The Uptake of Mercury and Relationship to Food Habits of Target Fish Species in the South River and South Fork Shenandoah River

Transcription

1 The Uptake of Mercury and Relationship to Food Habits of Target Fish Species in the South River and South Fork Shenandoah River G. Murphy, T. Newcomb, and D. Orth Department of Fisheries and Wildlife Sciences Virginia Tech

2 Virginia Tech Study OBJECTIVE 1: Determine diet composition of the target fish species in study and references reaches Asian clam Darter

3 Target Fish Species White sucker Smallmouth bass Channel catfish Redbreast sunfish

4 Study Reaches South River: - Waynesboro to Port Republic South Fork Shenandoah River: - Port Republic to Front Royal South River North River (reference): - Port Republic to Bridgewater South Fork

5 Fish Sampling Sites Shenandoah River North Fork North River South Fork N Middle River South River Contamination Point miles

6 Fish Collection Methods Boat & barge electrofishing Hoop netting Goal = 30/species/reach Maximize age/size range Seasonally

7 Fish Processing Methods Fish identification ppm clove oil anesthetic Measured TL (mm) Weighed (g) Sexed

8 Fish Processing Methods Stomach or intestine: - 10% formalin - diet analysis Otoliths (earstones): - age analysis

9 Laboratory Methods Food item identification: - invertebrates (order) - fish (species) Blotted dry Weighed to 0.001g Stored in 70% ethanol

10 Fish Collection Results April + July South River South Fork CCF RDB SMB WHS North River Totals

11 South Fork Channel Catfish Preliminary Findings

12 South Fork Channel Catfish Percent by Weight (g) 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% April July Food Item

13 South Fork Channel Catfish Fish Analysis 60% April July Percent by Weight (g) 50% 40% 30% 20% 10% 0% PDUF Redbreast Sunfish Sunfish Smallmouth Bass Food Item

14 South Fork Channel Catfish Summary Mainly consume sunfishes (centrarchids) in April & July Green algae important in July Opportunistic feeders: - meadow vole - crayfish -fish - green algae - aquatic insects

15 White Sucker Preliminary Findings

16 White Sucker April Percent by Weight (g) 70% 60% 50% 40% 30% 20% 10% 0% South River South Fork North River Food Item

17 White Sucker Insect Analysis Percent by Weight (g) 60% 50% 40% 30% 20% 10% 0% South River South Fork North River Food Item

18 White Sucker Summary Mainly consume aquatic insects: - Ephemeroptera (North River) - Trichoptera (South Fork) - Diptera (South River) Large amount of unidentifiable organic matter Mollusca important in South Fork Diptera

19 Redbreast Sunfish Preliminary Findings

20 Redbreast Sunfish < 126 mm Percent by Weight (g) 100% 80% 60% 40% 20% South River South Fork North River 0% Food Item

21 Redbreast Sunfish mm Percent by Weight (g) 100% 80% 60% 40% 20% South River South Fork North River 0% Food Item

22 Redbreast Sunfish mm Percent by Weight (g) 100% 80% 60% 40% 20% 0% South River South Fork North River Food Item

23 Redbreast Sunfish > 175 mm Percent by Weight (g) 100% 80% 60% 40% 20% 0% South River South Fork North River Food Item

24 Redbreast Sunfish Insects Analysis Percent by Weight (g) 60% 50% 40% 30% 20% 10% 0% South River South Fork North River Food Item

25 Redbreast Sunfish Summary Mainly consume aquatic insects Larger cohorts have a more variable diet Larger cohorts shift to terrestrial insects from April to July Ephemeroptera, trichoptera, and diptera most common Decrease in ephemeroptera and increase in trichoptera from April to July in all reaches Trichoptera

26 Smallmouth Bass Preliminary Findings

27 Smallmouth Bass < 100 mm 100% South River South Fork North River Percent by Weight (g) 80% 60% 40% 20% 0% Food Item

28 Smallmouth Bass mm Percent by Weight (g) 100% 80% 60% 40% 20% South River South Fork North River 0% Food Item

29 Smallmouth Bass mm Percent by Weight (g) 100% 80% 60% 40% 20% South River South Fork North River 0% Food Item

30 Smallmouth Bass > 299 mm Percent by Weight (g) 100% 80% 60% 40% 20% South River South Fork North River 0% Food Item

31 Smallmouth Bass Fish Analysis Percent by Weight (g) 70% 60% 50% 40% 30% 20% 10% 0% South River South Fork North River Food Item

32 Smallmouth Bass Summary < 100 mm cohort mainly consuming aquatic insects Smaller cohorts in South River consuming more fish Larger cohorts consume mostly crayfish and fish Larger cohorts consume more crayfish and less fish from April to July Fish species consumed differ Crayfish

33 Final Summary Diet results agree with literature review Good representation from each trophic group Fish, aquatic insects, and crayfish are most commonly consumed Shiner Plecoptera Crayfish

34 Upcoming Events October fish sampling event (14 of 16 completed) - sample final 2 sites on North River tomorrow December fish sampling event Continue diet and age analysis South Fork

35 Acknowledgements Committee Members: Steve Reeser Tammy Newcomb Don Cherry Don Orth John Ney South River Science Team

36 Questions?