Researchers Use Fish Earstones to Collect Hatched Fish Data
OutdoorHub Reporters 02.20.12
Fish otoliths have been commonly used as a way to determine the age of a fish. Otoliths have an added benefit to research, tied to those fish originating from hatcheries. Otoliths are small bones, often called earstones, that grow lines with age, much like a tree trunk does. They also can show water quality and other environmental factors in the water.
Bowling Green State University scientists have found that the otoliths can help determine the origin of fish’s birth and its habits on returning to its birth place for spawning. This information will supply fishery managers with information on the return rates of their fish which in turn influences the recreational fishing season.
The research is made possible by the Ohio Sea Grant which is a statewide program that supports research, education and outreach of Lake Erie and the Great Lakes. It is part of the National Oceanic and Atmospheric Administration (NOAA) Sea Grant College Program.
Original press release issued by Bowling Green State University on February 20th, 2012:
Ongoing Ohio Sea Grant research is assisting fisheries managers in states around Lake Erie in evaluating and improving their stocking efforts for steelhead trout, a popular sport fish in the region. Researchers from Bowling Green State University have found that the chemical signature of a fish’s otoliths, small bones located behind the eyes, can aid in determining where fish were hatched and whether they return to that same location for spawning.
Dr. John Farver, Associate Professor of Geology, and Dr. Jeffrey Miner, Associate Professor of Biological Sciences, are able to determine the origins of adult steelhead trout in the Great Lakes region with better than 90% accuracy (100% for Ohio-raised fish). This finding becomes an important tool for state fishery managers in Ohio, Pennsylvania, Michigan, and New York, who can use the information to determine the return rates of steelhead trout stocked into local streams to extend the recreational fishing season. The project is currently funded by Ohio Sea Grant.
“Fisheries managers stock about two million steelhead into Lake Erie each year,” explains Miner. “It’s a very substantial fishery that primarily occurs from October until April because that’s when the fish come up into the rivers to spawn. This provides an economic opportunity for the region at a time of year when other recreational activities are not at their peak.”
Steelhead trout are related to salmon, and like their cousins, most individuals will return to their “home stream” to spawn once they reach maturity, with 8 to 10% of fish raised in hatcheries deviating from this pattern and moving to a different stream. Steelhead fishing in Ohio alone contributes $12 million or more to the state’s economy, so fisheries managers want to make sure they raise fish that will return to their home state instead of essentially supporting another state’s economy. Ohio’s yearly investment into stocking steelhead is about $340,000.
Because steelhead are not native to this region, they can’t reproduce successfully in most streams that flow into Lake Erie—the water gets too warm during the summer months for the offspring to survive—and hatcheries along the lake stock juvenile fish into tributaries each year. Miner and Farver are able to determine which hatchery a fish came from based on chemical elements incorporated into the fish’s otoliths during growth, and combine that information with where it was caught to determine return rates for each hatchery along Lake Erie.
“If you look at an otolith, it looks very much like a tree that’s been cut in half, with rings that are demarcations of changes in growth,” says Miner. The center part of the otolith represents the fish’s early life, and rings are added as the fish continues to grow. In addition, using chemical elements such as strontium and barium that typically incorporate into the otolith, researchers can determine the water chemistry of where the fish spent certain parts of its life, and correlate that to various regions of Lake Erie and its tributaries.
Ohio State University’s Ohio Sea Grant program is part of NOAA Sea Grant, a network of 32 Sea Grant programs dedicated to the protection and sustainable use of marine and Great Lakes resources. For information on Ohio Sea Grant and Stone Lab, visit ohioseagrant.osu.edu.
For more information about this research, please visit go.osu.edu/otoliths.
