OCS Study

BOEM 2020-030

US Department of the Interior

Bureau of Ocean Energy Management

Environmental Studies Program

Movement and Habitat Selection by 

Migratory Fishes within the Maryland 

Wind Energy Area and Adjacent 

Reference Sites
OCS Study

BOEM 2020-030

US Department of the Interior

Bureau of Ocean Energy Management

Environmental Studies Program

Movement and Habitat Selection by 

Migratory Fishes within the Maryland 

Wind Energy Area and Adjacent 

Reference Sites

February 2020 

Authors:

David Secor, Michael O’Brien, Ella Rothermel, Caroline Wiernicki, and Helen Bailey 

Prepared under BOEM Award 

Cooperative Agreement M16AC00008

by 

University of Maryland Center for Environmental Science 

Office of Research Administration and Advancement

P.O. Box 775 

2020 Horns Point Road

Cambridge, MD 21613-0775
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DISCLAIMER

Study collaboration and funding were provided by the US Department of the Interior, Bureau of Ocean 

Energy Management (BOEM), Office of Renewable Energy Programs, Sterling, VA, under Agreement 

Number M16AC00008. This report has been technically reviewed by BOEM, and it has been approved 

for publication. The views and conclusions contained in this document are those of the authors and should 

not be interpreted as representing the opinions or policies of the US Government, nor does mention of 

trade names or commercial products constitute endorsement or recommendation for use.

REPORT AVAILABILITY

To download a PDF file of this report, go to the US Department of the Interior, Bureau of Ocean Energy 

Management Data and Information Systems webpage (http://www.boem.gov/Environmental-StudiesEnvData/), click on the link for the Environmental Studies Program Information System (ESPIS), and 

search on 2020-030. The report is also available at the National Technical Reports Library at 

https://ntrl.ntis.gov/NTRL/.

CITATION

Secor D, O’Brien M, Rothermel E, Wiernicki C, Bailey H. 2020. Movement and habitat selection by 

migratory fishes within the Maryland Wind Energy Area and adjacent reference sites. Sterling 

(VA): U.S. Department of the Interior, Bureau of Ocean Energy Management, Office of 

Renewable Energy Programs. OCS Study BOEM 2020-030. 109 p.

ABOUT THE COVER

Cover photos taken by Mike O’Brien and Ella Rothermel.

ACKNOWLEDGMENTS

E. Rothermel (UMCES) drafted this Final Report. The following BOEM offices or programs contributed to 

this document: Office of Renewable Energy Programs. We thank project officer B. Hooker at BOEM for 

his assistance with funding administration and study guidance throughout this project. We acknowledge 

Environmental Studies Chief M. Boatman for her helpful comments on an earlier draft of this report. We 

are grateful to the numerous Atlantic Coastal Telemetry network scientists who shared transmitter data. In 

particular, we thank D. Haulsee, M. Oliver, M. Breece, and D. Fox at University of Delaware and 

Delaware State University for their willingness to share data and discuss study design elements. We must 

also acknowledge B. Gahagan (MA Division of Marine Fisheries), and A. Higgs and J. Best (NY State 

Dept. Environmental Conservation) for their cooperation with striped bass tagging efforts. We also thank 

Cory and Kerry Harrington of the F/V Sea Born and Michael Hulme and Robert Nilsen of the R/V Rachel 

Carson (UMCES) for their assistance with acoustic receiver array deployment and maintenance.
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Contents

List of Figures............................................................................................................................................... iv

List of Tables................................................................................................................................................vii

List of Abbreviations and Acronyms............................................................................................................viii

1 Introduction ...........................................................................................................................................3

1.1. Statement of Purpose..................................................................................................................3

2 Background...........................................................................................................................................3

2.1 Wind energy development in the Middle Atlantic Bight ...............................................................3

2.2 Review of wind energy development impact studies on migratory fishes ...................................4

2.3 Rationale for baseline telemetry study and gradient design........................................................4

2.4 Introduction to test species: Atlantic sturgeon and striped bass .................................................5

2.5 Introduction to MD WEA physical and ecological setting ............................................................6

2.6 Study hypotheses and objectives ................................................................................................6

3 Design and Methods .............................................................................................................................7

3.1 MD WEA telemetry array design .................................................................................................7

3.2 BOEM consultation and changes to study design.......................................................................8

3.3 Telemetry receiver deployments, maintenance, and database management.............................8

3.4 Receiver range testing...............................................................................................................10

3.5 Striped bass transmitters...........................................................................................................14

3.6 Atlantic sturgeon transmitters ....................................................................................................17

3.7 Environmental data sources: temperature, wind, storms, noise, bottom characteristics ..........17

3.8 Data analysis .............................................................................................................................18

3.8.1 Seasonal incidence ...............................................................................................................18

3.8.2 Transit rates and patterns .....................................................................................................18

3.8.3 Distribution and depth of occurrence for tagged striped bass...............................................19

3.8.4 Environmental covariates of MD WEA incidence..................................................................19

3.9 Predictive habitat models...........................................................................................................20

3.9.1 Daily relative abundance model ............................................................................................20

3.9.2 Environmental and individual drivers of weekly residency....................................................21

4 Results ................................................................................................................................................22

4.1 Database guidance and total detection summary .....................................................................22

4.2 Receiver range testing...............................................................................................................26

4.2.1 Modeled frequency of detection ............................................................................................31

4.3 Study site benthic characteristics and bottom type ...................................................................33
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4.4 Study site seasonal temperature changes ................................................................................36

4.5 Study site ambient noise levels .................................................................................................37

4.6 Seasonal incidence....................................................................................................................38

4.7 Transit rates and patterns..........................................................................................................42

4.8 Distribution and depth of occurrence for tagged striped bass...................................................48

4.9 Environmental covariates of MD WEA incidence ......................................................................52

4.10 Predictive habitat models...........................................................................................................56

4.10.1 Daily relative abundance model........................................................................................56

4.10.2 Environmental and individual drivers of weekly residency................................................65

5 Discussion...........................................................................................................................................72

5.1 Migration through the MD WEA.................................................................................................72

5.2 Functional habitat attributes of the MD WEA.............................................................................74

5.3 Spatial and temporal patterns of habitat use by test species....................................................76

5.4 Study design limiting assumptions ............................................................................................77

5.5 Prediction of migratory habitat use in the MD WEA ..................................................................77

6 Conclusions and Recommendations ..................................................................................................78

6.1 Overview findings related to functional habitat attributes of the MD WEA................................78

6.2 Recommendation related to timing and location of potential impacts and benefits of wind tower 

construction within the MD WEA.............................................................................................................79

6.3 Recommendation for future studies to build on the current baseline study ..............................79

7 Research Products..............................................................................................................................79

7.1 Presentations.............................................................................................................................79

7.2 Outreach ....................................................................................................................................81

7.3 Theses .......................................................................................................................................81

7.4 Publications ...............................................................................................................................81

8 References..........................................................................................................................................82

Appendix A: Cruise Reports........................................................................................................................92
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List of Figures

Figure 1. BOEM Lease Areas .......................................................................................................................4

Figure 2. Acoustic receiver array design.......................................................................................................8

Figure 3. VEMCO VR2AR Acoustic Release receiver, transponder and deck box......................................9

Figure 4. Acoustic Release receiver detection (left) and acoustic release mooring design (right).............10

Figure 5. Range test transect schematic. ...................................................................................................11

Figure 6. Summary incidence of all species detected in the MD WEA throughout the study.....................26

Figure 7. Box-whisker plots of the frequency of detection for Inner and MD WEA arrays in the AutumnWinter 2018 (A), Spring-Summer 2018 (B), and Autumn-Winter 2019 (C) seasons..................................28

Figure 8. Modeled 50% detection distance (black line) and 95% population prediction interval (gray band) 

at the Inner and MD WEA study sites.........................................................................................................29

Figure 9. Principal component analysis of daily mean records (points) of environmental variables (arrows) 

to be used in a predictive detection range model. ......................................................................................30

Figure 10. GAM-predicted proportional daily detections (contours) for combinations of 69 kHz ambient 

noise and ΔT at 250, 500, and 800 meters from source.............................................................................32

Figure 11. Results of modeled range test predictions for the entire time series of the study (November 

2016 - December 2018), ordered by stratum..............................................................................................33

Figure 12. Bathymetry and benthic characteristics surrounding acoustic telemetry array receiver sites...35

Figure 13. Mean hourly bottom temperature (°C) for each receiver in the Inner (pink), MD WEA (green), 

and Outer (blue) strata of the current array. ...............................................................................................36

Figure 14. Daily ΔT in the Inner, MD WEA, and Outer arrays from November 11, 2016 through December 

5, 2018. .......................................................................................................................................................37

Figure 15. Average daily noise level (mV) for the Inner (pink), MD WEA (green), and Outer (blue) strata.

....................................................................................................................................................................38

Figure 16. Seasonal occurrence of Atlantic sturgeon. ................................................................................39

Figure 17. Patterns of Atlantic sturgeon incidence throughout the study period. .......................................40

Figure 18. Seasonal occurrence of striped bass. .......................................................................................41

Figure 19. Patterns of striped bass incidence throughout the study period................................................42

Figure 20. Boxplot of total hours present in the array.................................................................................44

Figure 21. Boxplot of total days present in the array. .................................................................................45

Figure 22. Summary of transit information for striped bass ........................................................................47

Figure 23. Locations of depth-transponding striped bass tag detections. ..................................................49

Figure 24. Summary of depth-transponding striped bass returns. .............................................................49
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Figure 25. Depth of detection (meters) of individually-tagged striped bass through time. .........................50

Figure 26. Density of tagged striped bass depths (in meters) by telemetry array. .....................................51

Figure 27. Depth of striped bass detection by transect within the MD WEA receiver array. ......................52

Figure 28. Hot spots of species occurrence across the acoustic receiver array. .......................................53

Figure 29. Density of detections by receiver-recorded temperature...........................................................54

Figure 30. QI plots for Atlantic sturgeon during each season.....................................................................55

Figure 31. QI plots for striped bass during each season ............................................................................55

Figure 32. GAMM Summed effects of the magnitude of sea surface temperature change over the 

previous 4 days (SST Δ4; top) and chlorophyll-a concentration (CHL-A; bottom) on the relative 

abundance of Atlantic sturgeon. .................................................................................................................58

Figure 33. GAMM response function for the interaction between day-of-year and depth from the best 

model of Atlantic sturgeon relative abundance...........................................................................................59

Figure 34. Summary plots for Atlantic sturgeon relative abundance model temporal residuals.................60

Figure 35. Semi-variogram of residuals from best Atlantic sturgeon relative abundance model using 

latitude and longitude to calculate distance between sites.........................................................................61

Figure 36. GAMM Summed effects of magnitude of sea surface temperature change over the previous 17 

days (SST Δ17; top) and chlorophyll-a concentration (CHL-A; bottom) on the relative abundance of 

striped bass.................................................................................................................................................62

Figure 37. GAMM response function for the interaction between day-of-year and depth from the best 

model of striped bass relative abundance. .................................................................................................63

Figure 39. Semi-variogram of residuals from best striped bass relative abundance model using latitude 

and longitude to calculate distance between sites......................................................................................65

Figure 40. Atlantic sturgeon: GAMM partial effects for sea surface temperature (SST, left), week-of-year 

(right)...........................................................................................................................................................67

Figure 41. Striped bass: GAMM partial effects for sea surface temperature (SST, top left), week-of-year 

(top right), and chlorophyll-a concentration (CHL-A, bottom left). ..............................................................68

Figure 42. Predicted residency function (days per week ± 2 se) of Atlantic sturgeon for each tagging 

region based on the sea surface temperature (SST) across the MD WEA................................................69

Figure 43. Predicted residency function (days per week ± 2 se) of Atlantic sturgeon in the MD WEA array 

for each tagging region based on week-of-year. ........................................................................................70

Figure 44. Predicted residency function (days per week ± 2 se) of striped bass for each tagging region 

based on the sea surface temperature (SST) across the MD WEA. ..........................................................71

Figure 45. Predicted residency function (days per week ± 2 se) of striped bass in the MD WEA array for 

each tagging region based on week-of-year...............................................................................................71

Figure 46. Predicted residency function (days per week ± 2 se) of striped bass in the MD WEA array for 

each tagging region based on chlorophyll-a concentration (CHL-A). .........................................................72
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Figure 47. Conceptual diagram of seasonal MAB distribution for Atlantic sturgeon...................................73

Figure 48. Conceptual diagram of seasonal MAB distribution for striped bass..........................................74
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List of Tables

Table 1. Metadata of variables to be used in the predictive detection range model. .................................13

Table 2. List of active acoustic transmitters associated with large research projects on striped bass and 

Atlantic sturgeon during the period of the proposed study. ........................................................................15

Table 3. Tagged striped bass information...................................................................................................16

Table 4. Summary of intended purpose and modeling approach for each research question...................21

Table 5. Total species detected and PIs contacted during receiver array deployment period...................23

Table 6. Summary of proportional detection within the deployed range test arrays...................................27

Table 7. Seasonal and spatial differences in Atlantic sturgeon incidence..................................................39

Table 8. Seasonal and spatial differences in striped bass incidence. ........................................................41

Table 9. Number of Strata visited by each individual striped bass and Atlantic sturgeon during each 

season and year..........................................................................................................................................43

Table 10. Striped bass transit rate linear mixed model results...................................................................48

Table 11. Summary of GAMM model formulas for the top ten predictive models for each species...........56

Table 12. Parameter and pairwise factor comparison significance for weekly species residency GAMMs.

....................................................................................................................................................................66
viii

List of Abbreviations and Acronyms

ACF Autocorrelation Function

ACT Atlantic Cooperative Telemetry Network

ARIMA Autoregressive Integrated Moving Average

BACI Before-After-Control-Impact

BAG Before-After-Gradient

BOEM Bureau of Ocean Energy Management

CHL-A Chlorophyll-a

CI Confidence Interval

D50 Distance at 50% frequency of detection

DE WEA Delaware Wind Energy Area

DOY Day-of-Year

DPD Detection-Positive Day

ERDDAP Environmental Research Division's Data Access Program

GAM Generalized Additive Model

GAMM Generalized Additive Mixed Model

HGAM Hierarchical Generalized Additive Model

MAB Middle Atlantic Bight (US)

MD WEA Maryland Wind Energy Area

PACF Partial Autocorrelation Function

QI Quotient Index

RMSE Root Mean Square Error

SST Sea Surface Temperature

ΔT Delta T, Sea Surface Temperature-Bottom Temperature

UMCES University of Maryland Center for Environmental Science
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EXECUTIVE SUMMARY

Wind farms within inner shelf regions of the southern Mid-Atlantic Bight (DelMarVa region) will greatly 

increase the amount of structured habitat for coastal fishes. Installed wind turbines present permanent 

(decades) impervious structures, which can alter movement behaviors by fishes and the fisheries 

associated with impacted species. Fish concentrations surrounding oil rigs are but one example of how 

artificial structures can influence both fish and fisheries. We hypothesized that many coastal migratory 

fishes currently use southern Mid-Atlantic Bight shelf waters as a migration corridor, but that fields of 

wind turbines in this relatively “featureless” region could alter behaviors of migratory fishes causing them 

to dwell on high relief wind turbine structures.

The objective of this project was to measure seasonal transit and habitat occurrence of striped bass and 

Atlantic sturgeon in relation to depth, temperature, and other oceanographic and benthic variables in and 

adjacent to the Maryland Wind Energy Area (MD WEA). We used biotelemetry deployed in a beforeafter-gradient design centered in the Maryland Wind Energy Area to gather baseline measures of seasonal 

patterns of migration by Atlantic sturgeon and striped bass and model their incidence against gradients of 

depth, temperature, and other oceanographic variables. This study leverages recent and concurrent 

telemetry studies in NW Atlantic shelf regions and the availability of hundreds of acoustically-tagged 

striped bass and Atlantic sturgeon. Specific objectives included (1) two-year deployment of an extensive 

telemetry receiver array within the MD WEA and adjacent shelf reference regions; (2) analysis of patterns 

of incidence, transit, and depth; (3) development of predictive habitat models for the MD WEA shelf 

region; and (4) extensive data sharing through the Atlantic Cooperative Telemetry Network and the MidAtlantic Telemetry Observing System.

In triannual cruises beginning November 2016 and ending December 2018, we deployed, maintained, and 

retrieved 20 VEMCO VR2AR Acoustic-Release receivers in the test MD WEA array. We deployed 

additional receivers at two sites to test receiver detection distances for the period December 2017-

December 2018 under different oceanographic conditions. To augment tagged coastal striped bass 

available for detection, 40 large striped bass were surgically implanted with depth-transponding 

transmitters. Environmental data for the array was compiled from receiver-logged bottom temperature 

and noise levels and from NOAA buoys, and remote sensing platforms. Patterns of seasonal species 

incidence and environmental dynamics were analyzed together with transit rates between the MD WEA 

and DE Wind Energy Area. Incidence data was transformed into relative density based on modelled 

detection probability across seasons and strata. Generalized Additive Mixed Models were developed to 

predict the relative density and weekly residence of striped bass and Atlantic sturgeon based on 

environmental features of the MD WEA. Our main findings were:

• Atlantic sturgeon and striped bass occurred extensively in the MD WEA, with seasonal incidence 

supporting the hypothesis that the MD WEA occurred within migration corridors for both species. 

Detections of Atlantic sturgeon occurred throughout autumn and early winter and throughout 

spring and early summer. Striped bass occurrence was more concentrated during winter months 

and brief during spring. Within these periods of occurrence:

o Atlantic sturgeon were at mid-range depths in the MD WEA during autumn, but occurred 

in shallower regions within and outside the MD WEA in spring.

o Striped bass broadly utilized the MD WEA cross-shelf region during spring, and were 

more abundant in deeper areas during winter.
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• Hot spots of individual occurrence did not reveal singular areas of intensive use. Detections for 

both species showed stronger association with cross-shelf depth and environmental gradients 

rather than specific seabed characteristics.

• Temperature was a strong driver of striped bass incidence patterns. Detections occurred within a 

narrow range of 5-15°C. Striped bass shifted toward greater depths during winter as shelf 

temperatures cooled to avoid the colder inshore temperatures. Atlantic sturgeon showed broader 

temperature tolerance, 4-24°C, selecting warmer temperatures than striped bass.

• Both species were relatively transient in the array, with mean detection durations of 1.6 and 2.5 

days respectively for individual Atlantic sturgeon and striped bass. However, striped bass tended 

to spend more time in the area during winter months (mean= 3.06 days), which could suggest this 

shelf region functions as overwintering habitat in some years.

• Habitat models were complex owing to concurvity among fitted oceanographic terms, but 

provided strong explanatory power for species abundance and residency. Model performance was 

markedly improved through inclusion of changes in daily telemetry detection ranges. Predictions 

reinforced the importance of depth and temperature variables, and their interactions with season, 

in determining species distribution. 

The cross-shelf telemetry sampling design allowed key inferences in the MD WEA as a key migration 

corridor habitat pertinent to likely impacts of wind energy development. Summer-time wind turbine 

construction would minimize interactions with both test species: striped bass and Atlantic sturgeon. 

During fall, winter and spring striped bass distributions centered within the footprint of the MD WEA, 

whereas Atlantic sturgeon would overlap with inshore transmission lines. Detections of many other 

tagged species occurred in the MD WEA throughout the year, which will also need due consideration in 

Construction and Operation Planning. 

The telemetry gradient design is well suited for evaluating impacts of wind farm development across 

WEAs in the Mid-Atlantic Bight and Southern New England, which together comprises a multispecies 

“flyway.” Cooperation among researchers, expanded scale of acoustic telemetry arrays, and increased 

incorporation of oceanographic variables, physiological data, and individual characteristics will all serve 

to improve understanding of how fishes will respond to wind energy development in the US NW Atlantic 

Ocean.
3

1 Introduction

1.1. Statement of Purpose

Recent increases in the reliability, cost-effectiveness, and widespread use of acoustic biotelemetry 

provides a timely opportunity to evaluate population-level responses by migratory species to wind energy 

development. At present, limited information is available on the fine-scale seasonal patterns of 

distribution and abundance of migratory fishes in and around offshore wind energy areas. This 

information is necessary for BOEM and developers to meet their obligations under the National 

Environmental Policy Act, the Endangered Species Act, and the Magnuson-Stevens Fishery Conservation 

and Management Act. These considerations are of particular importance for protected species, such as the 

Endangered Atlantic sturgeon, and commercially important ones, such as striped bass. Information on the 

seasonal occurrence of migratory species within wind lease areas will help minimize potential impacts of 

turbine construction and provide a baseline with which to compare future changes in migration behavior 

and habitat selection during the decades following construction (Bailey et al. 2014, Petruny-Parker et al. 

2015). In this study, we have used acoustic telemetry to characterize the seasonal distribution, habitat 

selection, and migratory patterns of Atlantic sturgeon and striped bass in the Maryland Wind Energy Area 

(MD WEA) along gradients of depth, temperature, and other oceanographic variables.

2 Background

2.1 Wind energy development in the Middle Atlantic Bight

Motivated to promote offshore wind energy and thereby reduce carbon emissions (White House 2013), 

BOEM and state actions have resulted in industrial leases of large Wind Energy Areas (WEAs) in MidAtlantic and other federal waters (Figure 1). As an example, US Wind Inc. was competitively awarded 

two lease areas - since combined into one lease area - comprising the entire Maryland WEA (Figure 1). 

This area, c. 36,000 ha in extent, could support >100 turbines, and produce sufficient energy to sustain 

hundreds of thousands of households (DOI 2014). WEAs have been sited to reduce marine use conflicts 

including shoreline vistas, commercial navigation and fishing, recreational fishing, artificial reefs (e.g., 

fish havens), historical sites (e.g., wrecks), and restricted military areas 

(http://portal.midatlanticocean.org/). Ecological impacts are another central concern to siting and 

development of WEAs (McCann 2012; Petruny-Parker et al. 2015). 
4

Figure 1. BOEM Lease Areas

WEAs within US Mid-Atlantic and NY Bight federal waters (left; as of 2018), and inset showing the MD WEA (blue) 

and DE WEA (green). The MD WEA is located 16-46 km offshore in depths ranging 12-35 m. Lease area shape files 

obtained from BOEM.

2.2 Review of wind energy development impact studies on migratory 

fishes

The future construction and maintenance of offshore wind energy farms are hypothesized to cause several 

classes of ecological impacts to migratory fishes in the US Mid-Atlantic Bight (MAB) shelf ecosystem. 

During the construction of wind turbines, the noise associated with pile driving and vessel traffic could 

lead to physiological stress, avoidance, or evacuation of the area by fishes (Thomsen et al. 2006; Popper 

and Hastings 2009; Gill et al. 2012). The operation of wind turbines could also create broader adverse 

impacts to the MAB through altered electromagnetic fields, pollution from vessel traffic, or release of 

contaminants from the seabed (Gill 2005; Westberg and Lagenfelt 2008; Boehlert and Gill 2010; 

Normandeau et al. 2011). Positive impacts may also occur. The shelf region of the MAB is commonly 

described as a relatively homogenous and flat seabed habitat, composed primarily of soft sediments 

(Stumf and Biggs 1988; Poppe et al. 1994). Wind turbines will create novel vertical structure throughout 

the water column, a feature which has been known to attract fish aggregations. Small fish and 

invertebrates often school around structures such as submerged oil and gas rigs both to forage on 

encrusting organisms and to obtain refuge from predators (Boehlert and Gill 2010). Larger fish can be 

attracted to such aggregations, creating a chain of effects that can alter local foodwebs (Wilhelmsson et al. 

2006; Inger et al. 2009; Bergström et al. 2013).

2.3 Rationale for baseline telemetry study and gradient design

We employed an in-situ gradient design centered on the MD WEA to measure seasonal patterns of 

incidence by Atlantic sturgeon, striped bass, and other migratory fishes. The complex spatial and 
5

temporal impacts of planned offshore wind energy farms on mobile fauna can be best understood through 

the use of a Before-After-Gradient (BAG) study design. BAG designs are an extension of the classical 

Before-After-Control-Impact (BACI) approach (Green 1979). Although BACI designs are traditionally 

used in environmental impact studies, these methods can have confounding assumptions related to the 

scale of effect and selection of reference sites. The gradient-based extension of the BACI approach 

largely resolves these issues by considering the distance of sampled sites from the area of impact (Bailey 

et al. 2014). The BAG design still incorporates the before-after elements of BACI to control for temporal 

confounders, but eliminates the issue of arbitrary control site selection by taking samples along a gradient 

of distance from the impact stratum. Gradient-based designs incorporate the spatial scale of impacts and 

have been proven to be more effective for detecting changes due to environmental disturbance than 

classical randomized Control Impact designs (Ellis and Schnieder 1997). Additionally, in this study, the 

BAG approach permits collection of data across the environmental gradients likely to influence the 

movements of striped bass and sturgeon (Cushman et al. 2010, Alvarez-Berastegui et al. 2014). By 

gathering information across biologically relevant spatiotemporal gradients, the BAG study design lends 

itself to the development of predictive oceanographic models of species occurrence that can help inform 

management decisions and assess long-term impacts.

2.4 Introduction to test species: Atlantic sturgeon and striped bass

This baseline study focused on striped bass and Atlantic sturgeon, both of which represent indicator 

species in evaluating the impact of offshore wind farms on migratory fishes owing to, (1) seasonal 

migration behaviors, which cause them both to frequently occur in Mid-Atlantic WEAs; (2) public and 

management priorities related to their recovery from endangered status (Atlantic sturgeon) and 

importance to commercial/recreational fisheries (striped bass); and (3) the fact that these species comprise 

the majority of acoustic-tagged fish currently active within US Middle Atlantic Bight (MAB) shelf 

waters. 

Atlantic sturgeon Acipenser oxyrhynchus are a large, long-lived, anadromous demersal species that range 

widely in the Northwest Atlantic (Florida to Quebec). Generally, adult Atlantic sturgeon undertake largescale coastal migrations north in the spring and south in the fall and winter. Recent biotelemetry 

applications have provided key insights into the coastal migrations of Atlantic sturgeon. Once sturgeon 

reach maturity, they remain largely in shelf waters and in the mouths of estuaries for foraging until they 

progress into natal rivers to spawn (Dunton et al. 2012; Breece et al. 2016). Evidence has shown that 

Atlantic sturgeon tend to remain in areas relatively shallow and close to shore (10-50 m in depth) in the 

MAB, with a slightly broader shelf distribution in spring compared to autumn (Stein et al. 2004; Laney et 

al. 2007; Erickson et al. 2011). Some fish have been captured in depths up to 75 m (Colette and Klein‐

MacPhee 2002). Atlantic sturgeon aggregate at specific coastal features, such as the mouths of major 

estuaries, and that individual fish are more likely to be found over sand or gravel rather than silt or clay 

substrates (Bain et al. 2000; Stein et al. 2004; Laney et al. 2007). 

Similar to Atlantic sturgeon, the striped bass Morone saxatilis spawns in tidal freshwater and undertakes 

extensive migrations; however, striped bass are highly mobile pelagic and epi-demersal predators that 

exhibit complex and diverse movement patterns. Striped bass are also known to exhibit high levels of 

maneuverability around structure and are particularly adept at capturing prey in such environments, which 

may cause them to be attracted to structured habitat (Buckel et al. 2009). While some individuals remain 

in estuaries their entire lives, certain population contingents migrate into coastal waters from St. 

Lawrence, Quebec to Cape Hatteras, North Carolina (Secor 1999; Gahagan et al. 2015). Generally, MidAtlantic striped bass >80 cm become oceanic migrants that move northward in the spring and southward 

in the fall (Waldman et al. 1990, Dorazio et al. 1994; Secor and Piccoli 2007; Kneebone et al. 2014). 
6

Coastal telemetry arrays have confirmed the broad movement of individuals south in the fall and north in 

the spring, with some evidence for slightly faster northward migrations (Kneebone et al. 2014).

2.5 Introduction to MD WEA physical and ecological setting

The MD WEA occurs within the MAB, a large temperate shelf ecosystem characterized by strong 

seasonal changes in temperature and related oceanographic dynamics (Bigelow 1933; Bigelow and Sears 

1935; Beardsley and Boicourt 1981; Yoder et al. 2002). Physically, the MAB consists of a relatively 

broad (50-200 km wide) shelf area that stretches from Cape Hatteras, North Carolina to the southern flank

of Georges Bank off Massachusetts. However, the MAB also acts as a dynamic boundary between cooler 

sub-arctic waters and warmer sub-tropical waters. The currents associated with these hydrographic 

elements, along with seasonal changes in winds, currents, and temperature, and the inputs of several large 

rivers and estuaries, structure the seasonal changes in thermal conditions, fronts, and other density 

features (Fong and Geyer 2001; Choi and Wilkin 2007; Chant et al. 2008).

Biological dynamics in the MAB are tied to seasonal changes in stratification and oceanographic regimes. 

During summer, the cessation of strong winds, combined with the warming of surface waters, creates a 

persistent thermocline that extends over much of the shelf (Houghton et al. 1982; Lentz 2017). 

Stratification effectively traps cooler winter waters under warmed surface waters, resulting in a “cold 

pool” bounded by warmer near-shelf waters and dense, saltier waters at the shelf break (Houghton et al. 

1982, Rassmussen et al. 2005). Summer months are therefore characterized by a cross-shelf gradient of 

decreasing temperature with distance from shore. Cooling, storm events, and wind-driven mixing with the 

onset of fall break down this stratification regime, leading to relatively homogeneous shelf water 

temperatures throughout the water column during winter months. (Castelao et al. 2010; Gong et al. 2010; 

Lentz 2017). However, a cross-shelf gradient still exists with more rapid shelf cooling in shallow waters 

and comparatively warm waters at the outer shelf. Although seasonal patterns of temperature and 

stratification have fundamental effects on the MAB ecosystem (Malone et al 1983; Flagg et al. 1994; 

Shofield et al. 2008), little is known about how the MAB’s thermal regime influences fish migration

(Secor et al. 2019).

2.6 Study hypotheses and objectives

The objective of this project was to measure seasonal transit and habitat occurrence of striped bass and 

Atlantic sturgeon in relation to depth, temperature, and other oceanographic and benthic variables in and 

around the MD WEA. We hypothesized that addition of wind farm construction in the “featureless” MD 

WEA could alter baseline behaviors of migratory fishes by causing them to increasingly dwell on high 

relief turbine structures as they seasonally transit through DelMarVa’s continental shelf waters. 

Furthermore, based on species biology, we expected that the movements of Atlantic sturgeon and striped 

bass would differ in terms of transit rate and habitat preference in the MD WEA. Because Atlantic 

sturgeon principally forage in soft-bottom habitats, they should select habitats similar to those that occur 

in the MD WEA (Vladykov and Greeley 1963; Savoy 2007; McLean et al. 2013). Sand and organic 

debris were a major component in the stomachs of sturgeon captured off the MAB, which provides 

evidence of benthic feeding behavior (Johnson et al. 1997). Other studies suggest that juveniles and nonspawning adults remain in coastal waters in order to increase foraging opportunities (Bain 1997; Stein et 

al. 2004). We therefore postulated that Atlantic sturgeon would transit more slowly through the shelf 

region, as they forage within coastal migration corridors. Unlike Atlantic sturgeon, adult striped bass are 

pelagic predators that frequently rely on mobile prey as a food source and are often associated with 

structure (Haeseker et al. 1996; Tupper and Able 2000; Harding and Mann 2003). Due to the relatively 

featureless nature of the MAB, we hypothesized that striped bass would not forage during their seasonal 
7

migrations through the area. In comparison to Atlantic sturgeon, we expected that striped bass would 

move more rapidly through MD WEA shelf waters.

3 Design and Methods

3.1 MD WEA telemetry array design

Passive acoustic receivers were deployed in a gradient design centered across the MD WEA to observe 

the seasonal patterns of Atlantic sturgeon and striped bass occurrence. With this design, a central and 

high-density receiver array was located within the WEA. Inshore and offshore arrays of less densely 

distributed receivers were adjoined to this central (MD WEA) array (Figure 2). Receivers were thus 

positioned across a broad width of the shelf environment, which Atlantic sturgeon and striped bass make 

use of as a migration corridor. The design featured key depth, temperature, and other oceanographic 

gradients that influence species transit and habitat selection. Additionally, the seasonal and inter-annual 

variations in migratory behaviors were accommodated by the two-year duration of the study. Thus, the 

design fulfilled the Before-phase of a BAG impact study, through inclusion of key gradient (e.g., 

confounding) features. 

Atlantic sturgeon and striped bass detections were assessed across gradients ranging from 10-50 km from 

shore and 10-45 m depth for the period November 2016- December 2018 (Figure 2). The main MD WEA 

array of 12 receivers were spaced at intervals of 3.2 km East-West and 3.6 km North-South. The Inner 

and Outer strata were located 8 km inshore and offshore of the MD WEA stratum and each consisted of 4 

receivers each at 8 km spacing (East-West and North-South). Receiver spacing allowed for approximately

50% detection in the MD WEA and 20% detection probabilities in the Inner and Outer strata, based on 

the a priori expectations of an 800 m maximum detection radius (but see 3.4. Receiver Range Testing).
8

Figure 2. Acoustic receiver array design

Twenty receivers are divided into three strata; Inner (pink), MD WEA (green), and Outer (blue). Bathymetric depth 

contours are shown at 10-m intervals.

3.2 BOEM consultation and changes to study design

Following discussions with BOEM staff, we augmented the study design to (1) increase the duration of 

receiver array deployment from November 2016-July 2018 to November 2016-December 2018; and (2) 

conduct a receiver range-detection test for the period November 2017-December 2018. An additional 

winter period deployment of the array was deemed important to capture two full years of seasonal 

patterns of striped bass and sturgeon incidence. Change in duration of the array deployment was 

implemented through a 1-year no-cost extension. The additional 2018 December cruise was supported by 

cost savings in vessel steam time by the R/V Carson from its berth in Solomons MD to Ocean City MD. 

These costs were shared by a separate funding source. Telemetry receiver detection ranges are not well 

documented, particularly in ocean shelf environments. To support study design assumptions related to 

array detection probabilities, we designed a 1-year study to evaluate detection ranges in two different 

shelf environments – the MD WEA, where summer stratification is pervasive and surface noise expected 

to be moderate, and the Inner Array, where stratification is less pervasive and surface noise is expected to 

be high (see 3.4. Receiver Range Testing). The design required four additional telemetry receivers, which 

were available from a separate study. Because these receivers were immediately adjacent to study array 

receivers, their deployment and retrieval were easily accommodated during array maintenance cruises.

3.3 Telemetry receiver deployments, maintenance, and database 

management

In triannual cruises beginning November 2016 and ending December 2018, we successfully deployed, 

maintained, and retrieved 20 VEMCO VR2AR Acoustic Release receivers (Figures 3, 4). We opted for a 
9

low vertical deployment profile (2.0-2.5 m) and a submerged buoy attachment to curtail losses due to 

vessel collision, theft, and tampering. The VR2AR receivers represent a substantial advance because the 

release mechanism is built into the receiver housing at a considerably reduced cost and without the need 

for retrieval lines, which can entangle upon retrieval (Figure 3). A transponding deck-based hydrophone 

communicates with a release trigger causing the receiver and attached buoy to separate from a sacrificial 

mooring anchor. The transponder further functions in triangulating the location of the receivers and 

querying the receiver for temperature, tilt, data memory, and battery life. Receivers were moored onto 

two 45-lb flat iron weight plates and maintained in the water column by a hard trawl float attached by a 

5/16” rope (Figure 4). Receivers detected and logged all telemetered fish on a continuous basis.

All receivers were recovered, cleaned of fouling organisms, had batteries replaced as needed, and were redeployed during maintenance cruises taking place approximately every 4 months (first year of cruise 

reports available in Appendix A). Detection and environmental parameter data were downloaded 

following each cruise and stored in a geospatial database for distribution, quality control, and analysis. 

Fish detection data were retained in R (R Development Core Team, 2005) and matched to scientists 

associated with individual transmitter codes using an R package developed from previous telemetry 

applications (available at https://github.com/mhpob/TelemetryR). Where data agreements were in place, 

detection data were retained for further analysis. Detections were further filtered to include only codes 

heard more than once to help correct for false detection and code collision (VEMCO guidelines). 

Metadata on environmental parameters and sent detections were stored in an MS Access database. Data 

were also archived internally in three-month cycles by archiving Chesapeake Biological Laboratory’s file 

server uploads to a removable drive and by uploading data to an external hard drive. Acoustic receiver 

detection data will also be provided to MATOS for future study, once the database is fully accessible.

Figure 3. VEMCO VR2AR Acoustic Release receiver, transponder and deck box.

The release mechanism at the bottom of the receiver is a bolt that unscrews and detaches leaving behind a sacrificial 

weight. The receiver is maintained in the water column through attachment by a short line to a float. Images from 

http://vemco.com/products/vr2ar-acoustic-release-and-transceiver/.
10

Figure 4. Acoustic Release receiver detection (left) and acoustic release mooring design (right).

3.4 Receiver range testing

Both ambient noise and changes in the speed of sound due to temperature, depth, and salinity can

influence the detection range of acoustic transmitters; these ranges have been rarely tested in shelf 

oceanic ecosystems. Research on black sea bass in the MD WEA (Secor et al. 2019) demonstrated that 

strong wind events interfered with telemetry detection rates through high ambient noise levels. Thus, we 

amended the study design to include range testing of the V2AR receivers. We tested our current assumed 

detection distance (800 m) against two other distances (250 and 550 m). Several acoustic-release 

receivers containing internal synchronization transmitters were made available at the conclusion of a 

complementary black sea bass telemetry project funded by the Maryland Department of Natural 

Resources (October 2017).

On December 20, 2017, we deployed two receivers each at two sites (AN3 and IS2; see Figure 2) to test 

our current assumed detection distance (800 m) against two other distances (250 and 550 m) in the MD 

WEA and Inner arrays, respectively (Figure 5). Internal synchronization transmitters are components of our 

acoustic-release receivers and were programmed to emulate those striped bass and sturgeon transmitters 

being detected within the present array. 
11

Figure 5. Range test transect schematic.

Synchronization receivers (blue dots) were deployed at 250 and 800 from a reference receiver, allowing for 

evaluation of detections from 250 (red), 550 (orange), and 800 (green) meter distances. Tests were conducted at 

sites AN3 and IS2 (see Figure 2).

Data from the range test sites were downloaded on April 11, August 9, and December 5, 2018. Daily 

frequency of detection was calculated for each distance in each site for a total of two measurements per 

distance, per site, per day. Proportional daily detection, hereafter referenced as “detections,” was 

calculated as 

ttttttttttttttttttttttttttiiii

ttttttttttttttttttttttttttii

where ttttttttttttttttttttttttttiiii are the transmissions from receiver detected at distance jj and ttttttttttttttttttttttttttii

are the total transmissions from receiver . To visualize changes in detections through time, detections

were modeled as a function of distance using nonlinear least squares, binomial regression with a logit link 

function, and binomial regression with a probit link function. The distance at 50% frequency of detection 

(D50) was calculated and the best model form was chosen from the fitted models:

Nonlinear Least Squares

DDDD = DD0 −

ln (

1 − 1)

kk

DD50 = DD0

Logit 
12

DDDD =

log 1 − − ββ0

ββ1

DD50 = −ββ0/ββ1

Probit

DDDD = ii ii( ) − ββ0

ββ1

DD50 = −ββ0/ββ1

As daily modeled D50 contained extreme outliers, the binomial regression modeling process was further 

refined by imposing covariance through estimating random day-by-site responses and solving the 

individual coefficients:

DDDD =

log 1 − − ββ0

ββkkkk

DD50 = −ββ0/ββkkkk

Where ββkkkk is the response at site kk on day .

A dominating feature in the MAB is seasonal stratification; weak salinity-driven stratification dominates 

in the winter, with strong temperature-driven stratification dominating in the summer (Li et al. 2015). 

Stratification, especially that associated with the cold pool (Section 2.5), entails large changes seawater 

density with increasing depth. The change in density affects the speed of sound, and so acoustic detection 

range will likely vary greatly between periods of cold pool presence or absence. To test for this influence, 

time series models were fit to the corrected modeled D50 and change point detection was conducted using 

the PELT algorithm with CROPS penalty to identify changes in mean and variance in the time series of 

modeled D50 (Killick et al. 2012, Haynes el al. 2014).

As daily D50 varied substantially through time (see Section 4.2), a generalized additive model was 

developed to scale recorded transmitter detections by a subset of recorded variables. A range of 

environmental, meteorological, and water quality variables were collected from in-situ receivers, the 

National Data Buoy Center, and remote sensing NOAA Environmental Research Division's Data Access 

Program (ERDDAP) servers that could be used to create a predictive detection range model (Table 1). 

Principal component analysis of daily mean records was used for model variable selection; prior to 

modeling, highly-correlated groups were culled to orthogonal representative variables.
13

Table 1. Metadata of variables used in the predictive detection range model.

Units, spatiotemporal resolution, and general description are provided. Stations of the National Data Buoy Center (*) 

are indicated.

Resolution

Variable Units Time Space Description

D50 Meters Hourly Array Distance at 50% frequency of 

detection

Modeled aggregate

Average 

noise

Millivolts 10 minutes Receiver Average noise level at 69 kHz

Recorded in-situ

Average 

temperature 

Degrees C Hourly Receiver Bottom water temperature

Recorded in-situ

Tilt angle Degrees Hourly Receiver Degrees from vertical of receiver

Recorded in-situ

sst Degrees C Daily Array Multi-scale Ultra-high Resolution Sea 

Surface Temperature

1 km satellite-derived

dt Degrees C Daily Array sst - Average temperature

wdir Degrees Hourly Array Wind direction; degrees from true 

north

OCIM2, 44009*

wspd Meters/second Hourly Array Wind speed averaged over an eightminute period

OCIM2, 44009*

gst Meters/second Hourly Array Peak 8 second wind gust speed

OCIM2, 44009*

wvht Meters Hourly MD WEA array Mean of the highest one-third of 

wave heights during the sampling 

period

44009*

dpd Seconds Hourly MD WEA array Dominant wave period: period with 

the maximum wave energy

44009*

apd Seconds Hourly MD WEA array Average wave period

44009*

mwd Degrees Hourly MD WEA array Mean wave direction; degrees from 

true north

44009*

pres Hectopascals Hourly Array Atmospheric pressure

OCIM2, 44009*
14

atmp Degrees C Hourly Array Air temperature

OCIM2, 44009*

wtmp Degrees C Hourly Array Surface water temperature

OCIM2, 44009*

The effect of the selected environmental variables on frequency of detection was modeled using a 

generalized additive model (GAM) with a binomial distribution and log link function. A linear term of

distance was used as a predictive variable, along with and additive terms of ΔT, noise (those parameters 

retained in the variable selection process, Section 4.2), and the interaction between ΔT and noise. 

Additive components were modeled using 5 knots and a cubic spline basis to control overfitting; the 

model was trained using the recorded range test data.

3.5 Striped bass transmitters

During the period of receiver deployment, >500 striped bass implanted with active transmitters were at 

large within the Mid-Atlantic Bight and southern New England (Table 2). The majority of these 

transmitters were associated with projects by Co-PI Secor; data agreements with other scientists allowed 

access to information for other tagged striped bass. During this BOEM project, an additional 40 large 

striped bass were implanted with depth transponders to evaluate depth behaviors in the MD WEA and 

provide additional incidence data (Table 3). A portion of these fish (n=28) were sampled from a pound 

net located in the lower Potomac River, Point Lookout State Park, MD during April – May 2017 and 

2018 under special permit from the Potomac River Fisheries Commission. An Investigational New 

Animal Drug permit was attained each year, permitting the use of Aqui-S, an FDA-controlled anesthetic, 

during acoustic transmitter implantation surgery. Fish were surgically implanted with depth-transponding 

acoustic transmitters (VEMCO®; model V16P-4H-S256; 67 mm, 10 g, 2.5 year expected battery life) 

according to tested (Wingate and Secor 2007) and IACUC-approved surgical protocols. Scales were 

collected for ageing. Additional tagging of a subset of large striped bass occurred off the coast of 

Massachusetts during August - October 2017 courtesy of the Massachusetts Department of Marine 

Fisheries. Past telemetry research showed that many coastal migrants from the Chesapeake Bay and other 

systems enter these waters during summer months (Kneebone et al. 2014). Thus, striped bass tagged in 

New England waters were expected to exhibit seasonal migrations through the MD WEA.
15

Table 2. List of active acoustic transmitters associated with large research projects on striped 

bass and Atlantic sturgeon during the period of the proposed study.

All PIs have agreed to share data with Co-PIs Secor and Bailey. SB=striped bass; AS=Atlantic sturgeon; 

UMCES=University of Maryland Center for Environmental Science; NYSDEC=NY State Department of Environmental 

Conservation; MADMF=MA Division of Marine Fisheries; MD DNR= MD Department of Natural Resources; 

VCU=Virginia Commonwealth University; SUNY=State University of NY. Stipulated period of tag activity is based on 

VEMCO specifications; transmitter lifespans are typically is excess of these periods.

Species PI Institution N Tagging 

Location

Stipulated Period of 

Tag Activity

SB D. Secor UMCES 71 Potomac River Spring 2014-Winter 2016

SB D. Secor UMCES 40 Potomac River Spring 2017-Winter 2019

SB D. Secor,

A. Higgs

UMCES,

NYDEC

100 Hudson River Spring 2016-Winter 2018

SB B. Gahagan MADMF 224 Coastal MA Summer 2015-Winter 2017

AS C. Stence MD DNR 30 Nanticoke Fall 2015-Fall 2025

AS D. Fox DE State Univ. >500 Delaware 2010-2025

AS M. Balazik VCU 155 James River 2010-2025

AS K. Dunton,

M. Frisk

SUNY Stony 

Brook

495 NY Bight 2010-2025
16

Table 3. Tagged striped bass information.

Characteristics of the 40 striped bass tagged between 4/21/17 and 5/11/17 in the Lower Potomac River, Point 

Lookout State Park, MD and off the coast of Massachusetts. All fish were surgically implanted with depthtransponding acoustic transmitters (VEMCO®; model V16P-4H-S256; 67 mm, 10 g, 2.5 year expected battery life).

Tag Date Transmitter ID Length

(TL, cm)

Weight 

(kg) Sex

Tagging

Location

5/11/2017 A69-9002-6757 77 5.1 Male Potomac

9/1/2017 A69-9002-6758 81 Massachusetts

9/1/2017 A69-9002-6759 76 Massachusetts

9/1/2017 A69-9002-6760 82 Massachusetts

9/1/2017 A69-9002-6761 78 Massachusetts

9/1/2017 A69-9002-6762 86 Massachusetts

9/1/2017 A69-9002-6763 77 Massachusetts

9/1/2017 A69-9002-6764 80 Massachusetts

9/1/2017 A69-9002-6765 81 Massachusetts

9/1/2017 A69-9002-6766 114.3 19 Female Potomac

9/1/2017 A69-9002-6767 107.3 Female Potomac

9/1/2017 A69-9002-6768 100.3 13 Female Potomac

9/1/2017 A69-9002-6769 100.3 13.2 Female Potomac

9/1/2017 A69-9002-6770 107.9 17.7 Female Potomac

9/1/2017 A69-9002-6771 106.7 16.8 Male Potomac

9/1/2017 A69-9002-6772 97.8 13 Female Potomac

9/1/2017 A69-9002-6773 106.7 15.6 Female Potomac

9/1/2017 A69-9002-6774 104.1 16.8 Female Potomac

4/21/2017 A69-9002-6775 75.7 5.1 Female Potomac

4/21/2017 A69-9002-6776 88.6 7.2 Male Potomac

4/21/2017 A69-9002-6777 99.8 9.8 Female Potomac

4/21/2017 A69-9002-6778 99.8 10 Female Potomac

4/21/2017 A69-9002-6779 99.7 11.7 Female Potomac

4/21/2017 A69-9002-6780 89.1 8.4 Female Potomac
17

Tag Date Transmitter ID Length

(TL, cm)

Weight 

(kg) Sex

Tagging

Location

5/8/2017 A69-9002-6781 81.4 6.5 Female Potomac

5/8/2017 A69-9002-6782 80.0 5.6 Female Potomac

5/8/2017 A69-9002-6783 98.9 10.2 Female Potomac

5/8/2017 A69-9002-6784 87.1 6.6 Male Potomac

5/8/2017 A69-9002-6785 81.7 9.4 Female Potomac

5/8/2017 A69-9002-6786 101. 10.6 Female Potomac

5/8/2017 A69-9002-6787 81.7 6.2 Male Potomac

5/11/2017 A69-9002-6788 85.7 7 Male Potomac

5/11/2017 A69-9002-6789 77.1 5.1 Male Potomac

5/11/2017 A69-9002-6790 83.0 5.8 Female Potomac

5/11/2017 A69-9002-6791 77.5 5.7 Female Potomac

5/11/2017 A69-9002-6792 99.5 11.7 Male Potomac

9/1/2017 A69-9002-6793 83 Massachusetts

9/1/2017 A69-9002-6794 86 Massachusetts

9/1/2017 A69-9002-6795 84 Massachusetts

9/1/2017 A69-9002-6796 75.5 Massachusetts

3.6 Atlantic sturgeon transmitters

Atlantic sturgeon with active transmitters in the Mid-Atlantic exceed 1000 in number, owing to long-term 

and intensive research programs on this endangered species and because transmitters are long-duration (~10 

years). Through the Atlantic Cooperative Telemetry (ACT) Network, multiple data-sharing agreements 

have been formed with researchers who have tagged sturgeon in systems ranging from Virginia to New 

York (Table 2). 

3.7 Environmental data sources: temperature, wind, storms, noise, bottom 

characteristics

Environmental, meteorological, and water quality variables were collected from receivers, the National 

Data Buoy Center, and remote sensing NOAA ERDDAP servers. Bathymetry (dataset ID usgsCeCrm2), 

Sea surface temperature (dataset ID jplMURSST41), and 8-d averaged chlorophyll-a concentration 

(dataset ID erdMH1chla8day) values were accessed from the CoastWatch West Coast Regional Node 
18

ERDDAP server (https://coastwatch.pfeg.noaa.gov/erddap/). Other meteorological variables were 

downloaded from the National Data Buoy Center. Deployed receivers also recorded tilt, ambient noise, 

and bottom temperature on an hourly basis, which provided supplementary in-situ data. The difference 

between satellite-observed sea surface temperature and receiver-recorded bottom temperature (ΔT) was 

calculated and used as an index of water column temperature stratification; higher absolute values of ΔT 

represent increased stratification strength. Bottom type information was obtained from the Northwest 

Atlantic Marine Ecoregional Assessment. Bathymetric, sediment grain-size, slope, and Ecological Marine 

Unit variables were visually assessed for general patterns and notable features in the MD WEA study 

region

3.8 Data analysis 

3.8.1 Seasonal incidence

Presence/absence was calculated at a daily time step to examine striped bass and Atlantic sturgeon 

incidence. Thus, single or multiple individual incidences over a 24-hr period were summed as a single 

daily incidence. Daily incidence data (no. individual fish d-1

) was summed by stratum (array) and season. 

For all analyses, seasons were divided equally and defined as winter (Dec, Jan, Feb), spring (Mar, Apr, 

May), summer (Jun, Jul, Aug), and autumn (Sep, Oct, Nov). Because incidence data was zero-inflated and 

skewed, non-parametric Kruskal-Wallis tests and post hoc Dunn’s test with the Bonferroni method for 

multiple comparisons were used to determine significant differences in number of individuals detected

between seasons and stratum (Inner, MD WEA, Outer). 

3.8.2 Transit rates and patterns

Indices of movement and residence were calculated from individual data aggregated into broad 

autumn/winter and spring/summer periods to facilitate comparisons between northern and southern 

migrations for each species. The autumn/winter season is referenced by the three years according to the 

year that the winter season ended: autumn/winter 17, or autumn/winter 18, or autumn/winter 19. We 

examined patterns of residence and movement across the entire MD WEA receiver array (all strata) for 

both species within these seasonal periods. Movement was evaluated by examining the number of 

receivers visited by individuals within migration seasons. Residency was calculated using original 

VEMCO detections that were run through the “RunResidenceExtraction” function in the R V-Track 

package (c/o Franklin Ecolab, The University of Queensland, St Lucia, Qld, Australia). In the function, a 

residence event began when an acoustically-tagged fish was detected at least two times and was 

terminated when the tag was detected at a different receiver or if no new detections were recorded for 12 

hours. Residence events were summed for each fish and each migration season and reported as hours 

detected. Cumulative unique days detected for each individual per season were also calculated to provide 

a comparative, coarse measure of residence. Differences in residence periods between species and seasons 

were compared using Wilcoxon rank sum tests. 

Rate of movement calculated within the MD array did not provide sufficient data given the number of 

sequential detections, cooperative data sharing with University of Delaware colleagues (D. Haulsee and 

M. Oliver) permitted evaluation of transit rates between the MD WEA and the adjacent DE WEA. 

Though residence and within-array movements were available for both species, transit rates between MD 

and DE arrays were only calculated for tagged striped bass. Detailed information on Atlantic sturgeon 

movement between the two arrays can be found in the complementary report to BOEM by Delaware 

colleagues (Haulsee et al. 2020; https://espis.boem.gov/final%20reports/BOEM_2020-020.pdf). Striped 

bass transit events between the MD WEA and DE WEA were evaluated using receiver locations to 

estimate transit (straight line) distance, time interval of serial detections, and direction of transit (North or 
19

South). To the extent that data were available, we estimated linear transit velocities as body lengths s -1

, 

which is a more ecologically relevant measure. Differences in log-transformed swimming speed between 

direction (north vs. south) were evaluated using Student’s t-tests. Transit rates were further tested for 

differences according to size and sex using linear mixed effect models (LMMs) in the R package nlme 

(Pinheiro et al. 2017). Rate of transit was the dependent variable with year, season, and sex as categorical 

variables and body size at tagging (TL in cm) as a continuous covariate. LMMs for log-transformed 

transit rate only included fish tagged in the Potomac and Hudson Rivers; tagging region was not 

investigated as a fixed effect due to limited sample size. Each individual (tag code) was included as a 

random effect in the models to account for repeated measures. The full model contained all biologicallyrelevant two-way interactions, including Sex*Season, TL*Season, and TL*Sex.

3.8.3 Distribution and depth of occurrence for tagged striped bass

Striped bass that received depth transponders provided depth of incidence data within the full MD WEA 

array as well as distributional information when records were received from ACT network participants. 

Broader migration and depth of occurrence data throughout ACT network sites were visually assessed for 

trends and patterns. Depth of incidence within the MD WEA region was examined for seasonal and strata 

differences. 

3.8.4 Environmental covariates of MD WEA incidence 

Since preliminary results in regional telemetry arrays indicated that some species, particularly Atlantic 

sturgeon, may select specific habitats that result in disproportionate detections at certain receivers (D. 

Haulsee, University of Delaware and C. Watterson, US Navy; pers. communication), we sought to 

evaluate whether high densities of detection corresponded with bottom type characteristics. Spatial

patterns of site (receiver) usage within the gradient array were assessed using the Optimized Hot Spot 

Analysis tool (Getis-Ord Gi*statistic) in ArcGIS. Separate analyses were conducted based on the number 

of unique individuals detected daily at each receiver within each season and over all seasons and years 

combined.

Single Parameter Quotient analysis (Lluch-Belda et al. 1991) was used to quantitatively investigate the 

average selection behavior of each species for temperature in autumn/winter and spring/summer seasons. 

Habitat selection was determined by presence over time for regions within the study array. Daily presence 

of fish was compared to all temperatures when fish were either present or not within seasonal periods. 

Temperature values were binned so that each interval contained a range of 5°C to reflect regional 

variability (Bonanno et al. 2014). For each season and temperature interval, a Quotient index (QI) was 

calculated as

QQQQii = %OOOO OO OOOO DD DD

EE . VV . FF FFii × 100

where is -th frequency histogram interval.

The resulting QI values compare the proportion of available habitat to the proportion of habitat in which 

detections occurred. A value of QI=1 represents even distribution across habitat types, values greater than 

1.0 indicate preference, and values lower than 1.0 indicate avoidance. Significant deviation from QI=1.0 

was tested using a randomization procedure. Confidence intervals (CI) were calculated based on the null 

hypothesis of a random association between biological and environmental variables. The calculated CI 

was then used to infer avoidance or selection of specific temperatures by Atlantic sturgeon and striped 

bass. QI values lying outside of the CI curve indicate significant selection or avoidance.
20

3.9 Predictive habitat models

3.9.1 Daily relative abundance model

Dynamic relative abundance models were formulated separately for each species. The response variable, 

daily individual incidence, was calculated by tallying the total number of unique tag codes (individual 

fish) detected at each receiver, each day. Since species occurrence was zero-inflated and expected to vary 

non-linearly with environmental variables, a Generalized Additive Mixed Model (GAMM) framework 

with a zero-inflated Poisson distribution was used (Table 4). All modeling was conducted in R statistical 

software (R Development Core Team, 2015) using the mgcv package (Wood and Wood 2019). To 

account for the variable detection range of receivers (see Section 3.4), modeled D50 predictions (sitespecific 50% detection range), were added as an offset to the GAMM habitat models. This predicted 

range represented an index of sampling effort and was used to adjust each day’s sum of detections such 

that abundance recorded on days with lower D50 values were up-weighted and abundance recorded on 

days with larger detection ranges were down-weighted. The D50 offset thus reduced temporal 

autocorrelation caused by underlying fluctuations in detectability. Receiver site and study year were 

added as random effects to limit spatial autocorrelation and to account for inter-annual differences in the 

number of fish detected. 

Previous results and past habitat-selection modeling in the Mid-Atlantic suggested that variables such as 

temperature, stratification, depth, and oceanographic satellite-derived measures of productivity would be 

important factors in the daily presence of both species (Manderson et al. 2011; Breece et al. 2017; 

Haulsee et al. 2018). We therefore selected bottom water temperature, sea surface temperature (SST), 

stratification (ΔT), bathymetry, and MODIS aqua-derived satellite measurements of chlorophyll a 

concentration as environmental covariates. Depth was chosen as the most representative bottom 

characteristic variable since preliminary telemetry results in the MD WEA suggested that species do not 

select habitats based on sediment type or benthic class in this section of the MAB shelf (PI D Secor, 

unpubl. data). We also considered magnitude of monthly SST change as a covariate; temperature change 

was calculated using the difference between current SST on a given day minus the lagged SST value over 

the previous 1-30 days (SST Δ1-30). 

Preliminary examination of collinearity through pairwise comparison and variance inflation factor 

calculation showed that SST, ΔT, and bottom temperature were highly correlated (r > 0.7, variance 

inflation factor > 3). SST was selected among these variables because it was most accessible via the 

ERDDAP server. Similarly, SST Δ1-30 was strongly correlated with SST; here models included either 

but not both variables. To account for seasonality in the data, day-of-year (DOY) was included as a 

predictor variable. The oscillatory nature of DOY was accommodated using cyclic splines (bs= “cs”; gam 

function, mgcv package) (Wood 2017). All other variables were modeled using singular smooth terms 

(formula= s, gam function, mgcv package) and thin plate regression splines (bs= “ts”, gam function, mgcv 

package) and were limited to 6 knots to reduce potential over-fitting (Wood, 2003). Interactions between 

environmental variables and DOY were also systematically included and a tensor product smooth term 

(formula= t2, gam function, mgcv package) was used to accommodate differing units among interaction 

variables (Wood et al. 2013). Only one interaction was allowed per modeling iteration to limit 

complexity. 

All possible relative abundance model combinations were tested and ranked according to AIC score. Final 

models were then checked for concurvity, the non-linear equivalent of collinearity using the “concurvity” 

function in the mgcv package. Concurvity occurs when there is similarity between the smooth functions 

of different variables. Concurvity can thus lead to difficulty in interpreting model effects and in severe 

cases can bias estimates of residual variance, leading to false confidence in results (Ramsay et al. 2003). 
21

Therefore, if observed values of concurvity were > 0.8 (values range 0-1, with higher values indicating 

increased concurvity), the model was dismissed from consideration. Because SST and SST Δ24-30 

always resulted in concurvity values exceeding 0.8, only models that included SST Δ1-23 were used for 

selection. Final model residuals were visually checked for temporal and spatial correlation using 

autocorrelation function (ACF), partial autocorrelation function (PACF), and semi-variogram plots. 

Overall model performance was evaluated with k-fold cross validation in which the data were randomly 

split into training (75%) and testing (25%) sets over each of 5 folds. The root mean square error (RMSE) 

and average error between observed abundance in testing data and training model-predicted abundance 

were then calculated and used to assess model predictive error (Potts & Elith 2006).

Table 4. Summary of intended purpose and modeling approach for each research question.

See Methods for additional explanation. GAMM=Generalized Additive Mixed Model; HGAM=Hierarchical Additive 

Mixed Model.

Category Objective Modeling 

approach

Response 

variable

Level of 

organization

Autocorrelation 

compensation

Random 

effects

Relative 

abundance

Predict finescale 

relative 

abundance 

of test 

species

GAMM Number of 

individuals 

per 

receiver

Temporal: 

Daily

Spatial: 

Receiverbased

Range test 

offset

Receiver 

site and 

Year of 

study

Individual 

weekly 

residence

Determine 

predictors of 

individual 

residence

GAMM Number of 

days per 

week

Temporal: 

Weekly

Spatial: 

Array-wide

Lagged 

residency 

response

Individual 

ID

Evaluate 

residence 

response by 

population 

(tagging 

origin)

HGAM 

submodel

Number of 

days per 

week

Temporal: 

Weekly

Spatial: 

Array-wide

Lagged 

residency r

response

Tagging 

origin

3.9.2 Environmental and individual drivers of weekly residency

Environmental drivers of individual residency on the MAB shelf were also assessed using a zero-inflated 

GAMM approach (Table 4). The response variable for residency models was the total number of days of 

positive detections within each week. Individual ID (transmitter code) was included as a random effect to 

account for correlation from repeated measures of the same individual. “Population”-level differences in 

individual response were tested in the same model by considering tagging region as a fixed effect. Only 

tagging regions with a sample size > 5 individuals were included in analyses. Differences between 

tagging regions was evaluated using the post-hoc multiple comparison, Wald test (wald_gam function, 

‘itsadug’ package; Van Reij et al. 2017). 
22

Week-of-year, CHL-A, and SST were examined for their effect on the weekly residency of individual 

fish. Thin plate splines with a limit of 6 knots were used to specify all environmental covariate functions 

with the exception of week-of-year, which was modeled with a cyclic spline. Although models likely 

suffered from concurvity, thus increasing the potential for biased estimates or Type I error (Amodio et al 

2014), SST and week-of-year were both retained so that the influence of each term could be evaluated

while accounting for individual-level variability.

Preliminary analysis showed that inclusion of individual random effects did not resolve all residual 

temporal autocorrelation and unlike daily-resolution modeling, the use of a D50 offset did not effectively 

diminish correlation at the weekly timescale. A state-dependence approach using lagged individual 

residency was used to model and reduce remaining serial autocorrelation in weekly residence probability. 

Three state-dependence sub-models were created that corresponded to how many days an individual fish 

was detected in the previous 1-3 weeks. Each considered submodel added the first- through third-order 

smoothed autocorrelation terms to find which structure most decreased autocorrelation while limiting 

complexity. Residual autocorrelation was again checked using ACF and PACF plots.

When significant differences in residency were identified between tagging regions (populations) in the 

GAMM post-hoc tests described in the previous section, hierarchical generalized linear models, or 

HGAMS, were used to further evaluate the group-level differences in response to environmental and 

temporal covariates (Table 4). HGAMs are used to allow for varying degrees of non-linear response over 

different grouping levels (Pedersen et al 2018). For hierarchical modeling, significant predictors of 

residency were each tested individually. The smoothed functional response in each model was allowed to 

vary by group (tagging region), but group-level functions were pooled in a common response. The 

hierarchical relationship between predictor variables and tagging-region groupings was specified using 

different variable and factor relationships. First, the global response of all groups to the variable of 

interest (either week-of-year, SST, or CHL-A) was specified using a singular thin plate regression spline. 

Next, the predictor was modeled according to each tagging group factor using the factor-by-smooth 

model specification (formula = “by”, gam function, mgcv package). However, a cyclic spline was still 

used to model the temporal week-of-year variable. Finally, a random effect for tagging group was 

explicitly included so that model intercepts could differ among the group factor levels (Pedersen et al 

2018). Collinearity between the global response and group-level responses was deliberately penalized and 

reduced using additional model terms (bs= “ts”; m=2, gam function, mgcv package), thereby increasing 

certainty around the global smoothed predictor (Wieling et al. 2016; Baayen et al. 2018). The best statedependence correlation structure identified in the full residency model was used in hierarchical models. 

Model diagnostics and performance were not assessed for HGAMs since their purpose was to support

visualization of group-level differences in response to individual environmental covariates and not to 

predict residency.

4 Results

4.1 Database guidance and total detection summary

Detailed species detection data were shared directly with BOEM project officers and will become 

publicly available through the MATOS network (the ACT network successor), which is currently still 

under development. All information necessary to directly reproduce study results are available via the 

Dryad data repository along with relevant metadata guidance (https://doi.org/10.5061/dryad.6hdr7sqx3).
23

From November 2016- December 2018, the array logged 745,385 detections of 1,286 acoustically-tagged 

fish, the bulk of which were target species of the current study: striped bass (n=315 individuals) and 

Atlantic sturgeon (n=352 individuals, Table 5). In addition to target species, 18 additional species were 

identified through the ACT network and included Atlantic cod, Atlantic bluefin tuna, black sea bass, and 

miscellaneous elasmobranchs (blacktip, bull, dusky, sand tiger, tiger, and white sharks; cownose ray) 

belonging to 39 different investigators (Table 5). Sixteen of the detected species were detected within the 

Wind Energy Area.

The focal species of this study tended to have longer periods of incidence in the array when compared to 

other identified species (Figure 6). A notable exception was white shark, which were frequently detected 

within the array throughout the study. However, most elasmobranch species tended to occur for shorter 

periods of time during summer months or late spring and early fall; Atlantic sturgeon and stiped bass 

were less common during these same periods (Figure 6). 

Table 5. Total species detected and PIs contacted during receiver array deployment period.

Receiver array deployment periods show timing of active deployment between tending of receiver and data 

downloads. The number of detections logged and number of principle investigators (PIs) represented by detected fish

are shown. Number of individual species by array is also shown.

Number Detected

Deployment Period Species 

Detected

Total Inner MD WEA Outer

11 Nov, 2016 - 29 Mar, 2017 Sand tiger shark 1 1

28,003 detections Atlantic sturgeon 157 57 101 12

24 PIs Striped bass 238 19 198 117

White shark 6 1 5 2

Black sea bass 4 3 1

Atlantic cod 2 2 1

Unidentified 6 3 7

29 Mar, 2017 - 23 Aug, 2017 Cownose ray 1 1

6,990 detections Sand tiger shark 21 19 2

31 PIs Bull shark 2 1 2

Atlantic cod 1 1 1

Atlantic sturgeon 115 100 18 1

White shark 19 8 12 7

Striped bass 115 7 100 23
24

Blacktip shark 10 2 5 4

Dusky shark 3 1 2 1

American shad 1 1

Black sea bass 4 3 1

Atlantic bluefin tuna 1 1 1

Tiger shark 1 1

Unidentified 14 7 6 3

23 Aug, 2017 - 20 Dec, 2017 Sand tiger shark 25 22 4

16,132 detections Striped bass 55 13 52

29 PIs Bull shark 2 2 1

Atlantic sturgeon 234 146 108 8

Dusky shark 19 14 15 2

Blacktip shark 13 6 9 2

White shark 20 4 14 4

Cownose ray 3 2 1

Smooth dogfish 3 3

Atlantic bluefin tuna 1 1

Atlantic cod 1 1

Shortnose sturgeon 1 1

Black sea bass 12 4 10

Sandbar shark 4 2 3

Unidentified 22 11 12 3

20 Dec, 2017 - 12 Apr, 2018 Atlantic sturgeon 90 29 55 9

208,740 detections Striped bass 199 25 162 85

17 PIs Winter skate 5 2 2

White shark 1 1

Atlantic cod 1 1 1

Black sea bass 1 1
25

Spiny dogfish 1 1

Unidentified 23 17 7 3

12 Apr, 2018 - 08 Aug, 2018 Sand tiger shark 23 22 1

226,145 detections Striped bass 29 2 20 7

Winter Skate 11 5 4 2

Atlantic sturgeon 172 144 25 3

Dusky shark 15 3 12

Blacktip shark 17 6 11

White shark 23 6 12 5

Cownose ray 1 1

Smooth dogfish 2 2

Sandbar shark 5 2 1 2

Tiger shark 1 1

Tarpon 1 1

Unidentified 49 30 17 2

08 Aug, 2018 - 12 Dec, 2018 Sand tiger shark 19 9 9 1

259,375 detections Striped bass 54 4 50

25 PIs Bull shark 1 1

Atlantic sturgeon 183 73 101 9

Dusky shark 23 9 8 6

Blacktip shark 29 12 12 5

White shark 17 3 8 6

Cownose ray 3 1 1 1

Smooth dogfish 4 1 1 2

Sandbar shark 3 1 1 1

Tiger Shark 1 1

Unidentified 130 47 64 19
26

Figure 6. Summary incidence of all species detected in the MD WEA throughout the study.

Colored points represent the presence of at least one tagged individual for 20 species detected in the MD WEA. 

4.2 Receiver range testing

Range and variation in transmitter detections varied with distance from each receiver, array segment

(Inner or MD WEA), and season (Table 6). Detections were higher within the MD WEA than the Inner 

array (ANOVA, p < 0.001), likely due to attenuation of surface noise in the deeper waters of the MD 

WEA. Detections were also substantially higher during the Spring-Summer 2018 season in both arrays 

(ANOVA, p < 0.001). 
27

Table 6. Summary of proportional detection within the deployed range test arrays.

The three modeling approaches (nonlinear least squares, binomial regression with logit link, and binomial 

regression with probit link) yielded similar estimates of D50 for each array in the Winter – Early Spring 

deployment period (D50Inner = 464, 478, 478 m and D50MD WEA = 609, 607, 603 m respectively; Figure 7). 

The binomial regression with a logit link function was chosen for further analysis due to its comparative 

generality and ease of use. Similar to the individual proportional detections (Table 6), the modeled 

frequency curve showed significantly higher detection range (i.e., greater D50 values) at the deeper MD 

WEA site in all seasons than the Inner site, and across sites in Spring-Summer 2018 when compared with 

the Autumn-Winter seasons (Chi-square, p < 0.001; Figure 7).

Array (Depth) Distance Minimum Mean ± SD Maximum Minimum Mean ± SD Maximum Minimum Mean ± SD Maximum

Inner 0 1 1 ± 0 1 1 1 ± 0 1 1 1 ± 0 1

16.5 – 19.5 m 250 0.08 0.88 ± 0.19 1 0 0.87 ± 0.24 1 0.16 0.89 ± 0.17 1

550 0 0.43 ± 0.33 1 0 0.68 ± 0.34 1 0 0.38 ± 0.32 1

800 0 0.12 ± 0.18 0.85 0 0.42 ± 0.30 0.93 0 0.17 ± 0.26 0.94

Overall 0 0.48 ± 0.40 1 0 0.66 ± 0.35 1 0 0.48 ± 0.40 1

MD WEA 0 1 1 ± 0 1 1 1 ± 0 1 1 1 ± 0 1

26.5 – 27.5 m 250 0.87 0.98 ± 0.02 1 0.42 0.97 ± 0.06 1 0.75 0.97 ± 0.03 1

550 0.01 0.71 ± 0.24 1 0 0.77 ± 0.28 1 0 0.63 ± 0.30 1

800 0 0.15 ± 0.16 0.83 0 0.52 ± 0.37 1 0 0.33 ± 0.34 1

Overall 0 0.61 ± 0.38 1 0 0.78 ± 0.31 1 0 0.64 ± 0.37 1

Autumn-Winter 2018 Spring-Summer 2018 Autumn-Winter 2019
28

Figure 7. Box-whisker plots of the frequency of detection for Inner and MD WEA arrays in the 

Autumn-Winter 2018 (A), Spring-Summer 2018 (B), and Autumn-Winter 2019 (C) 

seasons. 

Logit (blue), probit (green), and nonlinear least squares (red) detection frequency fits are shown for both Inner (solid) 

and MD WEA (dashed) arrays. Gray envelopes represent the standard error of the logit and probit regressions. Error 

was not calculated for the nonlinear least squares solution.

Modeled D50 varied between sites and across seasons (Figure 8), ranging from 130 to 1657 m in the 

Inner and 260 to 2221 m in the MD WEA array. A more-conservative estimate of D95 (95% proportional 

A.

B.

C.
29

detection) ranged from 97 to 1189 m in the Inner and 168 to 1578 m in the MD WEA. Detection 

probability was notably reduced in 2018 during March due to the winds of four nor’easters impacting the 

region on March 1-3, 6-8, 12-14, and 20-22. Following this, D50 increased in mid-April, reaching its 

maximum on September 7, after which it rapidly fell to levels similar to winter-spring 2018.

Both the MD WEA and Inner site D50 time series were best-fit by a ARIMA(2, 1, 2) model; that the 

model contains a differencing term along with autoregressive and moving averages suggests at least one 

abrupt shift in the series. Change point detection showed that time series for both sites had increases in 

the mean and variance D50 from winter to summer, followed by a decrease in early autumn. The Inner 

site increased from 488 ± 183 m to 890 ± 184 on April 27, while the MD WEA site similarly increased 

from 639 ± 137 m to 1204 ± 250 m on May 20. Both sites experienced a large reduction in D50 on 

September 8, falling back to levels similar to those early in the year (660 ± 195 m at the MD WEA site 

and 495 ± 156 m at the Inner site). These dates broadly correspond to the period of cold pool development 

and destruction (Section 4.3).

Figure 8. Modeled 50% detection distance (black line) and 95% population prediction interval (gray 

band) at the Inner and MD WEA study sites. 

Change points in the mean and variance of the time series are shown by breaks in mean (red line).

Of the variables investigated, D50 had a negative correlation with wind speed metrics, wave height, and

69 kHz noise (Figure 9). Conversely, D50 showed positive correlations with temperature-derived 

variables, while receiver tilt, atmospheric pressure, wind and wave direction, and wave period showed 

Inner

MD WEA
30

little correlation. The roughly-orthogonal variables of ΔT (dt in Figure 9), an index of stratification, and 

noise at 69 kHz were retained for predictive modeling of frequency of detection and D50.

Figure 9. Principal component analysis of daily mean records (points) of environmental variables 

(arrows) to be used in a predictive detection range model.

The first two axes explain 62% of variance. Variables include distance at 50% detection (D50), average noise, 

average temperature, tilt angle, sea surface temperature (sst), sea surface temperature -average temperature (dt), 

wind direction (wdir), wind speed (wspd), wind gust speed (gst), wave height (wvht), dominant wave period (dpd), 

average wave period (apd), mean wave direction (mwd), atmospheric pressure (pres), air temperature (atmp), 

surface water temperature (wtmp); see Table 1 for variable descriptions.
31

4.2.1 Modeled frequency of detection

Frequency of detection modeled as a function of distance, ΔT, noise, and ΔT-noise interaction explained 

82.6% of deviance with an adjusted R2 of 0.847. Generally, the proportion of possible transmissions 

detected decreased as ΔT approached 0 or as ambient noise and distance from source increased. Near-0 

values of ΔT, which correspond to a well-mixed, homogeneous water column, had a negative effect on 

the proportion of possible transmissions detected; higher indices of stratification (larger ΔT values, cold 

pool present) were found to increase the proportion of transmissions detected (Figure 10). The interaction 

between ΔT and noise revealed that when the water column was homogeneous, proportion of 

transmissions detected, and thus detection distance, declined with increased noise over 200 mV. 

However, detection distance was comparatively greater at higher ambient noise levels when the water 

column was stratified and decreased rapidly when noise levels exceeded 300-400 (mV) (Figure 10).

GAM predictions for the period of investigation (November 2016 – December 2018) were converted to 

D50 as outlined in Section 3.4. D50 for the entire telemetry dataset exhibited the expected patterns of 

larger detection range values during warmer, stratified months that increased with greater depth (D50Inner

< D50MD WEA < D50Outer; Figure 11). There was noticeable daily variability in estimated D50 that likely 

occurred due to fluctuating ambient noise levels (Section 4.5). Larger decreases in detection range were 

also apparent and were likely tied to increases and noise and decreases in stratification associated with 

anomalous wind events.
32

Figure 10. GAM-predicted proportional daily detections (contours) for combinations of 69 kHz 

ambient noise and ΔT at 250, 500, and 800 meters from source. 

Observed noise-ΔT combinations are shown as gray points.
33

Figure 11. Results of modeled range test predictions for the entire time series of the study 

(November 2016 - December 2018), ordered by stratum. 

Black lines show the mean predicted detection range across the array while shaded ribbons represent the range 

(minimum – maximum) of predicted values.

4.3 Study site benthic characteristics and bottom type

The shelf habitat off Maryland had the expected pattern of relatively homogenous sandy habitat, but some 

topographic complexity was revealed from assessment data visualization (Figure 12). Although depth 

generally increased with distance from shore, there were notable higher-relief ridges located directly West 

of the MD WEA (Figure 12; A). Most sediments were classified as sand bottom types, but certain study 

site patches contained regions of finer muddy substrates or more coarse gravel substrate (Figure 12; B). 

There was relatively little topographic complexity in terms of slope (Figure 12; C), but combined 

Ecological Marine Units did vary over the effective area surveyed by receivers; inshore sites tended to 

encompass shallow depression or high flat habitats while deeper MD WEA and Outer stratum sites 

corresponded with moderate depressions and moderate flats (Figure 12; D).
34

A.

B.
35

Figure 12. Bathymetry and benthic characteristics surrounding acoustic telemetry array receiver 

sites. 

Maps depict the study site region off the coast of Ocean City, MD along with the MD WEA footprint. The anticipated 

maximum detection radius of each receiver is also shown. Bottom type summaries include general depth gradients 

(A), sediment grain-size classifications (B), bathymetric slope calculations (C), and Ecological Marine Units (D). 

Ecological Marine Units represent a three-way combination of depth, sediment grain-size, and seabed forms that 

were found to influence ecological relationships of surveyed organism communities (Source: Northwest Atlantic 

Marine Ecoregional Assessment, The Nature Conservancy).

C.

D.
36

4.4 Study site seasonal temperature changes

Mean daily bottom temperature in the study array ranged from 2.6 to 24.3°C through the study period, 

with trends reflecting a seasonal gradient of shelf warming and cooling characteristic of the Mid-Atlantic 

Bight. During spring and summer months (March 1 – August 31), bottom waters had a mean daily 

temperature of 10.9°C and 10.1°C in 2017 and 2018, respectively, with cooler temperatures associated 

with increasing distance from shore (Figure 13). During the fall and winter, inshore bottom waters both 

cooled more-rapidly than offshore waters and displayed comparatively greater variation. This is likely due 

to the more-rapid cooling of shallow inshore water, leading to cooler bottom waters inshore and warmer 

waters offshore during winter months. Bottom temperatures did not differ noticeably between Northern, 

Middle, and Southern transects of the entire array.

Figure 13. Mean hourly bottom temperature (°C) for each receiver in the Inner (pink), MD WEA 

(green), and Outer (blue) strata of the current array. 

Data shown for all receiver records within each stratum.

Stratification, measured as ΔT, varied among season and arrays, with the range of values increasing with 

depth and distance from shore; Inner sites ranged from -1.84° to 13.07° ΔT, MD WEA sites from -2.14° 

to 18.22° ΔT, and Outer sites from -1.92° to 19.63° ΔT. As indicated by near-0 C° ΔT values, the water 

column in the fall/winter season of both years was mixed in all array segments (Figure 14). In 2017, 

stratification developed at a moderate rate through early-June with ΔT increasing rapidly through midJuly following a brief mixing event. After reaching maximum ΔT, the MD WEA and Inner arrays rapidly 

destratified to near-0 values in late July. Stratification developed again at all sites, but not to the same 

extent with the Outer sites regaining ΔT values similar to those observed pre-destratification. This process 

repeated twice more during summer 2017; destratification broke down and all sites became mixed by 

mid-September. A similar pattern occurred in 2018, although there were higher overall ΔT values and 

more frequent destratification events during the summer period. These dynamics reflect the expected 

seasonal progression of the Mid-Atlantic cold pool, which develops during the spring months, persists 

during summer and breaks down during fall (Houghton et al. 1982; Lentz 2017). 
37

Figure 14. Daily ΔT in the Inner, MD WEA, and Outer arrays from November 11, 2016 through 

December 5, 2018. 

Ribbon thickness shows the daily range of ΔT.

4.5 Study site ambient noise levels

Mean daily 69 kHz noise in the array ranged from 163 to 691 mV (note mV levels at 69 kHz correspond 

positively but coarsely with decibel levels; D. Secor, unpubl. data), with an average value of 234 mV. The 

number of days with “loud” (>300 mV) maximum noise levels decreased with increasing distance from 

shore, recorded on 567, 452, and 178 days across the Inner, MD WEA, and Outer strata, respectively. 

Similarly, the Inner and MD WEA strata had more days with average noise levels that exceeded 300 mV 

(121 and 94, respectively) than the Outer stratum (24; Figure 15). There was no apparent difference in 

daily noise patterns across the Northern, Middle, and Southern transects. 

Protracted noise events were often concurrent with rapid increases in bottom temperature (Figure 11) and 

decreases in stratification (Figure 14). This concurrence, in conjunction with the fewer recorded noise 

events in the deeper Outer stratum when compared to the two inshore strata, suggests that large, extended 

increases in bottom noise are caused by surface conditions during large wind events. Notably, four large 

pulses of noise across strata during March 2018 align with four recorded nor’easters during that time 

period. As previously mentioned (see Section 4.2. Receiver Range Testing), these storms can cause 

intense surface noise that likely impact receiver detection distance.
38

Figure 15. Average daily noise level (mV) for the Inner (pink), MD WEA (green), and Outer (blue) 

strata. 

Spikes above 300 mV indicate protracted noise events associated with wind events, which likely interfered with 

receiver detection efficiency.

4.6 Seasonal incidence

Recovered telemetry data indicate that both Atlantic sturgeon and striped bass were detected extensively 

within the MD WEA but patterns of incidence were highly seasonal. Atlantic sturgeon occurred over 

broad periods during early spring-early summer and early autumn-early winter each year (Figure 16), 

with very few detections during later summer or winter months. There were significant differences in the 

number of individuals detected seasonally for each species (Table 7). Pairwise comparisons using Dunn’s 

post hoc test showed that more Atlantic sturgeon were detected during autumn compared to all other 

seasons and that individual incidence was greater during the winter than the summer. Incidence did not 

significantly differ between spring and summer or winter and spring. Cross-shelf strata differences were 

evident across all seasons (Table 8). Pairwise comparisons of number of individual Atlantic sturgeon 

were significant for all strata with the Inner stratum exhibiting nearly 3-fold higher average incidence 

than the MD WEA and Outer regions, and the MD WEA stratum having higher individual incidence than 

the Outer stratum. These patterns were relatively consistent across years with sturgeon having a broader

distribution in autumn and winter months than in spring and summer (Figure 17). However, Atlantic 

sturgeon had somewhat higher individual incidence throughout 2018.
39

Figure 16. Seasonal occurrence of Atlantic sturgeon.

Number of unique individual Atlantic sturgeon recorded per receiver, summed per day. Gray shading represents the 

minimum and maximum values of incidence across the array. Black lines show the mean number of individuals 

detected across the array.

Table 7. Seasonal and spatial differences in Atlantic sturgeon incidence.

Statistical results from Kruskal-Wallis (K-W) and Dunn’s post-hoc tests on how number of individuals detected vary 

between seasons and strata. Asterisks indicate statistical significance.

K-W Dunn’s test

X2 p z p

Season 42.85 <0.001*

Autumn-Spring 4.257 <0.001*

Autumn-Summer 6.253 <0.001*

Autumn-Winter 3.120 0.006*

Spring-Summer 1.822 0.205

Spring-Winter -1.473 0.420

Summer-Winter -3.471 0.002*

Stratum 52.27 <0.001*

Inner-MD WEA 3.234 0.002*

Inner-Outer 7.092 <0.001*

MD WEA-Outer 5.452 <0.001*
40

Figure 17. Patterns of Atlantic sturgeon incidence throughout the study period. 

Figure shows mean number of individuals detected by receivers within each stratum and each season/year.

Compared to Atlantic sturgeon, striped bass had a higher mean number of individuals detected on each 

receiver per day (Figure 18). Additionally, striped bass exhibited more sporadic but concentrated seasonal 

incidence; greater numbers of individuals occurred December-February and early April both years. 

Striped bass were consistently absent from the array across summer and autumn months. Pairwise 

comparisons showed significant differences in striped bass incidence between all seasons except between 

spring and winter (Table 8). Individual striped bass incidence was highest in the winter and lowest in the 

summer. In terms of cross-strata differences in occurrence, striped bass incidence only varied 

significantly between the MD WEA and Inner strata; in this case, more individuals were detected in the 

MD WEA region over the study period. Across years, there was a consistent pattern in which striped bass 

displayed a higher concentration in the MD WEA stratum during winter that shifted toward the Outer 

region during spring (Figure 19). During 2018, there appeared to be reduced presence of striped bass in 

the MD WEA stratum and more detection occurred at Outer stratum sites compared to the preceding year.
41

Figure 18. Seasonal occurrence of striped bass.

Number of unique individual Atlantic sturgeon recorded per receiver, summed per day. Gray shading represents the 

minimum and maximum values of incidence across the array. Black lines show the mean number of individuals 

detected across the array.

Table 8. Seasonal and spatial differences in striped bass incidence.

Statistical results from Kruskal-Wallis (K-W) and Dunn’s post-hoc tests on how number of individuals detected vary 

between seasons and strata. Asterisks indicate statistical significance.

K-W Dunn’s test

X2 p z p

Season 86.20 <0.001*

Autumn-Spring -3.689 <0.001*

Autumn-Summer 3.266 0.003*

Autumn-Winter -5.856 <0.001*

Spring-Summer 6.349 <0.001*

Spring-Winter -1.549 0.364

Summer-Winter -8.504 <0.001*

Stratum 8.949 0.01*

Inner-MD WEA -2.863 0.006*

Inner-Outer -1.068 0.429

MD WEA-Outer 1.555 0.198
42

Figure 19. Patterns of striped bass incidence throughout the study period. 

Figure shows mean number of individuals detected by receivers within each stratum and each season/year.

4.7 Transit rates and patterns

Analysis of the number of unique strata visited by each individual fish revealed that yearly patterns of 

cross-shelf connectivity differed across species and seasons. Although their inshore-offshore movement 

was relatively limited, striped bass were more likely than sturgeon to transit between multiple strata, 

especially during their autumn/winter migration (Table 9). Striped bass showed comparatively less crossshelf movement during the spring/summer period, reflecting faster spring transit rates. Although sturgeon 

showed extended presence in the fall and winter during both years, they exhibited little movement 

between strata, suggesting a directed north/south movement in both seasons
43

Table 9. Number of Strata visited by each individual striped bass and Atlantic sturgeon during 

each season and year.

Season/Year # Strata visited by each individual

Atlantic Sturgeon

1 2 3

Autumn/Winter

2017 97 11 N/A

2018 152 30 N/A

2019 125 8 1

Spring/Summer

2017 88 5 N/A

2018 121 5 N/A

Striped Bass

1 2 3

Autumn/Winter

2017 167 60 4

2018 165 47 1

2019 48 3 N/A

Spring/Summer

2017 123 38 N/A

2018 90 5 N/A

Degree of residency tended to be low for both Atlantic sturgeon and striped bass; average cumulative time 

spent in the detection radius of receivers per migration season was less than 4 hr for both species (Figure 

20; Atlantic sturgeon: mean ± SE = 3.04 ± 0.26 hr; striped bass: 3.25 ± 0.13 hr). Total number of unique 

days detected for each species were also relatively low across migration seasons (Figure 21; Atlantic 

sturgeon: mean ± SE = 1.6 ± 0.04 d; striped bass: 2.55 ± 0.05 d). Differences in residency were 

statistically significant, with striped bass occurring for more hours and days than sturgeon (Wilcoxon rank 

sum test, hours: p < 0.001; days: p < 0.001). Striped bass were also detected for more hours and days 

during autumn/winter months compared to spring/summer months (hours: p < 0.001; days: p < 0.001). 

Like striped bass, sturgeon were detected for more days on average during autumn/winter months (p

<0.001) but hourly presence did not differ between migration seasons (p = 0.09). 
44

Figure 20. Boxplot of total hours present in the array.

Average number of hours each individual Atlantic sturgeon and striped bass was detected in the study array by 

season and year depicted normally (top) and with outliers removed to better visualize average duration of presence 

patterns (bottom). 
45

Figure 21. Boxplot of total days present in the array.

Average number of days each individual Atlantic sturgeon and striped bass was detected in the study array by 

season and year depicted normally (top) and with outliers removed to better visualize average duration of presence 

patterns (bottom). 

Serial detections of striped bass between the coastal MD and DE arrays mostly occurred in the 

expected direction of movement: south in autumn/winter and north in spring/summer (Figure 22). There 

were occasional instances where individuals made both north and south transits within a migration season 

(spring 2017: 3 of 38 individuals; autumn 2017: 3 of 33 individuals; autumn 2018: 8 of 23 individuals). 

Sequential detections between arrays were noticeably reduced during spring of 2018, in which 

telemetered fish were detected more often in the MD array than the DE array (Figure 22). During 

autumn/winter, mean transit rate in the southerly direction was 0.99 km hr-1 ± 0.11 SE and during 

spring/summer, mean transit rate in the northerly direction was 1.13 km hr-1 ± 0.2 SE. Although the fastest 

observed transit rates (> 2 km hr-1

) tended to occur in the northern direction during spring, speed was 
46

similar between the two directions of movement (t = –0.106, df = 108.43, p = 0.92). The maximum 

observed transit rates of 6 km hr-1 would translate to 1.7 m s-1

, or about two body lengths per second. 

Each of the best performing models (< 2 Δ AICc) predicting transit rates contained TL at tagging as a 

covariate and all models that included interactions were ranked lower than the null model (Table 10). 

Only TL was found to significantly affect transit rate with larger fish being more likely to transit faster 

between arrays (Table 10; Sex p = 0.41, Season p = 0.15, Year p = 0.29, TL p = 0.02). 
47

Figure 22. Summary of transit information for striped bass 

Transit rate of movement by tagging region (top panel), timing of detection for acoustically-tagged individuals by 

region of tagging (middle panel), and average bottom temperature recorded by receivers (bottom panel) are shown.
48

Table 10. Striped bass transit rate linear mixed model results 

Parameters and factors for the top 5 models for log-transformed striped bass transit rate (Log km hr -1) including Tag 

ID as a random effect (1 | Tag) to account for repeated measures. TL= Total length in cm. AICc = corrected Akaike’s 

Information Criterion; LogLik = Log Likelihood.

Model df AICc Δ AICc LogLik

Log km hr -1 ~ TL + (1 | Tag) 4 230.5 0.00 -110.992

Log km hr -1 ~ Season + TL + (1 | Tag) 5 231.5 1.07 -110.403

Log km hr -1 ~ Year + TL + (1 | Tag) 5 232.0 1.57 -110.654

Log km hr -1 ~ Sex+ TL + (1 | Tag) 5 232.5 2.02 -110.882

Log km hr -1 ~ 1 + (1 | Tag) 3 233.5 3.03 -113.600

4.8 Distribution and depth of occurrence for tagged striped bass

The vast majority (95%: 38 of the 40) of striped bass implanted with depth-transponding acoustic 

transmitters were subsequently detected in the ACT network of telemetry arrays (Figure 23) between 

April 24, 2017 and March 27, 2019, but less than half (19) were detected in the MD WEA array and were 

recorded during either December 2017 – January 2018 (n=11), April 2018 – May 2018 (n=12), or 

December 2018 (n=8). Other detections were provided to us through the ACT Network arrays in: 

Chesapeake and Delaware Bays; Merrimack, Hudson, Potomac, and James Rivers; coastal Massachusetts, 

New York, New Jersey, Delaware, Maryland, and Virginia (Figure 23). The greatest number of detections 

occurred in the Merrimack River (n=11,349), which was likely the result of prolonged residence and close 

proximity to receivers by four Massachusetts-tagged individuals (Figure 24). With the exception of these 

high-density return records from the Merrimack River, most detections occurred along the Massachusetts 

coastline (n=8,151) and in the upper Chesapeake Bay (n = 4,936). Depictions of detection returns should 

not be interpreted as absolute presence or absence, as they do not indicate when receivers were deployed 

or removed and some data may not have been shared with project PIs as of the date of this report 

(February 2020).
49

Figure 23. Locations of depth-transponding striped bass tag detections. 

Figure 24. Summary of depth-transponding striped bass returns.

Timing of detection for individual striped bass tagged in the Potomac River, MD (n = 26, upper panel) and Coastal 

Massachusetts (n = 12, lower panel). Colors indicate the array of detection.
50

Fish tagged in the Potomac River showed two distinct movement patterns: 1) directed movement to, and 

residency in, the upper Chesapeake Bay and 2) migration into shelf waters, summer residency in 

Massachusetts, and gradual southerly movement from fall through and early spring with some fish 

eventually residing in waters off Virginia for a protracted period of time (Figure 24). All striped bass 

tagged in coastal Massachusetts departed from the area by November and gradually moved south through 

coastal New York, Delaware, and Maryland after the first year of tagging. This movement mirrors that of 

the late-April-tagged migratory-Potomac group, although Potomac fish appear to depart Massachusetts 

waters earlier (Figure 24). Detection histories were noticeably less complete during late 2018 (due to 

removal of receivers or lack of data-sharing), but migration trends appeared to be similar for the two-year 

duration of the study. Still, there were individuals and small groups of tagged striped bass that exhibited 

extended stopovers in areas like the Hudson, James, and Merrimack Rivers that deviated somewhat from 

mean group behavior (Figure 24).

Depths of tagged striped bass ranged from 0 to 36 m over the study period, with no noticeable differences 

in depth preference between fish or tagging groups (Figure 25). General depth of occurrence instead 

appeared to align with observed migration patterns; shallow detection depths were observed when striped 

bass occurred in nearshore and estuarine habitats while deeper detections corresponded with known 

periods of movement through coastal waters (Figure 25). Densities of detection depth by region 

confirmed that striped bass occurred at greater depths across coastal arrays compared to other sites 

(Figure 26). Among coastal arrays, mode of depth selection was slightly deeper in the Maryland and 

Virginia arrays than in Delaware or New York. Detection depths were the most shallow in the Merrimack 

River, Coastal Massachusetts, near Long Island, and in the Delaware River, while deeper modes were 

found in nearshore New Jersey and in tributaries of the Chesapeake Bay. Striped bass in the Hudson River 

strongly preferred depths just above 5 meters. High detection densities away from the surface occurred in 

the Upper Chesapeake Bay (~ 5 m depth) and was especially noticeable at the mouth of the Chesapeake 

Bay (~ 15 m depth).

Figure 25. Depth of detection (meters) of individually-tagged striped bass through time.
51

Figure 26. Density of tagged striped bass depths (in meters) by telemetry array.

Within the MD WEA array, 19 depth-transponding striped bass were detected from December 2017 

through December 2018. During the autumn/winter 18 period, striped bass were initially detected at 

shallower depths in the WEA array before shifting to deeper water in the Outer array through January 

(Figure 27). In autumn/winter 19, striped bass occurred at more shallow WEA locations. In April and 

May 2018, striped bass were detected throughout the water column in the Outer array during an early 

spring migration interval and near the surface in the WEA during a later migration interval, respectively. 
52

Figure 27. Depth of striped bass detection by transect within the MD WEA receiver array.

4.9 Environmental covariates of MD WEA incidence

The two shallowest receivers were a hot spot for Atlantic sturgeon within the array, especially during 

spring and summer seasons (Figure 28). This hot spot diminished during the autumn, with simultaneous 

evidence for a cold spot (90% confidence, p < 0.1) at the deepest Outer stratum receivers in the same 

season. During winter, there was an area of increased clustering for Atlantic sturgeon in the deeper 

section of the MD WEA stratum and a significant cold spot (99% confidence, p < 0.01) at the deepest 

sites. Striped bass detection hot spots were only identified within the Middle region. However, clustering 

occurred at shallower depths during the autumn compared to winter and spring. No striped bass were 

detected during summer months. 
53

Figure 28. Hot spots of species occurrence across the acoustic receiver array. 

Results reflect annual (left) and seasonal (insets, right) numbers of individual Atlantic sturgeon (top) and striped bass 

(bottom) detected per receiver.

Atlantic sturgeon were detected over nearly the entire range of bottom temperatures recorded by receivers 

(4.3 - 24.2°C), suggesting little to no temperature limits in this region (Figure 29). This is reflected in 

large pulses of detections in both the warm- (April – July) and cold-water (September – January) periods 

(Figure 16).
54

In comparison to Atlantic sturgeon, striped bass were detected over a relatively narrow temperature band 

(5°C - 15°C), completely absent during the highest temperatures occurring in the summer (Figure 29). In 

both autumn/winter 17 and 18, number of individual striped bass day-1 increased at offshore strata, 

departing more shoal strata as temperatures were cooling in winter (Figure 19). 

Figure 29. Density of detections by receiver-recorded temperature.

Kernel density estimate of the bottom temperature distribution for detections for Atlantic sturgeon and striped bass.

Single Parameter Quotient analysis showed that in all seasons, sturgeon preferred relatively warm bottom 

temperatures between 9-22°C (Figure 30). Warmer seasonal conditions were only avoided by Atlantic 

sturgeon when temperatures exceeded 22°C in autumn. During autumn months, sturgeon actively selected 

relatively cool temperatures between 10-14°C but were still broadly tolerant of temperatures between 14-

22°C. Otherwise, across winter, spring, and summer, sturgeon avoided cooler seasonal temperatures.

As anticipated from incidence data (Figures 18-19), striped bass significantly avoided temperatures higher 

than 15°C and were not present at all during the warm summer months (Figure 31). During autumn,

striped bass selected the coolest available temperatures < 14°C and during winter, they preferred 

temperatures between 9-12°C. Similar to autumn months, striped bass avoided warmer seasonal 

conditions during winter, but the coolest regional temperatures, <6°C, were also significantly avoided. 

Temperature selection by striped bass occurred within a narrow window during spring months, between 

4-12°C, with preference occurring within the 6-7 °C temperature bin. Temperatures higher than 12°C

were avoided by striped bass during this season, but wider confidence bands (as a result of low sample 

size) limit this inference.
55

Figure 30. QI plots for Atlantic sturgeon during each season. 

Each plot shows the observed QI curve (solid red line), its CI (dashed red lines), and the frequency histogram of 

temperature. The dotted black line in each plot indicates the value QI = 1.

Figure 31. QI plots for striped bass during each season

Each plot shows the observed QI curve (solid red line), its CI (dashed red lines), and the frequency histogram of 

temperature. The dotted black line in each plot indicates the value QI = 1.
56

4.10 Predictive habitat models

4.10.1 Daily relative abundance model

A total of 753 potential predictive models were considered for each species. For Atlantic sturgeon, the top 

10 models all contained an interaction between depth and DOY (Table 11). The top three ranked models 

all included significant effects of CHL-A, the interaction between DOY and depth, and the magnitude of 

SST change over the previous 3-4 days. AIC scores and deviance explained were similar among these 

three models (<Δ2 AIC; <Δ1% deviance explained), but the model containing a smooth for SST Δ4 d had 

the best overall performance and was selected as the best fitted GAMM.

For striped bass, the interaction between depth and DOY was also retained in the 10 best models (Table 

11). However, in contrast to the importance of SST change on the 3-4 day timescale identified in Atlantic 

sturgeon models, the top ranked models for striped bass showed that abundance was more influenced by 

the magnitude of SST change over the previous 15-20 days. Though top-ranked striped bass GAMs 

explained a similar amount of deviance (<Δ2% deviance explained), the best model, which contained a 

significant effect of SST Δ17, resulted in an AIC score that was substantially lower than the next best 

model (>Δ10 AIC).

Table 11. Summary of GAMM model formulas for the top ten predictive models for each species.

Degrees of freedom (df), Akaike information criterion (AIC), and percent deviance explained are shown for models, 

ordered by AIC score. Considered predictors are chlorophyll-a concentration (CHL-A), magnitude of SST change 

(SST Δ1-13), day-of-year (DOY), and depth. Model term “s” represents singular smooth terms (single factors) and “t2” 

represents tensor-product smooth interactions (interaction between factors with different scales). Selected models 

are at the top of the table for each species.

Model terms df AIC Deviance 

explained

Atlantic Sturgeon

s(CHL-A) + s(SST Δ4) + t2(DOY, Depth) 51.99133 5042.376 79.9%

s(CHL-A) + s(SST Δ2) + t2(DOY, Depth) 53.02093 5043.901 79.9%

s(CHL-A) + s(SST Δ3) + t2(DOY, Depth) 52.58188 5044.783 80%

s(CHL-A) + s(SST Δ23) + t2(DOY, Depth) 53.71414 5045.779 79.7%

s(SST Δ4) + t2(DOY ,Depth) 45.59794 5047.142 79.5%

s(SST Δ2) + t2(DOY, Depth) 46.97376 5047.626 79.4%

s(CHL-A) + s(SST Δ9) + t2(DOY, Depth) 52.24633 5047.696 79.5%

s(SST Δ3) + t2(DOY, Depth) 46.65425 5049.766 79.5%

s(CHL-A) + s(SST Δ5) + t2(DOY, Depth) 50.25464 5050.407 79.7%

s(CHL-A) + s(SST Δ22) + t2(DOY, Depth) 52.45791 5050.455 79.5%
57

Striped Bass

s(CHL-A) + s(SST Δ17) + t2(DOY, Depth) 57.19528 7090.493 60.1%

s(CHL-A) + s(SST Δ16) + t2(DOY, Depth) 56.85801 7103.559 60.1%

s(CHL-A) + s(SST Δ19) + t2(DOY, Depth) 57.85631 7112.665 59.6%

s(SST Δ17) + t2(DOY, Depth) 52.41223 7116.058 59.9%

s(CHL-A) + s(SST Δ18) + t2(DOY, Depth) 57.08371 7123.809 59.5%

s(SST Δ16) + t2(DOY, Depth) 52.65560 7125.717 59.9%

s(SST Δ19) + t2(DOY, Depth) 52.26835 7141.836 59.4%

s(SST Δ18) + t2(DOY, Depth) 52.31685 7147.398 59.3%

s(CHL-A) + s(SST Δ20) + t2(DOY, Depth) 58.17577 7159.898 58.6%

s(CHL-A) + s(SST Δ15) + t2(DOY, Depth) 56.28915 7161.697 58.9%

The best predictive model for Atlantic sturgeon revealed a bimodal response to the magnitude of SST 

change over the previous 4 days; individuals were most likely to occur when surface temperature had 

decreased ~ 2.5°C or when it had increased more rapidly, by up to 4°C (Figure 32). Greater abundance of 

Atlantic sturgeon was also more likely at lower CHL-A concentrations with a peak in predicted 

occurrence just above a concentration of 5 mg m -3

. Atlantic sturgeon exhibited a complex response to 

depth in which individuals were more likely to occur at shallow depths (< 20 m) during the spring but 

were more broadly distributed across mid-range and shallow depths (~15-35 m) during autumn and winter 

(Figure 33). The 5-fold cross-validation RMSE of the model was 0.29 ± 0.01 and average error was -

0.001 ± 0.004, meaning the model-predicted abundance was 0.06 of the maximum number of sturgeon 

per receiver deployed (maximum =5) with an error <0.01 of the maximum and thus error was small 

compared to the units of individual incidence. Model diagnostics did not show spatial or temporal 

autocorrelation in residuals (Figures 34 and 35).
58

Figure 32. GAMM Summed effects of the magnitude of sea surface temperature change over the 

previous 4 days (SST Δ4; top) and chlorophyll-a concentration (CHL-A; bottom) on 

the relative abundance of Atlantic sturgeon. 

Shading represents ± 2 standard error. Both predictions are made on day-of-year =300 and depth=15 m to represent 

conditions when sturgeon are expected to occur. Mean SST Δ4 and CHL-A were set as the conditions in each 

corresponding prediction. Random effects were excluded to allow for interpretability across all sites and years.
59

Figure 33. GAMM response function for the interaction between day-of-year and depth from the 

best model of Atlantic sturgeon relative abundance. 

Visualizations are on the response scale and warmer colors indicate a higher predicted number of individuals.
60

Figure 34. Summary plots for Atlantic sturgeon relative abundance model temporal residuals 

Distribution of residuals over time (top panel), autocorrelation function plot of residuals (ACF, middle panel), and 

partial autocorrelation plot of residuals (Partial ACF, bottom panel). 
61

Figure 35. Semi-variogram of residuals from best Atlantic sturgeon relative abundance model 

using latitude and longitude to calculate distance between sites.

The selected GAMM for striped bass predicted the highest number of individuals when SST had 

decreased ~ 4°C or increased more than 4°C over the preceding 17 days (Figure 36). Higher striped bass 

abundance was also likely when SST had remained relatively constant (Δ0) over 17 days. Striped bass 

had increased likelihood of occurrence as CHL-A concentration increased. Like Atlantic sturgeon, striped 

bass abundance varied spatially over the DOY. During early winter, relative abundance was highest at 

mid-range depths (20-30 m) but shifted toward greater depths (> 35 m) during later winter months (Figure 

37). Striped bass were likely to occur over a broader range of depths during spring, but were predicted to 

have the highest abundance at depths between 25 and 30 m. The optimal model had a 0.05 error rate 

compared to the maximum (maximum=15; RMSE 0.84 ± 0.07) with an average error <0.01 (average 

error 0.003 ± 0.022) calculated by k-fold cv score. There was no residual spatial or temporal 

autocorrelation patterns apparent in ACF, PACF, of semi-variogram plots (Figures 38 and 39).
62

Figure 36. GAMM Summed effects of magnitude of sea surface temperature change over the 

previous 17 days (SST Δ17; top) and chlorophyll-a concentration (CHL-A; bottom) 

on the relative abundance of striped bass.

Shading represents ± 2 standard error. Both predictions are made on day-of-year =350 and depth=25 m to represent 

conditions when striped bass are expected to occur. Mean SST Δ17 and CHL-A were set as the conditions in each 

corresponding prediction. Random effects were excluded to allow for interpretability across all sites and years.
63

Figure 37. GAMM response function for the interaction between day-of-year and depth from the 

best model of striped bass relative abundance. 

Visualizations are on the response scale and warmer colors indicate a higher predicted number of individuals.
64

Figure 38. Summary plots for striped bass relative abundance model temporal residuals

Distribution of residuals over time (top panel), autocorrelation function plot of residuals (ACF, middle panel), and 

partial autocorrelation plot of residuals (Partial ACF, bottom panel). 
65

Figure 39. Semi-variogram of residuals from best striped bass relative abundance model using 

latitude and longitude to calculate distance between sites.

4.10.2 Environmental and individual drivers of weekly residency

Inclusion of the first-order lagged weekly occurrence markedly improved residual temporal 

autocorrelation in all individual residency models for both species. Although addition of second and third 

order correlation terms increased the explained deviance, these terms added excess complexity and did 

not considerably improve ACF and PACF-visualized autocorrelation. Analysis thus proceeded with the 

use of a first-order autocorrelation structure, or 1-day state-dependence residency lag only. 

The weekly residency models for Atlantic sturgeon and striped bass showed that SST and week-of-year 

were significant predictors of the number of days individuals were present in the array (Table 12). 

However, unlike predictive habitat models, CHL-A concentration was not a significant predictor of 

Atlantic sturgeon occupancy at the αα = 0.05 level. The residency model for Atlantic sturgeon showed that 

the individual random effect was important and that response differed between Chesapeake Bay vs. South 

Carolina Rivers, Chesapeake Bay vs. Virginia Rivers, and Coastal Delaware vs. Virginia River tagging 

regions (Table 12: Wald test, p < 0.05 ). For striped bass, the effect of CHL-A concentration on residency 

was significant; however, the random effect of transmitter was not significant. Pairwise comparison 

between tagging regions revealed differences in response between the Delaware River vs. Coastal 

Massachusetts and Delaware River vs. Hudson River origins (Table 12: Wald test, p < 0.05 ).
66

Table 12. Parameter and pairwise factor comparison significance for weekly species residency 

GAMMs.

Significance of model parameters and pairwise tagging region factors (Origin) are indicated by asterisks (<0.001= ***; 

0.001-0.009 =**; 0.01-0.009=*; 0.05-0.1=.). For Atlantic sturgeon, tagging regions are CB = Chesapeake Bay; SC = 

South Carolina Rivers; DE Coast = Atlantic Coast of Delaware; VA = Virginia Rivers. Striped bass tagging regions 

are: Hudson = Hudson River, New York; Potomac = Potomac River, Maryland; MA = Coastal Massachusetts; 

Kennebec = Kennebec River, Maine.

Species Term p-value df AIC Deviance 

explained

Atlantic Sturgeon

s(SST) 0.017 * 85.20 7453.49 68.6%

s(Week) <0.001 ***

s(CHL-A) 0.112

s(Lag 1 Residency) <0.001 ***

s(Transmitter) 0.012 *

Origin: CB with SC 0.039 *

Origin: DE Coast with SC 0.058 .

Origin: CB with VA 0.033 *

Origin: DE Coast with VA 0.028 *

Origin: DE Coast with CB 0.503

Origin: SC with VA 0.542

Striped Bass

s(SST) <0.001 *** 25.83 9899.17 56.2%

s(Week) <0.001 ***

s(CHL-A) <0.001 ***

s(Lag 1 Residency) <0.001 ***

s(Transmitter) 0.593

Origin: Hudson with Potomac 0.200

Origin: Hudson with Kennebec 0.417
67

Origin: MA with Potomac 0.255

Origin: Hudson with MA 0.674

Origin: Kennebec with Potomac 0.789

Origin: DE River with Potomac 0.967

Origin: DE River with Kennebec 0.767

Origin: Kennebec with MA 0.507

Origin: DE River with MA 0.025 *

Origin: DE River with Hudson 0.025 *

Partial effects of environmental and temporal variables in species residency GAMMs were largely 

consistent with the responses observed in relative abundance modeling, but revealed variation in how 

these factors affected the amount of time individuals spent in the area. Additionally, contrasts between 

species were apparent. Atlantic sturgeon had a bimodal response to SST in which individuals were more 

likely to occupy the region when weekly, array-wide surface temperatures were around 10°C or 20°C 

(Figure 40). Temperatures between and outside these general ranges had a negative effect on sturgeon 

residency. Week-of-year was the most significant term in the model and showed that Atlantic sturgeon 

occupancy was highest during spring and autumn, with peaks in the number of days present around week 

20 (mid-May) and week 45 (mid-November), respectively. In contrast to Atlantic sturgeon, partial effects 

showed that temperatures <15°C were associated with higher striped bass residency while temperatures 

higher than this threshold negatively affected residency duration (Figure 41). Similar to the GAMM 

abundance model, striped bass were likely to occur for more days per week during winter and spring 

months and were unlikely to reside in the area during summer. Though CHL-A observations were 

skewed, striped bass occupancy was highest when concentrations were either just above 0 mg m-3 or very 

high between 10-20 mg m-3

.

Figure 40. Atlantic sturgeon: GAMM partial effects for sea surface temperature (SST, left), week-ofyear (right).

Chlorophyll-a concentration not plotted due to lack of significance. Rugs along the x-axis represent the distribution of 

observations.
68

Figure 41. Striped bass: GAMM partial effects for sea surface temperature (SST, top left), week-ofyear (top right), and chlorophyll-a concentration (CHL-A, bottom left).

Rugs along the x-axis represent the distribution of observations.

HGAM-predicted residency revealed that Atlantic sturgeon responded differently to SST and week-ofyear depending on their tagging origin. For sturgeon tagged in the Chesapeake Bay, Santee River, and 

Virginia Rivers, longer residency was most likely when SST was between 15-20°C (Figure 42). The 

group tagged off the Atlantic coast of Delaware differed in that individual residency was more likely at 

lower surface temperatures between 10-15°C. The highest predicted increases in residency in response to 

SST occurred for the Chesapeake Bay and South Carolina River groups. Individuals tagged in coastal 

Delaware and Virginia Rivers did not show the same magnitude of response to SST and were predicted to 

reside in the array for less time. There were also group-level differences in timing of arrival and amount 

of seasonal residency for Atlantic sturgeon in response to week-of-year. The week-of-year hierarchical 

model showed that degree of residency was fairly similar between spring and fall for sturgeon tagged in 

the South Carolina and Virginia Rivers (Figure 43). In contrast, individuals tagged on the Atlantic Coast 

of Delaware and in the Chesapeake Bay were more likely to reside longer in the area during autumn 

compared to spring. Sturgeon tagged off Delaware were predicted to arrive slightly earlier in the MD 

WEA array over both migration seasons compared to relatively later arrivals and peaks in residency for 

the Chesapeake Bay and Virginia tagging regions.
69

Figure 42. Predicted residency function (days per week ± 2 se) of Atlantic sturgeon for each 

tagging region based on the sea surface temperature (SST) across the MD WEA.
70

Figure 43. Predicted residency function (days per week ± 2 se) of Atlantic sturgeon in the MD WEA 

array for each tagging region based on week-of-year.

Group-level differences occurred in how striped bass responded to SST and week-of-year, but variation in 

response to CHL-A concentration was less apparent. Residency predictions were highest when SST was < 

15°C, with striped bass tagged in the Delaware and Potomac Rivers showing peaks in the number of days 

detected at 10°C (Figure 44). Individuals tagged in coastal Massachusetts and the Kennebec River had a 

slightly flatter response to SST and were predicted to reside for less time over a broader range of 

temperatures (5-10°C) compared to the other groups. All tagging regions showed a similar pattern of 

lower residency in the spring and higher residency in the winter, but individuals tagged in the Hudson 

River were predicted to occupy the region for the greatest amount of time in both seasons (Figure 45). 

The peak in spring residency also appeared to occur slightly earlier in the spring for Hudson fish 

compared to other groups. Group-level heterogeneity was not obvious in the response of striped bass to 

chlorophyll-a concentration (Figure 46).
71

Figure 44. Predicted residency function (days per week ± 2 se) of striped bass for each tagging 

region based on the sea surface temperature (SST) across the MD WEA.

Figure 45. Predicted residency function (days per week ± 2 se) of striped bass in the MD WEA 

array for each tagging region based on week-of-year.
72

Figure 46. Predicted residency function (days per week ± 2 se) of striped bass in the MD WEA 

array for each tagging region based on chlorophyll-a concentration (CHL-A).

5 Discussion

5.1 Migration through the MD WEA

Biotelemetry of striped bass and Atlantic sturgeon in the MD WEA confirm that this region is occupied 

extensively and used by the two species as a migration corridor. Large numbers of both species were 

detected during the two-year study – 378 tagged Atlantic sturgeon and 316 tagged striped bass – with 

most of the returns within the footprint of the MD WEA, but movement metrics and analyses indicated 

that this MAB shelf region mainly functions as a transient migration corridor for these species. Few

individuals were detected in the array for longer than two days, which implies relatively rapid movement 

through the study area. However, there were notable differences in migration patterns between seasons 

and species. Both species were more likely to reside for multiple days during the autumn and winter 

months and cross-shelf movements were also more common during these months. Although some 

individual sturgeon exhibited multiple-day residency in the array, those that transited through within a 

day did so more rapidly than striped bass. 

In contrast to our original hypothesis, Atlantic sturgeon appeared to migrate through the MAB shelf 

region relatively quickly, with only a few instances (n=15) of seasonal residence ≥ 24 hr. These transit 

rates may indicate a lack of favorable conditions available for Atlantic sturgeon in the MD WEA. Species 

like sturgeons are known to exhibit reduced movement rates in habitats with favorable conditions, while 

faster movement rates are more likely to occur where conditions are less suitable or physically taxing 

(Avgar et al. 2013). The lack of residency by Atlantic sturgeon may also relate to this shelf region serving 

as a transit route between northern spawning and nearshore summer feeding grounds and southern winter 

habitat (Figure 47). Atlantic sturgeon in the coastal ocean are known to concentrate around the mouths of 

inlets and estuaries in spring, summer, and fall (Dunton et al. 2010; Erickson et al. 2011). Within these 

regions, sturgeon have been found to associate with river plumes or sandy and muddy substrates that may 

offer increased foraging opportunities (Savoy and Pacileo, 2003; Laney et al. 2007; Oliver et al. 2013; 

Breece et al. 2016). Catches and returns of Atlantic sturgeon in southern overwintering areas in Virginia 

and North Carolina similarly reflect an association with specific benthic types that support food resources 
73

(Laney et al. 2007; Erickson et al. 2011). The telemetered sturgeon detected in this study may be moving 

relatively quickly through Maryland’s shelf waters in order to reach spawning grounds or more favorable 

nearshore (estuarine outlet) foraging habitats. Relevant detailed information on Atlantic sturgeon 

migration behaviors (in terms of transit and occupancy) can be found in the final report produced by 

University of Delaware colleagues responsible for the complementary DE WEA acoustic array (Haulsee 

et al. 2020; https://espis.boem.gov/final%20reports/BOEM_2020-020.pdf).

Figure 47. Conceptual diagram of seasonal MAB distribution for Atlantic sturgeon.

Distribution during autumn/winter months is shown on the left; spring/summer on the right. Horizontal shading 

indicates recognized aggregation areas, which are also labeled. Arrows show general movement patterns with line 

thickness corresponding to the shelf-scale spatial distribution of individuals (wide for broad distribution, narrow for 

more limited distribution).

Striped bass showed greater relative residency than Atlantic sturgeon during fall and winter and very 

rapid spring time migration through the MD WEA. Further, residency and transit results revealed 

previously undocumented occupancy of striped bass in outer shelf waters during winter months. Rapid 

movement through the study area was common for striped bass, with larger fish showing faster transit 

rates than smaller individuals. Striped bass movement behavior during spring supported our original 

hypothesis of rapid transit through the MAB shelf region associated with post-spawning migrations. The 

highest rates of transit tended to occur in a northerly direction in the spring, corresponding with 

northward movement toward Delaware and Hudson River spawning areas or summer foraging grounds 

located off the coast of Massachusetts (Figure 48; Koo 1970; Collette and Klein-MacPhee 2002; Welsh et 

al. 2007). Spring transits > 4 km hr-1 would translate to 1.1 m s-1

, or roughly 1-1.5 body lengths s

-1 for an 

80 cm TL striped bass. Although these speeds are well below maximum sustained swimming speeds of 

2.9–3.3 body lengths s-1 for striped bass (Freadman 1979), they are greater than mean southern transits, 

which were closer to 0.3 m s-1

, or 1/3 body lengths s

-1

. Still, uniform directionality was not always 

observed and sequential detections were not consistent during spring 2018, leading to equivalent northern 

vs. southern transit rates. Although striped bass appeared to move through the region between the MD and 

DE WEAs relatively rapidly in our study, this does not preclude extended stopovers in other areas such as

New Jersey estuaries or Long Island Sound during the spring, which have been recorded in the past (Able 

and Grothues 2007; Grothues et al. 2009; Kneebone et al. 2014). Other telemetry studies have found 

highly variable rates of transit among individual striped bass during spring, but together with this study 

suggest that striped bass emigrate relatively quickly from overwintering and spawning regions, likely 

motivated by warming temperatures (Kneebone et al. 2014; Callihan et al. 2015).
74

Figure 48. Conceptual diagram of seasonal MAB distribution for striped bass.

Distribution during autumn/winter months is shown on the left; spring/summer on the right. Horizontal shading 

indicates recognized aggregation areas, which are also labeled. Arrows show general movement patterns with line 

thickness corresponding to the shelf-scale spatial distribution of individuals (wide for broad distribution, narrow for 

more limited distribution).

The current function of the MD WEA as a migration corridor could be altered with the addition of wind 

turbine structures, causing increased stop-over behavior during seasonal migrations owing to alterations 

in local food webs. As a possible analogous example, oil and gas production rigs in the Gulf of Mexico

and off California provide habitat and promote increased abundance of numerous fish species (Wilson et 

al. 2003; Lindquist et al. 2005; Claisse et al. 2014). Though production of biomass versus attraction of 

individuals as the source of such observations is debated (Bohnsack 1989), platform structures lead to 

demonstrable behavioral changes in demersal reef fishes and transient pelagic top-order predators alike 

(Keenan et al. 2007; Szedlmayer 2007; Todd et al. 2009). Like other large predators, striped bass may be 

attracted to smaller fish schooling around turbine structures and could dwell longer in the region as they 

forage on these prey species. Fish aggregations patterns have been noted around wind turbine foundations

(Reubens et al. 2013) and inactive tidal turbines (Viehman et al. 2018). Beyond fish assemblages, 

petroleum or wind energy platforms influence entire food webs, often promoting increased benthic 

biomass that may have spillover effects to the larger area surrounding the structures themselves 

(Lindeboom et al. 2011; Macreadie et al. 2011; Coolen 2017). Changes in benthic resources may thus

alter local Atlantic sturgeon movement as well; sturgeons are known to exhibit fidelity to regions with 

substrates that support infaunal prey availability (Lepage et al. 2005; Parsley et al. 2008). Depending on 

the type of benthic organisms that benefit from spillover effects of turbine installations, Atlantic sturgeon 

may, like striped bass, dwell longer in the MD WEA to forage during their migration through the area.

5.2 Functional habitat attributes of the MD WEA

Analysis of benthic, in-situ, and satellite-derived variables highlighted the heterogeneous and dynamic 

nature of the MD WEA habitat. Although the broader shelf region has been historically characterized as a 

relatively homogenous soft-bottom habitat, categorical descriptors of sediment and topography varied at a 

fine resolution over the MD WEA. Similar subtle complexity has been noted in previous shelf habitat 

assessments as factors that could affect the movement and behavior of fishes (Guida et al. 2017). 

Temperature, both at the surface and bottom of the water column, was seasonally dynamic in this study. 

Indeed, the MAB shelf is characterized by large changes in seasonal temperature (Δ 18°C sea surface 

temperature; He et al. 2010; Richaud et al. 2016), which shape regional shelf ecosystems. In our array, 
75

temperature preference and differential distributions suggest that Atlantic sturgeon and striped bass select 

distinct depth and temperature gradients rather than specific benthic characteristics.

Our results are consistent with past studies, in which adult and sub-adult Atlantic sturgeon in the Atlantic 

Ocean were frequently found over sand or mud substrates that are favorable for foraging. (Savoy and 

Pacileo 2003; Stein et al. 2004; Laney et al. 2007). Nearshore regions of the MAB are hypothesized to 

support benthic prey resources for Atlantic sturgeon (Bain 1997; Stein et al. 2004) and individuals 

captured along the shelf have shown evidence of feeding (Dovel and Berggren 1983; Johnson et al. 1997). 

A spatial shift in occurrence between spring/summer and autumn/winter has also been observed 

previously; Atlantic sturgeon are thought to utilize a broader range of depths during their autumn 

occupancy in the coastal ocean compared to a relatively shallow distribution during the spring (Stein et al. 

2004; Laney et al. 2007; Erickson et al. 2011; Breece et al. 2017). In our array, Atlantic sturgeon were in 

fact most likely to occur at the two receiver sites closest to shore, particularly during spring and summer. 

These inshore sites are associated with mostly fine sandy substrates and shallow flats with some NE-SW 

trending crests (Figure 12). Clustering at shallow sites was less apparent during autumn and winter, with a 

hot spot of sturgeon occurrence within a deeper portion of the MD WEA stratum. This area has relatively 

higher muddy sediment concentrations and more topography compared to the rest of the MD WEA sites.

Although we were unable to detect fine scale use of different substrate types, that may have been

associated with varying prey densities, broad spatial clustering rather than intensive use of specific sites in 

our study indicates the MD WEA serves more as a migration corridor than exclusive foraging habitat. 

Combined with rapid transit through the MD WEA (see previous section), results suggest that this portion 

of the shelf off Maryland does not currently provide optimal foraging conditions for Atlantic sturgeon. 

Throughout our study, striped bass clustered at receiver sites within the MD WEA stratum, but their 

distribution shifted seasonally. During spring, striped bass were more concentrated at deeper sites in the 

MD WEA stratum and in autumn, distribution shifted to the shallower portion of the MD WEA, which is 

near a known angler reef zone characterized by prominent cobble and gravel substrates (Guida et al. 2017, 

Figure 12). This area may provide increased structure or foraging opportunities compared to the rest of 

the Maryland MAB shelf since striped bass are known to be structure-oriented (Haeseker et al. 1996; 

Tupper and Able 2000; Harding and Mann 2003). Though there was little clustering in winter, striped 

bass did show some preference for a deeper site while avoiding more shallow sites. In general, striped 

bass were distributed over the deeper sites of the array, including the Outer stratum. Striped bass, like 

Atlantic sturgeon, likely utilize different migration corridors seasonally and prefer broader depth and 

temperature gradients rather than specific benthic characteristics. This inference is also supported by the 

fact that striped bass tended to utilize the entire water column during their incidence in the area. Given 

their pelagic distribution, individuals are likely not responding to benthic characteristics.

Temperature conditions had a stronger apparent influence on the habitat selection of both species

compared to substrate type. While Atlantic sturgeon were broadly tolerant of a wide range of 

temperatures, they were more likely to select the warmest available conditions. The temperature 

preferences identified here are supported by previous bioenergetic studies in which sturgeon metabolic 

rates (albeit those of juveniles < 1 m total length) increased with temperature but leveled off at warmer 

extremes of 24-28°C (Niklitschek and Secor 2009; 2010). Other work has suggested that temperature is 

key in structuring Atlantic sturgeon movement behavior. In the Delaware Bay, adult Atlantic sturgeon are 

known to transition from resident to active movement behaviors when sea surface temperatures decrease 

below 18-19°C (Breece et al. 2018). Lower temperature may therefore cause Atlantic sturgeon to move 

through the region more quickly in order to reach spawning destinations or more favorable foraging 

habitats along their migratory route. Striped bass differed from Atlantic sturgeon in that they preferred a 

relatively narrow range of cool bottom temperatures. Preferred temperatures between ~ 6-15°C are 

considerably lower than thermal niches reported for striped bass in landlocked environments, which are 

thought to range between 18-25°C (Coutant 1985) with a hypothesized fundamental niche between 19-
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23°C (Coutant 1990). However, striped bass are known to acclimate to a remarkably wide range of 

temperatures; the species may tolerate temperatures up to 30°C to avoid hypoxic conditions (Jackson and 

Hightower 2001; Thomson et al. 2010; Kraus et al. 2015) and remain active as low as 1.0°C (Clark 1968; 

Tagatz 1961). Notably, striped bass avoided the coolest temperatures that occurred during winter months 

in our study and likely shifted distribution toward regionally warmer deeper sites to maintain favorable 

habitat conditions.

5.3 Spatial and temporal patterns of habitat use by test species

The observed spatial and temporal patterns of Atlantic sturgeon presence were consistent with those 

previously described for this species along the US East Coast. Atlantic sturgeon were most abundant 

during the fall and spring months, when they are known to undertake coastal migrations (Smith, 1985; 

Erickson et al. 2011). Like our findings, tagging and bycatch records in the MAB shelf region have 

reported the highest numbers of sturgeon captures occurring in the spring and fall (Collins et al. 2000; 

Stein et al. 2004). The timing of this seasonal presence is likely dependent on movements between 

spawning rivers and coastal habitat during those same periods. Atlantic sturgeon from regions in the 

Chesapeake Bay and south are known to spawn during fall and may also have spring spawning runs while 

Atlantic sturgeon in regions north are known to have only a spring run (Balazik and Musick 2015; Hilton 

et al. 2016; ASMFC 2017). Atlantic sturgeon tended to be absent in our array when they were occupying 

riverine spawning and nearshore foraging habitats from the late spring through early fall (Borodin 1925; 

Stein et al. 2004). During the winter, sturgeon may be inhabiting relatively warmer habitats to the south, 

near Virginia and Cape Hatteras, where they have been shown to aggregate (Moser et al. 1998; Laney et 

al. 2007; Stein et al. 2004; Dunton et al. 2010, Figure X1). Similar to our results, past studies have 

recorded higher abundance of Atlantic sturgeon in shallow, near-shelf areas compared to deeper waters in 

the coastal region (Stein et al. 2004; Erickson et al. 2011; Ingram et al. 2019). Although there have been 

occasional instances of sturgeon occurring at greater depths (110 m, Timoshkin 1968), the species has 

been thought to remain relatively close to shore during its seasonal occupancy in oceanic waters. 

Patterns of striped bass occurrence also aligned with established seasonal migrations south in the fall and 

north in the spring, but revealed patterns of oceanic abundance that have not been documented in the past. 

Evidence for striped bass overwintering in the nearshore waters off Cape Hatteras has existed for some 

time (Chapoton and Sykes 1961; Benton 1992; Laney and Cole 1994, Figure X2), but other findings have 

suggested that a portion of the migratory contingent may winter in the shelf region as far north as Cape 

Cod, Massachusetts (Clark 1968; Wirgin et al. 1997). Although it has been postulated that striped bass 

may overwinter in areas along the MAB shelf, ours is the first to measure striped bass presence in the 

offshore Maryland region using acoustic telemetry. Further, a previous view was that striped bass seldom 

occur more than 6 to 8 km offshore (Bain and Bain 1982), however, our results show that individuals 

move to areas > 40 km from the coast. For autumn and winter, our results contradicted the original 

hypothesis that the coastal stock of striped bass would rapidly transit through the MD WEA. Instead, 

detections occurred throughout winter months and shifted toward the outer shelf as temperatures began to 

cool more rapidly near shore.

Striped bass showed a winter-time cross-shelf distribution pattern that was likely related to nearshore 

cooling; as winter progressed individuals selected deeper waters. A variety of other fish species in the 

Northwest Atlantic are known to undertake similar cross-shelf distributional shifts, including black sea 

bass, fluke (Paralichthys dentatus), and scup (Stenotomus chrysops) (Nesbit and Neville, 1935; 

Colvocoresses and Musick, 1984). Like these species, striped bass may select warmer shelf waters over 

the cooler winter waters of the inshore region to maintain preferred temperature conditions. Temperature 

data from receivers supported the persistence of warmer temperatures at outer shelf sites compared to 

cooler MD WEA and inshore sites during autumn/winter 2017. The diminished presence of striped bass 

during autumn/winter 2018 may be due to the cooler winter temperatures that occurred in 2018 
77

throughout all shelf strata. These relatively cooler temperatures may have caused striped bass to move 

faster or farther offshore, leading to fewer overall detections during the second autumn/winter season.

5.4 Study design limiting assumptions

Here we used biotelemetry to sample rather than entirely census regions for tagged fish incidence. One of 

the key assumptions of our original study was an assumed maximum detection distance of 800 m, which 

would have permitted approximately 50% detection in the MD WEA and 20% detection in the Inner and 

Outer strata. To better evaluate the probability of acoustic tag detection over the dynamic spatial and 

temporal gradients in the study area, we conducted a 12-month range test. Detection distance (measured 

as 50% detection recovery) was noticeably reduced during loud wind and storm events, but increased

during warmer summer months with the onset of stratification. Understanding and quantifying detection 

efficiency is key to drawing robust inferences in acoustic telemetry studies; underlying detection range 

dynamics have been known to lead to false conclusions regarding species biology (Payne et al. 2010). 

Here, the weighted adjustment based on detection range significantly reduced temporal autocorrelation in 

predictive models, which suggests that raw counts of individuals were influenced by underlying patterns 

in tag detectability. These findings indicate that future biotelemetry offshore studies will benefit from 

range test incorporation.

The gradient telemetry array allowed us to evaluate species habitat selection on relevant spatiotemporal 

scales (Cushman et al. 2010, Alvarez-Berastegui et al. 2014). However, other study designs may be more 

useful for evaluating specific questions. Originally, we had expected to be able to track latitudinal 

movements through the array. However, early analysis showed that receiver spacing did not provide 

sufficient coverage to resolve the direction of movement; there was no strong pattern of directionality 

within sequences of individual detections. Thus, we sought out additional data from the DE WEA to 

evaluate transit rates, data provided by colleagues at University of Delaware from a separate BOEM 

study. 

The vast majority of focal species were within the detection range of receivers for < 24 hr, which suggests 

that the shelf waters surrounding the MD WEA function primarily as a migration corridor for Atlantic 

sturgeon and striped bass. Though residency, as recorded here, is conservative due to the limited spatial 

detection range of receivers. Further, the occupancy of these species in the region may ultimately be 

related to seasonal migration cues more than physical habitat conditions. For example, though interannual 

differences in the wintertime occurrence and cross-shelf distribution for striped bass could be related to 

measured habitat variables within the study site, the timing and speed of migration probably depends on 

conditions and seasonal cues occurring in other shelf regions or spawning tributaries such as the Hudson 

River and Chesapeake Bay. Migratory behavior is often considered preemptive in that individuals will 

depart areas before they become unfavorable (Dingle and Drake 2007). In the case of estuaries like the 

Chesapeake Bay, striped bass will emigrate before temperatures become too warm and metabolically 

demanding, particularly for large individuals > 90 cm TL (Coutant 1985; Hartman and Brandt 1995). 

However, local habitat attributes still likely influenced patterns of occurrence; striped bass may have 

transited through the area using deeper offshore waters during winter and spring of 2018 because they 

were avoiding excessively cold nearshore temperatures. 

5.5 Prediction of migratory habitat use in the MD WEA

As expected from previous habitat selection modeling (Manderson et al. 2011; Breece et al. 2017; 

Haulsee et al. 2018) and preceding results, relative abundance of test species was highly dependent on 

shelf environmental gradients, especially depth and temperature. However, response to dynamic factors 

was also seasonally variable: Atlantic sturgeon were more broadly distributed during autumn compared to 
78

spring while striped bass shifted to deeper waters as winter months progressed. Temperature and season 

(DOY) were key predictors of weekly species residency in the region for both species, with Atlantic 

sturgeon exhibiting the highest degree of residency during autumn and spring when SSTs were generally 

warm, between 10-20°C, and striped bass residing for more days during winter compared to spring when 

surface temperatures were cooler, near 10°C. Although CHL-A was retained and significant in all of the 

best-performing models besides the sturgeon residency model, this variable appeared to have less 

predictive value compared to DOY, depth, and SST. Although the interaction between DOY and depth 

was most influential in explaining relative abundance, other important unmeasured factors include 

mesoscale oceanographic features, physiological constraints, prey availability, and broader migration cues 

were influencing the distribution and behavior of test species. Lagged SST values were also deemed 

significant for both species suggesting that temperatures occurring outside the MD WEA were 

influencing (cueing) shelf movements through the study area. 

Weekly residency modeling also revealed potential variation in migration behavior between distinct 

tagging regions for each species. Still, these differences were subtle and eclipsed by principal 

environmental variables and week-of-year. Our results may indicate that individuals originating from 

diverse locations ultimately utilize the shelf migration corridor in a similar manner. However, the key 

assumption that tagging region indexed different populations could not be substantiated. The statistical 

modeling approach nevertheless shows a way forward should future telemetry studies incorporate genetic 

assays for population-origin. 

6 Conclusions and Recommendations

A broad cross-shelf biotelemetry survey through the MD WEA confirmed year-round presence of 

Atlantic sturgeon and striped bass with the noticeable absence of striped bass during summer months. 

Atlantic sturgeon were distributed inshore, inclusive of the MD WEA, with incidence peaks during fall 

and spring. Striped bass incidence data was more squarely centered in the MD WEA as they migrated 

north during spring and south during fall. Incidence and transit data supported short-term residence (<2 d) 

and rapid movement (~1 body length s-1

) through the MD WEA for striped bass. Still, the extended period 

of incidence among individual striped bass suggested that the MD WEA might in some years function as 

an overwintering habitat. Habitat models selected SST, depth, proxies of seasonality, and interaction 

terms as most influential in predicting incidence, while sediment type or benthic class were weak 

predictors of occurrence in this section of the MAB. 

6.1 Overview findings related to functional habitat attributes of the MD 

WEA

• Both species occur frequently in the MD WEA with seasonal incidence showing that the MD 

WEA occurs within the MAB migration corridor for both species.

• Striped bass tended to occur in deeper and more distant mid-shelf waters while Atlantic sturgeon 

were biased toward shallow nearshore waters

• Striped bass were associated with a relatively narrow range of bottom temperatures (5-15°C) and 

preferred cooler sea surface temperatures

• Atlantic sturgeon were more likely to coincide with warmer bottom and sea surface temperatures

than striped bass

• Atlantic sturgeon may respond to temperature changes on shorter time scales than striped bass
79

• Differences in MD WEA habitat use between tagging origins was subtle at the scale of concern to 

management

6.2 Considerations related to timing and location of potential impacts and 

benefits of wind facility construction within the MD WEA

• Based on study results of animal occurrence, ideal timing for activities that may negatively 

impact both species is summer

• The installation and maintenance of renewable energy export cables may cause interactions with 

inshore sturgeon distributions 

• Turbine structures may alter behaviors, especially for striped bass – a structure-oriented forager -

leading to longer residency within the shelf region off Maryland seasonally, when environmental 

conditions are favorable

6.3 Recommendation for future studies to build on the current baseline 

study

• Increased incorporation of oceanographic variables, physiological data, and multi-species 

information is feasible with new observing system capabilities and could greatly improve 

dynamic habitat models for Atlantic sturgeon, striped bass, and other migratory species

• Large offshore telemetry studies are feasible here and in other WEAs and should be deployed and 

coordinated in baseline, impact, and post-impact phases of wind energy development 

• Sampling biotelemetry survey designs (here, a Before After Gradient design) hold advantage in 

coverage of larger cross-shelf ecosystems and seminal environmental variables

• Opportunities for aligned biotelemetry survey design and data sharing should be encouraged 

across WEA regions

7 Research Products

7.1 Presentations

Secor, DH. 2017. Before-after-gradient designs in monitoring the ecological impacts of offshore wind 

development. National Academy of Sciences Workshop. New Bedford MA.

Rothermel, E, MHP O’Brien and DH Secor. 2018. Seasonal migrations of striped bass and Atlantic 

sturgeon through the Maryland Wind Energy Area. American Fisheries Society, Tidewater Chapter 

Annual Meeting, Beaufort, NC, January 25-27.

Secor, DH, Rothermel E, MHP O’Brien and H Bailey. 2018. Movement and Habitat Selection by 

Migratory Fishes within the Maryland Wind Energy Area and Adjacent Reference Sites. Environmental 

Studies Program Science Exchange, BOEM Sterling VA, February 14.
80

Rothermel, E, MHP O’Brien, D Fox, B Gahagan, I Park, M Balazik, and DH Secor. 2018. Seasonal 

migrations of Atlantic Sturgeon and Striped Bass through the Maryland Wind Energy Area. National 

American Fisheries Society Annual Meeting, Atlantic City, NJ, August 19-23.

Rothermel, E, MHP O’Brien and DH Secor. 2018. Understanding the seasonal movements of Striped 

Bass and Atlantic Sturgeon in Maryland’s coastal waters. MEES Colloquium, Frostburg MD, October 5-

6.

Secor, DH. 2018. Designing research and monitoring studies to effectively detect impacts. State of the 

Science Workshop on Wildlife and Offshore Wind Energy Development, Woodbury NY, November 13-

14.

Rothermel, E, MHP O’Brien, D Fox, B Gahagan, I Park, M Balazik, and DH Secor. 2018. Understanding 

the Seasonal Movements of Atlantic Sturgeon and Striped Bass in the Maryland Wind Energy Area. State 

of the Science Workshop on Wildlife and Offshore Wind Energy Development, Woodbury NY, 

November 13-14.

Rothermel, E, MHP O’Brien, D Fox, B Gahagan, I Park, M Balazik, and DH Secor. 2019. Seasonal and 

environmental predictors of Atlantic sturgeon and striped bass occurrence in the Maryland Wind Energy

Area. American Fisheries Society, Tidewater Chapter Annual Meeting, Salisbury, MD, February 7-9.

O’Brien, MHP and DH Secor. 2019. Increased ultrasonic transmitter detection range in bottom waters due 

to thermal stratification in the Mid-Atlantic Bight. American Fisheries Society, Tidewater Chapter Annual 

Meeting, Salisbury, MD, February 7-9.

Rothermel, E, MHP O’Brien, D Fox, B Gahagan, I Park, M Balazik, and DH Secor. 2019. Seasonal and 

environmental predictors of Atlantic Sturgeon and Striped Bass occurrence in the Maryland Wind Energy 

Area. Oral presentation for the Chesapeake Biological Laboratory Brown Bag Series. Solomons, MD, 

March 1.

Rothermel, E, MHP O’Brien, D Fox, B Gahagan, I Park, M Balazik, and DH Secor. 2019. Science 

Updates: Atlantic Sturgeon and Striped Bass in the Maryland Wind Energy Area. Oral presentation at the 

Mid-Atlantic Telemetry Workshop. Newark, DE, April 18-19.

Rothermel, E, MHP O’Brien, D Fox, B Gahagan, I Park, M Balazik, and DH Secor. 2019. Seasonal and 

environmental predictors of Atlantic Sturgeon and Striped Bass occurrence in the Maryland Wind Energy 

Area. Oral presentation at the 5th International Conference on Fish Telemetry. Arendal, Norway, June 24-

28.

Rothermel, E, MHP O’Brien, D Fox, B Gahagan, I Park, M Balazik, and DH Secor. 2019. Seasonal 

incidence of Atlantic Sturgeon and Striped Bass in the Maryland Wind Energy Area. Oral presentation at 

the 25th Biennial Coastal and Estuarine Research Federation Conference. Mobile, AL, Nov. 3-7.

Rothermel, E. 2019. Seasonal migrations of Atlantic Sturgeon and Striped Bass through the Maryland 

Wind Energy Area. Thesis defense presentation for the Chesapeake Biological Laboratory Solomons, 

MD, Dec. 6.

Secor, D.H. E. Rothermel, C. Wiernicki, and M.O’Brien. 2019. Before after gradient (BAG) designs to 

evaluate coastal and wind farm impacts to migratory and sedentary fishes. Oral presentation at the 25th 

Biennial Coastal and Estuarine Research Federation Conference. Mobile, AL, Nov. 3-7.
81

7.2 Outreach

PI Secor served on expert panel discussions at National Academy of Sciences Workshop on Offshore 

Wind. New Bedford MA, 2017 and at the State of the Science Workshop on Wildlife and Offshore Wind 

Energy Development, Woodbury NY, 2018.

PI Secor served on the Organizing Committee, 2018 Coastal Fisheries and Offshore Energy 

Development: Managing a Multi-Use Ocean. AFS Annual Conference, August 2018, Atlantic City, NJ.

BOEM-funded student Ella Rothermel worked with UMCES outreach coordinator, Sarah Brzezinski, to 

produce an outreach video summarizing her research for a general public audience, sent to BOEM winter 

2019. The URL is available at https://www.umces.edu/news/next-generation-ellie-rothermel

PIs Secor and Bailey and E. Rothermel visited US Wind (T. Sumner) in Baltimore during early 2020 to 

discuss BOEM research findings and provide input on COP and Fishery Communication planning.

7.3 Theses

The research presented in this report directly contributed to the BOEM-funded Masters of Science thesis, 

successfully defended Dec. 6, 2019:

Rothermel, ER. 2019. Seasonal migrations of Atlantic Sturgeon and Striped Bass through the Maryland 

Wind Energy Area. Marine, Estuarine, and Environmental Sciences Program, University of Maryland 

Center for Environmental Science and the Graduate School of the University of Maryland, College 

Park, MS thesis. 153 p.

7.4 Publications

Data and analyses from this report have contributed to a submitted paper to Plos One and two manuscripts 

in preparation.

Rothermel, ER, MT Balazik, JE Best, MW Breece, DA Fox, BI Gahagan, DE Haulsee, AL Higgs, MHP 

O’Brien, MJ Oliver, IA Park, and DH Secor. In Review. Comparative migration ecology of Striped Bass 

and Atlantic Sturgeon in the US Southern Mid-Atlantic Bight flyway. Plos One. 

In Preparation: Increased ultrasonic transmitter detection range in bottom waters due to thermal 

stratification in the Mid-Atlantic Bight.

In Preparation: Seasonal and environmental predictors of migratory species occurrence in a Wind Energy 

Lease area of the Mid-Atlantic Bight.
82

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Appendix A: Cruise Reports

10-11 November 2016

MD Wind Energy Area Fish Movement

Cruise Report

Cruise Participants

Dave Secor (Chesapeake Biological Laboratory, Chief Scientist)

Mike O’Brien (Chesapeake Biological Laboratory)

Michael Hulme (R/V Rachel Carson, Captain)

Rob Nilsen (R/V Rachel Carson, Mate)

Thursday, 10 November, 2016

Conditions

NNW winds: 15 – 20 kts, gusts to 30 kts. Waves 4-6 ft. Air temperature 43 - 55° F.

Summary

0700 Scheduled departure delayed due to weather.

0900 Depart Sunset Marina, Ocean City, MD aboard the R/V Rachel Carson.

0930 Abort cruise due to wind/sea state. Return to Ocean City, MD.

1000 Arrive in Ocean City, MD

Friday, 11 November, 2016

Conditions

NW winds, 15 – 20 kts. Waves 5-7 ft, decreasing to 3-4 ft. Air temperature 45 – 64° F. 
93

Summary

0815 Depart Sunset Marina, Ocean City, MD aboard the R/V Rachel Carson.

0944 Arrive at ON2 and deploy mooring.

0945 Communicate with deployed receiver to gather depth and tilt data.

0947 Depart ON2, proceed to next site.

0947 –

Repeat process for all 20 sites. Refer to Deployment Summary for complete deployment data.

– 1450

1450 Break cruise. Depart for Ocean City, MD.

1320 Arrive at Sunset Marina, Ocean City, MD.
94

Deployment Technique

• Rope was passed through hole in weight plates. One end was held by hand with the other cleated 

to the vessel.

• Mooring was pushed by hand off the stern.

• The rope was slowly released until weights were below the surface of the water. At this point, the 

rope was completely released to complete deployment.

Deployment Summary

Site Latitude Longitude Depth (m) Tilt (°) Arrive Deploy Depart

ON2 38.36898 -74.54183 36 3 9:44 9:44 9:47

OS2 38.30435 -74.54175 40 0 10:04 10:05 10:08

OS1 38.30395 -74.63365 32 2 10:39 10:39 10:43

ON1 38.36907 -74.63370 32 3 11:02 11:02 11:04

AN4 38.36893 -74.72530 28 1 11:25 11:26 11:30

AN3 38.36893 -74.76205 24 3 11:38 11:38 11:45

AN2 38.36897 -74.79857 24 2 11:50 11:52 11:55

AN1 38.36895 -74.83567 14 1 12:01 12:02 12:05

AM1 38.33612 -74.83513 18 1 12:12 12:13 12:15

AM2 38.33608 -74.79850 20 2 12:22 12:24 12:32
95

AM3 38.33620 -74.76170 24 4 12:37 12:38 12:42

AM4 38.33618 -74.72507 26 2 12:48 12:49 12:52

AS4 38.30385 -74.72512 26 1 13:00 13:01 13:03

AS3 38.30395 -74.76187 20 0 13:09 13:10 13:13

AS2 38.30388 -74.79867 20 4 13:20 13:20 13:24

AS1 38.30390 -74.83538 26 2 13:31 13:32 13:35

IS2 38.30387 -74.92695 16 3 13:50 13:51 13:55

IN2 38.36890 -74.92688 14 0 14:08 14:10 14:12

IN1 38.36900 -75.01862 12 2 14:27 14:31 14:33

IS1 38.30382 -75.01858 14 2 14:47 14:47 14:50
96

Figure 1. Maryland coastline and wind energy area. Location of deployed receivers (points) and site 

names are displayed.

28-29 March 2017

MD Wind Energy Area Fish Movement

Cruise Report

Cruise Participants

Dave Secor (Chesapeake Biological Laboratory, Chief Scientist)

Mike O’Brien (Chesapeake Biological Laboratory)

Caroline Wiernicki (Chesapeake Biological Laboratory)

Cory Harrington (F/V Sea Born)

Tuesday, 28 March, 2017

Conditions
97

S winds: 5 - 10 kts, Waves 3 ft. Air temperature 51 - 64° F.

Summary

0600 Depart Fisherman’s Marina, Ocean City, MD aboard the F/V Sea Born.

0757 Arrive at AS1.

0801 Communicate with, release, download, and reset receiver.

0819 Depart AS1 for AS2.

0819 –

Repeat process for AS2, AS3, AS4, OS1, OS2, ON2, ON1, AN4, AM4, AM3, AN3, and AN2.

- 1606

1622 Arrive at AM2. Attempt communication with release.

1700 Communication unsuccessful. Return to Ocean City, MD.

1820 Arrive in Ocean City, MD

Wednesday, 29, March, 2017

Conditions

N winds, 10 - 15 kts. Waves 4 ft. Air temperature 39 – 57° F. 

Summary

0630 Depart Fisherman’s Marina, Ocean City, MD aboard the F/V Sea Born.

0815 Arrive 0.25 miles west of AM2. Attempt communication with receiver.

0840 Communication failed. Proceed to AM2.

0845 Arrive at AM2. Attempt communication with receiver.

0915 Communication failed. Deploy replacement VR2AR. Move 0.25 miles south of AM2.

0925 Arrive 0.25 miles south of AM2. Attempt communication with original receiver.

0930 Communication failed. Proceed to location 0.25 east of AM2.

0933 Arrive 0.25 miles east of AM2. Attempt communication with original receiver.

0937 Communication failed. Proceed to location 0.25 north of AM2.

0940 Arrive 0.25 miles north of AM2. Attempt communication with original receiver.
98

0945 Communication failed. Proceed to AM1.

1004 Arrive at AM1.

1007 Communicate with, release, download, and reset receiver.

1023 Depart AM1 for AN1.

1045 –

Repeat process for AN1, IN2, and IS2.

- 1316

1316 Arrive at IS1.

1318 Communicate with, release, and download receiver.

1329 Deploy receiver 0.25 to the north to avoid trawling.

1333 Depart IS1 for IN1.

1408 Arrive at IN1.

1409 Communicate with, release, and download receiver.

1423 Deploy receiver offshore, outside the 3-mile line, to avoid trawling.

1426 Return to Ocean City, MD.

1530 Arrive in Ocean City, MD.

Deployment Technique

• Rope was passed through hole in weight plates. One end was held by hand with the other cleated 

to the vessel.

• Mooring was released into the water, by hand, over the starboard-side gunwale.

Recovery and Deployment Summary

Date Site Latitude Longitude Depth (m) Tilt (°) Arrive Recover Deploy Depart

20170328 AS1 38.3039 -74.8363 28 0-11 7:57 8:03 8:15 8:19

20170328 AS2 38.3037 -74.7985 23.8 0-11 8:35 8:42 8:56 8:53

20170328 AS3 38.3041 -74.7617 21.9 0-11 9:06 9:15 9:22 9:25

20170328 AS4 38.304 -74.7252 29.9 2 9:40 9:48 9:54 9:58
99

20170328 OS1 38.3039 -74.6336 35.4 2 10:32 10:37 11:29 10:46

20170328 OS2 38.3042 -74.5416 41.1 4 11:19 11:24 11:29 11:33

20170328 ON2 38.369 -74.5418 36 3 12:06 12:12 12:16 12:19

20170328 ON1 38.3691 -74.6336 36.6 1 13:00 13:04 13:09 13:13

20170328 AN4 38.3688 -74.7252 29.1 0-11 13:53 13:58 14:02 14:06

20170328 AM4 38.3362 -74.725 25.8 2 14:22 14:28 14:31 14:38

20170328 AM3 38.3361 -74.7617 24.1 4 14:54 14:59 15:02 15:08

20170328 AN3 38.3689 -74.762 26.5 1 15:25 15:30 15:35 15:39

20170328 AN2 38.369 -74.7985 24.7 4 15:54 15:58 16:02 16:06

20170329 AM2 38.3361 -74.7985 22.9 2 8:45 9:17 9:22

20170329 AM1 38.336 -74.8351 19.5 1 10:04 10:10 10:18 10:23

20170329 AN1 38.3689 -74.8356 16.8 4 10:45 10:49 10:55 11:07

20170329 IN2 38.3688 -74.9268 14 4 11:44 11:48 11:56 11:59

20170329 IS2 38.3038 -74.9271 17.8 1 12:27 12:33 12:39 12:42

20170329 IS1 38.3089 -75.0117 15.2 2 13:16 13:20 13:29 13:33

20170329 IN1 38.3693 -74.9975 14 3 14:08 14:12 14:23 14:26
100

Figure 1. Maryland coastline and wind energy area. Location of deployed receivers (points) and site 

names are displayed.
101

Figure 2. Detections of unique, individually-tagged striped bass and Atlantic sturgeon during the period 

of deployment (11/9/2016 – 3/28/2017).

11-12 April 2018

MD Wind Energy Area Fish Movement

Cruise Report

Cruise Participants

Mike O’Brien (Chesapeake Biological Laboratory)

Ellie Rothermel (Chesapeake Biological Laboratory)

Aimee Hoover (Chesapeake Biological Laboratory)

Cory Harrington and mate (F/V Sea Born)

Wednesday, 11 April, 2018

Conditions

E winds: 0 - 10 kts, Flat seas. Air temperature 28 - 48° F.
102

Summary

0524 Depart Fisherman’s Marina, Ocean City, MD aboard the F/V Sea Born.

0716 Arrive at AS1.

0719 Communicate with and release receiver. Immediate data download failed, hot swap with spare 

receiver.

0725 Depart AS1 for AS2. Clean, download, and reset receiver in transit.

1053 –

Repeat process for AS3, AS4, OS1, OS2 using the previous site’s receiver to hot swap.

- 1030

1030 Arrive at T-2C (Bailey site, pickup only).

1037 Retrieve CPOD.

1039 Anchor on deck.

1041 Depart T-2C for T-3C.

1144 Arrive at T-3C (Bailey site, pickup only).

1147 Retrieve CPOD.

1150 Anchor on deck.

1152 Depart T-3C for ON2.

1305 Arrive at ON2.

1308 Communicate with, release, hot swap using the previous site’s receiver.

1310 Depart ON2 for ON1. Clean, download, and reset receiver in transit.

1343 Arrive at ON1.

1346 Communicate with, release, hot swap using the previous site’s receiver.

1348 Depart ON1 for AN4. Clean, download, and reset receiver in transit.

1421 Arrive at AN4.

1424 Communicate with, release, hot swap using the previous site’s receiver.
103

1425 Depart AN4 for A-5C. Clean, download, and reset receiver in transit.

1441 Arrive at A-5C (Bailey site, tending)

1535 Depart A-5C for AM4

1536 Arrive at AM4

1540 Communicate with, release, hot swap using the previous site’s receiver.

1542 Depart AM4 for new1. Clean, download, and reset receiver in transit.

1553 Arrive at new1 (Bailey site, tending)

1633 Depart new1

1641 Arrive at AN3.

1647 Communicate with, release AN3 and AN3_250 simultaneously.

1648 Recover AN3.

1649 Recover AN3_250.

1649 Depart for AN3_800. Clean, download, and reset both receivers in transit.

1650 Arrive at AN3_800

1653 Communicate with, release, hot swap using the previous site’s receiver. Clean, download, and 

reset AN3_800 receiver in transit back to AN3.

1702 Hot swap AN3_250.

1706 Hot swap AN3.

1706 Depart AN3 for new2.

1710 Arrive at new2 (Bailey site, tending).

1730 Depart new2 for IS2_800.

1905 Arrive at IS2_800.
104

1911 Communicate with, release receiver.

1913 Depart for IS2_250. Clean, download, and reset receiver in transit.

1918 Arrive at IS2_250.

1920 Communicate with, release IS2_250 and IS2 simultaneously. Clean, download, and reset both 

receivers in transit back to IS2.

1929 Hot swap IS2_800.

1932 Hot swap IS2_250.

1936 Hot swap IS2.

1936 Depart IS2 for T-1C.

1950 Arrive at T-1C (Bailey site, deployment).

1958 Redeploy T-1C.

2000 Return to Ocean City, MD.

2126 Arrive in Ocean City, MD.

Thursday, 12 April, 2018

Conditions

SW winds, 10 - 15 kts. Waves 2-3 ft. Air temperature 45 - 64° F.

Summary

0510 Depart Fisherman’s Marina, Ocean City, MD aboard the F/V Sea Born.

0730 Arrive at BSB site “InnerSW”.

0730 No communications after multiple attempts.

0735 Depart InnerSW for new4.

0737 Arrive at new4 (Bailey site, pickup only).

0740 Retrieve CPOD.

0744 Anchor on deck.
105

0747 Depart new4 for C5-1.

0800 Arrive at C5-1 (Bailey site, pickup only).

0802 Retrieve CPOD.

0805 Anchor on deck.

0807 Depart C5-1 for AN2.

0825 Arrive at AN2.

0829 Communicate with, release, hot swap using the previous day’s final site receiver.

0830 Depart AN2 for AM3. Clean, download, and reset receiver in transit.

0830 –

Repeat process for AM2, AM1, AN1, IN2 using the previous site’s receiver to hot swap.

- 1050

1119 Arrive at IN1

1126 Communicate with receiver, establish communication with presumed lost IN1 receiver (deployed 

August 2017). Successfully release, recover both IN1 receivers. Hot swap with prepared receiver.

1130 Depart IN1 for IS1. Clean, download, and reset receiver deployed in December 2017 in transit.

1202 Arrive at IS1.

1206 Communicate with, release, hot swap receiver.

1208 Return to Ocean City, MD.

1256 Arrive in Ocean City, MD.

Recovery and Deployment Details

Date Site Latitude Longitude Depth (m) Arrive Recover Deploy Depart

20180411 AS1 38 18.230 -74 50.125 28.3 7:16 7:19 7:25 7:25

20180411 AS2 38 18.231 -74 47.917 22.8 7:46 7:50 7:52 7:52

20180411 AS3 38 18.238 -74 45.712 20.7 8:07 8:12 8:13 8:14

20180411 AS4 38 18.226 -74 43.507 29.1 8:28 8:32 8:35 8:35

20180411 OS1 38 18.240 -74 38.020 35.4 9:10 9:22 9:24 9:24

20180411 OS2 38 18.255 -74 32.499 40.5 10:01 10:05 10:08 10:08
106

20180411 ON2 38 22.141 -74 32.519 36.9 13:05 13:08 13:10 13:10

20180411 ON1 38 22.146 -74 38.033 37.2 13:43 13:46 13:48 13:48

20180411 AN4 38 22.134 -74 43.519 29.8 14:21 14:24 14:25 14:25

20180411 AM4 38 20.177 -74 43.508 26.8 15:36 15:40 15:41 15:42

20180411 AN3 38 22.139 -74 45.722 27.4 16:41 16:48 17:06 17:06

20180411 AN3_250 38 22.132 -74 45.899 27.2 16:49 16:49 17:02 17:02

20180411 AN3_800 38 22.133 -74 46.286 26.7 16:50 16:53 16:55 16:55

20180411 IS2_800 38 18.236 -74 56.166 19.5 19:05 19:13 19:29 19:29

20180411 IS2_250 38 18.236 -74 55.792 16.9 19:18 19:21 19:32 19:32

20180411 IS2 38 18.236 -74 55.612 18 19:23 19:23 19:36 19:36

20180412 AN2 38 22.135 -74 47.909 25.2 8:25 8:29 8:30 8:30

20180412 AM3 38 20.164 -74 45.702 25 8:53 8:55 8:56 8:57

20180412 AM2 38 20.166 -74 47.914 22.3 9:13 9:17 9:19 9:20

20180412 AM1 38 20.166 -74 50.100 18.9 9:35 9:42 9:43 9:43

20180412 AN1 38 22.131 -74 50.141 16.5 10:00 10:03 10:04 10:04

20180412 IN2 38 22.135 -74 55.602 13.1 10:43 10:49 10:50 10:50

20180412 IN1 11:19 11:26

20180412 IN1 38 22.160 -74 59.846 15.2 11:19 11:26 11:29 11:30

20180412 IS1 38 18.531 -75 00.701 17.4 12:02 12:06 12:08 12:08

19-20 December 2017

MD Wind Energy Area Fish Movement

Cruise Report

Cruise Participants

Mike O’Brien (Chesapeake Biological Laboratory)
107

Ellie Rothermel (Chesapeake Biological Laboratory)

Cory Harrington and mate (F/V Sea Born)

Tuesday, 19 December, 2017

Conditions

W winds: 5 - 10 kts, Waves 1 ft. Air temperature 33 - 57° F.

Summary

0645 Depart Fisherman’s Marina, Ocean City, MD aboard the F/V Sea Born.

0953 Arrive at OS1.

1000 Communicate with, release, download, and reset receiver. Update firmware.

1013 Re-deploy mooring. Depart OS1 for OS2.

1053 –

Repeat process for OS2, ON2, ON1, AN4, and AM4.

- 1417

1417 Return to Ocean City, MD.

1650 Arrive in Ocean City, MD

Wednesday, 20 December, 2017

Conditions

NW winds, 10 - 15 kts. Waves 2-3 ft. Air temperature 28 - 54° F. 

Summary

0600 Depart Fisherman’s Marina, Ocean City, MD aboard the F/V Sea Born.

0707 Arrive at IS2_800 (new range test site). Deploy synchronization receiver.

0712 Arrive at IS2_250 (second range test site) and deploy synchronization receiver.

0715 Arrive at IS2.

0717 Communicate with and release receiver. Hot swap with new receiver.
108

0721 Depart IS2 for AS1. Clean, download, update firmware, and reset receiver in transit.

0756 –

Repeat process for AS1, AS2, AS3, AS4, and AM3 using the previous site’s receiver to hot swap.

- 0928

0945 Arrive at AN3. Communicate with and release receiver. Hot swap with synchronization receiver.

0955 –

Deploy range test receivers at AN3_250 and AN3_800.

- 0959

1010 –

Repeat hot-swap and maintenance-in-transit procedures for AN2, AM2, AM1, AN1, and IN2.

1206

1238 Arrive at IN1 and attempt communication with receiver. Pings are heard on the first attempt (5 of 

the 7 needed to connect), but no communication occurs after multiple attempts.

1328 Abandon IN1 recovery attempts and deploy new receiver.

1409 Arrive at IS1. Communicate with, release, download, and reset receiver. Update firmware and 

redeploy.

1430 Return to Ocean City, MD.

1530 Arrive in Ocean City, MD.

Recovery and Deployment Details

Date Site Latitude Longitude Depth (m) Arrive Recover Deploy Depart

20171219 OS1 38 18.240 -74 38.021 35.1 9:53 10:00 10:13 10:13

20171219 OS2 38 18.262 -74 32.512 40.2 10:53 10:56 11:09 11:09

20171219 ON2 38 22.143 -74 32.514 36 11:42 11:46 11:58 11:58

20171219 ON1 38 22.133 -74 38.029 36 12:35 12:37 12:51 12:51

20171219 AN4 38 22.139 -74 43.510 29 13:27 13:31 13:47 13:47

20171219 AM4 38 20.173 -74 43.505 26.1 14:03 14:06 14:17 14:17

20171220 IS2_800 38 18.231 -74 56.168 19.8 7:07 7:10 7:10

20171220 IS2_250 38 18.235 -74 55.795 17.4 7:12 7:13 7:13
109

20171220 IS2 38 18.241 -74 55.605 18 7:15 7:18 7:21 7:21

20171220 AS1 38 18.230 -74 50.119 26.5 7:56 7:59 8:02 8:02

20171220 AS2 38 18.239 -74 47.921 23.2 8:15 8:18 8:21 8:21

20171220 AS3 38 18.247 -74 45.710 21.3 8:34 8:38 8:40 8:41

20171220 AS4 38 18.230 -74 43.508 29.6 8:54 8:57 8:59 9:00

20171220 AM3 38 20.169 -74 45.701 25.3 9:02 9:26 9:28 9:28

20171220 AN3 38 22.134 -74 45.720 26.8 9:45 9:49 9:53 9:53

20171220 AN3_250 38 22.134 -74 45.889 26.8 9:55 9:55 9:55

20171220 AN3_800 38 22.136 -74 46.275 26.5 9:58 9:58 9:59

20171220 AN2 38 22.142 -74 47.910 25.3 10:10 10:13 10:15 10:16

20171220 AM2 38 20.167 -74 47.970 22.3 10:31 10:36 10:39 10:39

20171220 AM1 38 20.165 -74 50.109 18.9 10:54 10:57 10:59 10:59

20171220 AN1 38 22.133 -74 50.141 15.8 11:16 11:19 11:23 11:23

20171220 IN2 38 22.139 -74 55.615 14 11:59 12:03 12:06 12:06

20171220 IN1 38 22.154 -74 59.844 15.2 12:38 13:28 13:28

20171220 IS1 38 18.531 -75 00.700 17.4 14:09 14:14 14:30 14:30

Individual fish detected: Sept – Dec 2017

Species Inner WEA Outer

Atl. sturgeon 98 106 8

Dusky shark 11 14 2

White shark 4 14 4

Blacktip shark 3 8 2

Winter skate 1

Striped bass 13 52

Sand tiger shark 8 4

Bull shark 2 1
110

Smooth dogfish 3

Atl. bluefin tuna 1

Atl. Cod 1

Shortnose sturgeon 1

Black sea bass 4 10

Cownose ray 1

Sandbar shark 1
Department of the Interior (DOI)

The Department of the Interior protects and manages the Nation's natural 

resources and cultural heritage; provides scientific and other information about 

those resources; and honors the Nation’s trust responsibilities or special 

commitments to American Indians, Alaska Natives, and affiliated island 

communities.

Bureau of Ocean Energy Management (BOEM)

The mission of the Bureau of Ocean Energy Management is to manage 

development of U.S. Outer Continental Shelf energy and mineral resources in 

an environmentally and economically responsible way.

BOEM Environmental Studies Program

The mission of the Environmental Studies Program is to provide the 

information needed to predict, assess, and manage impacts from offshore 

energy and marine mineral exploration, development, and production activities 

on human, marine, and coastal environments. The proposal, selection, research, 

review, collaboration, production, and dissemination of each of BOEM’s 

Environmental Studies follows the DOI Code of Scientific and Scholarly 

Conduct, in support of a culture of scientific and professional integrity, as set 

out in the DOI Departmental Manual (305 DM 3).