Migrating fish find help getting home

Passages: Bluebacks, shad and perch are returning to waters they haven't been able to reach for centuries.

May 09, 2001|By Joel McCord | Joel McCord,SUN STAFF

UNICORN LAKE - The fish with bright bluish-green stripes down their backs stream through the rushing water in droves, headed for an aluminum tube at the base of the dam that created this Queen Anne's County lake.

They pause a few seconds in the calm pools at the top, then dart out into the lake, answering nature's imperative to reproduce.

This is the largest spawning run of blueback herring since the tube was built in 1998 to help fish get past the dam, says Sid Compton, who manages a state-run fish hatchery here. It is also part of an unusually heavy blueback run through most of the state's Chesapeake Bay tributaries.

The homecoming is due largely to a 12-year effort to remove or otherwise bypass thousands of dams that have destroyed spawning runs of such migratory fish as shad, bluebacks and perch.

The rectangular tube is a piece of a national movement to open rivers to migrating fish by tearing down obsolete dams or providing ways around them to spawning areas they haven't reached in centuries.

Americans have built about 75,000 dams since Colonial days to harness the power of water or to provide drinking water and recreational areas. But those dams have kept migrating fish from getting upstream to their spawning grounds, decimating shad and herring populations.

River herring, the collective name for alewives and bluebacks, once were among the top five fish harvested in Maryland, with landings reaching 5 million to 8 million pounds a year in the 1930s.

But by the mid-1970s, the population, battered by fishing pressure and habitat loss, including dams that curtailed spawning runs, had all but collapsed.

State and federal agencies have launched campaigns to remove dams or find a way for fish to get around them to more fruitful spawning areas upstream. The bay restoration agreement signed last summer calls for reopening more than 1,350 miles of rivers by 2003.

Fish hatched upstream, with less competition for food and more places to hide from predators, will be bigger and stronger than their downstream cousins when they begin the annual migration back to the ocean.

Since 1989, Maryland has completed 61 fish-passage projects, restoring nearly 350 miles of upstream habitat in 18 river systems.

The Unicorn Branch passage in Queen Anne's County re-opened almost 15 miles of stream that had been closed for at least 150 years.

Three years ago, DNR installed the tube that allows fish to pass this dam, which once provided water power for a 19th-century wool mill.

Numbers grow each year

The first year the passage at Unicorn Lake was open, only a few herring made their way into the lake. But each year the number has grown, says Compton.

One morning last week, 340 bluebacks poured out of the opening at the top in 15 minutes and 260 in a 15-minute stretch that evening.

In previous years, 10,000 fish found their way to the lake during the weeklong spawning run. This year it appears 50,000 will pass this way, says Compton.

Three-year cycle

In the spring, fish such as blueback herring, shad and alewives travel thousands of miles from the open ocean to the freshwater streams of their birth to spawn.

Their young return three years later and every year after that to continue the cycle.

The blueback rush last week probably was triggered by suddenly warmer weather that raised the water temperature enough to get the fish moving, says Bob Lunsford, DNR's director of fish restoration and enhancement. "Probably, they've been waiting in deep pools down the Chester for the right moment."

The newly mature males using the fish passage this year probably were hatched at the base of the dam the year the passage opened and are "imprinted" with the waters of the stream, Lunsford says.

Window of warm weather

Statewide, the blueback run has been "very large in numbers, but very, very short in duration," Lunsford says.

The cold front that passed through the region Sunday, sharply dropping temperatures, may have choked off the run.

A year-old fish passage on a Choptank River tributary in Caroline County shows how quickly herring learn to find their way upstream.

On a sunny day last week, the shallow pools of Broadway Branch below the dam at privately owned Lake Bonnie were alive with the swirl and splash of bluebacks.

Reach out and grab one

Their fins broke the surface as they swam in agitated circles, and they lay so thick in some pools that often one was squeezed high out of the water, then plopped back in as the others scattered.

It looked as if you could reach out and grab one, but they swam away instantly at a strange touch.

Ten-inch-long herring lingered under a bridge across the dam, apparently not sure whether to keep going until one chanced it, then another. Soon, they were hustling into the lake by the dozen.

"This is the first spring this has been open and already they've figured it out," says Lunsford. "In all likelihood, it's just going to get better as they become more familiar with it."

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