Mercury contamination of sport fish in the Delta and its watershed CBDA Fish Mercury Project, Year 1

1
Mercury contamination of sport fish in the Delta
and its watershed CBDA Fish Mercury Project,
Year 1

• Letitia Grenier, Aroon Melwani, Jen Hunt, Shira
  Bezalel, Jay Davis
• San Francisco Estuary Institute
• Gary Ichikawa, Billy Jakl
• California Department of Fish and Game
• Wes Heim, Autumn Bonnema
• Moss Landing Marine Laboratories
• Margy Gassel
• California Office of Environmental Health Hazard
  Assessment

2
Presentation Overview

• Scope of captures (how many fish, where)
• Fish size and mercury
• Overall mercury impact (all species)
• Differences between fish species
• Differences across the Delta watershed

3
Field Collection

• Late July to mid December 2005
• California Department of Fish and Game
• Electrofisher boat and fyke nets
• Clean handling techniques
• Length measurements

4
FMP Sport Fish Sampling, 2005

• 2124 individual fish
• 24 species
• 70 sport fishing locations
• Coordinated sampling
• Central Valley Regional Water Quality Control
  Board
• Sacramento River Watershed Project

5

• Sampling
• Locations
• 2005
• Colors represent different types of sampling
  sites

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Take Home Message

• We caught a lot of fish from a lot of sites!
• This was the most extensive and intensive sport
  fish sampling in this region to date

7
Size of Fish Can Matter
Largemouth Bass
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Take Home Message

• For fish of the same species, mercury is often
  higher in bigger fish
• This is not a bad rule of thumb, even though some
  species and some sites do not show an increase in
  mercury with fish size

9

• Overall
• Impact
• Highest Species
• Colors represent relative mercury contamination
• Symbol shapes represent species with highest
  average concentration
• Size limits applied, minimum sample size is one
  fish

10

• Overall
• Impact
• Lowest Species
• Colors represent relative mercury contamination
• Symbol shapes represent species with lowest
  average concentration
• Size limits applied, minimum sample size is one
  fish

11

• Relative
• Impact by
• Species
• Colors represent relative mercury contamination
• Quadrants represent species
• Gray quadrants mean species not collected
• Size limits applied, minimum sample size is one
  fish

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Colors represent relative mercury contamination
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Take Home Message

• Different fish species have different levels of
  mercury contamination
• At the same site, some species may be high in
  mercury, while others are low
• Remember that this analysis does not take
  organics into account

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• Largemouth
• Bass
• Colors represent relative mercury contamination
• Height of bar represents mean concentration
• Size limits applied, and minimum sample size is
  one fish

15

• Bluegill
• Colors represent relative mercury contamination
• Height of bar represents concentration
• Size limits applied, and minimum sample size is
  one fish

16
White Catfish
Prospect Slough
Old River at Tracy Blvd
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Take Home Message

• The same kind of fish of the same size can have
  different mercury concentrations at different
  locations
• Some sites in the central Delta tend to have
  lower mercury in most species relative to the
  surrounding rivers

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Summary

• Most extensive and intensive sport fish sampling
  in this region to date
• For fish of the same species, mercury is often
  higher in bigger fish
• Different fish species have different levels of
  mercury contamination
• The same kind of fish of the same size can have
  different mercury concentrations at different
  locations

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Acknowledgements

• California Bay-Delta Authority
• Fish Mercury Project
• Steering Committee
• Peer Review Panel
• Co-PIs and Collaborators