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Molly Payne Wynne Dr. Karen Wilson University of Southern Maine

Examining Freshwater and Marine Habitat Use by Juvenile Blueback Herring ( Alosa aestivalis ) Through Otolith Microchemical Methods. Molly Payne Wynne Dr. Karen Wilson University of Southern Maine Departments of Biological Sciences and Environmental Science. Acknowledgements.

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Molly Payne Wynne Dr. Karen Wilson University of Southern Maine

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  1. Examining Freshwater and Marine Habitat Use by Juvenile Blueback Herring (Alosaaestivalis) Through Otolith Microchemical Methods Molly Payne Wynne Dr. Karen Wilson University of Southern Maine Departments of Biological Sciences and Environmental Science

  2. Acknowledgements Maine Sea Grant Maine EPSCoR Sustainability Solutions Initiative Alewife Stock Structure in the Gulf of Maine Project (NFWF Grant) Dr. T. Willis and the Wilson/Willis Lab Members The Alewife harvesters of Maine and Maine Department of Marine Resources

  3. River Herring Landings (NMFS)

  4. spawning adults eggs young of year Juveniles Freshwater Spring Fall Ocean adults

  5. Approach: Otoliths as Natural Tags Otoliths reflect ambient water chemistry (Campana 2005) Calcium Strontium Barium Manganese Sectioned Otolith at 400x: M. Payne 2012

  6. Otoliths as Natural Tags:Require Differences in Water Chemistry Freshwater: ↓Sr↑Ba Seawater:↑Sr↓Ba

  7. Otoliths as Natural Tags: Field Verification Sr:Ca

  8. Otoliths as Natural Tags: Field Verification Ba:Ca

  9. Research Questions • Habitat Use: ↑Estuary = ↑ Residency • Growth: ↑Estuary =↑Growth • Differences Among Runs: Otolith A ≠ Otolith B

  10. Methods

  11. Site Selection Study Sites

  12. Otoliths Rostrum First Annulus Dorsal Edge First Annulus Core Ventral Edge 1mm Postrostrum M. Payne 2013

  13. Otolith Microchemistry Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS)

  14. Core (age=0) Otolith at 400x - M. Payne 2013 1mm

  15. Otolith Microchemistry: Interpretation Migration Peak Migration Peak Freshwater/ Low Salinity

  16. Low Salinity Habitat Use Value (LSHU) LSHU= 0.48 <1 = migrated to sea before the end of the first year of growth >1 = migrated after the first year; overwintered in estuary

  17. Regime Shifts (Rodionov 2004) • # of shifts • Magnitude of Sr:Ca 2 4.15 3.00 3 1 1.65

  18. Back Calculation: Length at Year 1 and Egress Otolith Width at Egress Otolith Width at Year 1

  19. Back Calculation: Length at Year 1 and Egress

  20. Multiple Discriminant Function Analysis LSHU No. of Regime Shifts (Sr, Ba, Mn) Growth Proxy

  21. Results James McCarthy 2013

  22. Habitat Use: Alternative Life Histories

  23. Habitat Use: Alternative Life Histories Winnegance

  24. Growth: Lengths at Year 1 and Egress Seven Tree Orland Dam Benton Falls Winnegance Patten Pond Hadley Lake Dresden Mills

  25. Differences Among Runs:Multiple Discriminant Function Analysis • Growth Proxy • LSHU Value • # Regime Shifts • [Sr: Ca, Ba:Ca, Mn:Ca]

  26. Conclusions • Habitat Use: ↑Estuary ≠ ↑ Residency • Two rivers showed habitat use as predicted although overall a correlation with estuary size and distance to sea was not found • Growth: ↑Estuary ≠↑Growth • Fish with the lowest LSHU (Winnegance) were significantly shorter at Egress • Wetland habitat (Mn:Ca) may infer a growth advantage; longer lengths at Egress • Differences Among Runs: Otolith A ≠ Otolith B • Winnegance and Patten Pond show alternative migratory patterns compared to other runs • Otolith methods are promising in terms of run differentiation

  27. Implications/ Future Directions Otolith microchemistry can be used to study habitat use in Maine rivers! Freshwater and estuary habitats are important for recruitment to adult populations Variation in Ba:Ca and Mn:Ca signatures in freshwater (otolith and water chemistry) could be used to identify origin at a finer scale

  28. Questions? Zachary Whalen 2013

  29. Length at Egress and Mn:Ca r = 0.641

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