.
I've had the pleasure of knowing Jens ever since we were graduate students together at the University of Idaho. Our lab specializes in otolith microchemistry, and collecting samples from these endangered megafishes will allow for unprecedented insight into their migratory histories. Jens is incredibly hard-working and passionate about this system, and he possesses the skill set and drive necessary to undertake this ambitious project.
Large-bodied fishes in Earth’s major river systems have two unfortunate things in common. First, their ecology is largely unknown, and second, because of this, their populations are often imperiled. Because of the scale of their movements it has been difficult to obtain even basic life-history information. The proposed research will gather critical data on the fundamental ecology of these species. When such data exist and are publicly available, it means that decision makers cannot overlook them.
This is a fascinating project in an under-studied corner of the globe, and Jens is absolutely the right person to help lead it. As a scientist, musician, writer and editor, Jens is thorough and thoughtful. If there's a way to figure out how these fish migrate using their bones and teeth, Jens will find it — and he'll narrate the process with interesting and insightful posts, to boot. Maybe, if we're lucky, he'll even write a song about it!
As a fisheries scientist and ardent conservationist, I see this project as the start of what could easily become a major study on fish migration in the Amazon basin and how best to protect these fishes from the effects of dams and other anthropogenic impacts. As important as goliath catfish and largetooth sawfish are, protecting their migratory movements could have huge benefits for many other freshwater species. I have enormous confidence in the integrity and competence of the scientific team, Mr Hegg and Dr. Giarrizzo.
The impacts of the proposed dams in the Amazon basin to the amazing diversity of aquatic life that lives in those rivers could be devastating. We are only recently beginning to gain an appreciation for what freshwater ecologists have to learn from studying the unique species in this system. The research that Jens is proposing would be an important step in understanding the unique migration ecology of these species and what could be done to protect their populations from the fragmenting effects of dams in this system.

Meet the Team

Jens Hegg
Jens Hegg

Team Bio

Jens Hegg and Dr. Tommaso Giarrizzo collaborated on the first study using otolith microchemistry to reconstruct movement in Amazonian goliath catfish.

Dr. Giarrizzo is a professor at the Federal University of Pará in Belém, Brazil. He has published extensively in Amazon fish ecology, with a recent paper in Science on hydropower in the Amazon.

Ecologists Without Borders, an all-volunteer non-profit, is a supporter and plans to provide volunteer support & financial oversight as the project grows.

Jens Hegg

I am currently a PhD candidate at the University of Idaho in the interdisciplinary Water Resources Program, with a M.S. Degree from the same program. This project is an independent side project, which will be completed in January 2017 after my PhD is complete.

I am interested in the ecology of animal movement and migration, specifically the trade-offs that animals must balance to optimize their fitness within a complex and changing environment full of competition from other organisms and rapidly changing evironmental conditions.

Within this focus on life history and migration I use isotopic tracers, bio-energetic modeling, growth trajectories and geospatial modelling techniques to understand the selective pressures that shape the life-history of fish populations across the landscape.

I maintain active research in several areas: Fall Chinook salmon in the Snake River of Idaho, giant migratory catfish in the Amazon basin of Brazil, geologic prediction of strontium isoscapes, and data sonification and virtualization for data exploration, artistic expression and scientific outreach.

This video is a funny and instructive introduction to me and the basics of my work.

Outside ecology I have many interests, coming to academia on a circuitous path, starting with a B.A. in Biology from Macalester College in 2000. In the intervening years I worked in the field studying endangered river mussels in the Hornbach Lab, the distribution of non-game fish with the Minnesota Pollution Control Agency among others. I also spent significant time working in research and development laboratories; in renewable bio-plastics with Natureworks LLC, and designing new coronary stents with Boston Scientific which lead to 4 US patents.

Additional Information

Otolith microchemistry, the technique we use to determine the movements of fish from their ear bones, or otoliths, is a super cool technique. But, it's hard to explain without some visuals. The videos below help explain what the otolith is, how it can be used to determine the age of a fish both in years and in days, and finally how the chemistry from rivers can be uncovered and used to detemine where a fish travelled during it's life. Watch them in order and you'll get a good idea of how this technique works. Keep in mind that sawfish teeth grow in a similar way and the same information can be gleaned from them...but it's only been done a few times, so there aren't any fancy videos to explain it.

Project Backers

  • 162Backers
  • 214%Funded
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