Intersex bass found in Delaware waters
Researchers suggest culprit could be runoff from big poultry operations
By MOLLY MURRAY • The News Journal • November 13, 2010
http://www.delawareonline.com/article/20101113/NEWS02/11130346
Dozens of male largemouth bass collected in two southern Delaware ponds and one lake show female sex traits – a new and unsettling finding in state waters that could be linked to runoff from poultry operations.
A research team at the University of Maryland’s Wye Research and Education Center, which studied the fish, suggests the culprit may be a naturally occurring steroid that chicken excrete in manure.
But the scientists say more research is needed, as they try to duplicate the phenomenom in lab experiments on other fish species.
“The more you get back in the field, the harder it is to make a link,” said Daniel J. Fisher, senior research scientist at the University of Maryland’s Wye Research and Education Center in Queenstown, Md. “We’re just kind of guessing.”
The fish also were found in three Maryland lakes.
The findings could be significant because the four lakes and two ponds are in mostly rural areas – not urban or industrialized areas where significant chemical pollution has been identified. No one is certain whether the male fish continue to reproduce when they have eggs in their gonads.
Runoff from poultry operations has been linked to high levels of nitrogen in ground and surface water, and phosphorus on soil particles. The two chemicals, components of agricultural fertilizers, have been linked to algae blooms and fish kills.
Poultry farmers in Delaware manage their chicken waste through plans that are supervised by the Delaware Nutrient Management Commission.
“It’s not a real-world study,” said Richard L. Lobb of the National Chicken Council. “The farmers are doing what the science has told them to do.”
Lobb said fish exposed to poultry litter in the intense setting of the lab would likely react differently from fish in the wild, where weather, rainfall and other factors have an influence.
The research had two parts. First, Fisher and his team electrofished the lakes and ponds to stun and catch largemouth bass.
Fisher said they targeted that species because they knew it was susceptible to male fish producing female eggs. The fish were the first discovered in Delaware and the Eastern Shore with the intersexual characteristics.
For the field work, the researchers looked at fish in Hearns Pond near Seaford, McColleys Pond near Milford and Moores Lake south of Dover. They found that 60 percent to 100 percent of the male largemouth bass they caught carried eggs in their gonads.
Fisher said that is not normal.
The team also looked at three lakes on Maryland’s Eastern Shore: Smithville Lake, Tuckahoe Lake and Williston Lake. There, between 33 percent and 80 percent of male largemouth bass carried eggs.
The fish were collected in the summer of 2008.
Fisher and his team have been looking at the ecological impacts of poultry manure for more than a decade. One reason is that an estimated 600 million birds are produced annually on the Delmarva Peninsula – about 7 percent of the national total.
Litter – a mixture of chicken manure and wood shavings – is typically applied to fields as a fertilizer. Chicken houses get a full cleanout every two years.
Scientists at the Environmental Protection Agency analyzed poultry litter and found that it contains about 4 percent nitrogen and 1.5 percent phosphorus by weight. They also found bacterial and viral pathogens, traces of pesticides, antibiotics, metals like copper, zinc and arsenic, and polyaromatic hydrocarbons. There were also the steroids estradiol and testosterone.
Fisher said male largemouth bass carrying eggs have been found on the Potomac and Shenandoah rivers. He said the Delmarva ponds and lakes, though mostly rural, may have been exposed to other sources of pollution such as septic tanks.
State environmental officials have issued a fish consumption advisory for Moores Lake near Dover because of DDT and polychlorinated biphenyls – chemicals that were outlawed decades ago.