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Map: Shad Abundance (2010)

Date created: Mar 29 2011 / Download

American shad were once the most abundant and economically important species in the Chesapeake Bay. Shad are anadromous fish and spend most of their lives in the ocean, returning to freshwater rivers to spawn after they reach maturity. Data for the York and Potomac Rivers were provided by the Virginia Institute of Marine Science via an ongoing Catch per Unit Effort (CPUE) study involving American Shad gill-netting. Data for the Susquehanna and James Rivers represent published fishway passage values for Conowingo and Boshers Dams, respectively.

shad2010 (57.5 KB)       
shad2010 (55.5 KB)       

Importance

American shad form an important link in the Bay food web. Shad feed on zooplankton and are preyed upon by larger fish, including bluefish, weakfish and striped bass.

Historically, local economies flourished from the annual shad run in the spring, when the fishes’ upriver migration begins. But shad populations were decimated in the 1970s by overfishing, pollution, and dams and other blockages that prevent the fish from reaching their upstream spawning grounds.

Goal

Spawning shad stocks are tracked in four major river systems: the Susquehanna, Potomac, York and James. Two of these rivers have fish passage systems in place so shad can bypass dams and other blockages.

Each river system has its own numeric target:

1. Susquehanna River: Two million shad passing York Haven Dam annually
2. James River: 500,000 shad passing Boshers Dam annually
3. Potomac River: 31.1 Catch per Unit Effort (CPUE)
4. York River: 17.4 CPUE

Trends

Long-term trend (2000-2010)

The trend varies among rivers: 

• Bay-wide: As a whole, the Chesapeake Bay American shad indicator has steadily increased from 9.2 percent to 28.3 percent of the goal. Shad abundance trends in the Potomac and York rivers are responsible for driving the overall Bay-wide trend, since shad passage at York Haven and Boshers dams remains negligible.
• Susquehanna River: Abundance has remained minimal at less than 1 percent of the goal. Few shad that pass Conowingo Dam reach and pass York Haven Dam. There is optimal spawning habitat above York Haven Dam.
• James River: Abundance has remained minimal at less than 1 percent of the goal.
• York River: Abundance increased slightly in 2001, then stabilized at approximately 40 percent of the goal. But since 2005, shad abundance has declined to 20 percent of the goal.
• Potomac River: Unlike the other three rivers, abundance has steadily increased over the past 10 years from 12.4 percent to 96.8 percent of the goal.  

Short-term trend (10-year trend)

Same as the long-term trend

Change from previous year (2009-2010)

• Bay-wide: Increased from 26.6 percent to 28.3 percent of goal achieved
• Susquehanna River: Remained below 1 percent of goal achieved (increased from 402 to 907 shad passing York Haven Dam)
• Potomac River: Increased from 89.5 percent to 96.8 percent of goal achieved (28.1 to 30.2 CPUE)
• York River: Decreased minimally from 21 percent to 19.7 percent of goal achieved (decreased from 6.2 to 6.02 CPUE)
• James River: Remained below 1 percent of goal achieved (decreased from 100 to 25 shad passing Boshers Dam)

Additional Information

American Shad Restoration Goal

The restoration goal for American shad is an estimate of the spawning shad stock that can be supported with existing river blockages. The demographics and population dynamics of such a restored shad population are unknown and the potential response to harvest has not been explored. Therefore, attainment of the Chesapeake Bay restoration goals is not connected to fisheries management decisions regarding this species.

American shad are a coastal species. Therefore, the Atlantic States Marine Fisheries Commission (ASMFC) makes management decisions, such as the harvest moratorium and allowable bycatch.

Low shad abundance in the Bay and along the Atlantic coast is thought to be the partial result of bycatch issues in offshore fisheries (located in the Exclusive Economic Zone, or EEZ).

Susquehanna and James River Shad

The Susquehanna and James river counts are determined by fish passage data at York Haven and Boshers Dams, respectively.

• Assessment of the Susquehanna River changed from shad passage at Conowingo Dam to shad passage at York Haven Dam to reflect the goal of two million shad passing the York Haven Dam annually.
• On the James River, American shad passage at Boshers Dam is compared to a passage goal of 500,000 shad.

The Susquehanna River restoration goal of two million American shad above the York Haven Dam was developed for the 1981 FERC hearings during hydro-project relicensing.

• Research in the Connecticut and Columbia rivers estimated up to 50 American shad per acre during the spawning run.
• Acres of available spawning habitat in the Susquehanna River were estimated and then multiplied by 50 shad per acre.
• The resulting estimate of two million shad represents how many spawning shad can be supported above the York Haven Dam, assuming effective fish passage downstream.

The James River restoration goal of 500,000 American shad above Boshers Dam is based upon the number of shad that can be supported by the 137 miles (11,930 acres) of habitat that became available following construction of the Boshers Dam fishway.

• The number of acres was multiplied by 50 shad per acre, which is consistent with the Susquehanna River methodology and studies of the Connecticut and Columbia rivers.
• A total of 568,200 shad can be supported between Boshers Dam and Lynchburg, Virginia, including tributaries in between.
• The Boshers Dam fishway was sized to pass 500,000 shad annually.

York and Potomac River Shad

Values for the York and Potomac rivers are determined using gill-net data from the Virginia Institute of Marine Science and pound net bycatch and discard data from the Potomac River Fisheries Commission. To determine goal achievement, the 1950s commercial Catch per Unit Effort (CPUE) is compared to the current commercial (Potomac River pound net) or fishery-independent York River monitoring CPUE

Contact

Bruce Vogt
National Oceanic and Atmospheric Administration (NOAA)
(410) 267-5655