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Aroon R. Melwani, S.N. Bezalel, J.L. Grenier, J.A. Hunt, A.H. Robinson, and J.A. Davis (SFEI)

The Relationship Between Landscape Features and Sport Fish Mercury in the Sacramento-San Joaquin Delta Watershed. Aroon R. Melwani, S.N. Bezalel, J.L. Grenier, J.A. Hunt, A.H. Robinson, and J.A. Davis (SFEI).

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Aroon R. Melwani, S.N. Bezalel, J.L. Grenier, J.A. Hunt, A.H. Robinson, and J.A. Davis (SFEI)

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  1. The Relationship Between Landscape Features and Sport Fish Mercury in the Sacramento-San Joaquin Delta Watershed Aroon R. Melwani, S.N. Bezalel, J.L. Grenier, J.A. Hunt, A.H. Robinson, and J.A. Davis (SFEI) Presentation at the Fish Mercury Project Annual Meeting, Sacramento, CA. June 5th, 2007

  2. Outline of Presentation • Goals and hypotheses of the landscape analysis • GIS Methods: landscape data, creating fish watersheds • Sport fish dataset: largemouth bass, catfish • Results • Atmospheric deposition • Mining features • Wetland features

  3. Goals/Hypotheses • Quantify relationships between landscape features and sport fish mercury • Atmospheric deposition • Mining sources • Habitat features • Watershed-scale • Near-field influence (~ fish home range)

  4. GIS Datasets • Mining • Sport fish • Wetlands • Hydrography Gold + Mercury Mines Fish Sampling Locations data unavailable National Wetlands Inventory National Hydrography Dataset

  5. Sport fish Dataset • Largemouth bass widely distributed • Channel catfish outside the Delta • White catfish inside the Delta Study Area: Ecosystem Restoration Program Boundary Largemouth Bass White Catfish Channel Catfish

  6. Fish Watersheds Hg = 0.64 ppmWetland = 0.8%Mines = 2286 Hg = 0.26 ppm Wetland = 1.4%Mines = 856

  7. Near-field Influence • Approximate the home range of the fish (1-km and 5-km) • Same GIS calculations as watershed-scale

  8. Atmospheric Deposition • Largemouth bass • Lakes/reservoir watersheds lacking mines (n = 8) • No significant difference (p = 0.75)

  9. Watershed-scale Mines = 1034 (0.1 mines/km2) Wetland area = 5% Hg = 0.18 ppm

  10. Watershed-scale • Low density of mines • Low wetland area • Relatively high mercury - Mines = 832 (0.04 mines/km2) - 3% wetland area - Hg = 0.55 ppm

  11. Largemouth Bass Near-field Influence • High mercury concentrations at some sites • Regardless of mine density or wetland area

  12. Channel Catfish and Wetlands • Lakes/reservoir sites using near-field (5km) influence • Opposite trend to what was expected

  13. Largemouth Bass Hg in the Delta

  14. Delta Habitat • No overall relationship to sport fish mercury concentration in 1-km or 5-km buffers • Relationship to habitat types different between Delta regions • Vegetated wetland • Temporarily inundated wetland

  15. White Catfish % wetland area • Negative relationship in Sacramento R. • Other areas have unclear pattern

  16. Largemouth Bass% temporarily flooded area • Negative relationship in Sacramento R. • Other areas have unclear pattern

  17. Conclusions • Fish mercury influenced by complex factors, such as methylation, biogeochemistry, etc. • No obvious correlations to landscape features • Small sample size of fish locations (especially on tributaries) • GIS Data gaps • Mines: Production quantity, size • Wetlands: Missing coverage, other features of wetlands not captured (such as biochemistry)

  18. For more information: Contact the San Francisco Estuary Institute Aroon Melwani – aroon@sfei.org Jay Davis – jay@sfei.org

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