## 201 2 San Joaquin River Sturgeon Spawning Survey

Final Annual Report

Prepared by:

Zachary J. Jackson 1 * and Joel P. Van Eenennaam 2

1 U.S. Fish and Wildlife Service

Stockton Fish and Wildlife Office

850 Guild Ave nue , Suite 105

Lodi, C alifornia 95240

2 University of California

- Davis

Department of Animal Science

One Shields Avenue

Davis, California 95616

* Corresponding author : Zachary_Jackson@fws.gov

March 201 3ii Disclaimer

The mention of trade names or commercial products in this report does not constitute

endorsement or recommendation for use by the federal government.

Cover Photo: White sturgeon egg sampled from the San Joaquin River on 2 A pril 201 2 using

artificial substrate samplers. Photo courtesy of University California

- Davis using an

Olympus dissecting microscope and a Nikon DS

- U1 digital camera

.

The correct citation for this report is:

Jackson , Z. J.

, and J. P. Van Eenennaam

. 201 3

. 201 2 San Joaquin River s turgeon s pawning

s urvey

. Stockton Fish and Wildlife Office

, Anadromous Fish Restoration Program

, U.S. Fish and Wildlife Service, Lodi

, California

.iii Preface

The following is the final report for the U.S. Fish and Wildlife Service’s investigations on

anadromous sturgeon spawning in the San Joaquin River between RK 119 and RK 14 3

, funded by the Central Valley Project Improvement Act (CVPIA) Anadromous Fish

Restoration Program in Fiscal Year 201 2 . Title 34, Section 3406(b)(1) of the CVPIA, P ublic

Law 102

- 575, requires the Secretary of the Interior to develop within three years of

enactment and implement a program which makes all reasonable efforts to ensure that, by the

year 2002, natural production of anadromous fish in Centr al Valley rivers and streams will be

sustainable, on a long

- term basis, at levels not less than twice the average levels attained

during the period of 1967

- 199 1. Section 3406(b)(1) also states that "this goal shall not apply

to the San Joaquin River betwe en Friant Dam and the Mendota Pool."

The purpose of these investigations is to provide scientific information to the Central Valley

Project Improvement Act Anadromous Fish Restoration Program to assist in developing

restoration recommendations that will help meet program objectives and achieve its

anadromous fish doubling goal

.iv 201 2 San Joaquin River Sturgeon Spawning Survey

Zachary J. Jackson

U.S. Fish and Wildlife Service

, Stockton Fish and Wildlife Office

, 850 Guild Ave nue , Suite 105, Lodi, C alifornia 95240 , USA

Joel P. Van Eenennaam

Department of Animal Science, University of California,

One Shields Avenue, Davis, California 95616, USA

Abstract

. — Several researchers ha ve suggested that sturgeon ( genus Acipen s er ) may

s pawn occasionally in the San Joaquin R iver during high

- water years

. Initial documentation

of w hite sturgeon Acipenser transmontanus spawning in the San Joaquin R iver s ystem

occurred in 2011 near Grayson, CA ( river kilometer 142, rkm

, measuring from its confluence

with the Sacramento River ). However, whether sturgeon spawn in the San Joaquin River in

normal and drier water year types remained unknown. Artificial substrate samplers (i.e., egg

mats) were deployed at four sites within a 2 4

- km reach of the San Joaquin River from

Sturgeon Bend ( rkm 119 ) to Grayson Road Bridge ( rkm 14 3 ) from 16 February to 1 June

201 2 . During the sample period, 65 white sturgeon eggs were collected among four sites

, 45

of which were viable and between developmental stages 4 a nd 2 8

. Based upon capture

location, date of capture, water temperature, stage of development, and the assumption that a

female takes 12

– 20 hours to release all of her eggs, the eggs likely represent a t least six

different females that spawned between 2 0 March and 14 May 2012

. The r esults of this

survey confirm that white sturgeon do spawn in the San Joaquin River in both wet

- and dry

year conditions and may be an important source of production for the white sturgeon

population in the Sacramento

- San Joaqu in r iver s ystem

.v Table of Contents

Preface.................................................................................................iii

Abstract

................................ ................................ ................................ .............................. i v

List of Tables

................................ ................................ ................................ ..................... v i

List of Figures

................................ ................................ ................................ ................... vi i

Introduction

................................ ................................ ................................ .......................... 1

Study Area

................................ ................................ ................................ ........................... 1

Methods

................................ ................................ ................................ ................................ 2

Results

................................ ................................ ................................ ................................ .. 3

Discussion

................................ ................................ ................................ ............................ 4

Acknowledg e ments

................................ ................................ ................................ .............. 6

Literature Cited

................................ ................................ ................................ .................... 8

Tables....

................................ ................................ ................................ ............................ 1 1

Figures

... ................................ ................................ ................................ ............................. 1 9vi List of Tables

Table Page

1. Location of sites sampled on the San Joaquin River, California, by river kilometer

(rkm), dates sampled, effort in wetted mat days, and the proportion of effort at

each site in relation to total effort expended during 2012 egg s ampling. A wetted

mat day is equivale nt to one mat set for 24 hours

................................ ........................ 1 2

2. Size, collection location, estimated spawn timing, and developmental stage of

white sturgeon eggs collected on the San Joaqu in River, California during 2012

...... 1 3

3. Minimum, maximum, and mean depths of sites sampled with egg mats during

2012 in the San Joaquin River, California. Sample sites expressed as river

kilometers ( rkm ), depths (m) sampled at each site throughout the season, and

depth s (m) of mats that collected white sturgeon eggs

. ................................ ............... 1 6

4. Minimum, maximum, and mean hourly water temperatures for each sample site

for the duration of the study and during the period from estimated spawn timing to

collection for each white sturgeon egg collection in the San Joaquin River,

California during 2012

................................ ................................ ................................ . 17

5. Minimum, maximum, and mean daily river discharge for each sample site for the

duration of the study and during the period from estimated spawn timing to

collection for each white sturgeon egg collection in the San Joaquin River,

California during 2012

................................ ................................ ................................ . 18vii List of Figures

Figure Page

1. Location of egg mat sample sites on the San Joaquin River, California between

Sturgeon Bend (rkm 119) and Grayson Road Bridge (rkm 14 3 )

................................ . 20

2. Mean daily discharge ( m 3 s - 1 ) and mean daily water temperature ( ° C) observed in

2012 on the San Joaquin River near rkm 119

. The black parallelogram and the

black circle represent the date when white sturgeon eggs were collected and the

estimated spawn date , respectively, at rkm 1 19 . Discharge and temperature

measureme nts were obtained from the California Data Exchange Center for the

gauging station near Vernalis , California and thermographs attached to individual

egg mats , respectively. Horizontal bars indicate upper and lower optimal

spawning temperatures for white s turgeon (Parsley et al. 1993; McCabe and Tracy

1994)

. ................................ ................................ ................................ ........................... 21

3. Mean daily discharge ( m 3 s - 1 ) and mean daily water temperature ( ° C) observed in

201 2 on the San Joaquin River near rkm 131

. The black parallelogram and the

black circle represent the date when whit e sturgeon eggs were collected and the

estimated spawn date , respectively, at rkm 1 31. Discharge data for rkm 131 were

estimated by subtracting Stanislaus River discharge at Ripon from the discharge

reported at Vernalis

. Discharge and temperature measurements were obtained

from the California Data Exchange Center and thermographs attached to

individual egg mats , respectively

. Horizontal bars indicate upper and lower

optimal spawning temperatures for white sturgeon (Parsle y et a l. 1993; McCabe

and Tracy 1994)

. ................................ ................................ ................................ .......... 22

4. Mean daily discharge ( m 3 s - 1 ) and mean daily water temperature ( ° C) observed in

201 2 on the San Joaquin River near rkm 14 2

. Black parallelograms and black

circles represent dates when white sturgeon eggs were col lected and the estimated

spawn date s, respectively, a t rkm 1 4 2 . Discharge and temperature measurements

were obtained from the California Data Exchange Center for the gauging station

near Patterson, California and thermographs attached to individual egg mats

, respectively. Horizontal bars indicate upper and lower optimal spawning

temperatures for white sturgeon (Parsley et al. 1993; McCabe and Tracy 1994)

. ....... 23

5. Mean daily discharge ( m 3 s - 1 ) and mean daily water temperature ( ° C) observed in

201 2 on the San Joaquin River near rkm 143

. Black parallelograms and black

circles represent dates when white sturgeon eggs were collected and the estimated

spawn date s, respectively, a t rkm 143. D ischarge and temperature measurements

were obtained from the California Data Exchange Center for the gauging station

near Patterson, California and thermographs attached to individual egg mats

, respectively. Horizontal bars indicate upper and lower optima l spawning

temperatures for white sturgeon (Parsley et al. 1993; McCabe and Tracy 1994)

. ....... 24viii

6. White sturgeon egg collection from San Joaquin River in left panel. Right panel

shows same egg after careful removal of fine sediment

................................ .............. 25

7. San Joaquin River mean daily discharge ( m 3 s - 1 ) during the January through June

period of 1993

- 2012 at the gauging s tation near Vernalis, California

......................... 261 201 2 San Joaquin River Sturgeon Spawning Survey

Introduction

Two species of sturgeon ( genus Acipenser ), white sturgeon A. transmontanus and green

sturgeon A. medirostris

, occur in California

. M igration and spawning of both white sturgeon

and green sturgeon in the Sacramento River system has been well documented by direct

observation, angler catch, and detection of eggs, larvae, and young

- of

- the

- year sturgeon

(Kohlhorst 1976; Schaffter 1997; Beamesderfer et al. 2004 ; Poytress et al. 2009 , 2010, 2011)

. Several researchers have speculated that sturgeon also spawn within the San Joaquin River

system occasionally (Kohlhorst 1976; Schaffter 1997; Beamesderfer et al. 2004), such as

‘when flows and water quality permit’ (Moyle 2002). However, spawning had not been

confirmed through any direct sampling activities in the San Joaquin River, C alifornia until

recently when fertilized white sturgeon eggs were collected by the U.S. Fish and Wildlife

Service (USFWS; Gruber et al. 201 2 )

.

Information regarding sturge on distribution in the San Joaquin River was limited to anecdotal

reports and C alifornia D epartment of F ish and Wildlife (CDF W ) sturgeon report card data

(Gleason et al. 2008; DuBois et al. 2009, 2010, 2011 , 2012 ). I nformation regarding sturgeon

habitat use and movements throughout the San Joaquin River is lacking, but critical to

improve management and protection of these species. Angler fishing report cards (Gleason

et al. 2008; DuBois et al. 2009, 2010, 2011 , 2012 ) document a small sturgeon fishery in the

reach of the San Joaquin River upstream of Stockton, California ( river kilometer , hereafter

rkm, 64 ; Figure 1). Since implementation of the Sturgeon Report Card in 2007, anglers have

reported catching 1 69 white sturgeon and 6 green sturgeon on the Sa n Joaquin River

upstream from Stockton (Gleason et al. 2008; DuBois et al. 2009, 2010, 2011 , 2012 ). Of the

reported fish, 10 8 ( 64 %) white and 5 (83%) green sturgeon were caught between Stockton

and the H igh w a y 140 bridge ( rkm 202). The remaining 61 ( 36 %) white and 1 (17%) green

sturgeon were caught upstream of the H igh w a y 140 bridge. Reports indicated anglers

concentrate in two areas known locally as Sturgeon Bend ( rkm 119) and Laird Park ( rkm

14 3 ; H. Rutherford, CDF W warden, personal communication). Additionally, anglers and

game wardens indicate that sturgeon caught during March and April commonly expel milt or

eggs during handling, indicating that spawning could be occurring nearby.

The primary focus of this study was to determine if sturgeon are spawning in the San Joaquin

River in various water

- year types by collecting fertilized sturgeon eggs on artificial substrate

samplers. Understanding the spatial and temporal distribution of sturgeon in the San Joaquin

River is vital for the management and recovery of these important species. Further,

understanding the physical characteristics of the areas being used by sturgeon will help

identify future restoration actions.

Study Area

The San Joaquin River originates from the central Sierra Nevada and drains parts of the

Sierra Nevada and Diablo r ange s

. It flows through 531 k m of the state, first west towards the

floor of the Central Valley of California, then north towards the Sacramento

- San Joaquin

Delta

, eve ntu ally reaching the Pacific Ocean. Fria nt Dam ( rkm 43 1 )

, constructed in 1942,2

form s a complete barrier to upstream anadromous fish passage

. Downstream of Friant Dam,

the river encounters increasingly greater anthropogenic influence through water diversions

and habitat alteration. Sampling occ urred at four locations in a 24

- km reach of the San

Joaquin River from Sturgeon Bend ( rkm 119) to Grayson Road Bridge ( rkm 143 ) in

Stanislaus County, CA (Figure 1).

Methods

S turgeon eggs were s ampl ed by deploying artificial substrate samplers (i.e., egg mats) in

close proximity to presumed spawning areas based on hydraulic conditions, side

- scan sonar

images

, and angler and warden observations . Egg mats were constructed from two 89 x 6 5

-

c m rectangular sections of furnace filter material secured back to back within a welded steel

framework ( McCabe and Beckman 1990; Sc haffter 1997; Poytress et al. 2009). The

orientation of the furna ce filter material allowed either side of the egg mat to collect eggs.

Egg mats were held in position by a 2.0

- k g anchor attached to the upstream end of the egg

mat with two 76

- cm lengths of 9.5

- mm diameter braided polypropylene rope. A labeled float

was attached to the downstream end of each egg mat with a 9.5

- mm diameter b raided

polypropylene rope. Float line length varied between egg mats

, depending on water depth

and velocity

. Mats were predominantly deployed in areas of accelerating velocities ( i.e.,

areas flanking deepest po rtions of pools ) and were set in pairs

. Sampling occurred from 16

February to 1 June 2012.

Environmental and sample effort data were collected during bot h the setting and retrieval of

egg mats. Environmental data consisted of depth, GPS coordinates

, temperature, turbidity,

river discharge, a nd weather condition. Depth (m) and GPS coordinates were recorded

directly above each egg mat with a Lowrance depth finder (Model StructureScan HDS 10

-

m ). Hourly water temperature was monitored at each egg mat with a temperature logger

(Model Stowaway Ti dbit)

. Turbidity (nephelometric turbidity units, NTUs) was measured

with a Hach turbidimeter (Model 2100P)

. All discharge data were obtained through the

California Data Exchange Center. D ischarge data for rkm 119 were obtained from the

gauging station located near Vernalis , CA

. Discharge data for rkm 131 were estimated by

subtracting Stanislaus River discharge at Ripon , CA from the discharge reported at Vernalis.

Discharge data for rkm 142 and 143 were obtained from the gauging station located near

Patterson , CA

. Sample effort data consisted of the date and time individual egg mats were

set and retrieved.

Egg mat sampling consisted of visual inspection, generally twice per week, throughout the

sample period. E gg mats were retrieved from the river after initial deployment, placed on the

deck of a boat in a custom

- made egg mat carrier, and initially inspected on both sides by at

least two field crew members. After initial inspection, egg mats were rinsed with water to

remove debris and sediment and then re

- inspected. Rinse water and debris were filtered by a

removable 3.2

- mm mesh net placed within the egg mat carrier below each egg mat to capture

any dislodged eggs. After the second egg mat inspection and inspection of the mesh nets, the

mats were redeployed.3

All eggs removed from the egg mats were counted and identified to species in the field with

an egg key ( Reyes et al. 2007; Wang 2010; Reyes 2011 ). All suspected sturgeon eggs and

unidentified eggs were placed into v ials of 95% ethyl alcohol (EtOH) for laboratory

identification and further analysis. Suspected sturgeon eggs were sent to the U niversity of

California

- Davis (UCD) for species confirmation, photography, measurement of egg

diameter, and determination of dev elopmental stage ( Dettlaff et al. 1993 ). Egg l ength and

width were measure d (± 0.001 mm) with an Olympus dissecting microscope with a camera

lucida and a Nikon Microplan II digital image analyzing tablet. Representative photographs

were taken with a Nikon DS

- U1 digital camera connected to the microscope.

Estimates of d ate and time of fertilization (i.e., spawn timing) were based on an average

water temperature for the time period between egg col lections

, estimated egg developmental

stage

, and rates of embryonic development established for white sturgeon ( Wang et al. 1985

, 1987 ).

Results

Cumulative e gg mat sampling total ed 670. 9 wetted mat days ( wmd; one mat set for 24 hours)

between four sample sites (Table 1)

. Eight y

- two percent ( 552.3 of 670

. 9 wmd ) of the total

s ampling effort was expended approximately evenly across three sample sites downstream of

Laird Park ( rkm 119

, rkm 131 , and rkm 142 )

. Mats were added at the rkm 143 site during

the sixth week of sampling due to observations of sturgeon in the area, which accounted for

17.7% of total effort ( 1 1 8

. 5 wmd )

.

Sixty

- five white sturgeon eggs were collected among four sampling sites between 20 March

and 14 May 2012 and transferred to UCD for analysis

. Twenty eggs (31%) were not viable

,

many of which were covered in fungus. It could not be determined if these were fertilized

eggs that died during embryogenesis or were un

- fertilized eggs (Table 2)

. Forty

- five eggs

( 69% ) were viable and determined to be in various stages of post

- fertilized embryonic

development (Table 2; Dettlaff et al. 1993).

Egg mats were deployed at river depths ranging from 0.4

– 9.3 m ( = 3.8 m; Table 3). Egg

samples were collected from mats dep loyed at depths ranging from 1.6

– 9.1 m with a mean

depth of 3

. 8 m. San Joaquin River water temperatures recorded during the study are

summarized in Table 4. Daily average w ater temperatures ranged from 12.8

– 19.4 °C ( =

16.3 °C) at the lowest site (rkm 119 ; Figure 2 )

, 13.1

– 24.9 °C ( = 18.7 °C) at rkm 131

(Figure 3), 13.4

– 24.8 °C ( = 19.2 °C) at rkm 142 (Figure 4)

, and 16.1

– 24.7 °C ( = 20.8 °C)

at rkm 143 (Figure 5) during the sample period. The 19 April egg collections at rkm 142

, and the 10 May collections at the rkm 142 and 143 sites

, included the highest recorded

hourly water temperatures during the period from estimated spawn timing until collection,

ranging from 18.2

– 20.9 °C, 19.7

– 23.2 °C , and 19.7

– 23.0 °C, respectively (Ta ble 4)

. San

Joaquin River discharge ranged from 35.0

– 125.1 m 3 s - 1 ( = 63.0 m 3 s - 1 ) at rkm 119 (Figure

2), 20.0

– 80.5 m 3 s - 1 ( = 35.2 m 3 s - 1 ) at rkm 131 (Figure 3), and 12.7

– 43.0 m 3 s - 1 ( = 21.6 m 3

s - 1 ) at the upper sites (rkm 142 and 143; Figures 4 and 5) throughout the sample period

(Table 5). Turbidity grab samples ranged from 9.3

– 68.3 neph e lometric turbidity units (NTU)4

among sites during the sample period and from 19.0

– 63.9 NTU among sites on days when

eggs were collected.

Minimum and maximum egg diameter were measured in the lab on 88 % (n = 57 ) of egg

samples after carefully removing attached debris

. Lab measurements were not taken on eggs

that had become covered in fungus (n = 8) , making accurate measurement s of size

im possible. The mean maximum diameter (as the eggs are slightly oblong in shape) was

3.54 mm ± 0.10 (ranging 3.35

– 3.76 mm), and mean minimum diameter was 3.40 mm ± 0.11

(ranging 3.11

– 3.62 mm).

D iscussion

During 2012, egg mat sampling identified white sturgeon spawning at four locations

extending over 24 km of the San Joaquin River

. Eggs were collected at rkm 119, 131, 142

, and 143 on one, one, four, and two occasions, respectively (Table 2 ), representing at least six

distinct spawning events

. On two occasions, eggs were collected at successive sampling sites

on the same day. Whether or not the eggs collected on 2 April and 10 May 2012 at both the

rkm 142 and 143 sites at similar stages of embryo genesis were from the same female or

di fferent females cannot be concluded. Given the time over which a female spawns ( 12

– 20

hours; J. P. Van Eenennaam , unpublished) and the proximity of the sites, it is possible that a

single female spawned at both sites

. However, future genetic analyses may be able to

confirm whether the sampled eggs were from a single female or from multiple females.

Optimal spawning temperatures for white sturgeon have been reported to be 10

– 18°C in the

Columbia River (Parsley et al. 1993; McCabe and Tracy 1994)

. Ko hlhorst (1976) reported

the optimal spring spawning temperature for white sturgeon to be 14

– 16°C in the Sacramento

River. Optimal temperatures for development and survival of white sturgeon embryos are

reported to be 14

– 17°C, with hatching rates decreasin g at 20°C and complete arrest of

embryonic development at 23°C in laboratory experiments (Wang et al. 1985 ). Although

some of the days during the one

- week spawning and embryo incubation period had elevated

water temperatures above what has been reported a s optimal, there were no obvious signs of

deformities at the stages of embryonic development observed in any viable eggs that were

collected. However, it is at later stages of embryogenesis and post

- hatch larvae when

obvious problems have been observed th at were related to elevated incubation temperature in

green sturgeon embryos (e.g., substantial shortening of the embryo body, decrease in percent

dry weight, lordosis, kyphosis, edema; Van Eenennaam et. al. 2005 ). Fertilization and early

cleavage stages did not appear to be affected by temperature in the majority of the eggs, as

abnormal cleavage could lead to gastrulation arrest and, consequently, mortality before

neurulation (Sytina and Shagaeva 1987). Sytina and Shagaeva (1987) also reported the

compl ete block of egg cleavage at temperatures outside the spawning range (e.g., ≥ 28°C) in

stellate sturgeon A. stellatus

.

One may question whether the percent of non

- viable eggs (31%) could be related to the

elevated temperatures; however, some of these non

- viable eggs were found early in the

spawning season when temperatures were closer to optimal. A number of factors other than5

temperature may be causing or contributing to mortality of embryos, including sampling

related damage and contaminants.

Several of the viable eggs were almost completely covered in sand particles which were

carefully removed by gently scraping the egg with fine needle forceps until the stage of

development could be discerned ( Figure 6 ). Kock et al. (2006) suggest that sediment cover

may be an important early life stage mortality factor in rivers where white sturgeon spawn

over fine substrates. Eggs completely buried in shifting sand would likely die from lack of

oxygen. Efforts to accurately characterize the substrate types pr esent in the known spawning

areas have been initiated, but are not complete. Regardless, the river bed within the sampling

area is dominated by sand and silt substrates. However, if the eggs are attached to cobble or

other types of large substrate and be come coated in silt or sand as the jelly coat forms, they

will likely remain viable as long as they are exposed to sufficient water flow. The degree of

jelly coat formation on fertilized sturgeon eggs is not fully understood

, but recent work has

documente d variations among species ( Van Eenennaam et al. 2012 ).

C alifornia D epartment of F ish and Wildlife S turgeon R eport C ard d ata indicate six green

sturgeon and 169 white sturgeon were reported by anglers in the last five years within the

San Joaquin River upstream of Stockton, five of which were caught in March and April

(Gleason et al. 2008; DuB oi s et al. 2009 , 2010, 2011 , 2012 ) . Al though the data indicate the

presence of a limited number of green sturgeon

, it is possible that some fish go un reported

(e.g., poaching; Beamesderfer et al. 2004) or a re misidentified as white sturgeon

. I t remains

unknown how and to what extent green sturgeon use the S an Joaquin River. H owever

, the

reported presence of green sturgeon in the San Joaquin River coincides with the spawn ing

migration period of the Southern Distinct Population Segment of green sturgeon with in the

Sacramento River (Poytress et al. 200 9 , 2010, 201 1 ). Although there is a temporal overlap in

spawn timing between white and green sturgeon (Kohlho rst 1976; Poytress et al. 200 9 )

, no

documentation exist s where these two sturgeon species spawn in close proximity to each

other

. Turbidity may be driving th e separation of spawning locations . Generally

, green

sturgeon spawn in areas wh ere turbidity is less than 10 NTU (Poytress et al

. 200 9 , 2010,

201 1 ). Conversely, white sturgeon spawn in areas that are generally turbid in nature ( = 42

NTU ; Perrin et al. 2003)

. Because of elevated turbidity levels in the San Joaquin River

, we

hypothesize that g reen sturgeon on a spawning run within the San Joaquin River system may

be seeking less turbid water upstream of the sampled area in the mainstem or wit h in on e of

the tributaries where turbidity is lower

. T herefore

, focusing future egg sampling efforts

between rkm 119 and rkm 14 3 may limit the ability to detect spawning green sturgeon in the

S an Joaquin River.

In addition to egg sampling, larval sampling with a benthic D

- net has been accepted as an

effective method to document the spawn timing of sturgeon species (Kohlhorst 1976).

Although larval samples will not provide information on specific spawning locations,

methods from Dettlaff et al. (1993) can be used to estimate spawn timing. Larval captures

could help d etermine if there were deformities at hatch, but many deformed larvae would

likely be unable to “swim

- up” and thus captures would be expected to be rare. Larval

captures would confirm the presence or absence of normal swim

- up larvae during the periods

of elevated water temperatures. The bridge abutments at the Airport Way ( rkm 11 6 ) and6

Grayson Road ( rkm 143) crossing s provide an ideal tie

- off location for larval D

- net sampling

of known white sturgeon spawning locations at rkm 119 , 131, 142 , and 143

. L arv al sampling

at these two locations would provide the opportunity for detection of larval green sturgeon

dispersing from speculated spawning locations within the Stanislaus, Tuolumne, Merced, or

upper San Joaquin r ivers. Furthermore, without documentation of larval white sturgeon in

the San Joaquin River upstream of the Delta , it i s unknown if spawning events within the San

Joaquin River are a source of larval production for the Sacramento

- San Joaquin white

sturgeon population.

Average daily discharge in the San Joaquin River in early 2011 was two to three times higher

than the mean daily discharge for water years 199 3 to 201 2 (Figure 7 ). As speculated by

researchers (e.g., Kohlhorst 1976; Schaffter 1997; Moyle 2002 ; Beamesderfer et al. 2004)

,

r iver discharge levels of this magnitude may have trigger ed white sturgeon to enter and

spaw n within the San Joaquin River in 2011

. River discharge levels in 2012 were generally

half or less than the 20

- year average. However, documentation of at least six distinct

spawning events during 2012 show that spawning also occurs in dry years and may occur

annually. T here was a general trend of collecting eggs around short

- duration peaks in river

discharge during the 2012 sampling season (Figure s 2, 3, 4, and 5 )

. Spring pulses of

discharge from the Merced and Tuolumne rivers in late April and early May intended to

increase survival of emigrating salmon ids preceded collection of white sturgeon eggs at all

four sampling locations. Water temperatures at most sampli ng sites had been over 18 °C and

increasing for several weeks, yet a late peak in spawning activity occurred around the time

that short

- duration increases in discharge from the tributaries arrived at the sampling

locations. This suggests the possibility th at there were a number of white sturgeon holding in

the lower San Joaquin River that responded to the change in environmental conditions (e.g.,

river discharge, temperature) to initiate spawning

.

Additional sturgeon e gg and larval sampli ng

, in conjunction with acoustic tracking of adults

, should be continued throughout a variety of water year types to better understand the spatial

and temporal distribution and habitat preferences of white sturgeon in the San Joaquin River.

Continued study of th e response of white sturgeon to changes in river discharge and

temperature may be important for informing fishery and water management decisions.

Understanding the effects of water management in a regulated system like the San Joaquin

River may result in increased spawning activity, spawning success, and recruitment of white

sturgeon. Additionally, a better understanding of white sturgeon distribution and use and the

potential to encounter various life

- history stages of green sturgeon within this system may

enhance the understanding and ability to manage for both species.

A cknowledgements

This project was funded by the Anadromous Fish Restoration Program under the authority of

the Central Valley Project Improvement Act (P.L. 102

- 575) . Bill Powell

, Tim Matt, Ron

Smith, Patrick Hapgood, Steve Tsao, Dave Dominguez, Jonathan Thompson, and Kes Benn

assisted in the field

. Alexandra Fitzgerald assisted with table and figure development

. Bill

Poytress, Zoltan Matica, Michelle Workman, Nina Kogut, Josh Gru ber, Alexandra7

Fitzgerald, Paul Cadrett, Ramon Martin, and Donnie Ratcliff provided comments that

improved this report.8 Literature Cited

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Historical and current information on green sturgeon occurrence in the Sacramento

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Deng, X., J. P. Van Eenennaam

, and S. I . Doroshov. 2002. Comparison of early life stages

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DuBois, J., M. Gingras

, and R. Mayfield. 2009. 2008 s turgeon f ishing r eport c ard:

p reliminary d ata r eport

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, and T. Matt. 2010. 2009 sturgeon fishing report card: preliminary

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DuBois, J., T. Matt

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. 2011. 2010 sturgeon fishing report card: preliminary

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. California Department of Fish and Game , Stockton, California

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DuBois, J., T. MacColl, and E. Haydt. 2012. 20 11 sturgeon fishing report card: preliminary

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preliminary data report

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sturgeon spawning survey. Stockton Fish and Wildlife Office, Anadromous Fish

Restoration Program, U. S. Fish and Wildlife Service, Stockton, California.

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– 141.

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, Jr. 1993. Spawning and rearing habitat

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– 165.

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Reclamation, Red Bluff, California

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- San Joaquin river

delta. U.S. Department of Interior, Bureau of Reclamation, Tracy Technical Bulletin

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– 20.

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– 21.10

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incubation temperature on green sturgeon embryos, Acipenser medirostris

. Environ mental Biology of Fishes 72:145

– 154.

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. Tank spawning of

first generation domestic green sturgeon. Journal of Applied Ichthyology 28:505

–

511

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development of white and lake sturgeon, Acipenser transmontanus and A. fulvescens

. Environmen tal Biology of Fishes 14:43

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- San Joaquin river delta and adjacent waters,

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Reclamation, Tracy Series Volume 44 Special Publication.11 Tables12

Table 1.

— Location of sites sampled on the San Joaquin River, California, by river kilometer

( rkm ), date s sampled , effort in wetted mat days, and the proportion of effort at each site in

relation to total effort expended during 201 2 egg sampling

. A wetted mat day is equivalent

to one mat set for 24 hours

.

Sample s ite (rkm) Sample d ates Wetted mat d ays % Effort

119 16 Feb

– 1 Jun 188.6 28.1%

131 16 Feb

– 1 Jun 181.7 27.1%

142 16 Feb

– 1 Jun 182.0 27.1%

14 3 22 Mar

– 1 Jun 118.5 17.7%

Total Effort 16 Feb

– 1 Jun 670.9 100.0%13

Table 2

. — Size, collection location, estimated spawn timing, and developmental stage of white sturgeon eggs collected on the San Joaquin

River, California during 2012.

Sample

d ate Location

(rkm) Egg d iameter (mm) Spawning Developmental

s tage Comments Min Max Date Hour s

22 Mar 142 3.368 3.468

- - - not viable

22 Mar 142 3.433 3.512

- - - not viable

22 Mar 142 3.302 3.370 21 Mar 0035 18 blastopore closure

22 Mar 142 3.522 3.543

- - - marbled, not viable

22 Mar 142 3.349 3.402

- - - marbled, not viable

22 Mar 142 3.435 3.641 20 Mar 1835 19 early neurulation

22 Mar 142 3.359 3.414

- - - marbled, not viable

22 Mar 142

- - - - - crushed, appears not viable

22 Mar 142 3.490 3.490

- - - marbled, not viable

22 Mar 142 3.263 3.720

- - - oblong shaped, early neurulation

22 Mar 142 3.416 3.567

- - - marbled, not viable

22 Mar 142 3.177 3.422 20 Mar 1835 19 early neurulation

22 Mar 142 3.226 3.615 20 Mar 1835 19 early neurulation

22 Mar 142 3.198 3.584 20 Mar 1835 19 early neurulation

22 Mar 142 3.303 3.598 20 Mar 1835 19 early neurulation

22 Mar 142 3.461 3.573 20 Mar 1835 19 early neurulation

22 Mar 142 3.602 3.691 20 Mar 1835 19 early neurulation

22 Mar 142 3.356 3.731

- - - oblong, not viable

22 Mar 142

- - - - - collapsed/crushed

22 Mar 142 3.259 3.426

- - -

22 Mar 142 3.302 3.611 20 Mar 1835 19 early neurulation

22 Mar 142 3.573 3.602 20 Mar 1835 19 early neurulation

22 Mar 142 3.365 3.546 20 Mar 1835 19 early neurulation

22 Mar 142 3.415 3.581 20 Mar 1835 19 early neurulation

22 Mar 142 3.491 3.759

- - - marbled, not viable

22 Mar 142 3.370 3.552 20 Mar 1835 19 early neurulation

2 Apr a 3.575 3.591 31 Mar am 22 initial separation of tail region

2 Apr a

- - - - - fungus covered, not viable

2 Apr a 3.335 3.346 31 Mar am 22 initial separation of tail region14

Table 2.

— Continued (See page 14 for heading). Table 2.

— Continued (See page 14 for

heading).

Sample

date Location

(rkm) Egg d iameter (mm) Spawning

Spawning Comments

Min Max Date Hour s

2 Apr a

- - - - - fungus covered, not viable

2 Apr a 3.345 3.385 31 Mar am 22 initial separation of tail region

2 Apr a 3.390 3.599 31 Mar am 22 initial separation of tail region

2 Apr a 3.397 3.516

- - - some fungus, not viable

2 Apr a 3.614 3.614 31 Mar am 22 initial separation of tail region

19 Apr 142

- - - - - collapsed/crushed sturgeon egg

19 Apr 142 3.472 3.478 18 Apr 0313 22 late

- neurulation

19 Apr 142 3.113 3.449 18 Apr 0313 22 late

- neurulation

19 Apr 142 3.437 3.476 18 Apr 0313 22 late

- neurulation

19 Apr 142 3.345 3.453

- - - marbled, not viable

10 May 142 3.432 3.708 8 May 1911 26 initial separation of tail region

10 May 142 3.472 3.531 8 May 1911 26 initial separation of tail region

10 May 142 3.366 3.691 8 May 1911 26 initial separation of tail region

10 May 143

- - - - - fungus covered, not viable

10 May 143 3.443 3.575 8 May 1317 28 separated tail and straight cardiac tube

10 May 143 3.302 3.435 8 May 1317 28 separated tail and straight cardiac tube

10 May 143

- - - - - fungus covered, not viable

10 May 143 3.539 3.598 8 May 1317 28 separated tail and straight cardiac tube

10 May 143 3.354 3.368

- - - marbled, not viable

10 May 143 3.509 3.617 8 May 1317 28 separated tail and straight cardiac tube

10 May 143 3.388 3.495 8 May 1317 28 separated tail and straight cardiac tube

10 May 143 3.615 3.673 8 May 1317 28 separated tail and straight cardiac tube

10 May 143 3.567 3.612 8 May 1317 28 separated tail and straight cardiac tube

10 May 143 3.330 3.526 8 May 1317 28 separated tail and straight cardiac tube

10 May 143 3.579 3.616 8 May 1317 28 separated tail and straight cardiac tube

10 May 143

- - - - - fungus covered, not viable

14 May 131 3.365 3.545 13 May 0612 18 blastopore closure

14 May 131 3.416 3.586 13 May 0612 18 blastopore closure

14 May 131 3.536 3.711 13 May 0612 18 blastopore closure15

Table 2.

— Continued (See page 14 for heading). Table 2.

— Continued (See page 14 for

heading).

Sample

date Location

(rkm) Egg d iameter (mm) Spawning

Spawning Comments

Min Max Date Hour s

14 May 131 3.402 3.456 13 May 0612 18 blastopore closure

14 May 131 3.363 3.590 13 May 0612 18 blastopore closure

14 May 119 3.292 3.500 13 May 1540 14 G astrulation

14 May 119 3.289 3.369 14 May 0040 14 G astrulation

14 May 119 3.303 3.472 14 May 0040 14 G astrulation

14 May 119 3.402 3.476 14 May 0040 14 G astrulation

14 May 119 3.473 3.474 14 May 0740 4 2

- cell

* Spawning date and time was estimated by back

- calculation based on the developmental stage of embryogenesis (Dettlaff et al. 1993), developmental rates of white

sturgeon (Deng et al. 2002), and daily water temperatures recorded on temperature loggers attached to the egg mats on the San Joaquin River.

a Eggs were collected at both the rkm 142 and 143 site s on 2 April, 2012. However, due to lost datasheets, it is impossible to tell which eggs and how many were collected

at each site.16

Table 3

. — Minimum, maximum, and mean depths of sites sampled with egg ma ts during

2012 in the San Joaquin River, California. Sample sites expressed as river kilometers ( rkm ),

depths (m) sampled at each site throughout the season, and depth s (m) of mats that collected

white sturgeon eggs.

Sample d epths (m) White sturgeon egg sample d epths (m)

Sa mple s ite (rkm) Min Max Mean Min Max Mean

119 1.0 9.3 5.4 5.8 9.1 7.1

131 0.5 9.1 4.6 4.2 5.2 4.7

142 1.1 4.1 2.8 1.6 3.8 2.7

143 0.4 2.1 1.4 1.6 1.6 1.6

All sites 0.4 9.3 3.8 1.6 9.1 3.817

Table 4.

— Minimum, maximum, and mean hourly water temperatures for each sample site

for the duration of the study and during the period from estimated spawn timing to collection

for each white sturgeon egg collection in the San Joaquin River , California during 2012.

Sample hourly

temperatures (oC) Spawn timing to

collection hourly

temperatures (oC)

Sample site

(rkm) Sample

date Min Max Mean Min Max Mean

119 14 May 11.7 20.4 16.2 17.2 18.6 17.8

131 14 May 12.0 26.6 18.7 17.0 19.0 18.1

142 22 Mar 12.1 26.8 19.3 14.2 16.6 15.7

142 19 Apr 12.1 26.8 19.3 18.2 20.9 19.5

142 10 May 12.1 26.8 19.3 19.7 23.2 21.3

143 a 10 May 14.7 26.3 20.8 19.7 23.0 21.3

b 2 Apr 12.1 26.8 19.3 15.8 18.6 17.4

All sites 12.0 26.8 18.8 14.2 16.6 18.1

a Sample hourly temperatures for rkm 143 were based on data from 9 April

- 29 May 2012.

b Eggs were collected at both the rkm 142 and 143 sites on 2 April, 2012. However, due to lost datasheets, it is

impossible to tell which eggs and how many were collected at each site. S pawn timing to coll ection hourly

temperatures were calculated with temperature data gathered at rkm 142 d ue to an incomplete sample range at

rkm 143

.18

Table 5.

— Minimum, maximum, and mean daily river discharge for each sample site for the

duration of the study and during the period from estimated spawn timing to collection for

each white sturgeon egg collection in the San Joaquin River, California during 2012.

Sample discharge (m 3 s - 1 ) Spawn timing to collection

discharge (m 3 s - 1 )

Sample site (rkm) Sample date Min Max Mean Min Max Mean

119 14 May 35.0 125.1 63.0 124.1 125.1 124.6

131 14 May 20.0 80.5 35.2 80.5 80.5 80.5

142 22 Mar 12.7 43.0 21.6 34.2 35.8 34.9

142 19 Apr 12.7 43.0 21.6 25.5 31.4 28.5

142 10 May 12.7 43.0 21.6 30.3 34.7 32.9

143 10 May 12.7 43.0 21.6 30.3 34.7 32.9

a 2 Apr 12.7 43.0 21.6 19.6 20.5 20.2

All sites 12.7 125.1 35.3 19.6 125.1 50.6

a Eggs were collected at both the rkm 142 and 143 sites on 2 April, 2012. However, due to lost datasheets, it is

impossible to tell which eggs and how many were collected at each site.19 Figures20

Figure 1.

— Location of egg mat sample sites on the San Joaquin River, California between

S turgeon Bend ( rkm 119) and Grayson Road Bridge (rkm 143).21

Figure 2

. — Mean daily discharge ( m 3 s - 1 ) and water temperature ( ° C) observed in 2012 on the San Joaquin River near rkm 119

. The b lack parallelogram and the black circle represent the date when white sturgeon eggs were collected and the estimated spawn

date , respectively, at rkm 1 19 . Discharge and tempera ture measurements were obtained from the California Data Exchange Center

for the gauging station near Vernalis , California and thermographs attached to individual egg mats , respectively. Horizontal bars

indicate upper and lower optimal spawning temperatures for white sturgeon (Parsley et al. 1993; McCabe and Tracy 1994)

.22

Figure 3

. — Mean daily discharge ( m 3 s - 1 ) and water temperature ( ° C) observed in 201 2 on the San Joaquin River near rkm 131

. The b lack parallelogram and the black circle rep resent the date when white sturgeon eggs were collected and the estimated spawn

date , respectively, at rkm 1 31. Discharge data for rkm 131 were estimated by subtracting Stanislaus River discharge at Ripon

from the discharge reported at Vernalis

. Discharge and temperature measurements were obtained from the California Data

Exchange Center and thermographs attached to individual egg mats , respectively

. Horizontal bars indicate upper and lower

optimal spawning temperatures for white sturgeon (Parsle y et a l. 1993; McCabe and Tracy 1994)

.23

Figure 4

. — Mean daily discharge ( m 3 s - 1 ) and water temperature ( ° C) observed in 201 2 on the San Joaquin River near rkm 142

. Black parallelograms and black circles represent dates when white sturgeon eggs were colle cted and the estimated spawn date s

, respectively, a t rkm 142 . Discharge and temperature measurements were obtained from the California Data Exchange Center for

the gauging station near Patterson, California and thermographs attached to individual egg mats , respectively . Horizontal bars

indicate upper and lower optimal spawning temperatures for white sturgeon (Parsley et al. 1993; McCabe and Tracy 1994)

.24

Figure 5

. — Mean daily discharge ( m 3 s - 1 ) and water temperature ( ° C) observed in 201 2 on the San Joaq uin River near rkm 143

. Black parallelograms and black circles represent dates when white sturgeon eggs were collected and the estimated spawn date s,

respectively, a t rkm 143. Discharge and temperature measurements were obtained from the California Data Exchange Center for

the gauging station near Patterson, California and thermographs attached to individual egg mats , respectively . Horizontal bars

indicate upper and lower optimal spawning temperatures for white sturgeon (Parsley et al. 1993; McCabe and Tracy 1994)

.25

Figure 6

. —

White sturgeon egg collection from San Joaquin River in left panel. Right panel shows same egg after careful removal

of fine sediment.26

Figure 7

. — San Joaquin River mean daily discharge ( m 3 s - 1 ) during the January through June period of 1993

- 2012 at the gauging

s tation near Vernalis, California

.