A little river fish is getting big time attention

Researchers hunt for the bridle shiner

By JOHN JOSE

UPPER DELAWARE RIVER — A seemingly insignificant little fish, the bridle shiner, is raising big concerns among scientists keeping tabs on the health of the Upper Delaware River. Once common in the mid-Atlantic states, a dramatic decline in bridle shiner populations has prompted Pennsylvania to classify the fish as endangered and New York and New Jersey to designate it as a species of concern.

As with any animal or plant, managers, charged with protecting natural resources, need at least basic information on which to base effective management plans to protect a species that is showing signs of being in trouble. Such information on the region’s bridle shiner populations is currently lacking and that is where the Academy of Natural Sciences of Philadelphia and the National Park Service (NPS) enter the picture.

Bridle shiner study

Supported by a PA Department of Conservation and Natural Resources grant, the academy has partnered with the Upper Delaware Scenic and Recreational River and the Delaware Water Gap National Recreation Area to complete a project with an overall goal of ascertaining the status of the fish in the Upper Delaware River basin. As well as sites where the shiner has been previously documented, new potential locations are being investigated on the Pennsylvania side of the river from Hancock, NY south to Delaware Water Gap.

Investigations are currently focused on the river’s backwater habitats. Bridle shiners are often associated with shallow, slower moving waters that contain beds of submerged aquatic plants, such as Elodea. Streams and small ponds in proximity to the river may also be investigated if suitable habitat is found. Much still needs to be learned about this less than two-inch long fish, which is identified by, among other characteristics, its straw-colored body and a distinctive black band that runs from the tip of its snout onto the base of its tail.

Field work

Dave Keller and Shane Moser, fishery scientists with the academy, are currently conducting field studies for the project, which began in 2006 and will be completed in June 2008. Recently, Keller and Moser, assisted by Don Hamilton of the NPS, re-surveyed a backwater habitat area on the Delaware below Hancock, NY where the elusive fish was identified in 2006.

Although fair weather and good visibility in the river provided good search conditions, after an intensive effort involving snorkeling several hours in shallow water to try to spot the shiners and carefully identifying hundreds of fish?many no more than one-inch-long—collected with seine nets, no bridle shiners were located. However, in trying to establish where the species exists, not finding bridle shiners in a particular location is just as informative for the scientists as finding the fish in the sites they are searching.

Project benefits

Academy scientists have located the fish during searches of other locations within the study area and their investigations will continue, simultaneously documenting where shiner populations occur while expanding the existing knowledge base of the species’ habitat requirements. The researchers hope to find answers to the shiner’s water temperature requirements, what constitutes good habitat and, very importantly, the effect of changes in river flows on the species.

The study will also generate recommendations to support protection and management of the fish. For instance, depending on the results of the study, what is learned about the fish could contribute to the ongoing efforts of the Delaware River Basin Commission to revise flow management regimes for the river.