Passive acoustic monitoring of fishes in the mid-Atlantic:

providing the where and when for managers

Delaware State University, Department of Agriculture and Natural Resources, Dover, DE

dfox@desu.edu

Dewayne Fox

Outline

• Atlantic sturgeon– Phil Simpson

• Sandtiger shark– Johnny Moore

• Conclusions

Sturgeons• Fossil records back 85

MYBP• 25 species worldwide

with 9 species in North America

• Anadromous or restricted to freshwater

• Body with 5 rows of scutes

• Nearly all species are endangered or threatened

Sturgeon Harvesting

• Vulnerability due to life history traits

• “Black gold”– Ex-vessel prices >$50/lb– Retail >$200/ounce

• Delayed maturation and long life spans (>100 years)

• Limited prospects for natural recovery in many populations

Atlantic sturgeon(Acipenser oxyrinchus oxyrinchus)

• Anadromous• Range

– St. Lawrence River, Canada to St. Johns River, FL

• Long lived – Large (4.3m and 350 kg)– 60 years

• Late-maturing– Males 10-12 years– Females 13-20 years

• Spawning Requirements– Hard substrate with high flow

rates– Fresh water

Atlantic Sturgeon Migration

Spring

Atlantic Sturgeon Migration

Summer

?

?

?

?

Atlantic Sturgeon Migration

Fall

Atlantic Sturgeon Migration

Winter

100+ years of Atlantic Sturgeon Management in the Delaware

River• “The roe was considered

worthless except as bait to catch eels, and perch or to feed the hogs” • Cobb, J. N. 1900

• “Under the present conditions it is only a question of a few years until the day of the sturgeon fishery will have collapsed” • Tower, W. S. 1908

Atlantic sturgeon Fishery Management: Modern Challenges

• ASMFC issued Fishery Management Plan 1990

• Fishing moratorium (1998)

• Status review (1998)– Did not warrant protection

– Harvest moratorium issued

• Status review (Feb 2007)– 3 of 5 Distinct Population

Segments (DPSs) recommended for threatened status

Distinct Population Segments

(DPS)• Threatened

– Carolina– Chesapeake Bay– New York Bight

• Not listed– Gulf of Maine– South Atlantic

Status Review 2007

History of Delaware River Atlantic Sturgeon Fishery

• Leni Lenape Indians “celebrated the arrival of the sturgeon with an orgy of fishing”

• 1869 Penn’s Grove– “Albany beef”

• 1889 Caviar, NJ– 400 harvesters– 12-15 railroad cars

daily– Up to 5 railroad cars

of caviar daily

Caviar, NJ

Delaware River Atlantic Sturgeon Fishery

• Historic Abundance estimated at 180K Females in 1890

• Average weight– female 118 kg– male 29.5 kg

0

1

2

3

4

5

6

7

YearYear

Lan

din

gs

(mill

ion

lbs)

Lan

din

gs

(mill

ion

lbs)

Stock CollapseStock Collapse

Golden YearsGolden Years

Recruitment FailureRecruitment Failure

Secor and Waldman 1999

Delaware River• Largest freshwater

port complex in world• Over 3000 deep draft

vessels/year• 42 million gallons

crude oil moved daily

Juvenile Habitat Utilization

• Estuarine/marine residency– GROWTH

• May occupy non-natal estuaries during spring/summer

Objectives• Characterize habitat

use during period of estuarine residency– Substrate– Depth – Environmental

parameters

• Identify migratory patterns– Immigration/emigration

Methods: Collection/Telemetry

• Gill nets– Varying mesh sizes (15–

30.5 cm)– Anchored vs. drift

• Telemetry– Internal

transmitters– Previously

established surgical protocol

Telemetry Equipment

• Vemco ltd.– Sturgeon – 2 year tags– Battery life- 10 years– VR-2 passive receivers

• Data sharing– Delaware Estuary

• shortnose sturgeon

• striped bass

• horseshoe crab

• sandbar and sand tiger sharks

– Atlantic Cooperative Telemetry (ACT) Network

• 28 research groups ME-FL

VEMCO

VEMCO

VEMCO

Telemetry Array

• 2005 (n=38)

• 2006 (n=55)

• 2007 (n=56)

• 2008 (n=63)

Telemetry Equipment

Based on M. Moser design

Active Tracking• Focus on juvenile habitat

– Range based on C.A. Shirey (1997) telemetry study

• Methods– Weekly monitoring of

riverine section– Listen at 1 km intervals

2005-2007 Juvenile Sturgeon

Passive Relocations (n=279,167)

• 2005 (n = 15)– well defined concentration areas

• (Shirey 1997)

• 2006 (n = 12)– concentration zones less defined

• 2007 (n = 10*)– increased heterogeneity in habitat occupation

*based on returns, no new fish tagged

Atlantic sturgeon movement 2005-2007

2005

0

20

40

60

80

100

120

140

160

19-Mar 18-Apr 18-May 17-Jun 17-Jul 16-Aug 15-Sep 15-Oct 14-Nov

Date

river

kilo

met

er

0

5

10

15

20

25

30

35

Tem

pera

ture

(deg

rees

Cel

sius

)

2006

0

20

40

60

80

100

120

140

160

19-Mar 18-Apr 18-May 17-Jun 17-Jul 16-Aug 15-Sep 15-Oct 14-Nov

Date

rive

r ki

lom

eter

0

5

10

15

20

25

30

35

Tem

per

atu

re (d

egre

es C

elsi

us)

2007

0

20

40

60

80

100

120

140

160

19-Mar 18-Apr 18-May 17-Jun 17-Jul 16-Aug 15-Sep 15-Oct 14-Nov

Date

rive

r ki

lom

eter

0

5

10

15

20

25

30

35

Tem

per

atu

re (

deg

rees

Cel

siu

s)

2007 Juvenile Atlantic sturgeon

2007

0

20

40

60

80

100

120

140

160

19-Mar 18-Apr 18-May 17-Jun 17-Jul 16-Aug 15-Sep 15-Oct 14-Nov

Date

rive

r ki

lom

eter

0

5

10

15

20

25

30

35

Tem

per

atu

re (

deg

rees

Cel

siu

s)

• Representative data?

• Immigration and emigration patterns

• Movement driven by prey resources?– Polychaete or “mud”

worms (ECS 1993)• Johnson et al. 1997• Haley 1998

Polychaete bloom

Habitat Selection: DNREC Delaware Bay Benthic Mapping Program

Images courtesy of Bart Wilson

Habitat Utilization: Substrate

• Delaware state benthic mapping program dataset

• Independent sediment analysis– 90% correlation macro-

format classification

• Individual Chi-square test– Collectively, habitat

selection is occurring for gravel/hard-bottom substrate

• X2 (308.91) > test statistic (149.45), df = 100

0

20

40

60

80

100

Clayey Silt Silt, w ith Clay Sand/Silt, w ithClay

Sand Gravel Rock

Sediment Classification

Nu

mb

er o

f R

elo

cati

on

s

Expected

Observed

Habitat Utilization:

Depth• Data Source:

NOAA Bathymetric Maps

• Commonly relocated in/along navigation channel

• Anchorage areas

Habitat Utilization: Depth

0

10

20

30

40

50

60

70

80

0-4 4-8 8 -12 12-16 16-20 21-25

Depth (m)

Nu

mb

er o

f Rel

oca

tions

Expected

Observed• Deep water

habitat selection– Collectively,

selection for 8 – 16m depths

• X2 (238.4) > test statistic (149.5), df = 100

Conclusions for Delaware River Atlantic sturgeon

• Juvenile habitat utilization– Depth and substrate selection

• Deep water secondary channel/anchorage areas

• Coarse grain materials

– Migratory Patterns• March 19 immigration• November 24 emigration

– Migratory patterns indicate marine overwintering habitat

– Recent discovery (Feb 14, 2008) of juvenile mortality within estuary ( ≈river kilometer 80)

– Wide use of riverine habitat during estuarine residency

Conclusions• Deepwater habitat selection outside main traffic area

–Crown Landing LNG Proposal

–Delaware Deepening Project

• Critical habitat designation–Gravel/hard-bottom substrate, depth preferences, prey availability, physiochemical properties

•Migratory patterns indicate marine overwintering habitat

–March 19 return – Dec 17 exit

–Recent discovery (Feb 14, 2008) of juvenile mortality within estuary ( ≈river kilometer 80)

–Boat Strikes

Site fidelity and patterns of habitat use of sandtiger sharks (Carcharias

taurus) in Delaware Bay

                                                          

                  

Life History• Females

– Mature at 220-230 cm TL– 9-10 years of age

• Males– Mature at 190 cm TL– 6-7 years

• Maximum Size ≈ 4m

• Size at birth ≈ 1m

• Forage on fishes including other sharks/rays, horseshoe crabs, and mollusks

• Thought to be primarily nocturnal

Reproduction

• 2 year reproductive cycle– 9-12 month gestation

• Litter size of 2– embryophagy

• 1 female every other year assuming 1:1 sex ratio

• 0.5 female offspring per year

• Among lowest reproductive output for any known shark or ray

Management1993 - NMFS FMP large coastal

species

1997 - NMFS prohibited species category

1997 - petitioned for ESA listing

2007 Stock Assessment and Status Review (?)

Catch of Sandtiger Sharks Reported in US Commercial Fisheries 1981-2002

05000

100001500020000

250003000035000

4000045000

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

Year

Dre

esed

Wei

ght

(lb

s)

Sand Tiger Shark

Migration

MatingFebruary to May

Sand Tiger Shark

Migration

PuppingDecember to March

Pregnant females

do not migrate?

Sand Tiger Shark

Migration

Spring Migration

Salinit

ies to

o low

?

Pregnant females

do not migrate?

Age 1+

YOY??

Sand Tiger Shark

Migration

Age 1+

YOY??

Fall Migration

Methods

• Long line – 366 m length– Baited circle hooks (16/0)– 2 hour soak times

• Directed sampling and random NMFS Apex predator surveys

• All sand tigers were measured, sexed, fitted with an external tag, and had genetic samples collected

Tagging

• Implanted with long-life (800 days) standard acoustic transmitters (V16-6H)– 2006 n = 4– 2007 n = 15

• Implanted with long-life (800 days) depth sensing transmitters (V16-6H)– 2007 n = 10

Results

• Total of 29 sand tigers were implanted with acoustic transmitters– 2006 n = 4– 2007 n = 25

• 17 female • 12 male

2007 Results

• 2 / 4 sand tigers tagged in 2006 returned in 2007

• Both returned on June 17th

• All telemetered sand tiger sharks were detected

• Total detections = 72,241

Results

• Tagging initiated in June and completed in July

• > ½ of all telemetered Sand tiger sharks remained in Delaware Bay into October

Proportion of Sand Tiger Sharks Detected

0%

20%

40%

60%

80%

100%

June July August September October

Relative Detections by Receiver for 2007

• Importance of Delaware’s side of the Bay

• Relative absence along main channel area

• Cape May early in year

Relative Proportion of Detections by Sex

• Males tended to occupy lower salinity upper bay and nearshore areas

• Females detected more commonly in lower/deeper portions of the bay

Habitat Utilization: Depth

Mean Detection Depth (m) for 2007

7.00

7.25

7.50

7.75

8.00

June July August September October

Mean Detection Depth (m) by sex for 2007

5.0

6.0

7.0

8.0

9.0

10.0

June July August September October

Mean Depth (F)

Mean Depth (M)

Dep

th (

m)

05

101520253035

1786

6 7 8 9 10 6 7 8 9 10

Female Male

Month within Sex

Dep

th (

m)

05

101520253035

1786

6 7 8 9 10 6 7 8 9 10

Female Male

Month within Sex

Conclusions• Delaware Bay serves as

an important nursery habitat as well as summer foraging area for Sand tigers

• Majority of STS exhibit high fidelity for Delaware Bay (>60%)

• Importance of Delaware shoreline and Cape May regions– Anchorage area

• Sex-based distribution by area and depth

Acknowledgements• Students• Staff- Lori Brown• Brad Wetherbee-URI• NOAA EPP and

Anadromous Fish Conservation Act Funding

• United States Coast Guard– LCDR Retired Thomas

Flynn, Norfolk ATON Office

– USCG Cutter William Tate

• Bart Wilson, DNREC

Questions?

• www.hpl.umces.edu/ facilities/sturgeon.jpg