Is flow the cure for the summertime blues?

A 12-year record of summer growth for Delta Smelt

Jim Hobbs

UC Davis

2014 Delta Science Conference, October 28, 2014

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Climate Variability - Drought DWR Water Year Index

Food, Predation, Temperature,

Transport, Entrainment, Toxicity

Weather, Exports, Hydrology, Turbidity, Contaminants

Air Temperature, Flows, Turbidity, Contaminant Loading, Water Diversions

Food, Predation, Temperature, Entrainment, Toxicity

Food, Predation, Size and Location of LSZ, Toxicity

Weather, Hydrology, Turbidity, Clam Grazing, Nutrients, Contaminants

Food, Predation, Temperature Harmful Algal Blooms, Toxicity

Weather, Outflow, Turbidity, Clam Grazing, Nutrients, Contaminants

Tier 2 – Environmental Drivers

Tier 3 - Habitat Attributes

Tier 1 - Landscape Attributes

Erodible Sediment Supply, Proximity to Ocean, Proximity to Discharges, Proximity to Diversions, Bathymetry (Proximity to and Extent of Shallow Areas)

Adults Eggs & Larvae

Juveniles Subadults

Tier 5 - Life Stage Transition Seasons

Tier 4 - Delta Smelt Responses

March-June (Spring)

December-May (Winter)

September-December (Fall)

June-September (Summer)

Spawning

Survival

Survival Growth

Survival

Growth

How does drought affect delta smelt?

Drought

June·September (Summer)

H3, H4b H4a

Food AvJIUbihty 8 To.1u<itv from Quality ------- H<irmful AIS.ll

Blooms

H:l 'W.lter

Temperature

Hl Pred4t1Qn

Risk

---------t-----Aut1)(hfOOl\{)1j~ I

~nd Alk:ld1thQnt>Us Cl~m Grazin& Nutrients HydrolOiY Air t~mPl';f~turc Turbidity Predator\

food ~oduction & I I ISu[ m.,l _er_l _-.......,1 .... --.....,,.J (511lpeti r.e1 i Reter tion • _ Sau> fnv;rQ!l'flf!ITfQ' T .. _________ ... .._ __ .......... ______ c_ ~lrologv ~~~ W1nt~~rk

Location of LSZ 1n relation to Clam

Dlstrl bu ti on

Pro"Ki mity to Ocean

Erodible Sediment S1.1pply

Drought effects on delta smelt

H1: Growth will be lower during drought years for all life-stages H2: Life History Diversity will be reduced during drought years

Why growth is important?

1) Mortality is HIGH in early life stages of fish 2) Mortality is selective on fish size

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Back-calculated length at age 30 days post hatch Size-at-age

Source pop’n

Selection

How we measure growth

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2014Fork

Le

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Average Age

Growth Rate N =1397 fish Slope = 0.35mm/d

𝐺 =𝐿𝑜𝑔(𝐿𝑐−𝐿ℎ)

𝐴𝑔𝑒

The Study

→ Flow + Food + Temperature Mean Annual Growth Rate (G)

Drought - - +

Summer Townet Survey 1999-2014 w/o 2003,2008-2010

IEP-EMP mean density copepods Apr-July

DWR annual water year index

CDEC - continuous water quality Mean Temp April-July Rio Vista & Mallard Is.

Low < 2,600-m3

Mod High>4,000-m3

Wet Above normal Below normal Dry Critically dry

Cool < 17.1 °C

Mod High> 18.3 ° C

Water Year Index H

Water Vear Index 14

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:z:

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• • .: r • • - ·r • . 2m!!llml•Bt1 Sl2Bl:ISl4 .....

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ensity

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Rotifers

Nauplii (All)

Cycloploid Juvs

Calanoid Juvs

Cycloploid Adults

Calanoid Adults

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Model Results

Water Year Type Temperature Copepod Density

Model Results

Temperature Copepod Density Spring X2

Drought effects on growth

H1: Growth will be lower during drought (dry) for all life-stages

For juveniles during summer growth rate was lower in below normal, dry and critically dry years

H2: Life History Diversity will be reduced during drought years

• Natal origins - Migration history • Hatching Date

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Sacramento River Delta Low-salinity ZoneW D BN BN D D W

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North Delta-DWSC

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Hatchdate

Hatchdates → Temperatures

Drought effects on growth

H1: Growth will be lower during drought (dry) for all life-stages

For juveniles during summer growth rate was lower in below normal, dry and critically dry years

H2: Life History Diversity will be reduced during drought years • Natal origins - Migration history

• Hatching Date

Shift in phenotypes- more North Delta born fish early hatching dates

Thank You!

Undergraduate Research Assistants: Anna Schiller, Mackenzie Gilliam, Marielle Medina, Amy Taylor, James Chhor

Collaborators: William Bennett

Swee Teh, Ted Sommer, Louise Conrad The MAST-Drought Team. Agency: Carol Atkins-CDFW-ERP Erwin Van Nieuwenhuyse –BOR,

CDFW Ecosystem Restoration Project Grant #E1183004-02 Bureau of Reclamation-IEP Contract #R10AC20108

Funding Provided By:

Lab Technicians: Felipe La Luz, Eva Bush Naoaki Ikemiyagi