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All in the Family (?) Diversity of habitat use in anguillicolid eels Karin E. Limburg

All in the Family (?) Diversity of habitat use in anguillicolid eels Karin E. Limburg. Recall Paul Angermeier’s depiction of eel life history as a complex set of phases…much confusion, uncertainty.

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All in the Family (?) Diversity of habitat use in anguillicolid eels Karin E. Limburg

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  1. All in the Family (?) Diversity of habitat use in anguillicolid eels Karin E. Limburg

  2. Recall Paul Angermeier’s depiction of eel life history as a complex set of phases…much confusion, uncertainty. Turns out that eels do display a broad repertoire of habitat use. How we know this now is through studies of otoliths… First, basics Second, Swedish example Third, comparisons betw. 3 anguillid spp.

  3. Otoliths (earstones) are increasingly used as natural tags of fish life history • Part of hearing & balance system • Grow as fish grows, with daily and annual increments • Aragonite (CaCO3) precipitated on protein matrix – entrains other elements

  4. Otolith microconstituents increasingly used as natural tags • Sr is particularly useful to track diadromy • Sr, like Ca, is an alkaline earth element with similar ionic radius – can substitute for Ca in the otolith’s aragonite • Srsea generally >> Srfresh • Can use Sr:Ca ratios to trace salinity histories of fish

  5. Measuring Sr in otoliths Microanalytic techniques Wavelength dispersive electron microprobe (WDS), can make point transects on the order of microns

  6. Nuclear microprobe combined with proton-induced x-ray emission analysis (mPIXE) • - higher resolution technique • able to measure multiple elements at ppm levels • can map entire otoliths quickly

  7. Sweden began intensive stocking program in 1978 European eel, Anguilla anguilla • Catadromous • Highest value-added fishery • Catches of silver eels in Baltic Sea declining since 60’s Q: Do these fish contribute to the spawning stock, or just to “put and take” ???

  8. What do Baltic eels do? Hypotheses Westin ’90: stocked eels don’t swim in, so they can’t smell their way out – instead, they get “lost” in southern Baltic following thermal gradients Svedäng & Wickström ’97: no correlation between silver eel fat and maturity indexes – silver eels may halt migration and revert to feeding, to “bulk up” for the big swim

  9. What do Baltic eels do? Tsukamoto et al. ’98: catadromous eels do not contribute genes to spawning stock If we can trace the movement of eels, and collect them leaving or “lost” in the Baltic, we should be able to test all three hypotheses

  10. Salinity history recorded in a silver eel otolith

  11. Silver eels in the study Exiting Baltic Danish

  12. S1 = “stocked” as glass eel, stayed in fresh H2O • S2 = “stocked” from marine into Baltic as yellow eel • S3 = “stocked” into fresh H2O and moved into salt H2O Habitat use categories • M = 100% marine • MB = marine  brackish • B = brackish • CM = “complex migration” betw. marine and brackish • CAT = catadromous

  13. Does the proportion of wild to stocked silver eels differ by where they were caught?

  14. How does lipid content vary among presumably stocked eels?

  15. What do differential fat reserves imply for migrating to the Sargasso, 6000+ km away?

  16. Comparing among 3 species (Daverat et al., MEPS in press)

  17. Comparing among 3 species

  18. (H. Wickström) Stable brackish (female from Kullen)

  19. Type 2 Type 1 Type 3a Type 3b Type 3c Type 3d American eel, St Jean Estuary and Sirois Lake (Gaspé Peninsula)

  20. Type 1 Type 2 Type 3a Type 3b Type 3d Type 3e European eel, Gironde estuary

  21. 20 20 18 18 16 16 Type IV. Fresh to brackish Type I. Freshwater 14 14 12 12 Sr/Ca * 1000 Sr/Ca * 1000 10 10 8 8 6 6 20 4 4 18 "Twin peaks" 2 2 20 16 0 0 14 18 Type II. Gradient -2 -2 Distance (µm) 12 Distance from core (µm) 16 Sr/Ca * 1000 14 10 12 8 Sr/Ca * 1000 10 6 8 4 20 2 6 18 Type V. Change 0 4 16 2 -2 14 Distance (µm) 0 12 Sr/Ca * 1000 -2 10 Distance (µm) 8 6 4 2 0 -2 Distance (µm) 20 20 34 Type VI. Yellow into fresh water 18 32 18 Type III. Brackish "Saltmine" 30 16 16 28 26 14 14 24 12 22 12 20 Sr/Ca * 1000 10 Sr/Ca * 1000 Sr/Ca * 1000 10 18 16 8 8 14 6 12 6 10 4 4 8 6 2 2 4 0 2 0 0 -2 -2 -2 Distance (µm) Distance (µm) Distance (µm)

  22. Type 1 Type 2 Type 3a Type 3b Type 3c Type 3d Japanese eel, Kaoping River, Taiwan

  23. When do I leave?

  24. MR MR 6% BR FR BR 5% 26% 14% 17% N NF 60% NF NF 17% 81% 74% N MR N 2% 24% 25% BR NF 44% 39% NF BR NF FR 59% 60% 15% 17% FR 15% A. rostrata A. anguilla A. japonica Hudson River estuary (yellow eels) Kaoping estuary (yellow eels) Baltic Sea exit (silver eels) St Jean estuary (yellow & silver eels) Gironde estuary (yellow eels) Mikawa Bay (silver eels)

  25. Eel habitat use and Latitude

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