Chesapeake Bay Program



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Chesapeake Bay Program | Indicator Analysis and Methods Document

American Shad Abundance | Updated [5/4/2016]
Indicator Title: American Shad Abundance in the Chesapeake Bay
Relevant Outcome(s): N/A
Relevant Goal(s): N/A
Location within Framework (i.e., Influencing Factor, Output or Performance): N/A
A. Data Set and Source


  1. Describe the data set. What parameters are measured? What parameters are obtained by calculation? For what purpose(s) are the data used?

Used for long-term monitoring of American shad numbers in multiple regions of the Chesapeake Bay. Five tributaries are included in the indicator, each with their own target for American shad. Three different types of measurements are used among the tributaries. The Susquehanna River and the Upper James River measure actual number of American shad (and other fish) passed through fishways at the York Haven and Bosher's Dams, respectively. The Potomac River use American shad commercial pound net bycatch and discard data from the Potomac River Fisheries Commission as an index measured in catch per unit effort (CPUE). The York, Rappahannock, and lower James use gill net survey (fishery independent) data as an abundance index measured in CPUE. For each tributary, the percent achieved in relation to the tributary goal is calculated, and this is combined to calculate the percent of goal achieved for all 5 tributaries, referred to as the Baywide indicator. The contribution of each tributary is weighted based on area as a proxy for habitat availability.


  1. List the source(s) of the data set, the custodian of the source data, and the relevant contact at the Chesapeake Bay Program.

      • Source:

Fishway passage data was collected at York Haven Dam in Pennsylvania (PA FBC) and Bosher’s Dam in Virginia (VDGIF); Potomac River Fisheries Commission calculated catch-per-unit effort (CPUE) from Potomac River commercial pound net bycatch (landings) and discard data. VIMS calculated CPUE for the York, Rappahannock, and lower James from the VIMS staked gill net survey data.

      • Custodian: Source Data: Josh Tryninewski (PA FBC), Alan Weaver (VDGIF), Ellen Cosby (PRFC), Eric Hilton (VIMS).

      • Chesapeake Bay Program Contact (name, email address, phone number): Bruce Vogt (Bruce.Vogt@noaa.gov) and Emilie Franke (Emilie.Franke@noaa.gov).




  1. Please provide a link to the location of the data set. Are metadata, data-dictionaries and embedded definitions included?

Complete data sets for all five tributaries not available apart from information on Chesapeakebay.net website. The fish count for York Haven Dam (and other dams) on the Susquehanna River are published on the Pennsylvania Fish and Boat Commission website.

Information on the gill net survey, including the index data, used for the York, Rappahannock and lower James Rivers is published on the Virginia Institute of Marine Science website.

Information on the Bosher's Dam fishway is published on the Virginia Department of Game and Inland Fisheries website, but fish counts are not published.

The Potomac River Fisheries Commission pound net bycatch and discard index is not published on their website.



B. Temporal Considerations


  1. Data collection date(s): 2000-2015




  1. Planned update frequency (e.g., annual, biannual, etc.):

      • Source Data: annual

      • Indicator: annual




  1. Date (month and year) next data set is expected to be available for reporting: April 2017


C. Spatial Considerations


  1. What is the ideal level of spatial aggregation (e.g., watershed-wide, river basin, state, county, hydrologic unit code)? Tributary




  1. Is there geographic (GIS) data associated with this data set? If so, indicate its format (e.g., point, line polygon). The CBP GIS Team has a point data set for this indicator published on the indicator website in the form of a dynamic map. Users can click the polygon for each tributary to view the related data for that tributary.




  1. Are there geographic areas that are missing data? If so, list the areas.

Data from Maryland tributaries are not included in the indicator because restoration targets for American shad abundance has not been established for Maryland tributaries. Monitoring of American shad does occur in Maryland, and links to their juvenile survey data are provided on the dynamic map on the indicator webpage.


  1. Please submit any appropriate examples of how this information has been mapped or otherwise portrayed geographically in the past. The CBP GIS Team has a point data set for this indicator published on the indicator website in the form of a dynamic map. Users can click the polygon for each tributary to view the related data for that tributary.


D. Communicating the Data


  1. What is the goal, target, threshold or expected outcome for this indicator? How was it established?

This indicator includes shad monitoring data from five major river systems: the James, Potomac, Rappahannock, Susquehanna and York. The James River stock is tracked at two sites, Bosher's Dam and on the lower James. Each river system has its own numeric restoration target to meet or exceed (listed below). The target for the Potomac were established in accordance with the Atlantic States Marines Fisheries Commission, the target for the Susquehanna was established by Pennsylvania and the targets for the James, York and Rappahannock were established by Virginia.

  • James River:

    • Lower: 34.66 CPUE

    • Upper: 500,000 shad passing Bosher's Dam annually

  • Potomac River: 31.1 Catch per Unit Effort (CPUE) running average (see section 7b for further explanation)

  • Susquehanna River: Two million shad passing York Haven Dam annually

  • York River: 17.4 CPUE

  • Rappahannock: 7.85 CPUE

Shad are monitored in other areas of the Bay, including Maryland tributaries and the Upper Bay, but these data are not included in the indicator due to the absence of abundance goals for those areas.


New goals were established in 2013 for the Virginia tributaries (York, Rappahannock, Lower James). The previous goals were based on 1980s shad population targets; however it was determined that shad population levels were not optimal during this time. Based on catch data from the York River, new goals were established for the Virginia tributaries based on 1950s population levels, which were higher than 1980s levels. The ratio of 1980s York catch data to 1950s York catch data was used to estimate lower James and Rappahannock 1950s population levels to determine those tributary goals.


  1. What is the current status in relation to the goal, target, threshold or expected outcome?

38.8% of Baywide goal achieved in 2015.


  1. Has a new goal, target, threshold or expected outcome been established since the last reporting period? Why? No.




  1. Has the methodology of data collection or analysis changed since the last reporting period? How? Why?

No, methodology has not changed since the last reporting period.

Methodology did change in 2013. Data from the VIMS gill net survey was used to update the York River data and to add the lower James and Rappahannock to the indicator. Bosher's Dam and the lower James data are combined and weighted (Bosher's=45% and lower=55%) to get the overall James percent goal achieved. The Potomac, York Haven Dam, and Bosher's Dam data collection and analysis stayed the same.



The weighting scheme for the Baywide indicator was changed in 2013 from weighting by catch to weighting by watershed size. This new weighting scheme by watershed size is a proxy for available shad habitat. The tributaries are weighted as follows: Susquehanna=45%; Potomac=26%; York=5%; James=19%; Rappahannock=5%.
The addition of more tributaries improves the accuracy of the Baywide indicator as it includes data from more Bay tributaries. The revised tributary weighting scheme by watershed size is more accurate than weighting by catch data. As more tributaries are added to the indicator, the weighting scheme can be easily revised to incorporate the new tributary watershed area.
In 2015, the Shad Indicator team began exploring the possibility of adding new data for the Upper Bay and adding additional data to support the Potomac data. The team will continue to discuss new data sources in 2016.


  1. What is the long-term data trend (since the start of data collection)?

The data collection spans 2000-2015. The trend varies among rivers:

  • Bay-wide: As a whole, the Chesapeake Bay American shad indicator increased from 10.7% in 2000 to 44.3% of the goal in 2014 before decreasing to 38.8% of the goal in 2015. The shad abundance index trend in the Potomac Rivers is responsible for driving the overall upward Bay-wide trend, since shad passage at York Haven and Bosher's dams remains negligible, and since shad abundance index trends on the York, Rappahannock, and lower James are variable. The decreases in the index values for the Lower James, Rappahannock and York contributed to a decrease in 2015. Extremely low American shad passages at the York Haven and Bosher's dams continue to be seen.

  • James River: Abundance has been variable, with a peak of about 14% in both 2003 and 2011 and a low of about 2% in 2015, the lowest value in the 2000-2015 time series. Abundance index trends for the James River are a weighted combination of the Bosher's Dam (45%) and lower James (55%) data. Fish passage at Bosher’s Dam has remained negligible at less than 1% of the goal for the time series, while the lower James shows fluctuations between 4-25% of the goal. In 2015, Bosher’s Dam remained below 1% and the lower James hit its lowest point of 3.6%.

  • Potomac River: Unlike the other rivers, the Potomac’s abundance measurement is a running geometric mean calculated for all years since 1999. These data show that the abundance index has steadily increased over the past 15 years from 26.0% in 2000 to 133.1% of the goal in 2015.

  • Rappahannock River: Shad abundance index has largely fluctuated with multiple peaks and valleys. Index values peaked in 2014 at 110.3% of the goal then dropped to 64.7% of the goal in 2015. Its lowest values were in 2000 at 22.3% and 2010 at 25.9%.

  • Susquehanna River: Fish passage has remained minimal at less than 1 percent of the goal, including in 2015. Of the thousands of shad that pass Conowingo Dam, very few reach and pass York Haven Dam, above which is optimal spawning habitat.

  • York River: Shad abundance index values have largely fluctuated with multiple peaks and valleys. Abundance index values reached peaks in 2001 at 74.4% of the goal and 2014 at 57.7% of the goal. 2015 had the lowest reported index value at just 11.1% of the goal.




  1. What change(s) does the most recent data show compared to the last reporting period? To what do you attribute the change? Is this actual cause or educated speculation?

From 2014 to 2015:

  • Bay-wide: Decrease from 44.3% to 38.8% of goal achieved.

  • James River: Decreased from to 11.6% to 2.0% of goal achieved. This overall James River decrease increase resulted from the Lower James decrease from 21.2% to 3.6% of goal achieved (7.35 to 1.25 CPUE), and from Bosher's Dam remaining below 1% (0.01%) of goal (68 American shad passed Bosher's Dam in 2015 out of 500,000 goal).

  • Potomac River: Increased from 129.6% to 133.1% of goal achieved (40.3 to 41.4 CPUE).

  • Rappahannock River: Decreased from 110.3% to 64.7% of goal achieved (8.66 to 5.08 CPUE).

  • York River: Decreased from 57.7% to 11.1% of goal achieved (10.06 to 1.93 CPUE)

  • Susquehanna River: Remained below 1% (0.002%) of goal (0 achieved (43 American shad passed York Haven Dam out of 2,000,000 goal).

Cannot point to a specific cause. American shad population remains very low and faces many challenges.

  1. What is the key story told by this indicator?

While some progress has been made in restoring shad to the Chesapeake Bay, there is a long way to go to achieve restoration goals. The increase of American shad in the Potomac River seen in the indicator is responsible for the overall increase in of the indicator's % goal achieved. However, if the current trends continue then the shad indicator will decline and stabilize at a lower percent of the goal. At that point, further increases for attainment of the restoration goal can only occur if American shad abundance begins to increase in the other river systems.

Several challenges persist for restoration of American shad. American shad use the Chesapeake Bay for spawning and nursery habitat, and reside along the Atlantic Coast outside the Bay for most of their life. If the shad abundance trend reverses from increasing to decreasing, this suggests that there may be factors external to Chesapeake Bay such as predation influences and/or bycatch in coastal fisheries affecting American shad. As seen in the indicator, fish passage of American shad at Bosher's and York Haven dams are still extremely low.



The number of shad passed at the York Haven and Bosher’s dams and the CPUE of shad caught via gill net (York River) and pound net (Potomac River) are long term datasets that can be used for comparison with data from previous time periods. The data trends inform managers where efforts have been successful further study and restoration efforts are needed. Furthermore, these data are collected for other multi-jurisdictional management needs making these monitoring efforts relatively cost effective.

E. Adaptive Management


  1. What factors influence progress toward the goal, target, threshold or expected outcome?

Several challenges persist for restoration of American shad. American shad use the Chesapeake Bay for spawning and nursery habitat, and reside along the Atlantic Coast outside the Bay for most of their life. If the shad abundance trend reverses from increasing to decreasing, this suggests that there may be factors external to Chesapeake Bay such as predation influences and/or bycatch in coastal fisheries affecting American shad. As seen in the indicator, fish passage of American shad at Bosher's and York Haven dams are still extremely low..

  1. What are the current gaps in existing management efforts?

Management is coordinated by the Atlantic States Marine Fisheries Commission. Chesapeake Bay jurisdictions conduct monitoring and shad hatchery and stocking efforts.

  1. What are the current overlaps in existing management efforts? N/A




  1. According to the management strategy written for the outcome associated with this indicator, how will we (a) assess our performance in making progress toward the goal, target, threshold or expected outcome, and (b) ensure the adaptive management of our work? N/A


F. Analysis and Interpretation

Please provide appropriate references and location(s) of documentation if hard to find.


  1. What method is used to transform raw data into the information presented in this indicator? Please cite methods and/or modeling programs. Contact Data Custodians listed in question 2 of this document.




  1. Is the method used to transform raw data into the information presented in this indicator accepted as scientifically sound? If not, what are its limitations? N/A




  1. How well does the indicator represent the environmental condition being assessed? The indicator represents the best available survey data that are collected annually in the Chesapeake Bay. The indicator lacks data for the Upper Bay because there are no established restoration targets for that area.




  1. Are there established reference points, thresholds, ranges or values for this indicator that unambiguously reflect the desired state of the environment?

1950s population level estimates are the targets for the Potomac, York, Rappahannock, and lower James Rivers. Fish passage count goals previously established by Pennsylvania and Virginia are the targets for the York Haven Dam and Bosher's Dam respectively.


  1. How far can the data be extrapolated? Have appropriate statistical methods been used to generalize or portray data beyond the time or spatial locations where measurements were made (e.g., statistical survey inference, no generalization is possible)? Yes, appropriate statistical methods have been used.


G. Quality

Please provide appropriate references and location(s) of documentation if hard to find.


  1. Were the data collected and processed according to a U.S. Environmental Protection Agency-approved Quality Assurance Project Plan? If so, please provide a link to the QAPP and indicate when the plan was last reviewed and approved. If not, please complete questions 29-31. No.




  1. If applicable: Are the sampling, analytical and data processing procedures accepted as scientifically and technically valid?

Yes. See question 30 for links to information from the state agencies that provide the data.


  1. If applicable: What documentation describes the sampling and analytical procedures used?

  • 2007 ASMFC Shad Stock Assessment

  • VIMS Shad Monitoring

  • Susquehanna Passage

  • Bosher's Dam Fish Passage http://www.dgif.virginia.gov/fishing/fish-passage/#boshers



  1. If applicable: To what extent are procedures for quality assurance and quality control of the data documented and accessible?

Complete data sets for all five tributaries not available apart from information on Chesapeakebay.net website. The fish count for York Haven Dam (and other dams) on the Susquehanna River are published on the Pennsylvania Fish and Boat Commission website.

Information on the gill net survey, including the index data, used for the York, Rappahannock and lower James Rivers is published on the Virginia Institute of Marine Science website.

Information on the Bosher's Dam fishway is published on the Virginia Department of Game and Inland Fisheries website, but fish counts are not published.

The Potomac River Fisheries Commission pound net bycatch and discard index is not published on their website.




  1. Are descriptions of the study design clear, complete and sufficient to enable the study to be reproduced? Yes.




  1. Were the sampling, analytical and data processing procedures performed consistently throughout the data record? Yes.




  1. If data sets from two or more sources have been merged, are the sampling designs, methods and results comparable? If not, what are the limitations? See responses to questions 1 and 2 of this document for a description of the different data sets used to form this indicator.




  1. Are levels of uncertainty available for the indicator and/or the underlying data set? If so, do the uncertainty and variability impact the conclusions drawn from the data or the utility of the indicator? N/A




  1. For chemical data reporting: How are data below the MDL reported (i.e., reported as 0, censored, or as < MDL)? If parameter substitutions are made (e.g., using orthophosphate instead of total phosphorus), how are data normalized? How does this impact the indicator? N/A




  1. Are there noteworthy limitations or gaps in the data record? No, however the data time series began in 2000 which is a relatively short period of time. Also, he indicator lacks data for the Upper Bay because there are no established restoration targets for that area.


H. Additional Information (Optional)


  1. Please provide any further information you believe is necessary to aid in communication and prevent any potential misrepresentation of this indicator.

The goals for the Potomac, York, Rappahannock, and lower James Rivers are based on 1950s population levels. Catch data for this period is available for the Potomac and York Rivers, but not for the Rappahannock and lower James. The ratio of the York 1980s data the 1950s data was calculated, and this ratio was used to back calculate 1950s catch indices from available Rappahannock and lower James 1980s data. The major assumption is that the lower James and Rappahannock showed the same declining trend as the York from the 1950s to the 1980s.
The dynamic map on the indicator web page includes links to spreadsheets for each jurisdiction on shad stocking and restoration efforts in other tributaries throughout the Bay, including tributaries that are not included in the indicator calculations.




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