Teejay O’Rear (taorear@ucdavis.edu) and Peter Moyle (pbmoyle@ucdavis.edu) UC Davis Center for Watershed Sciences and Wildlife, Fish, and Conservation Biology

Cal-Neva AFS 2015 • Santa Cruz, CA

North Delta Arc working group: Matt Young, Denise DeCarion, Thomas Handley, Amber Manfree, Brian Williamson, Jacob Montgomery, Kathleen Berridge, Kousei Martin Perales, Felipe La Luz, Chris Jasper, Teejay O’Rear, Randy Dahlgren, William Fleenor, James Hobbs, John Durand, Peter Moyle

White Catfish and Adult Striped Bass Diets in Suisun Marsh

White Catfish and Adult Striped Bass Diets in Suisun Marsh

1. Key Suisun Marsh features

2. White catfish diets

3. Adult striped bass diets

Suisun Marsh

Water Clarity: Low

Win Aut Sum Spr

dry

wet wet

Managed Wetlands Water Management

Oxygen:Variable

a, b Year: 2009

Otter Trawl Rank: #2 (28,348 fish) of 54 spp. Beach Seine Rank: #6 (3,821 fish) of 38 spp.

Sacramento Splittail

Suisun Marsh – Why Do We Care?

a, c, d

a

Waterfowl!

Otter Trawl Rank: from #14 (1979-2001) to #5 (2002-2014) of 54 spp.

White Catfish

Adult Striped Bass

a

a

“They included Dorosoma petenense, Alosa sapidissima, Roccus saxatilis, Hypomesus olidus, Lampetra ayresi, Clupea pallasi, and Lepomis macrochirus.”

White Catfish – Delta (Turner 1966)

Striped Bass – Delta (Nobriga and Feyrer 2007)

e

f

White Catfish Diets in Suisun Marsh? Unknown

Questions: • What are white catfish eating? • Associated with habitat features? • Any habitat features explain piscivory of white catfish?

Methods: • Stomach-pump (deck hose!) white catfish from Suisun Marsh Fish Study trawls • Sampling period: June 2009 – May 2010 • Correlate habitat variables to diet items (sal, temp, clarity, depth, DO, diversion

density) • Test habitat variables on piscivory

White Catfish Diets in Suisun Marsh

• n = 304 fish • winter: 28 • spring: 135 • summer: 102 • autumn: 39

• 274 fish (90%) w/food

• mean SL: 216 mm (adults); few<182 mm

56

54 48 71

26

30

16

White Catfish Diets in Suisun Marsh

g

Eogammarus confervicolus

CA bay shrimp

overbite clam

shim. goby

stickleback Eogammarus confervicolus

Bio Photo Group, ON

Bio Photo Group, ON

Daphnia magna Daphnia magna Very Tiny Things

Very Tiny Things

wetland species bay/slough

species

(no smelt/salmon)

%Fish Mass in Diet of White Catfish: Correlates? Parameter Parameter Estimate t-ratio Probability > |t| Temperature 0.0063291 0.40 0.508 DO -0.078083 -2.54 0.014* Standard length 0.0013695 0.77 0.444 Temperature X DO 0.0053317 0.36 0.718 Temperature X standard Length 0.0003352 0.55 0.584 DO X standard length 0.0001548 0.22 0.829 Temperature X DO x standard length 0.0001271 0.38 0.706

Managed Wetlands Water Management

circulate water circulate water

dry

DO = 2.9 mg/L

g

Adult Striped Bass

• Sample period: October ‘09 – ongoing (opportunistic!)

• hook-and-line • stomach pumped • n = 373 fish

• winter: 122 • spring: 139 • summer: 24 • autumn: 88

• 315 fish (84%) w/food • mean TL: 55 cm (22 in);

range: 45 – 91 cm • 5 feeding areas:

• seams (13 fish) • drains (228) • pumps (52) • rock (18) • tidal creeks (40)

• PRELIMINARY!

81

20

54

39

79

17

35

25

Adult Striped Bass Diets: Fish Prey Numbers

Method Silversides Shads Sticklebacks Sculpins

Fish/Trawl 0.09 0.53 0.64 0.72

Fish/Seine 33.95 1.12 2.03 0.25

Fish/Pumped Striped Bass 0.08 0.04 15.9 0.84

2009 - 2014

(no smelt/salmon)

(?)

Adult Striped Bass Diets: Feeding Area

Adult Striped Bass Diets: Frequency of Occurrence

Conclusions

• Adult striped bass: fish diet dominated by slow-moving benthic/littoral fishes…turbidity?

• Both species: no salmon/smelt eaten/identified

• Both species: most food from wetlands…trophic relay?

Thanks!

Funding provided by California Department of Water Resources and private donors

Mike Wigginton, Phil Antipa, everyone at the Suisun Marsh Branch of DWR, the Suisun Resource Conservation District, Melissa Riley (CDFW), the entire North Delta Arc Working Group (especially Brian Williamson), Alison Furler (CDFW), Tommy Agosta (UCD), Rachel Johnson (NMFS), Fred Feyrer (USGS), Alpa Wintzer, Rob Schroeter, Jason Moore (DWR), Patrick Fuller, Amy Chandos, Nick Buckmaster (CDFW), Miranda Bell (UCD), Nicky Bunn, Angie Munguia (DWR – formerly!), Eva Bush (UCD), Nick Corline (“Mudbug”; UCD), Carson Jeffres (UCD), Emma Davidson (UCD), Josh Porter (EB Parks), Lily Tomkovic (UCD), Scott McDonald (CSUSJ), Hailey Pexton (UCD), Paul Takemoto (UCD), Robert Dunn (UCD), Joe Rogers, Georgia Ramos (UCD), Karin Petrites (Putah Creek Council), Emma Cox, Thaddeus Hunt, Quoc Van, Ethan and Janet Kean...

References a. O’Rear, unpublished data b. Siegel, S., P. Bachand, D. Gillenwater, S. Chappel, B. Wickland, O. Rocha, M. Stephenson, W. Heim, C. Enright, P. Moyle, P.

Crain, B. Downing, and B. Bergamaschi. 2011. Final evaluation memorandum, strategies for reducing low dissolved oxygen and methylmercury events in northern Suisun Marsh. Prepared for the State Water Resources Control Board, Sacramento, California. SWRCB Project Number 06-283-552-0.

c. California Department of Fish and Game. 1996, 1997, 1998. Fishery monitoring program a component of the Suisun Marsh Diversion Screening Program. University of California, Davis, California.

d. Pickard, A. A. Baracco, and R. Kano. 1982. Occurrence, abundance, and size of fish at the Roaring River Slough intake, Suisun Marsh, California during the 1980-81 and the 1981-82 diversion seasons. Technical Report 3, California, California Department of Fish and Game.

e. Turner, J. L. 1966. Distribution and food habits of ictalurid fishes in the Sacramento-San Joaquin Delta. Pages 130-143 in J. L. Turner and D. W. Kelley, editors. Ecological Studies of the Sacramento-San Joaquin Delta, part 2. California Department of Fish and Game Fish Bulletin 136.

f. Nobriga, M. L., and F. V. Feyrer. 2008. Diet composition in San Francisco Estuary striped bass: does trophic adaptability have its limits? Environmental Biology of Fishes 83: 495-503. g. O'Rear, T. A. 2012. Diet of an introduced estuarine population of white catfish in California. Master's thesis. University of California, Davis.