Cold could leave yellow perch in pink


The last few weeks of winter have been frustrating wet and cold except for a good part of last week, when the temperatures warmed, the winds subsided, the air began to carry the smells of spring and headwaters of many tidal rivers held the promise of yellow perch.

From several quarters, the word came that perch were running at Williston, Wye Mills, Red Bridges and in the Tuckahoe and Blackwater rivers. From the Red Bridges and Denton areas of the Choptank and the Blackwater, there also were reports of white perch nearing the spawning grounds.

A morning of casting grubs and small spinners along the banks of the Tuckahoe near Queen Anne on the Eastern Shore produced only three small yellow perch and a few chain pickerel, whose season now is closed until the end of April in tidal rivers.

Perhaps it is the type of late winter that will benefit the yellow perch, whose numbers have been steady in most bay tributaries for several years, but remain below the concentrations that existed 20 years ago.

A cold, wet winter will have water levels up, and presumably flowing well in areas where the yellow perch spawn and an extended period of cold, late-winter water and high flow are crucial to a good spawn.

According to Department of Natural Resources fisheries biologists, yellow perch need long periods of cold weather well before they spawn to ensure good egg development.

"A prolonged period of chill in December will allow the eggs to develop properly in the female," said Jim Uphoff, stock DTC assessment coordinator with the Department of Natural Resources.

"But that is only one part of an extended life cycle, and until these fish reach half an inch to an inch in length, you can't be certain what is going to happen with them. Once they reach that length, they seem to settle down."

Part of what is known about yellow perch is that cold water temperatures also trigger the spawn in freshwater areas of tidal tributaries.

A female can lay up to 150,000 eggs in amber strands that attach to structure in streams or along overgrown banks, where moving water cleans and oxygenates the eggs until they are ready to hatch.

"But then if water temperatures fluctuate a lot [after the spawn], it is detrimental," said Uphoff. "You may have good egg production and horrendously poor larval development."

If water temperatures remain cold for about two weeks after the spawn, then a high percentage of eggs will hatch in good health.

At a sustained water temperature of 39 degrees, biologists say, nearly 100 percent of the eggs will develop well enough to spawn. But at 50 degrees, fewer than a third will develop.

Uphoff said that age structures of yellow perch stocks are variable in different river systems. For example, the Choptank has shown steady structures, while the Chester has been variable.

Those two rivers, Uphoff said, are close enough geographically that climatological effects should be similar, but the Choptank .. stocks are far better than those in the Chester.

"You would think we could pin it down a lot better than we do," said Uphoff. "But yellow perch are not like rockfish, where large numbers spawn in relatively few areas. Yellow perch spawn in small numbers in many small places."

Pub Date: 3/17/96

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