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Deformities in Yellow Perch Eggs Linked to Suburban Sprawl

YellowperchYellow perch are popular sport fish, prized for their flavor. Their spawning runs up streams during the late winter are heralded as an early sign of spring in the Chesapeake Bay region.
 
But the ability of yellow perch to reproduce has fallen off sharply in recent decades, with many egg yolks abnormally formed.  Water pollution from suburban sprawl may be the cause, according to a new report by the U.S. Geological Survey, Maryland Department of Natural Resources, and U.S. Fish and Wildlife Service.
 
“The abnormalities were most frequent and severe in perch from the South and Severn Rivers, the two tributaries with the most highly suburbanized watersheds,” says the report, which was written by Dr. Vicki Blazer of the U.S. Geological Survey and six colleagues.  These abnormalities “may result from exposure to environmental contaminants,” although more studies are needed to determine exactly which pollutants.
 
In the Chesapeake Bay region, the problems with yellow  perch appear to be most severe in the highly suburbanized triangle formed by Washington, Baltimore, and Annapolis, according to the report.

In this area, the Maryland Department of Natural Resources surveyed the hatch rates of yellow perch eggs, which look like golden strands that cling to roots and fallen trees in freshwater streams in late winter and early spring.  From the 1920s through the 1960s, more than 80 percent of the eggs hatched. But from 2001 to 2005, fewer than 10 percent of the eggs hatched, according to the study.
 
When biologists examined the eggs closely, they found deformed yolks and abnormal sacs around the yolks. 
 
The researchers compared rates of these abnormalities in areas of the state with different amounts of suburban development, as expressed by the percentage of the land that was covered with blacktop or buildings.  The scientists examined the South River south of  Annapolis, where 25 percent of the land is developed; the Severn River north of Annapolis, where 21 percent of the land is developed; as well as the Mattawoman Creek area in southern Maryland (10 percent developed); Allen’s Fresh, also in southern Maryland (5 percent developed), and the Choptank River (2 percent developed).
 
The study  looked at fish eggs in 2007, 2008, and 2009, and found that the abnormal yolks and egg envelopes were found much more often in the more suburbanized landscapes (surrounding the Severn and South rivers).  In the Severn River area, for example, none of the eggs was fully developed, according to the report.
 
The implication is that pollution running off of the suburban landscape may be responsible for disrupting the reproduction of the fish.  Now, the next step for the researchers is to pinpoint which contaminant.

If it turns out that, in fact, polluted runoff from developed neighborhoods is the problem, then solutions might include tighter regulation of suburban sprawl.  Also helpful might be parking lots and driveways that are permeable to water, so less runoff flushes into streams; and stormwater control ponds and ditches full of wetlands plants to slow the flow of runoff and absorb pollutants.
 
To learn more about the problem, click here
 
By Tom Pelton

Chesapeake Bay Foundation
 

 

 

Comments

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The urbanized landscape continues to inflict damage even for those eggs that hatch. Studies by the Maryland Dept. of Natural Resources of the guts of yellow perch larvae find that the gut fullness declines as the density of structures in the watershed increases. What's more, even what the larvae are able to eat is less nutritious in more urbanized watersheds.

Mattawoman Creek, one of the tributaries studied, and heralded as Maryland's best fish nursery in the Bay as recently as 2005,is headed downhill from development. Yet the draft revision of Charles County's Comprehensive Plan intends to make things even worse. Without a strong public outcry, the land speculators who designed the comp plan will prevail, and another nail in the Bay's coffin will find its mark.

Excellent points, Jim! This is not an abstract question about biology -- it's a destruction of the Bay's life that is being threatened right now as more sprawl is planned in Charles County and elsewhere in the region.

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