# The Horrors of Sturgeon Matrimony



# in the Delaware Estuary Scutes of Death Matt Fisher

– Delaware Division of Fish and Wildlife Dewayne Fox and Matt Breece

– Delaware State University

# Background

• In 2005 DFW began tracking reports of sturgeon carcasses

– Reported in DE DFW ASMFC sturgeon compliance report



## – DSU created this poster to generate reports

– Brown and Murphy 2010
– Fisheries

# Study Area

• Ports range from river km 97 to 203 and over 3000 deep 

### draft vessels visit annually

– This long distance into the freshwater of an estuary is unusual



### • Port complex of Philadelphia, 6 th 

### busiest port in the U.S. (behind Houston, L.A., NY, New Orleans, San Fran)

• Vessels travel estuary through 

### a shipping channel maintained at 40’ by the U.S. ACOE

– Other commercial and recreational vessels travel daily

Figure1. Brown and Murphy 2010

# Methods

• Collect genetic tissue, spine for A+G, muscle tissue for contaminants

• Measure carcass

– If not whole use ratio to extrapolate measurements to estimate live length



## • Take pictures, assess cause of death, determine 

## sex, scan for tags

• Mark with orange spray paint and bury on site or back at the office

• Report shortnose carcasses to NMFS salvage network

# Carcass Locations

• Also received reports from

– Nanticoke R., NJ and RI coast

• Brown and Murphy 2010

- currents drive more carcasses to DE side

– Prevailing winds likely counteract the effect and reporting rate is effecting reports 71%

Land 29% Water

# Carcass reports annual frequency

0 5 10 15 20 25 30

2005 2006 2007 2008 2009 2010 2011If you find a sturgeon, please report it immediately:

302

- 735

- 8650. Don’t forget to include an exact location and contact information in your message. 

## Have you seen a sturgeon recently?

# Carcass reports annual frequency

0 5 10 15 20 25 30

2005 2006 2007 2008 2009 2010 2011 Mean=8.2 Mean = 17.5

# Carcass reports by month

0 10 20 30 40 Frequency

# Carcass reports by month

0 10 20 30 40 Frequency Juveniles Adults

# Carcass reports by month

0 10 20 30 40 Frequency Juveniles Adults sturgeon matrimony... interrupted

# Carcass reports by month

0 10 20 30 40 Frequency Juveniles Adults sturgeon matrimony... interrupted Just passing through for a

snack.... BAD decision

# Spring Adults

• Funnel shape estuary brings sturgeons into vessel path



## • Vessel strike carcasses are also being monitored in other 

## systems

– James R. occurring @ constriction point

– Hudson R.

– unknown location

# 2008 Atlantic Sturgeon Depth in the Delaware Estuary by Month

0
5
10
15
20
25
30
35 April n=322 May

n=519 June

n=7127 July

n=6266 August

n=15722 September

n=10636 October

n=5384 Depth (m) Federal Channel >40'

# 2008 Atlantic Sturgeon Depth in the Delaware Estuary by Month

0
5
10
15
20
25
30
35 April n=322 May

n=519 June

n=7127 July

n=6266 August

n=15722 September

n=10636 October

n=5384 Depth (m) Federal Channel >40'

During peak carcass report season juvenile sturgeon are on the move and not close to the bottom as frequently as they

are in the summer months

# Carcass cause of Death

38% unknown 62%

vessel strike

# Injuries

• 18 lethal gash (head, dorsal area, caudal area)

• 14 decapitation

• 19 tail cut off



### • 2 blunt force trauma

– 2 no visible injuries

natural causes

– 11 too decomposed to ascertain

– 10 unknown due to lack of photo or info



### • 0 gashes or trauma to 

### ventral areas only

# Deep draft vessel strikes

Dredged to 40’ depth

• Fully loaded deep draft vessels are known to drag bottom in depositional areas at low tide, hence the need for annual maintenance dredging (pers. com, U.S. ACOE)

• Propellers on large vessels pull water at 9 m/sec• Dead sturgeon like most fish with a swim bladder float belly up

• If vessel strike injuries are post

mortality then why are injuries never found on the ventral side?

• The mechanism that causes the strike to occur is poorly understood



### – Noise negative, positive, neutral?

# Small vessel strikes

• C+D canal report

– Recreational boater reported seeing a sturgeon jump ahead of him and 

### then looked behind and saw the floating carcass (DNREC law enforcement report, M. Grahofski)



## • Commercial crabber reported hitting an adult sized sturgeon w/ 

## outboard (DNREC C. Shirey pers. comm.)

# Discussion
– Solutions?

• Yield to sturgeon

– decrease traffic or time of year restriction?

– not likely or realistic 

### economically/politically



## • Slow, sturgeon crossing

– Speed limit in problem 

### areas?



## • Sturgeon at work

– Detour

# Credits

• NJDEP, USCG, PAFBC, DFW trawl survey, DFW shorebird survey, DFW law enforcement and public reporters

• DSU and DFW law enforcement for following up on reports



# • Co

- workers Jared and Cathy for working up stinky carcasses when I’m away on vacation