*Kevin L. Stierhoff, Damian C. Brady, Timothy E. Targett

1. Identification and Assessment of Fish Nursery Habitats:Examples of Hypoxia Impacts from Delaware’s Inland Bays *Kevin L. Stierhoff, Damian C. Brady, Timothy E. Targett University of DE-Graduate College of Marine Studies Robin M. Tyler Univ. of DE, and State of DE DNREC-Water Resources

2. Nursery Habitat • Estuaries are know to be juvenile habitat for many commercially and ecologically important finfish. • Favorable physicochemical conditions (i.e. temperature, salinity, turbidity) • Abundant prey • Low risk of predation

3. Essential Fish Habitat (EFH) • ‘One of the greatest long-term threats to commercial and recreational fisheries is the continuing loss of estuarine, marine, and other aquatic habitats’. • Magnuson-Stevens Fishery Conservation and Management Act reauthorized and amended, as the Sustainable Fisheries Act, to identify and protect Essential Fish Habitat (EFH). Those waters and substrates necessary to fish for spawning, breeding, feeding and growth to maturity

4. What is EFH? • By original definition, all coastal waters could be classified as EFH. • Presence/Absence • Distribution & Abundance • Condition & Growth • Adult Production • Any habitat that makes a greater than average contribution to the recruitment of adults (Beck et al. 2001, BioScience).

5. Hypoxia in Estuarine NurseriesLow dissolved oxygen (DO) • Chronic hypoxia • W. Long Island Sound • Chesapeake Bay • Neuse River, NC • Mississippi plume • Diel-cycling hypoxia • Childs River, MA • Delaware’s Inland Bays US Map

6. Delaware Bay Pepper Creek DE Inland Bays Delaware’s Coastal Bays

7. Temporal and Spatial DO Dynamics

8. Field Movements of Weakfish

9. x5 Laboratory Growth Studies

10. SGR P. dentatus P. americanus 20C 25C Dissolved oxygen (mg O2 l-1) Dissolved oxygen (mg O2 l-1)

11. Avoidance Behavior

12. Lab Experiments Consumption & Growth Mortality Avoidance Field Data DO, Temp, Salinity Effects Literature Data Temperature Salinity Dissolved Oxygen Individual-based Model Processes BEGIN Setup spatial grid Loop over days Update environmental conditions in cells Add new fish arrivals to population Loop over individual fish Growth Mortality Movement Individual Loop Daily output Average growth & survival rate Maps of fish spatial distributions Day Loop Summary output Summertime survival rate Mean growth rate of survivors END Quantitatively link water quality with survival, growth, and avoidance behavior

13. Mesocosm Swimming Studies Activity rates make up a large and variable portion of a fish’s energy budget (Boisclair & Sirois,1993)

14. Respirometry Oxygen consumption and swimming capacity under various DO conditions. Sepulveda & Dickson, 2000

15. An in situ growth approach • RNA:DNA and Growth rate • Growth rate responds rapidly (<24) to changes in feeding status • Growth is accomplished by protein synthesis • RNA:DNA reflects recent growth Transcription Translation Double-stranded DNA (constant concentration) Single-stranded RNA (changes with transcription rates ) Protein

16. Back-calculating Recent Growth Summer flounder From Malloy and Targett, 1994

17. Questions and Discussion