# DRAFT 

# 2015 Sturgeon Derby Report

Jennifer Sun

, April Robinson, Jay Davis , Phil Trowbridge

San Francisco Estuary Institute, Richmond, CA

Robin Stewart

United States Geological Survey, Menlo Park, CA

Vince Palace

Stantec Inc., Winnipeg, MB, Canada

Zachary Jackson

U

. S

. Fish and Wildlife Service, Lodi, CA2



## Table of Contents

Executive Summary

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

Introduction

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

Methods

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

Field Sample Collection

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

Laboratory Analysis and Data Quality Assurance

................................ ................................ ................... 7

Statistical Methods

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

Results and Discussion

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

Summar y Statistics for Selenium

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

Comparison with Historical Data

................................ ................................ ................................ ............. 9

Age, Length, and Tissue Se

................................ ................................ ................................ ..................... 11

Se Correlations Among Tissues

................................ ................................ ................................ .............. 11

C, N, and S Isotopes

................................ ................................ ................................ ................................ 11

Se in Fin Rays

................................ ................................ ................................ ................................ ......... 12

Se in Otoliths

................................ ................................ ................................ ................................ ........... 13

Conclusions

................................ ................................ ................................ ................................ ................. 13

Tables and Figures

................................ ................................ ................................ ................................ ...... 14

References

................................ ................................ ................................ ................................ .................. 283 Executive Summary

The Original Sturgeon Derby (Derby) is an annual fishing derby held in Bay Point, CA that
presents an opportunity to collect and analyze a variety of tissue samples from angler

- harvested female white sturgeon (

Acipenser transmontanus ) for selenium (Se). The collection and analysis

of these tissues sample d during the 2015 Derby helped to both develop non

- lethal sampling methods, and better understand the correlation between tissues that can be collected non

- lethally (muscle plug, fin ray) and those that are of greater toxicological interest (ovary, liver). Otolith samples were also collected t o inform the development of the fin r ay Se microchemical analysis. Between January 31 and February 1, 2015, tissue samples were obtained from 8 female white
sturgeon collected at the Derby and analyzed for Se. The fin rays were also used to estimate age of the fish, and the muscle plugs analyzed for C, N, and S isotopes, to provide information about recent habitat and foraging behavior.

Se concentrations in m uscle plug, liver, and ovary tissue samples were in the upper range of concentrations previously me asured in San Francisco Bay white sturgeon. Three of the eight muscle plug samples showed Se concentrations above the North Bay TMDL tissue target of 11.3

μg /g dw. Fish age and length were positively correlated, but were not correlated with tissue Se,

with the exception of a positive relationship between fork length and ovary Se. No clear relationship was observed between Se concentrations in muscle plug, liver, ovary, or fin ray samples (measured as the maximum or average value in the outer annulus). Isoto pe data suggested the majority of the fish collected had been feeding on invertebrates in Suisun Bay, although one may have been piscivorous and several may have been feeding in San Pablo Bay or

the Delta.

B ecause of the small sample size and narrow size range of the fish collected at the Derby, these preliminary results do not conclusively describe patterns of selenium concentration in white sturgeon or relationships between selenium in various sturgeon tiss ues . Additional data collected during the 2016 Derby will help to further evaluate the relationships observed in this data set.4

Introduction

Selenium is an essential micronutrient that can bioaccumulate and become toxic at concentrations just an order o f magnitude greater than those required for bi ological function (Baginska 2015 ). Since 1998, San Francisco Bay has been identified as impaired by selenium under the Clean Water Act, having been measured at levels of potential concern in fish and other

wild life, including white sturgeon ( Acipenser transmontanus ). D espite si gnificant selenium load reductions from major sources of selenium since 1998

, selenium concentrations in wildlife have continued to occasionally exceed toxicity threshold s and regulatory guidelines ( Presser and

Luoma 2013

, Baginska 2015 ).

In order to control and reduce selenium impairment, the San Francisco Bay Regional Water Qua lity Control Board initiated development of a selenium TMDL for North San Francisco Bay

in 2007 , and formally adopted the regulation in 2015. The TMDL establishe d a target

concentration of 11.3 μ g /g dw in white sturgeon muscle tissue as the basis for evaluating impairment (Baginska 2015). White sturgeon are particularly vulnerable to selenium exposure in the Bay b ecause its diet consists primarily of the selenium

- rich overbite clam ( Potamocorbula

amurensis ) (Beckon and Mau r er 2008; Stewart et al. 2004). In addition to their benthic feeding habits, other high

- risk factors for white sturgeon include their longevity ( lifespan of over 100 years), year

- round resident status in the Bay

- Delta system , and long egg maturation times (several years) (Beckon and Mau r er 2008).

The Regional Monitoring Program for Water Quality in San Francisco Bay (the RMP) was

established in 1993 to provide data and information to inform management decisions for the Bay. In 2014, t he RMP formed a Selenium Workgroup with the goal of identifying low

- cost, near

term Se monitoring elements to support policy developmen t and decision

- making, which n ow includes implementation of the North Bay TMDL

. In 2014, the Selenium Workgroup proposed a special study to collect a variety of tissue samples from white sturgeon at the 32 nd Annual Original Sturgeon Der by (Derby) for selenium analysis, in order to address the following objectives:

1. De velop methods for non

- lethal white sturgeon tissue sample co llection and selenium analysis, including muscle plug and fin ray sampling techniques ; and

2. Evaluate the relationship between tissues that can be monitored non

- l ethally (muscle plug or fin rays) and tissues that are more direc tly tied to adverse reproductive effects ( ovary and eggs ).

Evaluation of the non

- lethal muscle plug monitoring method began during the RMP’s 2009 and 2014 Status and Trends sampling event, du ring which 12 paired muscle plug and fillet samples

were collected per year throughout the San Francisco Bay (data can be accessed at cd3.sfei.org). The muscle plug method was further developed during the 2014 and 2015 Sturgeon Muscle Plug special studies, during which several muscle plug samples were collected from live white sturgeon during annual California Department of Fish and Wildlife sturgeon tagging efforts each

fall ( DuBois and Harris 2015; more information at http://www.dfg.ca.gov/delta/data/sturgeon/ bibliography.asp ) . Additional muscle plug samples collected during the Derby helped to further5

increase sample size and improve both the laboratory analysis and interpretation of this type of

data.

The 2015 Sturgeon Derby also presented the opportunity to evaluate a second non

- lethal monitoring method using fin ray samples. Dr. Vince Palace and Dr. Norman Halden at the University of Manitob a have developed a method for microchemi cal analysis of Se and other

trace metals in sturgeon fin rays as an alternative to microchemical analysis in otoliths, which are known to be stable tissues that are strong predictors of ovary selenium but cannot be collected

non

- lethally (Reash et al. 2014). Fin rays can be taken as a clip and are easy to collect by non

specialists, and have been shown to be non

- harmful to sturgeon (Collins and Smith 1996). Additionally, because fin rays have a regular growth pattern similar to otoliths , concentrations of

selenium and other elemen ts can be measured in each annual ring and assembled into a time

series of selenium concentrations. Th e s e data can potentially be used to better understand the relationship between water, prey, and sturgeon tissue concentrations over time

. The Derby also

p resented the opportunity to collect otoliths for a comparison analysis to establish the chemical stability of fin ray samples.

In addition to developing non

- lethal monitoring methods, the second objective of the Sturgeon Derby study was to establish a rela tionship between tissues that can be monitored non

- lethally and tissues that are more directly tied to adverse reproductive effects

– ovaries or eggs. The primary pathway of selenium exposure in white sturgeon is uptake through dietary seleno

methionine and maternal transfer to the egg yolk sac, where elevated sele nium concentrations can cause developmental deformities or mortality (Baginska 2015). In other species, linear or log

- transformed relationships have been established between muscle plug and ovar y concentrations (Osmundson and Skorupa, 2011). A similar rel ationship could also potentially be established using fin ray Se data.

The 2015 Sturgeon Derby study was implemented by the RMP, the U.S. Fish and Wildlife Service (USFWS), the U.S. Geological S urvey (USGS), and Stantec . In addition to addressing the objectives previously described, the study was designed to contribute useful information

relative to key questions identified by the RMP and the Selenium Strategy (Table 1).6

Table 1 . Key Selenium Strategy and RMP management questions addressed by this study

RMP Management Questions addressed

1. Are chemical concentrations in the Estuary at levels of potential concern and are associated impacts likely?
b. What potential for impacts on humans and aquatic life exists due to contaminants in the Estuary ecosystem?
4. Have the concentrations, masses, and associated impacts of contaminants in the Estuary increased or decreased?
b. What are the effects of management actions on the potential for adverse impacts on humans and aquatic life due to Bay contamination?

Selenium Strategy questions addressed

1. What are appropriate thresholds?

2. Are the beneficial uses of San Francisco Bay impaired by selenium?

3. What is the spatial pattern of selenium impairment?

4. How do selenium concentrations and loadings change over time?

Method s

Field Sample Collection

The Derby is an annual angling competi tion held by the Foundation Sportsman’s Club out of McAvoy Harbor in Bay Point, CA. The Derby provides a rare opportunity to collect tissue samples from white sturgeon harvested by anglers. The USGS initiated sample collections from the derby in 2000/2001(Stewart et al. 2004) and USFWS has collected samples more recently over the past several years, and helped facilitate the collection of additional samples for the

RMP.

The Derby awards cash prizes to anglers that bring in fish closest to a chosen target length. The target size in 2015 , chosen randomly from within the legal slot limit of 40

- 60 inches (101.6

- 152.4 cm fork length), was 51 inches (129.5 cm). Fish were permitted to be caught at any time between 7:00 am on January 31 , 2015 and 1:00 pm on February 1, 2015, and anywher e in the San Francisco Estuary. Fish were brought alive to McAvoy Harbor to be measured, and in some

ca ses, sacrificed and processed for their tissues.

Tissues were collected from all fish caught, except those that anglers wanted to release alive. A

total of 27 fish were sampled , in cluding 19 males and 8 females. Tissue samples collected for analysis by the RMP included muscle plugs, ovary (in female fish ), fin rays, and otoliths. Liver samples were coll ected and analyzed for this study pro

- bono by the USGS in Menlo Park. Because the RMP was primarily interested in understanding Se impacts on white sturgeon7

reproduction, only samples collected from the 8 f emale sturgeon were analyzed for the RMP.

The remai ning samples were stored for potential future analysis.

Additional tissue samples were collected by and for collaborating agencies. Blood samples were

collected for Se analysis by USGS, gut contents for d iet analysis by Cramer Fish Sciences, and additional ovary samples for histology analysis. USFWS collected a second set of fin ray and blood samples for each fish for aging and isotope anal ysis, as well as a variety of tissues f or histopathology analyses. Liver and gut samples were not collected from all males, and in several cases, otolith, blood plasma, and gut contents could not be collected. A description of all samples collected at the Derby, including samples that were archived or analyzed by other ag encies, is presented in the 2015 Sturgeon Derby Special Study Field Sampling Summary ( Robinson and

Sun , 2015 , included in this report as Appendix A ).

Once measured for length , fish were killed with a blow to the head by a 4 lb sledge hammer

. The

entire marginal fin ray was removed using a sharp knife, from the point of articulation down to the terminal end of the ray as described by Koch et al. 2008. Otoliths were accessed by cutting

int o the skull with a hacksaw

. For liver and ovary samples, several smal l samples were collected over the length of the organ and composited for analysis. Muscle plug samples were taken in a manner similar to the method used to collect muscle plugs for the RMP 2014 Stu rgeon Muscle Plug Special Study 1 (Sun et al., 2016) . T wo or three muscle plugs were collected from the region laterally adjacent to the dorsal fin with a 5 mm diameter biopsy plug, ensuring the collection of enough sample mass for selenium and isotope analysis

. Following sample collection, otoliths and fin rays w ere dried at room temperature. All other samples were frozen until they were sent to various labs for archiving or analysis. A more detailed description of the fish processing and sample collection methods is also documented in the 2015 Sturgeon Derby Special Study F ield Sampling Summary (Appendix A)

. Laboratory Analysis and Data Quality Assurance

Se and moisture in muscle plug (skin off) , liver, and ovary tissue w ere analyzed by USGS in one

lab batch

– includ ing 1 la b duplicate for each of the 3 tissue types. Three method blanks and 6 certified reference material (CRM) analyses were also analyzed. Results were reported blank

corrected. Accurac y was evaluated using CRMs with certified values for selenium, and precision was evaluated using duplicate samples and samples collected from other studies

. C, N, and S isotopes were analyzed by UC Davis in one lab batch, together with the nine samples collected for the 2014 Selenium Muscle Plug Study (Sun et al. 2016)

. One lab replicate was run for C and N isotopes, which were analyzed concurrently, but not enough sample mass was available to run a lab replicate for S isotopes. QC analyses inc luded four CRMs for C and N isotopes, 7 laboratory control materials (LCMs) for C and N percent masses, over 30 LCM

results for C and N isotopes, and 24 LCMs fo r S isotopes. No method blanks were analyz ed.

1 In contrast, muscle plugs colle cted during 2009 and 2014 RMP Status and Trends monitoring were collected using 8 mm biopsy plugs. During that study, plugs were taken from an arbitrary location on a fillet collected from the posterior, dorsal side of each fish.8

Selenium microchemi cal analysis was also conducted on 26 fin ray samples by Stantec

, including samples taken from both male and female fish

. A high powered laser ablation mass spectrometry technique (laser abla tion inductively coupled plasma mass spectrometry or LA

ICP

- MS ) enabled the analysis of Se down to the ng/g level from the core of the fin ray (representing early life) to the outer edge (representing late life) across each annular growth ring. Annuli were counted to estimate fish age. The fin rays were then analyzed as laser

- ablated tissue

with an ICP

- MS , resulting in multiple s elenium measurements per annulus . The resulting data

were correlated with the growth ring pattern, aggregated

, and ass embled into a life history time

series of selenium concentrations. The average and maximum Se concentrations in the outer ring of fin rays will be presented in this report. The full results from this analysis will be published by Stantec in a separate repo rt and presented in greater detail in the 2016 Sturgeon Derby report

. A

similar method will be used to conduct Se microchemi cal analyses in otoliths, which yield temporal signatures that are known to be chemically stable. The otolith results will then be u sed to evaluate the stability of the Se signature in fin rays.

Statistical Methods

Data analyses were performed using RStudy v0.99.489. The relationship between age and length of Sturgeon Derby fish was evaluated using a linear regression model. All other statistics were conducted using non

- parametric methods. Comparisons of data with previously published studies were conducted using non

- parametric Mann

- Whitney

- U tests. Correlations were determined using the non

- parametric Spearman’s rank correlation test.

Results and Discussion

Tissue s were obtained from a total of eight female white sturgeon collected at the Derby. The target size was 51 inches (129.5 cm) fork length, and samples were collected from fish ranging from 112.7 to 149.2 cm (median = 129.4 cm; mean = 129.1 cm). Estimated age s ranged from 14

to 20 yr (median = 17 yr , mean = 16.6 yr ). Exact sampling locations were not recorded, but informal conversations with anglers suggested that the majority of fish were collected in Suisun Bay

. Field measurements and the results of Se and isotope analyses in muscle p lug, ovary, liver

, and fin ray are presented in Table 2

. Selenium, C isotopes and N isotopes were analyzed in all eight female fish, but S isotopes were only measured in a subset of samples with enough sample mass for analysis. CRM recoveries and relative standard deviations met method quality objectives for selenium and isotopes (Ye et

al. 2015)

. Summary Statistics for Selenium

Se concentrations in muscle plugs collected from the eight female fish at the Derb y ranged from

6.2 to 22 μg/g dw, with a median of 8.9 and mean of 11.2 μ g /g dw, just below the TMDL target

of 11.3 μg/g dw. The standard deviation of muscle plug Se concentrations was 1.9 μg/g dw. Three of the eight muscle plugs (38%) had Se concentrations above the TMDL target

. These9

three values ( 15, 15 and 22) were substantially higher than the remainder of the samples, which

remained between 5 and 10 μg/g dw.

Se concentrations in ovaries ranged from 3.5 to 47 μg/g dw, with a median of 17 and mean of 20 μg/g dw. The standard deviation of ovary Se concentrations was relatively high, at 5.1 μg/g dw.

The dis tribution was driven by a couple particularly high values (47 and 32 μg/g dw; the next highest values were 23 and 17 μg/g dw).

Se concentrations in the liver were higher, ranging from 11 to 74 μg/g dw, with a median of 31

and mean of 36 μg/g dw. The standard deviation of liver Se concentrations was 6.8 μg/g dw. Again, the high mean Se concentration was driven in part by one particularly high Se value (74 μg/g dw) measured in the largest fish.

One anomalous fish ( WHST

- 27M ) accounted for a puzzling combination of the extreme values

in this small dataset. This individual had the lowest muscle plug Se value measured during this study , and was the largest , although not the oldest, fish. This individual also corresponded with

th e highest ovary and liver Se concentrations measured during this study.

Comparison with Historical Data

Tissue Se concentrations measured during the Derby were in the upper range of those measured previously in white sturgeon in San Francisco Bay ( Figure 1 ). The muscle plug Se concentration s measured during the Derby (8.9 μg/g dw , range= 6.2

- 22 μg/g dw ; n=8 ) were significantly greater

t han the plug and fillet concentrations measured in female sturgeon in RMP Status and Trends monitoring ( plugs: median 5.3 μg/g dw

, range 2.6

- 7.5 μg/g dw

, n= 11 measured in 2009 and 2014, p= 0.0003 ; fillets: median 4.7 μg/g dw

, range 1.8

- 12 μg/g dw, n=22 measured 1997

- 2014, p=0.001 ). Se concentration s in Derby plugs w ere also significantly greater than those measured

in female muscle fill ets reported by Linares

- Casenave et al. ( median 5.4 μg/g dw; range 2.6

– 19 μg/g dw; fish collected in 2003

- 2005 ; p=0.01 ) , and in the upper range of plug Se measured during the RMP’s 2014 Muscle Plug study ( median 4.4 μg/g dw; range 1.8

- 25 μg/g dw; n=8 ; p=0.06 ) (Sun et al. 2016)

. Ovary and liver tissue Se concentrations measured during the 2015 Derby were similarly relatively high compared to previous studies (Figure 1 )

. O vary Se concentration s measured in Derby study ( median 16.9 μg/g dw ; range 3.5

- 47 μg/g dw; n= 8 ) were significantly greater than

those reported by L inares

- Casenave et al. ( median 3.2 μg/g dw ; range 1.1

- 46.7 μg/g dw; n=29 ; p=0.03 ) , and higher but not significantly different from samples collected during the RMP’s 2014 Status and Trends monitoring event ( median 7 .3 μg/g dw; range 4.3

- 7.4 μg/g dw; n=3 ; p=0.19 ) , largely due to the small sample size of the latter dataset

. Liver Se concentrations ( median 31 μg/g dw; range 11

- 74 μg/g ; n=9) were even more elevated compared to concentrations previously reported in female sturgeon by Linares

- Casenave et al. ( median 7.9 μg/g dw; range 4.7

– 34 μg/g dw; n=24 ; p=0.00 04 ) and measured in female sturgeon collected by the RMP in 2009 ( median 7.2 μg/g dw; range 4.5

- 16 μg/g dw; n=7 ; p=0.00 1 )

.10

Two factors may be contributing to the high Se concentrations observed in this study relative to previous studies. First, the relatively high Se concentrations measured d uring this study may

have been influenced by elevated Se concentrations in P . amurensis , the primary prey item of white sturgeon in the North Bay, in recent years due to low river flows during the drought (Stewart, unpublished data) . Both muscle plug and liver concentrations measured during this study were more similar to Se concentrations measured by Stewart et al. (2004) in fish collected in January, after a period of low river flows

. Second, t he timing of sample collection, a nd its impact on f

ish reproductive status , may also have contributed to the observed Se concentration s. Female w hite sturgeon in San Francisco Bay spawn every two or more years in the spring, typically between late February are early May, with peak activity occurring in March and April (Ko h lhorst 1976 )

. Selenium can subst itute for sulfur in proteins of the egg yolk precursor vitellogenin , caus ing s elenium to accumulate in the liver and ovaries prior to spawning ( Linville

200 6 )

. Increased production of vitellogenin and egg yolk proteins in the liver and ovary of pre

spawning white sturgeon could be contributing to elevated Se concentra tions measured in these

tissues. This effect was observed in a study published by Linares

- Casenave and others in 2015,

in which s ignificantly higher Se levels were measured in the muscle, liver, and gona ds of vitellogenic compared to pre

- vitellogenic female white sturgeon (Student’s t

- test; muscle: p=0.02; ovary: p=0.0008; liver: p=0.0003; n=18 pre

- vitellogenic, 8 vitellogenic females). The authors of this study postulated that dietary changes prior to spawn ing could be contributing to

elevated Se in tissues as well.

S turgeon sampled between April and August during RMP Status and Trends monitoring, or between August and October as part of the 2014 Selenium in Sturgeon Muscle Plugs study,

would not be expecte d to be producing vitellogenin

. However , some females collected in late January and early February during this Derby could be expected to have begun vitellogenin production. Ovary and muscle plug Se measured during the Derby were more similar to the

distri bution of Se previously reported by Linares

- Casenave et al. (2005) for vitellogenic females ( muscle: median 9.5 μg/g dw ; ovary : median 20. 6 μg/g dw; n=8)

. Ovary Se concentrations in Derby fish we re significantly higher than those reported by Linares

- Casenave et al. in pre

vitellogenic females ( p=0.001 ), but not in vitellogenic females ( p=0.72 ). Similarly, muscle plug Se concentrations in Derby fish we re significantly higher than those in the pre

- vitellogenic females ( p=0.0001 ), but not v itello genic females (p=0.07). Liver Se concentrations measured during the Derby were significantly higher than both the pre

- vitellogenic and vitellogenic females measured by Linares

- Casenave et al (2015 )

. While reproductive stage was not identified for the 2015 Derby Study , 7 of the 8 females sampled were within the age range at which female white sturgeon typically mature (15 to 32 years). Histology analysis of ovaries collected during the 2016 Sturgeon Derby special study will

allow a direct evaluation of the impact of sturgeon maturity on muscle and ovary Se

concentrations.11

Age, Length, and Tissue Se

Similar to other studies, a significant positive correlation was observed between age and fork length in the 8 Derby sturgeon ( p =0.04

, R 2 =0.46 ) (Figure 2). However, when comparing age and fork length to tissue Se concentrations (Figure 3) , a significant positive relationship was observed only between fork length and ovary Se , based on a non

- parametric rank correlation test (Spearman’s rank correl ation, rho=0.80, p=0.02). No significant relationship between age or fork length and muscle plug Se was detected within this size range. In contrast, Linares

- Casenave et

al. (2015) found a significant po sitive relationship between (1) Se in muscle and fish age, and (2)

liver Se and fish length, based on a comparison of concentrations measured in fish separated into

three size classes ranging from 53 to 170 cm (age 4

- 2 8) . All fish collected durin g the Derby fell

within a much narrower size and age range (112.7

– 149.2 cm fork length; 12

– 20 yrs), making it more difficult to assess the relationship between these characteristics and measured Se

concentrations (Figure 3 )

. The small sample size of this data set also makes detection of

correlations more difficult. Se and histology data from a different size range of fish collected during the 2016 Derby will increase the sample size and allow for further evaluation of the

rela tionship s repo rted by Linares

- Casenave et al.

Se Correlations Among Tissues

Base d on the small number of samples analyzed in this study , no apparent positive or negative relationship among the tissues sampled wa s observable (Figure 4)

. The absence of a clear relationship may be related to the small sample size. P oor correlation was also observed between

these tissues in female sturgeon measured by L inares

- Casenave et al. (2015) (Figure 5) . In this study, as was previously described, these high Se concentrations largely corresponded with vitellogenic females sampled prior to the spawning season

. It is possible that in the pre

- spawning

season, w hen Se concentrations are high, the rate of Se incorporation into the liver and ovary is

more s trongly influenced by variable factors such as recent foraging location and temporal proximity to spawning. Additional data collected from fish of a different size and age range during the 2016 Sturgeon Derby , together with data on reproductive maturity, will hopefully help clarify relationships of Se concentrations in these tissues.

C, N, and S Isotopes

C, N, and S isotopes values were measured in a subset of the muscle plug samples with enough sample mass for analysis ( Table 2 , Figures 6

- 9 )

, and may provide information about habitat use and foraging. The measured isotope values generally fell within the range of values previously observed in white sturgeon collected in the North Bay (Stewart et al. 2004). δ 15 N values ranged

from 14.6 to 17.9 ‰

, suggesting mixed foraging patterns, similar to what was observed in the 2014 Muscle Plug study (Sun et al. 2016) . Fish with lower δ 15 N values we re likely foraging more on invertebrates, while fish with higher δ 15 N we re likely more piscivorous. However, th e measured δ 15 N values in fish collected both during the 2014 Muscle Plug study and the 201512

Derby study suggest that the majority of fish are feeding on P . amurensis

. No clear trend of

muscle Se relative to δ 15 N is apparent in the preliminary dataset (Figures 6 and 7 ).

δ 13 C values ranged from

- 21.7 to

- 28.8 ‰ , which is similarly consistent with expected values for sturgeon caught in North San Francisco Bay and the Delta , bas ed on recently collected δ 13 C

values measured in P

. amurensis ( Robin Stewart, personal communication ) . In contrast with fish caught in Suisun Bay during the fall 20 14 Sturgeon Muscle Plug study, the generally lower δ 13 C

values in the Derby fish may reflect a seasonal shift in P . amurensis δ 13 C values or a shift to foraging closer to the Delta. Across both studies, the highest muscle plug Se concentrations

were measured in fish collected between

- 23.0 and

- 26.7 ‰ δ 13 C ( Figures 6 and 7 )

. This

c o rre s pond s with δ 13 C values for clams in Suisun Bay, where selenium concentrations in P

. amurensis are highest (Stewart 2013).

δ 34 S values ranged from 12.4 to 17.9 ‰ , consistent with foraging in the fresh and brackish waters of the Bay

. The highest liver and ovary values were observed in sturgeon with wide ly varying stable isotope values.

Se in Fin Rays

Preliminary data on fin ray analyses were presented by Dr. Palace at the SETAC North America conference in November 2015 (Palace, 2015). Multiple selenium measurements can be made across a single annular ring of the fin ray, resulting in multiple measurements representative of sturgeon tissue Se for any given year. The average and maximum Se concentrations measured in

the outermost annular ring for each fish are presented in Table 2.

Additional analysis of the data planned by Dr. Palace, using different summation and averaging methods, will further probe the relationship between fin ray and muscle tissues, and the potential use of fin rays to non

- lethally monitor Se in sturgeon. Some initial observations are:

 The maximum Se concentrations measured in fin ray tissue deposited in the most recent

year ranged from approximately 0.2 to 0.8 μg/g , with the highest and lowest values

observed in males. The average across all fish (male and female) of the maximum Se concentration measured in the outermost annular fin ray ring has remained stable for the past 6 years at just below 0.5 μg/g

.

 Initial analyses show widely varying temporal patterns in the fin ray Se conce ntrations of

the 8 female fish . T ime series of the maximum annual Se concentrations show either increasing or decreasing trends in different fish in recent years, and longer time series over the lifespan of each fish reveal a similar level of variation in both trends and level of stability in Se concentration

.

 Initial analyses have not indicated a significant c orrelation between fin ray and tissue Se

concentration s (Figure 10) . The maximum and average Se concentrations as measured in the outer fin ray annulus of each fish , composed of the most recently deposited tissue, showed poor correlation with Se muscle plug concentrations.

Additional fin ray data will be collected at the 2016 Sturgeon Derby. The co mbined dataset from 2015 and 2016 will be analyzed and presented in the 2016 Derby report.13

Se in Otoliths

M icrochemi cal anal yses will be conducted on the 2015 Derby otoliths

, together with the otoliths

that will be collected at the 2016 Sturgeon Derby in February 2016. A comparison of otolith and fin ray results will help evaluate the stability of Se concentrations in fin ray annuli and inform the interpretation of the fin ray data. Analysis of the combined 2015 and 2016 dataset will be

include d in the 2016 Derby Report.

Conclusions

The muscle plug, ovary, and liver Se concentrations measured in this study were in the upper range of previously measured values. The relatively high Se concentrations observed during this study may be influenced by the select characteristics of the Derby fish, which were only females

collected shortly before spawning season

, following low flows, in a region known to have high

prey Se concentrations

. The isotope data suggest that although some fish collected during the Derby appeared to have been foraging into the Delta and possibly San Pablo Bay, the fish with the highest selenium concentrations were feeding largely on P . amurensis in Suisun Bay , where clam selenium concentrations are highest

.

The poor correlations among Se concentr ations in different tissues suggest that, at least within the narrow size range of fish collected during the Derby, muscle plug Se concentrations are not closely reflecting Se concentrations in the ovary and liver , and may not be reflective of Se toxicity impacts being experienced by these fish and their offspring. However, the sample size for this study was too small to draw conclusions. This hypothesis will be tested more rigorously

after additional data are collected in the 2016 Derby.

The low sample size and relatively narrow length and age range of fish caught during the Derby are likely contributing to the poor correlation observed between Se in various tissues , and between either length or age and tissue Se

. In contrast with previous studies, only fork length and ovary Se were significantly correlated. Additional data from a different size range of fish, as well as reproductive maturity data, collected during the 2016 Sturgeon Derby will be valuable in further evaluating these relationships. Otolith analysis will also contribute to the full evaluation of fin ray Se microchemistry as a reliable method to analyze Se bioaccumulation and predict Se

concentrations in other tissues. Collection of these add itional samples is planned for February 6

- 7, 2016, and the results of this study will be published in late 2016.14

Tables and Figures

Table 2

. 2015 Sturgeon Derby Study: field measurements, selenium and isotope results in female fish

.
Sample

ID Sample

Date Fork

Length (cm) Age

(yr) Muscle Plug Ovary Liver Muscle Plug Fin Ray
Sample Weight (mg dw) %

Moisture Selenium

( μg/g dw) Selenium

( μg/g dw) Selenium

( μg/g dw) d13C

Isotope ( ‰ ) d15N

Isotope ( ‰ ) d34S

Isotope ( ‰ ) Max

Selenium ( μg/g ) Average

Selenium ( μg/g )

WHST

03M 1/31/2015 124.5 16 64.5 53.8 7.0 4.6 30

- 27.9 16.8 17.5 0.53 0.32

WHST

06M 1/31/2015 124.1 14 35.1 71.4 22 17 2 9

- 26.7 16.5 17.2 0.47 0.28

WHST

08M 1/31/2015 131.9 17 15.5 74.0 1 5 3 2 11

- 23.0 16.6 14.7 0.60 0.28

WHST

09M 1/31/2015 131.4 17 36.3 75.8 15 1 6 48

- 25.3 17.0 17.2 0.40 0.27

WHST

10M 1/31/2015 112.7 12 31.4 74.4 9.5 3.5 22

- 27.2 15.0 12.4 0.54 0.40

WHST

15M 1/31/2015 127.3 20 16.7 80.1 7.5 1 7 31

- 26.0 15.4 14.0 0.45 0.30

WHST

17M 2/1/2015 131.4 18 38.0 79.1 8.3 2 3 45

- 21.7 17.9 16.9 0.37 0.26

WHST

27M 2/1/2015 149.2 19 35.0 57.6 6.2 47 7 4

- 28.8 14.6 15.1 0.51 0.29

Average 129.1 16.6 11 20 36

- 25.8 16.2 15.6 0.48 0.30

Median 129.4 17.0 8.9 1 7 3 1

- 26.4 16.5 16.0 0.49 0.29

Standard Error 3.6 0.9 1.9 5.1 6.8 0.9 0.4 0.7 0.03 0.0215

Figure 1. Muscle plug, ovary, and liver selenium concentrations measured in San Francisco Bay

white sturgeon during the 2015 Sturgeon Derby and previous studies. The previous studies from

which data are include d on these graphs are : Linares

- Casenave et al. (2015), 2014 Muscle Plug (RMP 2014 Sturgeon Muscle Plug Special Study) , RMP S&T (muscle fillets or plugs collected during RMP Status and Trends sport fish monitoring, 1997

- 2014 or 2009

- 2014, respectively)

. The white bars show the median concentration for each set of samples , and points represent

measurements of individual fish. Points are colored by se x and maturity, where data are available (M = male, U = unknown sex, F = female of unknown maturity, F preVTG = pre

- vitellogenic female, F VTG = vitellogenic female).

Jan/Feb Year

- Round Sept

- Oct April

- Aug April

- Aug

Jan/Feb Year

- Round April

- Aug

Jan/Feb Year

- Round April

- Aug16

Figure 2. Relationship between fish age and fork length in eight female fish caught during the Derby.17

Figure 3

. Relationship between selenium concentration in muscle plug, ovary, and liver tissue and fish age or length.18

Figure 4 . Relationship s between selenium concentrations in muscle, ovary, and liver tissue collected from female sturgeon at the 2015 Sturgeon Derby

.19

Figure 5. Relationships between selenium concentrations in muscle, ovary and liver tissue in female sturgeon, as reported in Linares

- Casenave et al., 2015.20

Figure 6

. Relationship between muscle plug selenium and C, N, and S isotopes in white sturgeon muscle plugs collected during the 2014 Muscle Plug study and 2015 Sturgeon Derby study. The
d34S value for 0924

- 01 was considered dubious by the analytical laboratory.2122

Figure 7

. Muscle plug s elenium concentration compared with C and N isotopes in white sturgeon collected during the 2014 Selenium in Muscle Plugs study and 2015 Sturgeon Derby study. Each point represents an individual fish. Points are labeled by muscle plug selenium concentration ( μg/g dw).23

Figure 8

. R elationship between ovary selenium and C, N, and S isotopes in white sturgeon ovary samples collected during the 2015 Sturgeon Derby study.2425

Figure 9

. R elationship between liver selenium and C, N, and S isotopes in white sturgeon liver samples collected during the 2015 St urgeon Derby study.2627

Figure 10. R elationship between the maximum and average selenium concentration measured in the outer fin ray annulus, and muscle plug, ovary, and liver concentrations.28

References

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