Questions and answers about the discovery of intersex smallmouth bass in the Shenandoah and Cowpasture rivers

Q. What is fish intersex?

A.  Intersex is a condition in which fish may exhibit characteristics of both sexes. In this case, immature eggs were found in the testes of male smallmouth bass. Most often, reproductive organ tissue must be examined under a microscope to verify intersex presence. 

Q.  What causes intersex in fish?

A.  Intersex has been linked to exposure to estrogenic compounds (hormone-disrupting compounds). These organic compounds are commonly found in pharmaceuticals, personal care products, agricultural products, herbicides and pesticides. More research is needed to understand how these organic compounds are connected to intersex.

Q.  Has the intersex condition been documented in other parts of the United States?

A.  Yes, in West Virginia, Colorado, Maryland, Iowa, Missouri and other states.

Q.  Has the intersex condition been found in other Virginia waters?

A.  No.  However, scientists have not examined fish from other Virginia waters for intersex.

Q.  What other fish species have been found with intersex?

A.  It has been documented in largemouth bass, white suckers, common carp, fathead minnows, sturgeon, trout and roach (a fish in the United Kingdom).

Q.  How long have smallmouth bass in the Shenandoah and Cowpasture rivers exhibited this condition?

A.  It is not known how long smallmouth bass from these waters have had the intersex condition.  There has not been any microscopic analysis directed toward intersex conducted in the past.

Q.  Is there any connection between intersex and the recent fish kills in the Shenandoah River?

A.  It is still unclear if there is a correlation between intersex and the recent fish kills. The intersex condition itself has not been documented to cause fish kills, but whatever caused the intersex condition may be involved with the fish kill. The Shenandoah Fish Kill Task Force continues to sponsor research and monitoring to determine the cause of the fish kills in 2004-05.  Additional fish health screenings are planned.

Q.  Does the intersex condition affect the ability of smallmouth bass to spawn successfully?

A.  Intersex may or may not affect smallmouth bass reproduction.  However, biologists with the Virginia Department of Game and Inland Fisheries have documented above-average smallmouth bass spawning success in the Shenandoah River the past two years. DGIF biologists have established that river flows are the main factor that determines spawning success in Virginia’s rivers. However, researchers will test the quality and quantity of  smallmouth bass sperm collected from throughout the Potomac River watershed in 2006.

Q.  Is it safe for people to eat intersex fish?

A.  To date, there has been no data linking the consumption of intersex fish with disease or human health disorders.

Q.  If I catch a smallmouth bass, will I be able to tell if it exhibits intersex characteristics?

A.  Probably not.  In most cases the only way to determine if a fish is intersex is by viewing a sample of reproductive organ tissue under a microscope. 

Q.  What can be done to reduce or stop this intersex condition in fish?

A.  We must first learn much more about what is causing this condition and where the pollutants are coming from.

Q.  As a concerned citizen, how can I help?

A.  Get involved with water quality issues in your local watershed and support research efforts directed at better understanding this problem. Also, it is important to understand that many of the chemicals linked to this condition in fish are used by humans in their everyday lives. These chemicals are found in pharmaceuticals, household pesticides and herbicides, and personal care products.

Q.  To date how many smallmouth bass collected from the Shenandoah River have been tested for intersex?

A.  In the initial screening work conducted in October 2005, 20 individual adult smallmouth bass were collected from each of four rivers: the North Fork Shenandoah, South Fork Shenandoah, main stem Shenandoah River, and Cowpasture River. For all samples, biologists attempted to test 10 males and 10 females from each river.

Q.  Who is conducting the microscopic studies on intersex?

A.  Scientists with the United States Geological Survey Leetown Science Center in West Virginia.