Atlantic sturgeon habitat regarding 

water quality requirements in the 

Delaware River

Matt Fisher

DNREC – DFW

4876 Hay Point Landing Rd.

Smyrna, DE 19977

302-735-8650

Matthew.Fisher@state.de.us
Life history overview

• Anadromous- part of their lives are spent in saltwater and 

spawn in freshwater

• Life history phases can be classified as 3 distinct behaviors 

and requirements

– Adults-live entirely in salt and brackish waters but spawn in 

freshwater late May-early June

• Females spawn 1 or 2 times every 5 years while males spawn almost 

every year

• Status review team in 2007 est. the DE adult pop <300 indivduals

– Egg/larval through early stage juvenile river resident phase 

(lasts 2 to 3 years) and requires freshwater <.5 ppt

– Late stage juveniles

• In the Delaware R. late stage juveniles enter brackish and freshwater 

to feed from April - Oct. and then return to the A. Ocean 
Current status

• Listed as an Endangered species by NOAAgoes into effect 4/6/2012

• Threats identified in the listing

– Vessel-strikes

– By-catch

– Dredging

– Water Quality
• Avg. Conductivity from 

June-October @ 

Chester gage

– 1997, 98 = 753, 651

– 2007, 08 = 946, 1046

• Figures show sturgeon 

concentrations shift 

upstream in 07-08 

compared to wet 97-98

– Salt water incursion 

moves freshwater 

habitat upstream into 

a narrower and smaller 

area due to the shape 

of the river. 

– Thus decreasing 

productive nursery 

capacity

Water quality - Salinity
• No Young of the 

Year have been 

located in salinity 

>.5ppt during DFW 

tracking and 

gillnetting

Water Quality - Salinity

DFW Young of the Year manual tracking locations, 2009 and 2011
Historical Spawning 

• Spawning adults prefer 

freshwater <.5ppt, hard 

bottom substrate

• Delaware City, DE (rkm 77) 

to Chester, PA (rkm 130)

• Early May to mid-June

• Water temperatures 13.3-

17.8°C

• Estimates from fisheries 

dependent data prior to 

1925

RKM 130

RKM 77

Slide courtesy of Matt Breece-DSU
Likely Spawning Areas

• RKM 120-150

• RKM 170-190

• Staging area

– RKM 100-120

Slide courtesy of Matt Breece-DSU

• Beware-Estimated numbers 

ahead!! Real modeling 

needed.

• Trenton flows required to 

maintain <.5ppt (1100 cond) 

50% of the time from May-July 

during spawn and during 

sensitive <60 day old sturgeon 

@ Chester

– 50% = 3098 cfs

– 90% = 4800 cfs

• If site adjusted to include Fox

Point (lower spawning grounds)

– 50% = 3454 cfs

– 90% = 5400 cfs

• If site adjusted to Fox Point and 

effects of post deepening 

(0.10-.25ppt increase, ACOE 

models)

– 50% = 3607-3862 cfs

– 90% = 5600-6100 cfs
Water quality-Temp and DO

• In general, sturgeon are 

more sensitive than 

other fish species to 

water temperature and 

dissolved oxygen

Critical DO=metabolic response level

Threshold DO=lethality whereby basal 

metabolism can not be maintained

From Secor and Niklitschek 2001
From Secor and Niklitschek 2001
DFW Young of the Year results

• Presence of young of the year is indication of 

a successful spawn and recruitment

– 2009-34 YoY DFW captures, 32 YoY-ERC

– 2010-0 YoY DFW, 0 YoY-ERC

– 2011-51 YoY DFW, no effort from ERC

• 2011 YoY pop estimate = 356 (95% CI 121-1782)

• Though biased it indicates a small pop

Water Quality – Temp and DO

• Hatchery trials on water quality tolerances exist for 

young of the year Atlantic sturgeon

• Secor and Gunderson 1998, Secor and Niklitschek 2001

• However, tolerances for the egg or larval phase (<30 

days old) for Atlantic sturgeon are unknown

• Younger shortnose sturgeon (<30 days) are more 

sensitive to high water temp (>27 C) and DO then 70 

and 110 day juvs Jenkins et al. 1993
Summary

• Atlantic sturgeon egg to 30 day old juvs water quality 

tolerances are unknown-data is needed

– When shortnose tolerances are substituted the data suggests 

the 2010 year class was affected by water quality but the extent 

is unknown 

– DFW + ERC catch rates supports this

• With salt water incursion from deepening, water 

withdrawals and sea level rise, habitat at all life phases is 

lost within the Delaware Estuary

• Recommendation: Consider management strategies to 

address water quality (mainly DO and salinity) in the 

Delaware R. to improve Atlantic sturgeon survivability and 

reduce habitat loss