Number of Shad Returning to Susquehanna River Decreases for Fourth Consecutive Year

June 2007 -- Scientists counted 25,464 American shad lifted over the fish passageway at Conowingo Dam this spring—just 1 percent of the long-term restoration goal of two million fish per year. This is the fourth consecutive year that the number of American shad lifted over the dam has decreased, down from about 125,000 counted in 2003 and nearly 200,000 in 2001.

One of the ways scientists estimate spawning shad populations in the Susquehanna is by counting the number of fish annually lifted over Conowingo Dam, located near the mouth of the river in Maryland.

Fish passageways at the Holtwood and Safe Harbor dams, located farther up the Susquehanna, lifted 10,338 and 7,215 American shad, respectively.

Despite the decline over the past four years, the Susquehanna has experienced an overall increase in the amount of shad returning to the river to spawn. In the 1980s, scientists counted just a few hundred shad returning to the Susquehanna each year.

Potential causes of the recent decline include:

• American shad population declines along the Atlantic coast.
• By-catch problems at sea.
• Problems attracting the shad to the fish passageways.

Historically, the upper Bay was a very productive area for American shad harvest. From the late 1800s to the mid-1900s, shad was the most economically valuable food fish harvested in Maryland and Virginia waters. But over-harvesting and habitat degradation, combined with dams that blocked hundreds of miles of spawning and nursery grounds, caused a decline in the shad population that began in the early 1900s.

The permanent fish passage at Conowingo Dam, located near the mouth of the Susquehanna River in Maryland, was constructed in 1991. Fish passageways at the Holtwood and Safe Harbor dams were built in 1997.

In addition to installing fish passageways and removing old dams, the introduction of hatchery raised fish and a moratorium on shad fishing have helped to increase the number of shad in the Bay.

While the Bay Program is meeting short-term goals by restoring fish passage and introducing hatchery raised fish, there are currently very few measurements of stock assessment that indicate any gain towards the long-term abundance goal of two million shad per year. It is difficult to assess annual Bay-wide spawning shad populations because each river stock is unique. To provide better Bay-wide estimates, scientists are developing new monitoring methods to estimate shad populations in other key Bay tributaries, such as the James and Potomac rivers. An updated assessment is expected later this year.