June 18, 2008
Tagged Fish Are Marked to Provide Information
Most hunters are aware of bird bands. Those most familiar are the metallic leg bands on ducks and geese.
The band will typically include instructions for reporting identifying numbers or letters related to the organization doing the research. Hunters have always embraced and understood their role in these scientific studies, and banded birds are usually considered as a special trophy by the hunters who harvest them.To a lesser extent, the same is true for fish, except that fish captured for research projects typically have some type of tag attached instead of a band. The tags carry the same identifying features, and information returned is as valuable for fisheries managers as waterfowl bands are for wildlife management.
In particular, walleyes generate considerable angler interest. Walleye have a strong drive to return to the same spawning area each spring. More than 95 percent of returns during tagging include marked fish captured at the same location where they were originally tagged.
A recent study within North Dakota's portion of the Missouri River System provides a glimpse into the world of walleye. In this study, 70 percent of walleyes caught by anglers were landed within 20 miles of where they spawned. While there is a gradual movement away from spawning areas, as summer moves toward August, the fish start to move back toward spawning areas.
Within the Missouri system, walleye tagged on Lake Oahe at Beaver Bay near Linton and White Earth Bay toward the upper end of Lake Sakakawea, moved the greatest distances. Female walleyes tended to move farther from spawning areas than males.
Because of tagging studies, we know that walleye can move between dams within the Missouri system - that is, they can move downstream through Garrison Dam and Oahe Dam, but there is no evidence they can get from the Missouri River upstream through the dams. Tagged walleyes have even transferred from Lake Sakakawea to Lake Audubon through a water link under the U.S. Highway 83 embankment.
Knowing the extent and potential of this fish movement gives biologists many possible scenarios to weigh when making management decisions.
As with most studies, those involving fish have their norms and exceptions to those norms. Those odd and peculiar occurrences are the ones that throw trends out the back of the boat, so to speak , and prompt anglers and fisheries biologists alike to do a double- take.
One such exception was a walleye tagged at the Garrison Dam Tailrace and caught 294 miles downstream at Oahe Dam - six years later. Two walleyes tagged at White Earth Bay were caught at Fort Peck Dam Tailrace in Montana, 277 miles upstream from their original place of capture.
So far, however, the champion walleye traveler was a female tagged at White Earth Bay and caught by an angler 108 days and 321 miles later in Montana's Milk River.
Researchers urge anglers who catch and release tagged fish to please leave the tag on the fish, rather than keeping it as memento. But jot down the number on the tag before letting the fish go. Tagged fish that are released continue to provide information, as long as they are caught again.
Here's one particular sample fish history: A 15-inch male walleye (No. 7,779) was tagged at Lake Sakakawea's Parshall Bay in May 1996. He was caught during spawning at Parshall Bay in 1999, 2001 and 2002, and eventually was harvested by an angler at Shell Village in August 2003.
As you spend time angling this summer, if you land a tagged fish, please help fisheries researchers by logging onto the NDGFD Website, http://gf.nd.gov, where you can enter pertinent information, such as if the fish was kept, where it was caught, length, weight and tag number and color. Cooperating anglers will receive a return letter detailing the tagged fish's history.
Knowing where that fish was before it ran into your lure is a fish story just waiting to be told.
(Doug Leier, a former game warden, is a North Dakota Game and Fish Department biologist. His blog is on www.bismarcktribune.com. Leier may be reached by e-mail at [email protected])
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