October 24, 2012

Two million fish ear bones contain new environmental insights

The rings on a fish otolith.
Photo courtesy of Flickr user Eustatic
Creative Commons license

The rings in a tree stump can tell us a lot about the age and growth patterns of the tree, but did you know similar records are hidden inside the tiny ear bones of fishes?

The Burke Museum's fish collection is currently cataloging and moving a collection of nearly two million of these fish ear bones, called otoliths, to join our rapidly expanding collections and provide valuable information to researchers.

Most fishes have three small ear bones, called otoliths, located on each side of the rear of the skull, which aid in balance and hearing. Like a tree, the largest of the otoliths develop rings that contain all kinds of valuable information: where the fish was born, what it ate and the conditions and depth of the water that it swam in—all of which provide clues about environmental factors such as climate change and how they impact species and populations. Some fishes, such as the rockfishes, can live 100 years or more—giving researchers an entire century’s worth of data to study.

The study of otoliths interests not only ichthyologists, but researchers throughout the various fields of science. For example, geochemists are turning to otoliths to reconstruct earlier and unknown environmental histories. Paleontologists and archaeologists are studying otoliths recovered from fossil and archaeological sites to learn about previous climates and what people ate in the past. Otolith research has fundamentally changed our understanding of fishes and their environment and represents a truly transformative science.

For this reason, researchers like Ted Pietsch, curator of fishes at the Burke Museum, consider otoliths a true treasure. Ted and Burke collections manager Katherine Maslenikov, maintain one of the largest and most diverse fish collections in the nation—more than 10 million specimens—right here on the University of Washington (UW) campus.
The Styrofoam and cardboard boxes that
formerly housed the otoliths collection.

So when Ted learned that the National Oceanic and Atmospheric Administration (NOAA) had a massive collection of otoliths—nearly two million—in the Seattle area that they weren’t able to safely store, he worked in partnership with NOAA to transfer the collection to the UW fish collection.

The collection of otoliths began in 1971 when Alaska Fisheries Science Center (AFSC) and U.S. Domestic Fisheries Observer Program personnel started extracting otoliths from fishes they collected on the west coast of the U.S. from southern California to the Bering Sea.

Each sample is marked with important information about where and how the specimens were collected, such as their geographic location, date of capture, time of trawl, depth of gear, water temperature, etc. So far the collection contains 83 species of eastern North Pacific and Bering Sea fishes, each represented by hundreds—some by thousands—of unique otoliths.

For the past 40 years, the collection sat in an old airplane hangar built in the 1930s, but the collection has grown considerably over the years—as have the safety risks. With nearly two million ethanol-filled glass vials of otoliths in nearly 12,000 Styrofoam boxes housed in a pre-WWII structure, the risk of fire and losing the collection was very real.

Ted Pietsch holds a vial containing pairs of otoliths.
So, with a $526,000 grant from the National Science Foundation (NSF), the Burke’s ichthyologists will transfer the entire collection of nearly two million otoliths to the UW campus, replace the Styrofoam boxes with acid-free cardboard boxes and sort them on mobilized shelves in a fire-safe space near the existing fish collection. In addition, they’ll catalog and digitize the massive amount of biological and physical data from the collection and publish it online in a searchable database and image gallery.

To help with the tedious task of handling two million pairs of tiny fish bones, Ted and Katherine hired a team of eager undergraduate students to go through the old dusty Styrofoam boxes (some even covered in pigeon poop!), catalog, transfer, relabel the specimens, then move the collection from the airplane hangar to the UW.

“They’re so fast,” Ted said referring to Rebecca Anderson, Josh Borin, Ross Furbush, Eric Harris, Jake Kvistad, Felicia Muncaster and Ellie Robbins—many of whom are continuing to work on the project through the school year. It’s tedious and messy work, but the students are sorting the collection year-by-year and are already working on the otoliths collected in 2004.

“This is not only wonderful for science, but we’re so excited for how it will support our students,” said Ted referring to new student internship opportunities, increased access to the otoliths for UW biology classes, and public programs. In addition, Ted was able to recruit a new graduate student, Jeremy Harris, who comes to us with a M.S. degree from Loyola University Chicago, to help manage the project while also conducting otolith research as part of his doctoral dissertation.

The new, acid-free cardboard boxes of otoliths
in their new home at UW.
By saving and sharing these specimens, the Burke Museum is adding to our library of biodiversity–a library that gets referenced all the time. Otoliths are of enormous value to today’s researchers studying our natural and cultural history, with unlimited potential to aid future researchers in answering questions that haven’t even been asked yet.

Learn more about Jeremy's otolith research to prevent over-fishing of pollock in the Pacific Northwest in our QUEST Northwest article, "Fish Earbones Provide a Rare Glimpse into the Past and Future of Fisheries."

By Cathy Britt, Digital Communications