# At lan tic st urge on habit atre ga rd ing wate r quality r equir emen ts in the Delaw ar e Riv er

Matt Fisher DNRE C – DFW 4876 Ha y P oint Landing Rd. Sm yrna, DE 19977 302 - 735 - 8650 Matthew.Fisher@st ate.de.us

# Life his to ryov er view
• Anadr omous - part of their liv es ar e spen t in saltw ate r and spawn in fr eshwater • Life his tor y phases can be classified as 3 dis tinct beha vior s and r equir emen ts

– **Adults** - live entirely in salt and br ackish water s but spawn in freshwater late May - early June • Females spawn 1 or 2 times ev ery 5 y ears while males spawn almost every year • St atus review te am in 2007 est. the DE a dult pop <300 indiv duals

– **Eg g/**  **lar va**  **l thr ough early s** **ta ge**  **juvenile** river resident phase (lasts 2 t o 3 y ear s) and requires freshwater <.5 ppt

– **Late stage**  **juveniles** • In the Delaware R. lat e s ta ge juv eniles ent er br ackish and fr eshwater to feed fr om A pril - Oct. and then r eturn t o the A. Ocean

# Curr en t s tat us
• Lis te d as an Endanger ed species by NO AA goes int o e ffect 4/6/2012 • Thr ea ts iden tified in the lis ting

– Ve ssel - st rikes

– By - catc h

– Dr edging

– Wa te r Quality• Avg . Conductivity fr om June - Oct ober @ Ches ter g age

– 1997, 98 = 753, 651

– 2007, 08 = 946, 1046 • Figur es show s turgeon concentr at ions shift ups tr eam in 07 - 08 compar ed to wet 97 - 98

– Salt water incur sion moves freshwater habitat upstr eam into a narr ower and smaller area due to the shape of the river

.

– Thus decreasing productive nursery capacity

# Wa te r quality - Salinity

### • No Y

oung of the Ye ar ha ve been located in salinity >.5ppt during DFW tracking and gillnetting 

# Wa te r Quality - Salinity

DFW Y oung of the Y

ear manual tr acking locations, 2009 and 2011

# His to ric al Spa wning

• Spawning adults pr efer fr esh wate r <.5ppt, har d botto m subs trate • Delaw ar e City

, DE ( rkm 77) to Ches te r, P

A ( rkm 130) • Ea rly Ma y t o mid -June • Wa te r temperatur es 13.3 - 17.8 ° C • Es timates fr om fisheries dependen t dat a prior t o 1925 RKM 130

RKM 77 Slide court esy of Matt Br eece - DSU

# Likely Spawning Ar eas • RKM 120 - 150 • RKM 170 - 190 • St aging ar ea

– RKM 100 - 120

Slide court esy of Matt Br eece - DSU• Beware - Estimated number s ahead!! R eal modeling needed. • Tr en to n flows required to main ta in <.5ppt (1100 co nd ) 50% of the time fr om Ma y -July during spawn and during sensitive <60 da y old sturgeon @ Chest er

– 50% = 3098 cfs

– **90% = 4800** cfs • If sit e adjust ed t o include F ox Po in t (lower spawning gr ounds)

– 50% = 3454 cfs

– **90% = 5400** cfs • If sit e adjust ed t o F oxP oin t and effects of post deepening (0.10 - .25ppt increase, ACOE models)

– 50% = 3607 - 3862 cfs

– **90% = 5600 -**  **6100** cfs

# Wa te r quality - Te mp and DO

• In general, s turgeon ar e mor e sensitiv e than other fish species t o wate r te mperatur e and dissolved oxyge n Critical DO=met abolic re sponse level Thr eshold DO=lethality wher eby basal met abolism can not be maint ained From Secor and Niklitschek 2001From Secor and Niklitschek 2001

# DFW Y

oung of the Y

ear r esults
• Pr esence of y oung of the y ear is indication of a success ful spawn and r ecruitmen t

– 2009 - 34 Yo Y DFW captur es, 32 Yo Y - ERC

– 2010 - 0 Yo Y DFW

, 0 Yo Y - ERC

– 2011 - 51 Yo Y DFW

, no e ffort fr om ERC • 2011 Yo Y pop es timate = 356 (95% CI 121 - 1782) • Though biased it indicates a small pop

# Wa te r Quality – Te mp and DO

• Hat chery trials on w ater quality to lerances e xis t fo r yo ung of the y ear At lan tic st urgeon • Secor and Gunder son 1998, Secor and Niklitschek 2001 

### • However

, to lerances for the eg g or larv al phase (<30 da ysold ) for Atlan tic s turgeon ar e unknown • Y ounger shortnose st urgeon (<30 da ys ) ar e mor e sensitiv e to high w ater temp (>27 C) and DO then 70 and 110 da y juvs Jenkins et al. 1993

# Summary

• At lan tic s turge on egg t o 30 da y old juvs wate r quality toler ances ar e unknown - data is needed

– When shortnose to ler ances are substitut ed the dat a sugg ests the 2010 year class was affect ed by water quality but the e xt en t is unknown

– DFW + ER C catch r ates supports this • With salt water incur sion fr om deepening , w ate r withdr awals and sea level rise, habit at at all life phases is los t within the Delawar e Es tuary • Re co mmendation: Consider manag emen t s tr ate gies to addr ess water q uality (mainly DO and salinity) in the Delawar e R. to impr ove Atlan tic s turge on sur viv ability and re duce habit at loss