Tiny fish can yield big clues to Delaware Ri...( PHILADELPHIA Where have all the bri...)

PHILADELPHIA Where have all the bridle shiner gone" Thats the mystery The Academy of Natural Sciences fish scientists are trying to answer, and the outcome will shed light on the environmental health of the Upper Delaware River.

Bridle shinernot easy to spot at less than two inches longonce were abundant in the mid-Atlantic region, including small streams in Southeastern Pennsylvania. Their steady decline has prompted Pennsylvania to classify the fish as endangered. Now, the Academy is swimming the tide to lay the groundwork for an environmental management plan for the species and its habitat.

The Academys Patrick Center for Environmental Research, in partnership with the Upper Delaware Scenic and Recreational River and the Delaware Water Gap National Recreation Area, is in the midst of a two-year project to discover and describe the status of the little minnow in the Upper Delaware River basin. Academy fisheries scientists David Keller and Shane Moser, under the direction of Dr. Richard Horwitz, have cast their seine nets and gone snorkeling many times at various locations over the last year with varying results. Their findings will shed light on the health of the Upper Delaware River and will factor into decisions made about the flow of the river.

The presence and absence of fish helps us define preferred habitat for the fish, which helps us locate potential sites for sampling, explained Horwitz. We've located several sites with populations of the species, and in other places we've found a few fish on one visit, but not on subsequent visits. These sites may lead us to sites with large populations.

Academy studies reveal possible causes of the species decline may include changes in water quality due to siltation, nutrient enrichment and changes in flow patterns, and the introduction of predators, such as largemouth bass, as well as competitors for food. Interestingly, a decline in the beaver population also may factor into the decline.
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