62070 Federal Register / Vol. 75, No. 194 / Thursday, October 7, 2010 / Proposed Rules 

dated September 30, 1993. This rule is 

not a major rule under 5 U.S.C. 804. 

B. Regulatory Flexibility Act 

The Councils do not expect this 

proposed rule to have a significant 

economic impact on a substantial 

number of small entities within the 

meaning of the Regulatory Flexibility 

Act, 5 U.S.C. 601, et seq., because the 

rule does not impose any additional 

requirements on small businesses. An 

Initial Regulatory Flexibility Analysis 

has, therefore, not been performed. The 

Councils invite comments from small 

business concerns and other interested 

parties on the expected impact of this 

rule on small entities. 

The Councils will also consider 

comments from small entities 

concerning the existing regulations in 

parts affected by this rule in accordance 

with 5 U.S.C. 610. Interested parties 

must submit such comments separately 

and should cite 5 U.S.C. 610 (FAR Case 

2000–041) in all correspondence. 

C. Paperwork Reduction Act 

The Paperwork Reduction Act does 

not apply because the proposed changes 

to the FAR do not impose information 

collection requirements that require the 

approval of the Office of Management 

and Budget under 44 U.S.C. chapter 35, 

et seq. 

List of Subjects in 48 CFR Part 25 

Government procurement. 

Dated: September 28, 2010. 

Edward Loeb, 

Director, Acquisition Policy Division. 

Therefore, DoD, GSA, and NASA 

propose amending 48 CFR part 25 as set 

forth below: 

PART 25—FOREIGN ACQUISITION 

1. The authority citation for 48 CFR 

part 25 continues to read as follows: 

Authority: 40 U.S.C. 121(c); 10 U.S.C. 

chapter 137; and 42 U.S.C. 2473(c). 

2. Amend section 25.702–4 by 

revising paragraph (b), and adding 

paragraphs (c) and (d) to read as follows: 

25.702–4 Waiver. 

* * * * * 

(b) An agency seeking waiver of the 

requirement shall submit the request 

through the Administrator of the Office 

of Federal Procurement Policy (OFPP), 

allowing sufficient time for review and 

approval. Upon receipt of the waiver 

request, OFPP shall consult with the 

President’s National Security Council, 

Office of African Affairs, and the 

Department of State Sudan Office and 

Sanctions Office to assess foreign policy 

aspects of making a national interest 

recommendation. 

(c) Agencies may request a waiver on 

an individual or class basis; however, 

waivers are not indefinite and can be 

cancelled if warranted. 

(1) A class waiver may be requested 

only when the class of supplies is not 

available from any other source and it 

is in the national interest. 

(2) Prior to submitting the waiver 

request, the request must be reviewed 

and cleared by the agency head. 

(3) All waiver requests must include 

the following information: 

(i) Agency name, complete mailing 

address, and point of contact name, 

telephone number, and e-mail address. 

(ii) Offeror’s name, complete mailing 

address, and point of contact name, 

telephone number, and e-mail address. 

(iii) Description/nature of product or 

service. 

(iv) The total cost and length of the 

contract. 

(v) Justification, with market research 

demonstrating that no other offeror can 

provide the product or service and 

stating why the product or service must 

be procured from this offeror, as well as 

why it is in the national interest for the 

President to waive the prohibition on 

contracting with this offeror that 

conducts restricted business operations 

in Sudan, including consideration of 

foreign policy aspects identified in 

consultation(s) pursuant to 25.702–4(b). 

(vi) Documentation regarding the 

offeror’s past performance and integrity 

(see the Past Performance Information 

Retrieval System (including the Federal 

Awardee Performance Information and 

Integrity System at http:// 

www.ppirs.gov) and any other relevant 

information). 

(vii) Information regarding the 

offeror’s relationship or connection with 

other firms that conduct prohibited 

business operations in Sudan. 

(viii) Any humanitarian efforts 

engaged in by the offeror, the human 

rights impact of doing business with the 

offeror for which the waiver is 

requested, and the extent of the offeror’s 

business operations in Sudan. 

(d) The consultation in 25.702–4(b) 

and the information in 25.702–4(c)(3) 

will be considered in determining 

whether to recommend that the 

President waive the requirement of 

subsection 25.702–2. In accordance with 

section 6(c) of the Sudan Accountability 

and Divestment Act of 2007, OFPP will 

submit a report to Congress, 

semiannually on April 15th and October 

15th, on the waivers granted. 

[FR Doc. 2010–25266 Filed 10–6–10; 8:45 am] 

BILLING CODE 6820–EP–P 

DEPARTMENT OF THE INTERIOR 

Fish and Wildlife Service 

50 CFR Part 17 

[Docket No. FWS-R8-ES-2010-0013] 

[MO 92210-0-0008-B2] 

Endangered and Threatened Wildlife 

and Plants; 12–month Finding on a 

Petition to list the Sacramento Splittail 

as Endangered or Threatened 

AGENCY: Fish and Wildlife Service, 

Interior. 

ACTION: Notice of 12–month petition 

finding. 

SUMMARY: We, the U.S. Fish and 

Wildlife Service, announce a 12–month 

finding on a petition to list the 

Sacramento splittail (Pogonichthys 

macrolepidotus) as endangered or 

threatened under the Endangered 

Species Act of 1973, as amended. After 

review of all available scientific and 

commercial information, we find that 

listing the Sacramento splittail is not 

warranted at this time. However, we ask 

the public to submit to us any new 

information that becomes available 

concerning the threats to the 

Sacramento splittail or its habitat at any 

time. 

DATES: The finding announced in this 

document was made on October 7, 2010. 

ADDRESSES: This finding is available on 

the Internet at http:// 

www.regulations.gov at Docket Number 

FWS-R8-ES-2010-0013. Supporting 

documentation we used in preparing 

this finding is available for public 

inspection, by appointment, during 

normal business hours at the U.S. Fish 

and Wildlife Service, San Francisco Bay 

Delta Fish and Wildlife Office, 650 

Capitol Mall, Sacramento, CA 95814. 

Please submit any new information, 

materials, comments, or questions 

concerning this finding to the above 

street address. 

FOR FURTHER INFORMATION CONTACT: Dan 

Castelberry, San Francisco Bay Delta 

Fish and Wildlife Office (see 

ADDRESSES); by telephone at 916-930- 

5632; or by facsimile at 916-930-5654. If 

you use a telecommunications device 

for the deaf (TDD), please call the 

Federal Information Relay Service 

(FIRS) at 800-877-8339. 

SUPPLEMENTARY INFORMATION: 

Background 

Section 4(b)(3)(B) of the Endangered 

Species Act of 1973, as amended (Act) 

(16 U.S.C. 1531 et seq.), requires that, 

for any petition to revise the Federal 

Lists of Endangered and Threatened 


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Wildlife and Plants that contains 

substantial scientific or commercial 

information that listing the species may 

be warranted, we make a finding within 

12 months of the date of receipt of the 

petition. In this finding, we will 

determine that the petitioned action is: 

(1) Not warranted, (2) warranted, or (3) 

warranted, but the immediate proposal 

of a regulation implementing the 

petitioned action is precluded by other 

pending proposals to determine whether 

species are tendangered or threatened, 

and expeditious progress is being made 

to add or remove qualified species from 

the Federal Lists of Endangered and 

Threatened Wildlife and Plants. Section 

4(b)(3)(C) of the Act requires that we 

treat a petition for which the requested 

action is found to be warranted but 

precluded as though resubmitted on the 

date of such finding, that is, requiring a 

subsequent finding to be made within 

12 months. We must publish these 12– 

month findings in the Federal Register. 

Previous Federal Actions 

Please refer to the final listing rule (64 

FR 5963) for a discussion of Federal 

actions that occurred prior to February 

8, 1999. Please refer to the Notice of 

Remanded Determination of Status for 

the Sacramento Splittail (68 FR 55139) 

for a discussion of Federal actions that 

occurred after February 8, 1999, and 

prior to September 22, 2003. It is our 

intent, in this document, to reiterate and 

discuss only those topics directly 

relevant to this decision. 

On September 22, 2003, the Service 

published a Notice of Remanded 

Determination of Status for the 

Sacramento Splittail in the Federal 

Register (68 FR 55139) that removed the 

Sacramento splittail from the List of 

Endangered and Threatened Wildlife 

(50 CFR 17.11(h)). On August 13, 2009, 

the Center for Biological Diversity (CBD) 

filed a complaint in U.S. District Court 

for the Northern District of California, 

challenging the Service on the merits of 

the 2003 determination alleging 

improper political influence. In a 

settlement dated February 1, 2010 

(Case4:09-cv-03711-PJH), the Service 

agreed to open a 30–day public 

comment period for a new 12 month 

finding to allow for the submission of 

additional information by the public. 

The Service also agreed to submit to the 

Federal Register a new status review 

and 12–month finding as to whether 

listing the Sacramento splittail is 

warranted or not warranted. If 

warranted, the Service further agreed to 

publish, concurrently with the 12– 

month finding, a proposed rule to list 

the Sacramento splittail before 

September 30, 2010 and a final 

determination on or before September 

29, 2011. 

Definitions 

To assist the reader in understanding 

terminology used in this determination, 

we have provided below several terms 

with their corresponding definitions as 

they are used in this document. As used 

in this determination, the term ‘‘Delta’‘‘ 

refers to all tidal waters contained 

within the legal definition of the San 

Francisco Bay-Sacramento-San Joaquin 

River Delta, as delineated by section 

12220 of the State of California’s Water 

Code. Generally, the Delta is contained 

within a triangular area that extends 

south from the City of Sacramento to the 

confluence of the Stanislaus and San 

Joaquin Rivers at the southeast corner 

and Chipps Island in Suisun Bay at the 

southwest corner. The term ‘‘Estuary’’ as 

used in this determination, refers to the 

collective tidal waters contained in the 

Sacramento and San Joaquin Rivers, the 

Delta, and San Pablo and San Francisco 

bays. 

Species Information 

Species Description 

The Sacramento splittail is a fish 

species native to central California and 

represents the only extant species in its 

genus in the world (Baerwald et al. 

2007, p. 160). Splittail can grow to a 

length of 40centimeters (cm) (15 inches 

(in.)), and have an elongate body, small 

head, and enlarged upper tail lobe. 

Their body coloration is dusky olive 

gray on the back and silver on the sides. 

During breeding season, their fins 

become tinged with red-orange. 

Additionally, males develop white 

tubercles on their heads and become 

darker in color during the breeding 

season (Moyle 2002, p. 146). 

Taxonomy 

Splittail were first described in 1854 

by W.O. Ayres as Leuciscus 

macrolepidotus and by S.F. Baird and C. 

Girard as Pogonichthys inaeqilobus. 

Although Ayres’ species description is 

accepted, the species was assigned to 

the genus Pogonichthys in recognition 

of the distinctive characteristics 

exhibited by the two splittail species P. 

ciscoides and P. macrolepidotus 

(Hopkirk 1973, p. 24). Pogonichthys 

ciscoides, endemic to Clear Lake, Lake 

County, California, has been extinct 

since the early 1970s. The Sacramento 

splittail is currently classified as 

Pogonichthys macrolepidotus. Recent 

studies have revealed two populations 

of splittail that differ in their genetic 

makeup, one in the Napa/Petaluma 

drainages (hereafter referred to as the 

San Pablo population) and one in the 

greater Central Valley drainage 

(hereafter referred to as the Delta 

population) (Baerwald et al.2007, pp. 

159-167). 

Distribution 

Historically, Sacramento splittail were 

found as far north as Redding on the 

Sacramento River. Splittail were also 

found in the tributaries of the 

Sacramento River as far as the current 

Oroville Dam site on the Feather River 

and Folsom Dam site on the American 

River (Rutter et al. 1908, p. 131). Along 

the San Joaquin River, splittail were 

harvested by native peoples in Tulare 

and Buena Vista Lakes where splittail 

bones have been found in archeological 

middens (Moyle et al., 2004, p. 7). In the 

San Francisco Bay area, splittail have 

historically been reported at the mouth 

of Coyote Creek in Santa Clara County 

and the Southern San Francisco Bay 

(Snyder et al. 1905, pp. 327-338). 

Splittail were documented in Suisun 

and Napa marshes as well as Suisun Bay 

in the 1950’s (Caywood . 1974, p. 29- 

65). 

Splittail occur in the San Francisco 

estuary and its tributaries and are found 

most often in slow moving sections of 

rivers and sloughs including dead end 

sloughs and shallow edge habitats 

(Moyle 2002, p. 147; Daniels and Moyle 

1983, p. 653; Feyrer et al. 2005, pp. 164- 

165). Recent studies have shown the 

splittail’s range in the Sacramento, San 

Joaquin, Napa, Mokelumne and 

Petaluma rivers is significantly greater 

than previously thought when it was 

first petitioned in the early 1990’s as a 

threatened species (Sommer et al. 2007, 

pp. 27-28; Sommer et al. 1997, p. 970). 

The following chart created by Sommer 

and featured in his splittail paper 

follows (Sommer et al. 2007, p. 28). 


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TABLE 1. UPSTREAM-MOST LOCATIONS OF HISTORICAL AND RECENT SPLITTAIL COLLECTIONS (1998-2002). RIVER

KILOMETER (RKM) IS THE DISTANCE FROM THE MOUTH OF THE RIVER. Location (rkm) of splittail collection 

River System Historic 

(Rutter 1908) 

1970s 

(Cawood 1974) 

Mid- 1990s 

(Sommer et al. 1997) 

Recent 

(Freyer et al. 05) 

unless noted 

otherwise 

Distance to first dama

Sacramento 483 387 331 391b 387 

Feather 109 Present 94 94c 109 

American 49 37 19 No new data 37 

San Joaquin Widespread Present 201 218.5d 295 

Mokelumne NA 25 63 96e 63 

Napa NA 21 10 32 NA 

Petaluma NA 25 8 28 NA 

a Lowest dams in reach of river are Red Bluff (Sacramento), Oroville (Feather), Nimbus (American), Sack (San Joaquin), and Woodbridge 

(Mokelumne). Woodbridge is a seasonal dam. Napa River is not dammed within the range of splittail; first dam was removed from the Petaluma 

River in 1994. b D. Killam, California Department of Fish and Game, personal communication. c B. Oppenheim, NOAA Fisheries, personal communication. 

d R. Baxter, California Department of Fish and Game, unpublished data. e J. Merz, East Bay Municipal Utility District, November 2000. 

Distribution on the Sacramento River 

over the past 30 years has consistently 

ranged at least 232 to296 river 

kilometers (rkm) (144 to184 miles (mi)) 

upstream of the estuary (Feyrer et. al. 

2005, pp. 163-167). The consistent 

finding of splittail more than 200 rkm 

(124 mi) upstream of the Estuary may 

represent a population persisting there 

or may reflect the long distance that 

splittail migrate during dry years (Feyrer 

et al. 2005, pp. 165-166). Juvenile 

splittail have been recorded at the 

Glenn-Colusa Irrigation District Intake at 

rkm 331 (206 mi) on the Sacramento 

River year-round from 1994 - 2001. It is 

unknown why these individuals do not 

migrate downstream after spawning as 

do the majority of splittail (Feyrer et al. 

2005, pp 165-166). Splittail have been 

documented on the Toulumne River to 

rkm 27.4 (mi 17) (Heyne 2003, pers. 

comm.) and on the Merced River to rkm 

20.9 (13 mi) ( Heyne 2003, pers. comm.). 

Splittail have been recorded in recent 

times from within Salt Slough (Baxter 

1999a, p. 10; 1999b, p. 30). A 1998 

California Department of Fish and Game 

(CDFG) gillnet survey of the tidal 

reaches of the Lower Walnut Creek 

found splittail to be the most abundant 

fish in the creek (Leidy et al. 2007). 

Splittail are found in the Napa Marsh 

during years with high freshwater flow, 

but are rare during years of low 

freshwater outflow (Baxter 1999a, p. 11). 

Splittail can utilize a variety of 

habitats and having no known 

collection in an area does not mean that 

splittail are not there because it is 

impractical to survey the entire Delta. 

Splittail have been observed in a 

number of tributaries of major rivers 

such as the Sacramento and San Joaquin 

and are likely distributed much more 

widely in small creeks and marshes 

throughout the lower portions of the 

Estuary than known collections indicate 

(Kratville 2010, pers comm.). Suisun 

Marsh and Bay contain the largest areal 

extent of shallow water habitat available 

to the splittail and likely have the 

greatest concentrations of the species. 

Splittail’s spawning habitat includes 

the natural and newly-restored 

floodplains of the Cosumnes River, 

managed floodplains such as the Yolo 

and Sutter bypasses, and disjunct 

segments of floodplain adjacent to the 

Sacramento and San Joaquin rivers and 

tributaries. These areas approximate the 

large, open, shallow-water areas which 

once existed throughout the Delta 

(Sommer et al. 1997, p. 971). The largest 

portion of splittail spawning habitat 

occurs in the Yolo Bypass and higher 

splittail young-of-the-year abundances 

are strongly correlated with the flooding 

of the Yolo Bypass. The best spawning 

conditions for splittail occur in the 

bypass when water remains in the 

bypass until fish have completed 

spawning (at least 30 days), and larvae 

are able to swim out on their own 

during the draining process. 

In years where the Yolo and Sutter 

bypasses are not inundated for at least 

30 days, splittail spawning is confined 

primarily to the natural and newly 

restored floodplains of the Cosumnes 

River and the margins of rivers and 

other floodplain features that are 

inundated at lower river stages. The 

Cosumnes River is unique in that it is 

the only major river flowing into the 

Delta that does not host a major dam. 

There are indications, based on 

presence of larvae and juveniles, that 

spawning in the Sacramento River 

occurs relatively far upstream at Colusa 

(Baxter 1999a, p. 8; 1999b, p. 29). 

Splittail also utilize the San Joaquin 

River for spawning in wet years when 

river flow exceeds the capacity for 

storage and flooding occurs. The 

Tuolumne, Cosumnes, Feather, 

American, Napa, and Petaluma Rivers, 

and numerous other smaller waters also 

support splittail spawning activity. 

In summary, the geographic 

distribution of the splittail has not 

decreased detectably over the last 

several decades and is in fact larger than 

estimated in our last listing decision 

(Sommer et al. 2007, pp.27-28; 68 FR 

55139). 

Habitat Requirements 

Although primarily a freshwater 

species, splittail tolerate salinities as 

high as 10 to 18 parts per thousand (ppt) 

(Moyle and Yoshiyama 1992). Salinity 

tolerance in splittail increases in 

proportion to body length; adults can 

tolerate salinities as high as 29 ppt for 

short periods in laboratory conditions, 

but experience loss of equilibrium 

(bodily balance) when salinities exceed 

23 ppt (Young and Cech 1996, p. 668). 

Hospitable temperatures for nonbreeding splittail range from 5 to 24° 

Celsius (C) (75° Fahrenheit (F)) although 

acclimated fish can survive 

temperatures up to 33°C (91° F) for short 

periods of time (Young and Cech 1996, 

pp. 667-675). Splittail are also tolerant 


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of low dissolved oxygen and can be 

found in water where levels are around 

1 mg O2 L -1 (Moyle et al. 2004, p. 13). 

Splittail are frequently found in areas 

subject to flooding because they require 

flooded vegetation for spawning and 

rearing. Historically, the major flood 

basins (e.g., Colusa, Sutter, American, 

and Yolo basins; Tulare, Buena Vista, 

and Kern lakes) distributed throughout 

the Sacramento and San Joaquin valleys 

provided spawning and rearing habitat. 

These flood basins have all been 

reclaimed or modified for flood control 

purposes (i.e. as bypasses), and much of 

the floodplain area adjacent to the rivers 

is now inaccessible behind levees. 

Splittail make use of the Sutter 

Bypass, and particularly heavy use of 

the Yolo Bypass, for spawning under 

certain hydrologic conditions. The 

shallow, vegetated waters of the 

bypasses provide excellent rearing 

conditions for juvenile fish (Sommer et 

al. 2001, p. 11). The bypasses are 

primarily flood control facilities and 

secondarily, passively operated as 

agricultural lands. These lands are also 

managed for waterfowl and other 

wildlife habitat. Splittail using the 

bypasses are subject to the same threats 

found elsewhere, such as habitat loss, 

environmental contamination, harmful 

reservoir operations, competition with 

and predation by non-native fish, and so 

forth. 

The bypasses are only fully flooded 

when flows in the Sacramento River 

reach a certain level. The Yolo Bypass 

becomes inundated when the 

Sacramento River flow rate at the 

Freemont Weir exceeds 1,600 cubic 

meters per second (cms) (56,503 cubic 

feet per second (cfs)). This occurs when 

the River reaches approximately 9.0 

meters (m) (30 feet (ft.) (National 

Geodetic Vertical Datum standard) in 

depth at the Freemont Weir (Sommer et 

al. 2001, pp. 7-8). Partial flooding of the 

Yolo Bypass via high flows from Cache 

and Putah creeks can occur 

independently regardless of Sacramento 

River flows. Due to the unpredictable 

flooding frequencies and duration of the 

bypass, splittail, having migrated long 

distances upstream, could arrive at 

floodplains that have not been 

inundated and therefore the splittail 

could be denied the opportunity to 

spawn. In those cases where adult 

splittail successfully spawn, the eggs or 

larvae could become trapped and killed 

if waters recede too rapidly. Insufficient 

duration of floodplain inundation could 

also force egress of juvenile splittail 

before they have attained a size and 

swimming ability sufficient to avoid 

predation. The annual splittail 

spawning and reproductive success is 

strongly correlated with frequency and 

duration of Yolo bypass inundation 

(Sommer et al. 2007, pp. 33-34). 

The Fremont Weir has been 

overtopped—resulting in Yolo Bypass 

inundation—19 of the last 31 years with 

10 of these years producing inundation 

durations of more than 30 days (DWR 

2010a, pp. 1-2). Inundation durations of 

30-90 days are needed to produce robust 

splittail year classes on the bypass 

(Kratville 2010, pers. comm.). According 

to the ST5 (T. C. Foin) model, the 

inundation of floodplains that splittail 

utilize as spawning habitat must occur 

at a minimum of every 7 years for a 

minimum of 30 days for splittail 

populations to persist. Bypasses and 

other floodplains have historically been 

exceeding these parameters and we have 

no evidence that suggests they will not 

continue to do so in the foreseeable 

future. 

The Yolo Bypass supports agricultural 

crops such as corn and safflower and 

can support tomatoes in non-flood 

years. Optimal flooding conditions for 

the splittail (February through May) 

have negative effects on agricultural 

production in the area destroying and 

damaging crops, eroding soils and 

decreasing overall yields (Yolo Bypass 

Management Strategy 2001, ch. 2 p. 6). 

Because Yolo Bypass inundation is 

likely to be one of the most important 

factors in determining the continued 

production of high splittail population 

numbers, cooperation on the flood 

management between the landowners of 

the bypass and resource management 

agencies is essential. 

Splittail spawning occurs over 

flooded vegetation in freshwater 

marshes, sloughs, and shallow reaches 

of large rivers with depths of at least 1m 

(3.3 ft) (Moyle et al. 2007 , pp. 1-27). 

Observations of splittail spawning have 

indicated the species spawns at depths 

of less than 1.5 m (4.9 ft) in the 

Cosumnes River floodplain and at 

depths of less than 2 m (6.6 ft) in Sutter 

Bypass (Moyle et al. 2004, pp. 16-17). 

These studies show that splittail spawn 

in water depths between 1 to 2 m (3.3 

to 6.6 ft) depending on location of 

spawning. Splittail may not spawn 

again in the year following a successful 

effort (Moyle et. al. 2004, p. 32). 

It is speculated that Suisun Marsh is 

the late-stage rearing area for juvenile 

splittail hatched and reared in the 

extensive spawning habitat found 

within the Yolo Bypass because water 

flowing out of the Yolo Bypass tends to 

stay on the north side of the delta and 

be drawn into Suisun Marsh (Moyle et 

al. 2004, p. 31). 

Biology 

Splittail are relatively long-lived and 

larger fish may be 8 to 10 years old 

(Moyle 2002). Splittail reach about 110 

millimeters (mm) (4.3 in) standard 

length (SL) (tip of the snout to the 

posterior end of the last vertebra)in their 

first year, 170 mm (6.6 in) SL in their 

second year, and 215 mm (8.4 in) SL in 

their third year (Moyle 2002, p. 148). 

Male and female splittail generally 

mature by the end of their second year, 

but some males mature in their first year 

and some females do not mature until 

their third year (Daniels and Moyle 

1983, p.650). 

Estimates of splittail fecundity have 

shown high variability in numbers of 

eggs produced. Caywood (1974, p. 4015) 

found a mean of 165 eggs per mm of SL 

of fish sampled and reported a 

maximum of 100,800 eggs in one 

female. Feyrer and Baxter (1998, p. 123) 

found a mean of 261 eggs per mm of SL 

and a fecundity range of 28,416 to 

168,196 eggs. Bailey et al. (1999) 

examined fish held for a considerable 

time in captivity and found that 

fecundity ranged from 24,753 to 72,314 

eggs per female, which most closely 

agrees with Caywood’s (1974, p. 4015) 

observations. 

Splittail are benthic (feeding in the 

bottom of the water column) foragers 

that mainly feed in the daytime. 

Composition of splittail gut contents has 

revealed that they feed almost 

exclusively on aquatic invertebrates 

with chironomid larvae making up the 

largest portion of the diet in all areas 

except the Petaluma River where 

copepods make up the largest portion of 

the diet (Feyrer et al. 2007a, p. 1398). 

Until the 1980’s, opossum or mysid 

shrimp (Neomysis mercedis), made up a 

large portion of the diet along with 

amphipods and harpacticoid copepods 

(Moyle et al. 2004, p. 14). Introductions 

of the Asiatic clam (Corbicula fluminea) 

in 1945 and more importantly the 

overbite clam (Corbula amurensis) first 

recorded from the estuary in 1986) were 

followed by a sharp decline in shrimp 

abundance that started in 1987 and 

continued through 1999 (Feyrer et al. 

2003, p. 283). Splittail have shifted their 

diet from prey items such as mysid 

shrimp to a diet increasingly focused on 

bi-valves, in particular the overbite 

clam. Opossum shrimp in splittail gut 

contents were reduced from 24 percent 

(historically) to 2 percent by 2003 

(Feyrer et al. 2003, pp. 277-288; 

Kratville 2010, pers comm.). In the 

Estuary, clams, crustaceans, insect 

larvae, and other invertebrates also are 

found in the adult diet. Larvae feed 

mainly on plankton composed of small 


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animals (zooplankton), moving to small 

crustaceans and insect larvae as body 

size increases (Kurth and Nobriga 2001, 

EIP newsletter vol. 14, num.3, p. 41). 

Splittail populations fluctuate 

annually, depending on spawning 

success, which is positively wellcorrelated with freshwater outflow and 

the availability of shallow water habitat 

with submerged vegetation (Daniels and 

Moyle 1983; Sommer et al. 1997). 

Sexual maturity is typically reached by 

the end of their second year. Splittail 

are a migratory species that travel 

upstream into freshwater floodplain 

habitat to spawn. The onset of spawning 

is associated with rising water levels, 

increasing water temperatures, and 

increasing day length. Peak spawning 

occurs from February through May, 

although records of spawning exist for 

late January to early July (Wang 1986). 

One temporally stable cue for splittail is 

the timing of the vernal equinox (Feyrer 

2006, p. 221). Peak flow from the 

Central Valley enters the Estuary 

approximately at the same time as the 

vernal equinox (Feyrer 2006, p. 221) and 

these coinciding events commence 

splittail migration. In some years, most 

spawning may take place within a 

limited period of time. For instance, in 

1995, a year of high spawning activity, 

most splittail spawned over a short 

period in April (Moyle et al. 2004, p. 

16). Within each spawning season, older 

fish reproduce first, followed by 

younger individuals (Caywood 1974, p. 

50). 

Bailey (1994, p. 3) has documented 

that splittail eggs hatch in 3 to 5 days 

at 18.5° C, (65.3° F). Bailey (1994, p. 3) 

also found that at 5 to 7 days after 

hatching, the yolk sac is absorbed and 

the diet begins to include small rotifers. 

Splittail larvae remain in shallow, 

weedy areas close to spawning sites for 

10 to 14 days and move into deeper 

water as they mature and swimming 

ability increases (Sommer et al. 1997, 

pp. 961-976). When the flood waters 

recede juveniles typically leave the 

flooded areas and move downstream in 

May, June, and July to rear in estuarine 

marshes (Moyle et al. 2004, p. 17). 

Splittail can be easily identified at 20 to 

25 mm (0.8 to 1.0 in) total length (TL) 

and become fairly active swimmers at 

this time (Moyle et al. 2004, p. 17). 

Abundance 

History of abundance models and 

evaluations 

An estimate of splittail abundance has 

never been performed; however, survey 

data have been used to construct indices 

of abundance that have been used in the 

past to assess population trends 

(Sommer et al. 2007, p 29; Moyle et al. 

2004, p 7). In general, the applicability 

of survey data to a particular use arises 

from two factors: (1) How the data are 

collected; and (2) how the data are used 

to estimate or to index abundance. The 

key point with regard to the first factor 

is the degree to which the sample 

collected is representative of the 

sampled population. Gear type, 

configuration, and method of 

deployment all contribute to species, 

sizes, and life stages collected. Unequal 

vulnerability of different sizes of fish to 

a given sampling protocol results in 

systematic error in population 

estimation. Fish behavior, both between 

species and between life stages, also 

contributes to sampling error, as does 

habitat variation, because gear 

performance often differs among habitat 

types. The efficiency of open-water, or 

pelagic, sampling may be affected by 

physical factors such as flow velocity 

and turbidity, both in terms of gear 

performance and fish behavior. 

Splittail are a benthic (near-bottomdwelling) species, often occur in 

shallow edge habitat, and feed most 

actively in early morning (Moyle et al. 

2004, p 8; Moyle 2002, p 148). Splittail 

would not be expected to be collected 

efficiently in surveys that do not sample 

channel edges and bottom habitats 

effectively. Further, while combining 

data from the various surveys provides 

reasonably good coverage of the 

geographic range of splittail, individual 

surveys are often fairly limited in 

geographic scope. All surveys suffer 

from selection biases due to the type of 

gear deployed and the method of 

deployment (Ricker et al. 1975, pp 70- 

73; 92). None of the surveys used to 

construct the indices used to monitor 

the relative abundance of splittail was 

designed specifically to sample splittail, 

and each is limited in some manner in 

its ability to adequately represent 

splittail population trends. Therefore, 

the data collected do not represent a 

quantitative estimate of population size. 

The surveys and their limitations are 

described in the Service’s Notice of 

Remanded Determination of Status for 

the Sacramento Splittail (68 FR 55139). 

Sommer et al. (2007, pp 29-30) and 

Moyle et al. (2004, pp 8-13) also explain 

some of the important limitations of the 

surveys with respect to splittail. A chart 

summarizing the surveys and their 

limitations is provided below. 

TABLE 2. SUMMARY OF SPLITTAIL SAMPLING SURVEYS

Survey Brief Description Years Pros Cons 

CDFG Fall 

Mid— 

Water 

Trawl 

Designed to sample juvenile striped bass. 

100 sampling sites: 

San Pablo Bay in the west to Rio Vista on 

the lower Sacramento River 

and to Stockton on 

the San Joaquin River 

1967— 

present 

Catches all splittail 

size classes 

—Targets striped bass 

—Low adult catch rate 

—Sampling does not cover entire range 

—Does not sample benthos or shallow 

channel edges 

—Some years yield no splittail 

—Splittail are better able to see nets in 

recent years due to decreased turbidity 

San 

Francisco 

Bay Mid— 

Water 

Trawl and 

Otter Trawl 

Survey 

Samples west of the Delta 

seaward to south San Francisco Bay 

1980— 

present 

—Two types of sampling equipment 

and 

frequent sampling 

—Capture all size 

classes 

—Does not cover entire range 

—Non—specific; targets entire pelagic or 

benthic community 

—Incomplete data between 1989—1999 

—Splittail only caught in 5 percent or less 

of samples 


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TABLE 2. SUMMARY OF SPLITTAIL SAMPLING SURVEYS—Continued 

Survey Brief Description Years Pros Cons 

University of 

California 

at Davis 

(UC Davis) 

Suisun 

Marsh 

Otter Trawl 

Long—term study of the 

ecology of the entire fish community of the 

marsh at 21 sites and 9 sloughs 

1979— 

present 

Samples all size 

classes 

—Non—specific; targets entire 

fish community 

—Geographically limited 

—Larger fish less vulnerable to trawls 

Chipps Island 

Survey 

U.S. Fish and Wildlife Service conducts a 

sampling program for juvenile salmon in 

the deep water channel near Chipps 

Island, midwater trawl is pulled at the 

surface in 10 20—minute hauls per day during May and June 

1976— 

present 

—Samples well during high flow years 

—Good adult catch 

rates 

—Designed to sample juvenile salmonids 

—Geographically limited 

—Samples near—surface waters only 

—High turbidity in sampling area 

FWS Beach 

Seine 

Survey 

Samples 23 stations around Delta with 15— 

m beach seine in low velocity areas near 

shoreline 

1979— 

present 

—Broadest geographical coverage 

of all surveys 

—Good adult catches 

—Inconsistent from 1983—1992 

—Focused on out—migrating juvenile salmon 

——Low adult catch 

Salvage 

Operations 

The Central Valley Project (CVP) and State 

Water Project (SWP) operate fish screening facilities to divert fish away from the 

pump intakes into holding 

facilities where fish are counted, 

measured, and released. 

1979— 

present 

Highest number of 

splittail caught out 

of any survey for 

both adult and juvenile catches 

—Geographically localized—mainly reflective of San Joaquin River production 

—Catches are result of entrainment and 

often cause mortality 

Please refer to February 8, 1999, final 

listing rule (64 FR 5963) for a full 

discussion of methods used to estimate 

abundance in that rule. Please refer to 

the September 22, 2003, Notice of 

Remanded Determination of Status for 

the Sacramento Splittail (68 FR 55139) 

for a full discussion of methods used to 

estimate abundance for that document. 

In our January 6, 1994, proposed rule to 

list the Sacramento splittail as 

threatened (59 FR 862), we initially 

evaluated and analyzed splittail survey 

data using a method published by Meng 

and Moyle (1995, p. 541) in the 

Transactions of the American Fisheries 

Society. Meng and Moyle used a 

common data set from the years 1980– 

1992 to compare point estimates with 

the Mann-Whitney U-test. We used this 

same method during the development of 

our 1999 final listing rule (64 FR 5963, 

February 8, 1999), using abundance data 

provided and updated by CDFG, 

California Department of Water 

Resources (CDWR), and UC Davis. Using 

the aforementioned method, the 1999 

finding concluded that the splittail had 

declined by 62 percent in abundance 

over the last 15 years. 

In a document we published in the 

Federal Register on August 17, 2001 (66 

FR 43145), we requested public 

comments to assist us in reanalyzing our 

splittail abundance data. In that 

document, we presented a stratified 

Mann-Whitney U-test, which 

represented an improvement on what 

essentially remained a Meng and Moyle 

(1995, pp. 538-549) statistical approach. 

Following careful consideration of 

comments we received from numerous 

respondents to this document, including 

those provided through the peer review 

process, we concluded that the 

abundance indices and Multiple Linear 

Regression (MLR) model jointly 

developed and submitted by CDFG and 

U.S. Bureau of Reclamation (USBR) in 

2001 (hereafter referred to as the CDFG/ 

USBR MLR Model) provided the best 

scientific data (method) available for 

statistically evaluating temporal trends 

of splittail abundance information. We 

used this CDFG/USBR MLR Model as 

the basis of our September 22, 2003, 

Notice of Remanded Determination of 

Status for the Sacramento Splittail (68 

FR 55139), instead of the original Meng 

and Moyle (1995, pp. 540-542) 

methodology. We input 20 discrete sets 

of age-specific abundance monitoring 

data into the model. These data sets 

were obtained from the surveys 

described in Table 2 above. Running the 

model in a ‘‘worst case scenario’’ (alpha 

< 0.2 significance), we found nine 

significant downward-trending data sets 

and two significant upward-trending 

data sets, and we concluded that the 

population was in decline. 

Current evaluation of models and 

abundance 

In light of uncertainties in data for 

estimating splittail population 

abundance, alternative approaches for 

understanding population behavior and 

regulation have been developed. One 

such approach is the life history 

simulation model developed by T. C. 

Foin wherein splittail population 

characteristics can be explored and 

compared with known field biology to 

infer important life stage survival 

probabilities and potential conservation 

strategies (Moyle et al., 2004, pp. 32-37). 

Life history simulation models can be 

parameterized to the extent possible 

using relevant field/survey information, 

and then used in a series of ‘‘what if’’ 

exercises to explore simulated 

population dynamics under selected 

conditions. Using the model in this way 

for sensitivity analysis allows the 

experimenter to discern which life stage 

or life stage characteristic is crucial to 

long-term simulated survival, for 

example, or how often ‘‘sub-optimal’’ 

conditions must occur for the simulated 

population to be at risk for extinction. 

Such population viability analyses 

(PVAs) can form part of the basis for the 

Act’s listing decisions where sufficient 

life stage parameter estimates are wellknown (Shaffer 1981, pp. 131-133; 

Meffe and Carroll 1994, pp. 181-182). In 

the Estuary such a model was used to 

confirm field observations that flood 

plain dynamics and subsequent 

spawning response by splittail 

populations were critical to long-term 

population persistence in the absence of 

other exogenous drivers of splittail 

mortality (Moyle et al. 2004, pp. 32-27). 

In the present case of the Sacramento 

splittail, survey data appear sufficient to 


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point to supra-annual patterns of 

abundance (abundance changes over 

several or many years), but do not 

appear to support parsing into subannual or life-stage specific 

characterization of splittail population 

biology. Inaccuracies associated with 

intra-annual sampling and both relative 

and absolute gear inefficiencies make it 

very difficult to discern splittail 

population dynamics on a sub-annual 

basis. Life history traits of the splittail 

including their dependence on 

floodplain hydrology and seasonal 

flooding of riparian and floodplain 

lands make this species quite suited to 

exploration using population simulation 

approaches (Moyle et al., 2004,pp. 13- 

18, 32). 

The T. C. Foin splittail population 

simulation model (ST5) and related 

models have led to the following 

conclusions regarding Sacramento 

splittail population variability and 

longer-term population forecasts (Moyle 

et al., 2004, pp. 32-37). Splittail 

populations are highly variable and 

driven in large measure by rainfall and 

flooding; high variability in splittail 

populations can be modeled focusing on 

reproductive effort in those years with 

substantial added floodplain 

inundation. Simulations indicate that 

several dry years in succession are not 

likely to imperil splittail populations. 

Despite downward trends in simulated 

populations of splittail, this model 

indicates that low numbers of splittail 

reproducing along river margins can 

sustain the population through long 

drought periods and that a long series of 

dry years is unlikely to drive the 

splittail to extinction (Moyle et al. 2004, 

pp. 36-37). However, a large-scale, 

regional catastrophe combined with low 

population might lead to stochastic 

extinction. Adult mortality considered 

in isolation does not appear to be 

driving the population dynamics of 

splittail in the Estuary or in the models. 

Periodic (i.e., a minimum of every 7 

years) floodplain inundation seems 

essential to long-term population 

persistence. High variability is a 

fundamental property of splittail 

populations; therefore, little can be 

discerned regarding population status 

within a given survey year from annual 

indices of abundance. 

The splittail population model ST5 

and additional splittail models built in 

support of CALFED Science Program 

objectives use as a foundation biological 

characterization supplied by field 

biologists and species specialists (Moyle 

et al. 2004, pp.32-37). Noted in splittail 

life history is adaptation to ‘‘estuarine 

waters with fluctuating conditions’’ 

(Moyle 2002, p. 147). This includes the 

ability to respond to abrupt water level 

changes and the ability to utilize 

seasonally inundated floodplains for 

spawning. Sacramento splittail are 

highly fecund, with some large females 

reportedly able to produce over 100,000 

eggs (Moyle 2002, p. 148). As an 

iteroparous (producing offspring in 

successive cycles), moderately longlived (5 to 8 years) species with high 

reproductive potential, it is not 

surprising that splittail life history 

characteristics allow the species to 

persist even in the face of only 

moderately predictable conditions yearto-year. As long as favorable spawning 

conditions occur at a minimum of every 

7 years, populations can remain at 

relatively low levels and rebound when 

favorable spawning conditions occur 

(Moyle 2002, pp. 34-38). Recent survey 

records provided via Interagency 

Ecological Program (IEP) survey efforts 

for the Sacramento splittail have shown 

this pattern (Meng and Moyle 1995, pp. 

548; Sommer et al., 1997;DWR 2010c, p. 

16). This was demonstrated in 1995 

when populations retained a high 

reproductive capacity after a substantial 

decline following several years of 

drought (Sommer et al. 1997, p. 971)., 

Due to the deficiencies in the survey 

data discussed above, we are unable to 

discern a trend in adult abundance. The 

young-of-year splittail population 

experiences a natural fluctuation in 

numbers due to drought cycles in the 

region. 

Evaluation of Information Pertaining to 

the Five Threat Factors 

Section 4 of the Act (16 U.S.C. 1533) 

and implementing regulations (50 CFR 

part 424) set forth procedures for adding 

species to, removing species from, or 

reclassifying species on the Federal 

Lists of Endangered and Threatened 

Wildlife and Plants. Under section 

4(a)(1) of the Act, a species may be 

determined to be endangered or 

threatened based on any of the 

following five factors: 

(A) The present or threatened 

destruction, modification, or 

curtailment of its habitat or range; 

(B) Overutilization for commercial, 

recreational, scientific, or educational 

purposes; 

(C) Disease or predation; 

(D) The inadequacy of existing 

regulatory mechanisms; or 

(E) Other natural or manmade factors 

affecting its continued existence. 

In making this 12–month finding, 

information pertaining to the 

Sacramento splittail in relation to the 

five factors provided in section 4(a)(1) of 

the Act is discussed below. In making 

our 12–month finding on the petition 

we considered and evaluated the best 

available scientific and commercial 

information. 

In considering what factors might 

constitute threats to a species, we must 

look beyond the exposure of the species 

to a factor to evaluate whether the 

species may respond to the factor in a 

way that causes actual impacts to the 

species. If there is exposure to a factor 

and the species responds negatively, the 

factor may be a threat and we attempt 

to determine how significant a threat it 

is. The threat is significant if it drives, 

or contributes to, the risk of extinction 

of the species such that the species 

warrants listing as endangered or 

threatened as those terms are defined in 

the Act. 

Factor A. The present or threatened 

destruction, modification, or 

curtailment of its habitat or range 

Habitat Loss 

The Bay Institute has estimated that 

intertidal wetlands in the Delta have 

been diked and leveed so extensively 

that approximately 95 percent of the 

141, 640 hectares (ha)(350, 000 

acres(ac)) of tidal wetlands that existed 

in 1850 are gone (The Bay Institute 

1998, ch. 4, p. 17), and that 90 percent 

of the riparian forest and riparian 

wetlands of the Sacramento Valley have 

been cleared, filled, or otherwise 

eliminated. Diking, dredging, filling of 

wetlands, and reduction of freshwater 

flows through more than half of the 

rivers, distributary sloughs, and the 

Estuary for irrigated agriculture and 

urban use have widely reduced fish 

habitat and resulted in extensive fish 

losses (Moyle et al. 1995, p. 166-168). 

San Joaquin River flows have been 

degraded to a higher extent than flows 

in the Sacramento River (Feyrer et.al. 

2007a, p. 1396).Limited spawning can 

take place in river and stream habitats, 

but the persistence of the splittail is 

now dependent on seasonal floodplains 

including the Yolo and Sutter bypasses 

and Cosumnes River. 

Loss and degradation of shallow, 

near-shore habitat is a historic, current 

and future threat to the splittail. 

Riparian and natural bank habitats are 

features that historically provided 

splittail with spawning substrate, 

organic material, food supply, and cover 

from predators. Vast stretches of the 

Sacramento and San Joaquin Rivers, 

their tributaries, and distributary 

sloughs in the Delta have been 

channelized and much of the shallow 

nearshore habitat has been leveed and 

riprapped. The prevention of channel 

meandering by the placement of riprap 

is causing a continual loss of low 


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velocity shallow water breeding habitat 

(Feyrer et. al. 2005, p. 167). 

Beneficial Actions Offsetting Adverse 

Effects 

While habitat loss has occurred, a 

number of habitat restoration actions are 

also being undertaken. 

CALFED Habitat Restoration:The 

CALFED Bay Delta Program (CALFED) 

leadership has recently transitioned 

from the CALFED Bay Delta Authority 

to the Bay Delta Stewardship Council. 

This changed the name and governing 

structure of the program, but did not 

change the 2000 Record of Decision 

(ROD) for CALFED or any goals or 

objectives of the CALFED plan. 

The CALFED plan exists as a multipurpose (water supply, flood protection, 

and conservation) program with 

significant ecosystem restoration and 

enhancement elements, The program 

brought together more than 20 State and 

Federal agencies to develop a long-term 

comprehensive plan to restore 

ecological health and improve water 

management for all beneficial uses of 

the Bay-Delta system. The plan 

specifically addresses ecosystem 

quality, water quality, water supply, and 

levee system integrity. 

The CALFED Ecosystem Restoration 

Program (ERP) presented a strategic plan 

for implementing an ecosystem-based 

approach for achieving conservation 

targets (CALFED 2000a, pp. 1-3). The 

CDFG is the primary implementing 

agency for the ERP. The goal of ERP to 

improve the conditions for the splittail 

will remain whether the splittail is 

listed as threatened or endangered or 

not listed. In the CALFED process, the 

splittail’s status could be adversely 

affected by program elements to: 

Increase water storage in the Central 

Valley upstream of the Delta; modify 

Delta hydrologic patterns to convey 

additional water south, and upgrade and 

maintain Delta levees. However, as 

noted previously CALFED has an 

explicit goal to balance the water supply 

program elements with the restoration 

of the Bay-Delta and tributary 

ecosystems and recovery of the splittail 

and other species. Because achieving 

the diverse goals of the program is 

iterative and subject to annual funding 

by diverse agencies, CALFED has 

committed to maintaining balanced 

implementation of the program within 

an adaptive management framework. 

Within this framework of 

implementation, it is intended that the 

storage, conveyance, and levee program 

elements would only be implemented in 

such a way that the splittail’s status 

would be maintained and eventually 

improved. 

CALFED has identified 29 specific 

species enhancement conservation 

measures for splittail (CALFED 2000b. 

There are more than 150 projects that 

benefit the splittail or its habitat in the 

plan and more than half of those have 

been completed to date (2010 ERP 

database spreadsheets). Key 

accomplishments of the ERP include 

investments in fish screens, temperature 

control, fish passage and habitat 

protection and restoration (CALFED 

2007, p. 2). 

Additional projects such as Cosumnes 

River floodplain restoration and Liberty 

Island restoration are ongoing. Major 

obstacles to the completion of these 

projects , especially the acquisition of 

land have been overcome. Although 

discussion of all 150 programs currently 

benefitting splittail will not be practical 

in this document, we have highlighted 

several projects that have played an 

important role in offsetting threats to the 

splittail into the foreseeable future. 

Liberty Island lies at the southern end 

of the Yolo bypass. After years of active 

agricultural production on Liberty 

island, the levees were breeched in 1997 

and the island was allowed to return to 

a more natural state (Wilder 2010, 

PowerPoint s. 4). The CALFED program 

funded the purchase of the island in 

1999 by granting money to the Trust for 

Public Lands for the acquisition of the 

island (Wilder 2010, PowerPoint s. 5). 

Splittail are utilizing the flooded island 

and have been documented in a number 

of surveys including the beach seine 

survey in which they were the most 

abundant fish caught from August 2002 

to July 2003 (Wilder 2010, PowerPoint 

s. 22; Liberty Island Monitoring Program 

2005, p. 37; Marshall et al. 2006, p. 1). 

Splittail are utilizing the southern 

portion of the island more than the 

northern portion of the island (Webb 

2009, p. 1). In 2007, the Delta Juvenile 

Fish Monitoring program was awarded 

$2.5 million from the CALFED program 

for the Breach III study at Liberty Island. 

Work has been initiated and results will 

assist agencies in understanding the 

ecological system and developing 

recommendations for future restoration 

projects (Hrodey 2008). There are 

currently plans to remove additional 

levees by Wildlands Corporation which 

has acquired a portion of Liberty Island 

that it plans to return to natural 

floodplain habitat. Wildlands 

Corporation’s actions may be approved 

and initiated within the next year, but 

cannot be counted as a conservation 

measures at this time (Roper 2010, pers. 

comm.). When these actions are 

implemented, they are expected to 

further increase splittail spawning 

grounds on Liberty Island. 

Restoration efforts have also been 

undertaken at the Cosumnes River 

Preserve (hereafter referred to as the 

Preserve) under management of the 

Bureau of Land Management (BLM), 

The Nature Conservancy, and a number 

of other agencies and private 

organizations. Restoration activities that 

benefit splittail include riparian 

enhancement and intentional breaching 

of levees to restore floodplain function. 

The Preserve opened 81 ha (200 acres) 

to flooding in October of 1995 by 

removing a 15.2 m (50 ft) section in a 

levee along the Cosumnes River 

(Cosumnes River Preserve Management 

Plan March 2008). Following floods in 

1995 and 1997, the decision was made 

by the Preserve in coordination with the 

U.S. Army Corps of Engineers to not 

repair the portions of the levees 

breeched by the floods thus allowing for 

a more natural flood regime (Cosumnes 

River Preserve Management Plan March 

2008, ch. 2 pp. 6-7). Levees have been 

breached in a total of five locations to 

allow flooding of a variety of habitats 

including marshes and sloughs (Crain et 

al. 2004, p. 126). Restoration is ongoing 

and splittail are likely to benefit from 

these efforts, as the area has also been 

described as among the most important 

floodplain habitats still available to the 

species (Moyle et al. 2004, p. 17). 

Splittail used the Preserve floodplains 

during both years of a study conducted 

in 1999 and 2001 (Crain et al. 2004, p. 

140). Splittail larvae were present in 

2001 when only a small portion of the 

floodplain in the study area was 

inundated. Although spawning was not 

observed, it is presumed to have 

occurred in the last week of March or 

the first week of April since larvae 

appeared shortly after. Larvae moved off 

the floodplain during cold-water flow 

pulses in the last week of April and the 

first week of May (Crain et al. 2004, p. 

140). 

Other Habitat Restoration Projects: 

The Yolo Bypass Wildlife Area 

(Wildlife Area), located within the Yolo 

Bypass, currently encompasses 6,787 ha 

(16,770 ac). This area has increased 

substantially since CDFG’s original 

acquisition of approximately 1180 ha 

(2,917 ac) in 1991. The added area has 

allowed restoration actions that benefit 

splittail spawning efforts to proceed by 

creating new seasonal floodplains (Yolo 

Bypass Wildlife Management Land 

Management Plan, 2008, ch.1). 

In early 2002, the Sacramento River 

National Wildlife Refuge Complex 

(SRNWRC) began implementation of a 

Plan for Proposed Restoration Activities 

on the Sacramento River National 

Wildlife Refuge. The restoration 


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activities have resulted in the 

reestablishment or enhancement of 1707 

ha (4, 218 ac) of the SRNWRC (Silveria 

2010, pers. comm.). This restoration is 

expected to benefit splittail through 

improvement of vegetative conditions 

on floodplains. Restoration and 

enhancement involve the removal of 

crops, orchards, and related 

infrastructure (pumping units, barns, 

sheds, etc.) followed by replacement 

with native vegetation appropriate to 

each site. In addition to restoration 

efforts, levees have been removed at the 

Flynn and Rio Vista units and a levee 

has been breached at the La Barracna 

unit (Silveira 2010, pers. comm.). These 

efforts allow for a more natural 

floodplain regime and increase native 

vegetation that benefits splittail. 

Summary of Factor A 

Rip-rapping of river and stream 

habitat constitutes a potential threat to 

the Sacramento splittail. The 

implementation and magnitude of the 

CALFED, Central Valley Project 

Improvement Act (CVPIA) (discussed 

under Factor D) and other habitat 

restoration activities, which focus on 

the restoration of habitats that directly 

and indirectly benefit splittail go far 

beyond any foreseeable future habitat 

losses. The overall effect of habitat 

restoration activities is also expected to 

continue to be beneficial for splittail 

into the future. 

Efforts undertaken in the past decade 

have benefited the species by restoring 

its habitat. There is presently sufficient 

habitat to maintain the species, and 

inundation frequency and duration in 

key areas is sufficient to provide 

spawning to maintain the species. 

Furthermore, habitat restoration 

activities that have been completed are 

currently being implemented and those 

planned for the future are adding to the 

available habitat for the species. 

We conclude that the best scientific 

and commercial information available 

indicates that the Sacramento splittail is 

not now, or in the foreseeable future, 

threatened by the present or threatened 

destruction, modification, or 

curtailment of its habitat or range. 

Factor B. Overutilization for 

commercial, recreational, scientific, or 

educational purposes 

Recreational Fishing 

Splittail were historically abundant 

enough to be harvested by Native 

Americans and commercial fisheries, 

although no studies on abundance were 

begun until 1963 (Moyle et. al. 2004, p. 

7). Today, splittail are harvested for bait 

by the sport fishery and as a food 

source, but take is limited by the 

California Fish and Gave Commission to 

two individuals per day as further 

discussed under Factor D. The largest 

splittail may be the first to engage in the 

spawning migration (Caywood 1974; 

Moyle et al. 2004, p. 15). The earlyseason fishery potentially targets and 

removes females with high reproductive 

potential. The effect of this fishery in 

the Sacramento River may be relatively 

greater in dry years, when splittail 

spawning is largely confined to river 

margins where fishing effort is 

concentrated. Splittail is known to be an 

effective bait fish for striped bass and is 

commonly caught by anglers for this use 

(Moyle et al. 2004, p. 19). The splittail 

fishery is the smallest fishery targeted in 

the CDFG angler survey (SFRA 2008). At 

present, there is no evidence of any 

trend in the available data suggesting 

that larger fish are being 

disproportionally removed from the 

population or that the size structure of 

the splittail population has been altered 

by this small fishery. There is no 

indication that the intensity of fishing or 

bag limits will increase in the future. 

Scientific Collection 

Monitoring surveys conducted 

throughout the year, including the Fall 

Mid-Winter Trawl (FMWT), Summer 

Tow Net Survey (TNS), Beach Seine 

Survey, Chipps Island Trawl, Suisun 

Marsh Survey, and Spring Kodiak Trawl 

Survey (SKT) capture and record adult 

and juvenile splittail. These surveys 

sometimes result in the unintentional 

mortality of some individuals. Data from 

the last 12 years of surveys conducted 

by the Service are in Table 3. 

TABLE 3. TAKE (COLLECTION AND RELEASE) AND MORTALITY BY U. S. FISH AND WILDLIFE SERVICE SURVEYS FOR 1999- 

2010. 

Survey Number Taken Mortality 

Chipps Island 6887 339 

Mossdale 146,854 1,856 

Service Beach Seine 207,137 2,394 

An average of 383 splittail are killed 

every year in the course of conducting 

Service surveys. Adult splittail spawn 

up to 100,000 eggs per individual per 

fecundity event and the loss of a few 

thousand individuals from scientific 

collection over a 10 year period is not 

expected to have a significant effect at 

the population level. We have no 

information to indicate use of the 

species for other commercial, 

recreational, scientific, or educational 

purposes. 

Summary of Factor B 

The new CDFG regulation enacted in 

March 2010 limiting take of splittail to 

two individuals per day has eliminated 

any potential threat that fisheries may 

have posed. The best available scientific 

and commercial data shows that this 

current level of take does not adversely 

affect the splittail population or that this 

level of mortality will increase in the 

future. 

Annual Service surveys result in an 

average of 383 splittail being killed each 

year. However, due to the high 

fecundity rate of splittail, the average 

yearly loss has not had a significant 

effect at the population level and the 

information obtain from the surveys is 

being used to monitor the splittail 

populations. 

We conclude that the best scientific 

and commercial information available 

indicates that the Sacramento splittail is 

not now, or in the foreseeable future, 

threatened by the overutilization for 

commercial, recreational, scientific or 

educational. 

Factor C. Disease or predation 

Disease 

The south Delta is fed by water 

coming from the San Joaquin River, 

where pesticides (e.g., chlorpyrifos, 

carbofuran, and diazinon), salts (e.g., 

sodium sulfates), trace elements (boron 

and selenium), and high levels of total 

dissolved solids are prevalent due to 

agricultural runoff (64 FR 5963, 

February 8, 1999). Of specific concern 

are the threats posed by heavy metals 

such as mercury, selenium, and 

pesticides. There is some possibility 


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that disease in splittail could be a 

function of increased contaminant 

loading and subsequent immune system 

depression. Disease related to 

contaminants is further discussed under 

Factor E below. 

Splittail naturally carry parasites like 

most fish, but the effects of parasites 

such as anchor worms manifest 

primarily when fish are already stressed 

from other causes such as spawning 

(Moyle et al. 2004, p. 19). Post-spawn 

adult splittail and male fish in 

particular, are substantially weakened 

when migrating back to the estuary. We 

found no information to indicate disease 

is a threat to the species. We therefore, 

conclude that the best scientific and 

commercial information available 

indicates that disease does not 

constitute a significant threat to splittail 

now or in the foreseeable future. 

Predation 

Predators of splittail include striped 

bass (Morone saxatilis), largemouth bass 

(Micropterus salmoides), and other 

native and non-native piscivores (Moyle 

2004, p. 18). In the past, we have 

considered threats of predation to be 

minor because striped bass had 

coexisted with splittail for decades and 

because CDFG stopped hatchery rearing 

and release of striped bass in 2001 (59 

FR 862, 64 FR 5963). Striped bass 

populations have undergone a 

substantial decline starting in the mid 

1980’s shortly after the overbite clam 

was introduced (Kimmerer et al. 2008, 

p. 84). Furthermore, they are just one 

example of the many species impacted 

by the larger Pelagic Organism Decline 

(POD) that began in the beginning of the 

new millennium (Ballard et al. 2009, p. 

1). Changes in the foodweb, toxic 

effects, export pumping and lowered 

habitat quality are all potential causes of 

the POD. If non-native striped bass 

populations increase, all size classes of 

splittail could be under greater threat of 

predation. However, as stated above, 

striped bass populations are in decline. 

In contrast to striped bass, the 

abundance of largemouth bass has 

increased substantially in the Delta in 

the past three decades (Brown and 

Michniuk 2007, p. 195; Nobriga 2009, p. 

112). The evidence suggests that 

largemouth bass have taken advantage 

of the proliferation of submerged 

vegetation throughout much of the Delta 

and the increasing water clarity that has 

come with it (Brown and Michniuk 

2007, p. 195). Although, largemouth 

bass are a greater source of splittail 

mortality than they were several 

decades ago, populations of largemouth 

bass in critical rearing areas are low and 

predation levels appear to be minor. 

Also, the high reproductive nature of 

splittail life history has enabled it to 

overcome the predation that is occurring 

from largemouth bass. 

Based on a review of the best 

scientific and commercial information 

available, we find that predation is not 

a significant threat to the splittail now 

or in the foreseeable future. 

Summary of Factor C 

We found that disease occurs at low 

levels in the population, but does not 

constitute a significant threat to the 

species. Predation by striped bass 

appears to be unchanged from past 

levels. It is currently not a significant 

threat to splittail populations and is not 

expected to increase in the future. 

Largemouth bass populations have 

increased in the Estuary in the past 

three decades, but populations of 

largemouth bass in critical rearing areas 

are low, and therefore predation levels 

appear to be minor. We conclude that 

the best scientific and commercial 

information available indicates that the 

Sacramento splittail is not now, or in 

the foreseeable future, threatened by 

disease or predation. 

Factor D. The inadequacy of existing 

regulatory mechanisms 

State Laws 

The Porter Cologne Water Quality 

Control Act establishes the State Water 

Resources Control Board (SWRCB) and 

nine Regional Water Quality Control 

Boards that are responsible for the 

regulation of activities and factors that 

could degrade California water quality 

and for the allocation of surface water 

rights (California Water Code Division 

7). In 1995, the SWRCB developed the 

Bay-Delta Water Quality Control Plan to 

establish water quality objectives for the 

Delta. This plan is implemented by 

Water Rights Decision 1641, which 

imposes flow and water quality 

standards on State and federal water 

export facilities to assure protection of 

beneficial uses in the Delta (FWS 2008, 

pp. 21-27). The various flow objectives 

and export restraints are designed, in 

part, to protect fisheries. Objectives that 

benefit splittail by increasing water 

availability and in turn available habitat 

include specific outflow requirements 

throughout the year, specific water 

export restraints in the spring, and 

water export limits based on a 

percentage of estuary inflow throughout 

the year. The water quality objectives 

are designed to protect agricultural, 

municipal, industrial, and fishery uses; 

they vary throughout the year and by 

the wetness of the year. 

Assembly Bill (AB) 360, the State 

Delta Flood Protection Act, has a 

primary purpose of strengthening Delta 

levees with various ‘‘hard’‘‘ structures, 

including rip-rap. Habitat restoration 

components of AB 360, considered 

mitigation for concurrent State projects’ 

impacts to aquatic and terrestrial 

ecosystems in the Delta, require 

improvement rather than a strict 

mitigation approach which results in an 

increased habitat benefit and a net 

increase in habitat. 

The State Senate Bill (SB) 1086- 

funded Sacramento River Conservation 

Area Forum is an interagency group 

chartered to promote and guide 

protection and enhancement of riparian 

resources and fluvial function along the 

reach of the lower Sacramento River 

between Red Bluff and Colusa. The 

Nature Conservancy, working with the 

Sacramento River Conservation Area 

and local stakeholders, has restored 

more than 1214 ha (3,000 ac) to date 

(The Nature Conservancy Website, 

Sacramento River, 2010). These 

restoration efforts have replaced 

farmland with potential splittail 

spawning and rearing habitat. 

California Environmental Quality Act 

(CEQA) 

The California Environmental Quality 

Act (CEQA) requires review of any 

project that is undertaken, funded, or 

permitted by the State of California or 

a local government agency. If significant 

effects are identified, the lead agency 

has the option of requiring mitigation 

through changes in the project or to 

decide that overriding considerations 

make mitigation infeasible (CEQA Sec. 

21002). In the latter case, projects may 

be approved that cause significant 

environmental damage, such as 

destruction of listed endangered species 

or their habitat. Protection of listed 

species through CEQA is, therefore, 

dependent on the discretion of the lead 

agency. The CEQA review process 

ensures that a full environmental review 

is undertaken prior to the permitting of 

any project within splittail habitat. 

Streambed Alteration 

Section 1600 of the California Fish 

and Game Code authorizes CDFG to 

regulate streambed alteration. The CDFG 

must be notified of and approve any 

work that substantially diverts, alters, or 

obstructs the natural flow or 

substantially changes the bed, channel, 

or banks of any river, stream or lake. If 

an existing fish or wildlife resource 

including the splittail may be 

substantially adversely affected by a 

project, CDFG must submit proposals to 

protect the species to the person 


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proposing to alter the streambed within 

60 days (Section 1602 of the California 

Fish and Game Code). 

Federal Laws 

National Environmental Policy Act: 

The National Environmental Policy Act 

(NEPA) (42 U.S.C. 4321 et seq.) requires 

all federal agencies to formally 

document, consider, and publicly 

disclose the environmental impacts of 

major federal actions and management 

decisions significantly affecting the 

human environment. NEPA 

documentation is provided in an 

environmental impact statement, an 

environmental assessment, or a 

categorical exclusion, and may be 

subject to administrative or judicial 

appeal. However, the Federal agency is 

not required to select an alternative 

having the least significant 

environmental impacts, and may select 

an action that will adversely affect 

sensitive species provided that these 

effects are known and identified in a 

NEPA document. Therefore, we do not 

consider the NEPA process in itself to 

be a regulatory mechanism that is 

certain to provide significant protection 

for the splittail. 

Central Valley Project Improvement 

Act:The Central Valley Project 

Improvement Act (CVPIA) (Public Law 

102-575) signed October 30, 1992, 

amends previous authorizations of the 

Central Valley Project (16 U.S.C 695d695j) to include fish and wildlife 

protection, restoration, and mitigation 

as project purposes having equal 

priority with irrigation and domestic 

water supply, and fish and wildlife 

enhancement having equal priority with 

power generation (Public Law 102-575, 

October 30, 1992). 

Clean Water Act: The Clean Water Act 

(33 U.S.C. 1251 et seq.), established in 

1977, is the primary federal law in the 

United States governing water pollution. 

The Environmental Protection Agency 

(EPA) which is responsible for 

administering the Clean Water Act has 

given the responsibility of issuing a ‘‘303 

list’’ (impaired water body list) to the 

respective Regional Water Quality 

Control Board that has jurisdiction over 

the particular water bodies. Water 

bodies that do not meet applicable water 

quality standards are placed on the 

section 303(d) list of impaired water 

bodies and the State is required to 

develop a Total Maximum Daily Load 

Limit for the water body (TMDL). A 

TMDL is a calculation of the maximum 

amount of a pollutant that a water body 

can receive and still meet water quality 

standards. 

San Joaquin Drain TMDL for Selenium 

As discussed under Factor E, 

selenium has negative effects on 

splittail. The following paragraph 

discusses the regulatory mechanism in 

place to reduce selenium input into the 

Estuary. Selenium total maximum daily 

load limits have been established by the 

California Regional Water Quality 

Control Board (Waste Discharge 

requirement 5-01-234 2001, p. 12) for 

selenium discharged from the San Luis 

Drain. Selenium load limits are 

determined by wet or dry year classes 

and limits were incrementally lowered 

from 2994 kilograms (kg) (6600 pounds 

(lbs)) in 1996-1997 to 1604 kg (3236 lbs) 

in 2007-2008 (United States Bureau of 

Reclamation (USBOR) 2009, pp. 1-5). 

Following the implementation of these 

limits, selenium discharged from San 

Luis Drain was reduced from 3175 kg 

(7000 lbs) in 1996-1997 to 791 kg (1744 

lbs) in 2007-2008 (USBOR 2009, pp. 1- 

5)). Although this will have limited 

immediate effect on reducing selenium 

concentrations in splittail habitat, it is a 

protective measure that will have a 

long-term effect on reducing selenium 

loads in the Estuary and reducing or 

stabilizing the threat of selenium to 

splittail in the future. 

Lack of Total Maximum Daily Limits on 

contaminants at Wastewater Treatment 

Plants 

As discussed under Factor E, 

ammonia has negative effects on 

splittail. The following paragraph 

discusses the lack of regulatory 

mechanism acting to reduce ammonia 

input into the Estuary. The Sacramento 

Regional Wastewater Treatment Plant 

SRWTP is responsible for 90 percent of 

the total ammonia load released into the 

Delta. Monthly loads of ammonia from 

the SRWTP released into the 

Sacramento River doubled from 1985 to 

2005. Approximately 598 million liters 

(158 million gallons) per day were 

discharged from the SRWTP from 2001 

to 2005 (Jasby et al. 2008, p. 15). 

There are currently no regulations or 

limits on the amount of ammonia being 

discharged by waste water treatment 

plants that discharge into the Delta. The 

lack of Clean Water Act mechanisms 

limiting ammonia discharged from these 

plants constitutes a low magnitude 

threat to the splittail population. 

However, the EPA is currently updating 

freshwater ammonia criteria on 

ammonia discharged from the SRWTP 

(EPA 2009, pp. 1-46). On December 30, 

2009 (74 FR 69086), the EPA announced 

the availability of draft national 

recommended water quality criteria for 

ammonia for the protection of aquatic 

life entitled, ‘‘Draft 2009 Update Aquatic 

Life Ambient Water Quality Criteria for 

Ammonia—Freshwater.’’ The EPA 

accepted public comments on that draft 

document until April 1, 2010 (75 FR 

8698, February 25, 2010). The EPA is 

currently reviewing the comments and 

expects to begin enforcement of the 

criteria within 12 months. Ammonia 

and its detrimental effects on the 

splittail population are discussed under 

the contaminants section under Factor 

E. 

California Fish and Game Commission 

Take Limit 

The State of California Fish and Game 

Commission reduced a potential threat 

to splittail on March 1, 2010, when a 

new harvest limit on splittail was 

enacted through the addition of section 

5.70 to Title 14 of the California Code 

of Regulations (CDFG2010, p. 1). CDFG 

now limits the take of splittail species 

to two individuals per person per day. 

Secondary data collected during creel 

surveys for salmon and striped bass 

suggest that in the past, a total catch of 

hundreds of adult fish may have been 

caught on a daily basis (Moyle et. al. 

2004, pp. 6-13). The creel limit has 

reduced the impact of fishing on 

splittail. 

Summary of Factor D 

Federal and State regulations 

described above provide protection for 

the splittail and its habitat by limiting 

adverse affects from new projects, 

restoring habitat and limiting 

contaminants discharged into the 

Estuary. We acknowledge however that 

steps are currently being taken by the 

California Central Valley Regional Water 

Quality Control Board to enact new 

revised criteria on the ammonia that is 

discharged from the SRWTP. Ammonia 

may be affecting individuals within the 

population as discussed under Factor E, 

but we have no evidence that the 

current lack of regulatory mechanisms 

limiting ammonia discharges are having 

a significant population level effect on 

the splittail. 

We conclude that the best scientific 

and commercial information available 

indicates that the Sacramento splittail is 

not now, or in the foreseeable future, 

threatened by inadequate regulatory 

mechanisms. 

Factor E. Other natural or manmade 

factors affecting its continued existence 

We have identified the risk of water 

export facilities, agricultural and power 

plant diversions, poor water quality, 

environmental contaminants, climate 

change and introduced species as 


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potential threats to the Sacramento 

splittail. 

Water Export Facilities 

The Central Valley Project (CVP) was 

devised to tame the flood waters of the 

Sacramento River and provide irrigation 

water for the Central Valley of 

California. The project today includes 

20 dams, 800 km (500 mi) of aqueducts 

and up to 8.6 kilometers cubed (km·3) 

(7 million acre-feet (maf)) of water 

exported annually for agriculture, 

wildlife and urban uses (USBR Central 

Valley Project, 2009). The CVP’s Jones 

Pumping Plant consists of five pumps 

with a permitted diversion capacity of 

130 cubic meters per second (cms) (4, 

600 cubic feet per second (cfs)). The 

pumping plant raises water into the 

Delta-Mendota Canal, which supplies 

water to much of the San Joaquin 

Valley. This intricate system of water 

diversion and storage has changed the 

historical hydrological features of the 

watershed systems and affected the 

many species that are dependent on 

them including the splittail. Reservoir 

and flood control operations 

inadvertently drain shallow water 

spawning habitat along river corridors 

and exacerbate stranding of splittail. 

Operations of Shasta and Trinity Dams 

and water diversions including the 

Tehama-Colusa, Corning, and Glenn 

Colusa canals, and the Red Bluff 

diversion dam further reduce instream 

flows. These reductions in water flow 

have resulted in the elimination of large 

tracts of spawning habitat for the 

splittail. Furthermore, dams may have 

reduced the distribution of the splittail 

by restricting movement to potential 

spawning grounds and creating 

migration obstacles. These dams and 

diversions have altered and eliminated 

habitat for splittail, and have on-going 

affects. 

The State Water Project (SWP) 

consists of a network of dams, 

reservoirs, canals and diversion 

facilities. Oroville Dam, on the Feather 

River, and Lake Oreville, have a 

maximum operating storage of 3,537,580 

acre-feet. The Banks Pumping Plant has 

a capacity of 291 cms (10,300 cfs), 

which is effectively limited by 

regulation to 203 cms (7,180 cfs). Water 

is conveyed via the Old and Middle 

River channels, resulting in a net (over 

a tidal cycle or tidal cycles) flow 

towards the pumping plants. When 

combined State and Federal water 

exports exceed San Joaquin River 

inflow, the additional water is drawn 

from the Sacramento River through the 

Delta Cross Channel, Georgiana Slough 

and Three-Mile Slough. Combined flow 

in Old and Middle Rivers is referred to 

as ‘‘OMR’’ flows while flow in the lower 

San Joaquin River is referred to as 

‘‘QWEST.’’ 

Four major water diversion facilities 

exported between 4.85 and 8.7 km3

(3.93 and 7.05 maf per year from the 

Delta during the years 1995 through 

2005 (Kimmerer and Nobriga 2008, p 2). 

Of these, the State and Federal facilities 

exported between 4.7 and 8.4 km3 (3.81 

and 6.81 maf) averaging 7 km3 (5.7 maf) 

every year (DWR 2010b, p. 10). The 

Barker Slough Pumping Plant, with a 

capacity of 175 cfs, diverts water from 

the Barker Slough, south of the city of 

Dixon, into the North Bay Aqueduct for 

delivery to Napa and Solano Counties. 

Each of the ten pump bays is screened 

to exclude fish one inch or larger. The 

Old River intake for the Contra Costa 

Water District is located on Old River 

near State Route 4. It has a positivebarrier fish screen and a pumping 

capacity of 250 cfs. It supplies water to 

Contra Costa Canal and to Los Vaqueros 

Resovoir for use in the East Bay area. 

The State Water Resources Control 

Board’s revised Decision 1641 

established an expert-to-inflow 

operational objective that allow the 

SWP and CVP pumps to divert from 35 

percent to 65 percent of the Delta inflow 

(SWRCB 2000). From July through 

January, the objective is 65 percent and 

from February through June, the 

objective is 35 percent, to protect fish 

and wildlife beneficial uses. The State 

Board also established additional water 

quality objectives that may further limit 

export pumping. Both pumping stations 

are equipped with their own fish 

collection facilities that divert fish into 

holding pens using louver-bypass 

systems to protect them from being 

killed in the pumps. 

Operation of the CVP and SWP water 

export facilities directly affects fish by 

entrainment into their diversion 

facilities. Splittail are relocated if 

entrained. These salvaged fish are then 

loaded onto tanker trucks and returned 

to the western Delta downstream (Aasen 

2009, p. 36). The movement of fish can 

result in mortality due to stress, moving 

procedures, or predation at locations 

where the fish are moved too. It is 

unknown how many fish survive this 

process, but mortalities could be high 

due to overcrowding in the tanks and 

predation at drop-off points. Splittail 

females migrating upstream to spawn 

are transported back downstream by 

truck if entrained and could potentially 

be forced to start their migration again. 

It is speculated that this could result in 

their removal from the spawning 

population for that year (Moyle et al. 

2004, p. 20). 

The fish collection facilities entrain a 

great number of splittail in 

hydrologically wet years (approximately 

5 million splittail in 1995, 3 million in 

1998 (Moyle et al. 2004, p 21), and 5.5 

million in 2006 (Aasen 2007, p. 49)) 

when spawning on the San Joaquin 

River and other floodplains results in a 

spike in population numbers. However, 

entrainment is low during 

hydrologically dry years when 

recruitment is low (1,300 splittail in 

2007 (Aasen 2008, p. 55) and about 

5,000 in 2008 (Aasen 2009, p. 43)). 

These figures show the high annual 

variability of reproductive success. 

Research has shown no evidence that 

south Delta water exports have a 

significant effect on splittail abundance 

although that does not mean that 

entrainment never affects the species 

(Sommer et al. 2007, p. 32). Most 

entrained individuals tend to be young 

of the year migrating to optimal 

downstream rearing habitat, although 

some migrating adults do get entrained 

(Sommer et al. 1997, p. 973). If 

distribution of age 0 individuals was to 

shift toward the export pumps in a dry 

year with low reproductive output, 

there could be substantial effect on that 

year-class (Sommer et al. 1997, p. 973). 

However, this would only constitute a 

potential threat to that particular year 

class and still does not represent a 

significant threat to the overall 

population since it would occur only 

during a dry year. The pumping 

facilities do not represent a significant 

threat to the splittail because loss of 

substantial number of fish tends to 

occur during wet years in which the 

species is experiencing a high 

reproductive output. 

Agricultural Diversions for Irrigation 

Fish including splittail can become 

entrained in agricultural water 

diversions. This entrainment can result 

in injury or mortality. The diversion of 

water flows by agricultural pumping can 

also alter natural flow regimes and 

impede migration. Screening of 

agricultural diversions has been a 

common practice in recent years in 

order to conserve and restore 

populations of anadromous fishes in the 

Central Valley of California. There are 

over 3,700 diversions on the Sacramento 

and San Joaquin Rivers and their 

tributaries, and the Sacramento-San 

Joaquin Delta and Suisun Marsh. Over 

2,300 of these diversions are located in 

the Sacramento-San Joaquin Delta, with 

over 350 in Suisun Marsh. Of these 

3,700 existing diversions, over 95 

percent are currently unscreened (CDFG 

2010). 


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Under both the CALFED Bay-Delta 

Program and the Central Valley Project 

Improvement Act there have been 

significant efforts to screen agricultural 

diversions in the Central Valley and the 

Sacramento-San Joaquin Delta, 

particularly the larger unscreened 

diversions over 4.24 cms (150 cfs) on 

the Sacramento River. Entrainment of 

splittail at diversions is reduced if fish 

screens are installed at diversions 

within splittail habitat areas. 

Currently, all of the unscreened 

diversions on the Sacramento River 

main stem over 4.24 cms (150 cfs) have 

been screened or are currently proposed 

to be screened. There are a number of 

large unscreened diversions over 4.24 

cms (150 cfs) on the San Joaquin River. 

Many of these larger diversions will be 

considered for screening as part of the 

San Joaquin River Restoration Program. 

The Sacramento-San Joaquin Delta 

region is the location of the majority of 

unscreened diversions, with most of 

these diversions under 1.41 cms (50 cfs) 

(Meier 2010, pers. comm.). 

CALFED’s Ecosystem Restoration 

Program includes a program to 

consolidate and screen the remaining 

small agricultural diversions in the 

Delta, and the Sacramento and San 

Joaquin rivers. The NOAA Fisheries 

Restoration Center has also begun to 

fund small fish screen projects in the 

Sacramento River within the range of 

the splittail. 

The amount of entrainment that may 

occur at the remaining unscreened 

diversions is not well-known, and 

efforts to determine the effect of 

entrainment on splittail have been 

limited. In July of 2001 and 2002, 

Nobriga et al. sampled fish entrained 

within a 61 cm (24 in) diameter pipe at 

the CDWR Horseshoe Bend Diversion 

facility (Nobriga et al. 2004, p. 1). They 

collected only one splittail during two 

sampling periods, finding entrainment 

to be exceptionally low (Nobriga et. al. 

2002, p. 35-44). 115, 000 m3 of water 

passing through an unscreened 

diversion was sampled over a 69 hour 

period (Nobriga et al. 2004, pp. 1-16). 

Another study at the Morrow Island 

Distribution System showed that the 

diversions there took 666 splittail 

young-of-the-year-individuals, but only 

nine individuals of age one or older 

(Enos 2010, p. 14). After sampling 2.3 

million m3 (81.2 million ft3) of water, it 

was concluded that entrainment of 

special status species including the 

splittail was exceptionally low (Enos 

2010, p. 17). In analyzing these results, 

it is helpful to compare this take to the 

5million to 6 million splittail that can 

be entrained at the south Delta water 

export pumps in a single year. Research 

has shown no evidence that south Delta 

water exports have a significant effect 

on splittail abundance (Sommer et al. 

2007, p. 32). Splittail adults can yield 

up to 100,000 eggs in a single spawning 

event, therefore the loss of thousands or 

even a million young-of-year is not 

expected to effect the longterm 

population viability of the species. 

Furthermore, splittail may not be as 

vulnerable to agricultural diversions as 

other fish species are because adult 

splittail migrate during winter to early 

spring when agricultural diversion 

operations are at a minimum. 

We do not consider entrainment by 

agricultural diversions to be a 

significant threat to splittail. 

Additionally, these effects from 

agricultural diversions are expected to 

decrease in the future as additional 

diversions continue to be screened. 

Power Plant Diversions 

Two power plants located near the 

confluence of the Sacramento and San 

Joaquin rivers pose an entrainment risk 

to splittail: the Contra Costa Power Plant 

and the Pittsburg Power Plant. The 

intakes for the cooling water pumps of 

these power plants are located in close 

proximity to splittail rearing habitat 

(Moyle et al. 2004, p. 20). The 

maximum combined non-consumptive 

intake of cooling water for the two 

facilities is 91.7 cms (3,240 cfs), which 

can exceed 10 percent of the total net 

outflow of the Sacramento and San 

Joaquin rivers. Thermal and chemical 

pollution in the forms of raised water 

temperature and chlorine discharges 

may also have a detrimental effect on 

splittail (USFWS 2008, pp. 173-174). 

However, power plant operations have 

been substantially reduced since the 

1970s, and the plants are now either 

kept offline, or are operating at very low 

levels, except as necessary to meet peak 

power needs. Due largely to this 

reduction in the operation of the power 

plants and their associated pumping for 

cool water, we do not consider the 

operation of these power plants to 

constitute a significant threat to the 

splittail population. We have no 

indications of future plans to use these 

pumps more frequently and therefore, 

do not consider these operations to be 

a threat in the future. 

Water Quality and Environmental 

Contaminants 

Although recent research funded by 

CALFED and carried out in a large part 

by UC Davis has shed some light on the 

dynamics and impacts of contaminants 

entering the Delta system, the overall 

effects of these contaminants on 

ecosystem restoration and species 

health are still poorly understood. All 

major rivers that are tributaries to the 

Estuary are exposed to large volumes of 

agricultural and industrial chemicals 

that are applied in the Central Valley 

watershed (Nichols et al. 1986, pp. 568- 

569), as well as chemicals originating in 

urban runoff that find their way into the 

rivers and Estuary. In addition, reflooding of the Sutter and Yolo Bypasses 

and the use of other flooded agricultural 

lands by splittail for spawning can 

result in agricultural-related chemical 

exposures. 

A majority of the Delta has been 

placed on the Clean Water Act’s 303d 

list of impaired waterbodies due to the 

documented presence of 

polychlorinated biphenyls (PCBs), 

organophosphate pesticides, other 

legacy pesticides, and some metals – 

particularly mercury (CVRWQCB 2006, 

pp. 5-11). These contaminants can have 

adverse effects on fish (i.e., splittail), but 

the magnitude of effects are dependent 

upon: The chemical form of the 

contaminant in question; the 

contaminant’s bioavailability under 

certain water quality parameters (i.e., 

hardness, pH, etc.); the nature of the 

response being measured in the fish 

(acute toxicity, bioaccumulation, 

reproduction, etc.); and the nature/ 

status of the individual fish (age, 

weight, health, etc.). 

All life stages of splittail are 

potentially exposed to varying amounts 

and mixtures of chemical contaminants 

in the Delta and associated water 

bodies. Acid mine drainage has been a 

serious environmental problem in the 

northern portion of the Sacramento 

River Basin (Alpers et al. 2000a, p.4; b, 

p. 5). Several streams are listed as 

impaired because of high concentrations 

of metals such as cadmium, copper, 

lead, and zinc. Metals concentrations in 

previous years have been toxic to fish in 

the upper Sacramento River near and 

downstream from Redding (Alpers et al. 

2000a, p 4; b, p. 5). Recent mitigation 

efforts at one of the more contaminated 

sites in the Spring Creek drainage near 

Shasta Lake have significantly lowered 

concentrations of metals in the 

Sacramento River, and no toxic effects 

to fish were observed during the course 

of this investigation (Alpers et al. 2000a, 

p.3; b, p. 2). However, elevated levels of 

metals such as copper in streambed 

sediment can still be measured in the 

upper Sacramento River Basin 

downstream from Redding (MacCoy and 

Domagalski, 1999, p. 35). Copper and 

other metals may still affect aquatic 

organisms in upper portions of 

contributing watersheds of the Delta. 

However, five potential contaminant 

threats have been identified as a 


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concern specifically with respect to the 

splittail: (1) selenium, (2) mercury, (3) 

organophosphates, (4) pyrethroids, and 

(5) ammonium/ammonia. A summary of 

each identified contaminant threat is 

provided below. In part, these 

contaminant threats are of concern 

because they may be focused, to varying 

degrees, on habitat features and 

biological characteristics tentatively 

identified as particularly relevant to 

splittail conservation. 

Selenium 

The primary risk posed by selenium 

is a direct result of its propensity to 

cycle through the food web, its 

dominant exposure pathway, and its 

ability to cause reproductive 

impairment in fish (Lemly 1999, p. 150- 

151; Lemly 2002, p.47). The primary 

source of selenium coming into the 

Delta system enters through the San 

Joaquin watershed in the form of 

agricultural run-off via the San Luis 

Drain (Luoma et al. 2008, p. 63). Recent 

studies on selenium toxicity in aquatic 

food chains have generally reached the 

conclusion that a water-based criterion 

is not suitable due to ‘‘...temporal [and 

spatial] changes in concentrations, 

speciation, and rates of transfer between 

water, sediment and organisms...’’ 

(Hamilton 2004, p. 8). Since the primary 

route of exposure to selenium is via the 

diet, and selenium is highly 

bioaccumulative, these differences can 

mean that a concentration of selenium 

in water that results in adverse effects 

in one location may not result in 

adverse effects to the same species in 

another location. Thus, the current 

recommendation (USEPA 2004, p. 82; 

Chapman 2007, p. 21; Hamilton 2002, p. 

95; 2004, p. 22) for the appropriate 

media for regulation of selenium in the 

aquatic environment is not water, but 

rather tissue. 

To examine the potential adverse 

effect levels of selenium on splittail, 

Teh et al. (2004, pp. 6085-6087) fed 

juvenile splittail organic selenium for 9 

months in the laboratory. From this 

experiment, Teh et al. (2004, pp. 6087- 

6090) derived a no observed adverse 

effects level (NOAEL) and lowest 

observed adverse effects level (LOAEL) 

for deformities in juvenile splittail of 

10.1 and 15.1 mg/kg-dry weight (dw) in 

muscle tissue and 23.0 and 26.8 mg/kgdw in liver tissue, respectively. 

However, Rigby et al. (2010, p.77) 

performed a logistic regression using 

data from Teh et al. (2004, pp. 6087- 

6090) to derive a more precise estimate 

of the threshold for selenium toxicity in 

splittail and derived EC10 values of 0.9 

mg/kg-dw in feed, 7.9 mg/kg-dw in 

muscle, and 18.6 mg/kg-dw in liver for 

juveniles. The derived EC10 values by 

Rigby et al. (2010, p. 79) represent the 

predicted selenium concentration at 

which deformities would be observed in 

10 percent of the juvenile population. 

In a laboratory setting, research by 

Teh et al. (2004, p. 6092) has shown that 

the prevalence of deformities among 

juvenile splittail in the laboratory 

increase at dietary concentrations 

greater than 6.6 mg/kg-dw while 

concentrations of 26.0 mg/kg-dw and 

greater significantly decrease body 

weight, total length, and condition 

factors of juvenile splittail. This may be 

due to the liver’s inability to metabolize 

and excrete biochemicals due to its 

reaction to high selenium intake (Teh et 

al. 2004, p. 6092). 

In field settings, selenium 

concentrations analyzed from tissues of 

adult splittail captured in the Suisun 

Bay/Marsh area show elevated 

concentrations in muscle ranging from 4 

to 5 mg/kg (5 ppm), and liver 

concentrations ranging as high as 20 

mg/kg (20 ppm) (Stewart et al. 2000, p. 

1). The median selenium liver g/gdwconcentrations in splittail collected 

from Suisun Bay are about 13 (13 ppm) 

(Stewart et al. 2004, p. 4523). Although 

deformities typical of selenium 

exposure including lordosis (spinal 

deformities) have been observed in 

splittail collected from Suisun Bay 

(Stewart et al. 2004, p. 4524), the known 

data on muscle and liver concentrations 

in splittail adults are below the EC10

values derived by Rigby et al. (2010, pp. 

76-79). 

Current threshold tolerances of 

selenium exposures by splittail may be 

higher than other species that use upper 

portions of the water column (Teh et al. 

2004, pp. 6087-6090). However, 

laboratory and field studies cited above 

lead us to conclude that although 

selenium is considered elevated within 

the Delta, selenium exposures, although 

important, are not having a significant 

population-level effect on the species. 

Bioaccumulation of selenium by 

splittail in the Estuary is a potential 

concern because the diet of adult 

splittail consists of bivalves (including 

Asiatic clam and overbite clam), 

amphipods, cladocerans, harpacticoid 

copepods, mysids, and detritus (Moyle 

et al. 2004, p. 22). Asiatic and overbite 

clams are benthic filter feeders that take 

up and accumulate selenium (Stewart 

2004, p. 4522). The relationship 

between the bioaccumulation of 

selenium in the overbite clam and its 

predation by splittail may be significant 

because subsequent to the clam 

invasion, splittail shifted their diet from 

prey items such as estuarine copepods 

to a diet increasingly focused on 

bivalves, in particular, overbite clams 

(Feyrer et al. 2003, p. 285). 

The recent increased reliance of 

splittail on overbite clams as a food 

source may be a risk factor for increased 

selenium accumulation in splittail. 

Concentrations of selenium in overbite 

clams in the San Francisco Bay Estuary 

rose three fold from the mid 1980’s to 

1997. Some of this rise may have been 

a result of high run-off during the wet 

years of 1995-1997 (Linville 2002, p. 56- 

59) when the survey was concluding. In 

the San Francisco Bay, selenium 

concentrations in Asiatic and overbite 

species range from 2 to 9 and 5 to 20 

mg/kg-dw, respectively (Stewart et al. 

2004, p. 4522; Presser and Luoma 2006, 

p. 48) compared with other native diet 

items of amphipods and mysids which 

range from 1 to 3 mg/kg-dw (Stewart et 

al. 2004, p. 4522). These concentrations 

exceed the previously discussed dietary 

EC10 of 0.9 mg/kg-dw derived by Rigby 

et al. (2010, p.78). However, the EC10

value developed by Rigby et al. (2010, 

p. 78) reflects adverse effects upon 

juveniles from dietary exposures. In 

Suisun Marsh adult splittail gut 

contents are predominantly detritus 

(Feyrer et al. 2003, p. 281). Feeding 

behavior of splittail in Suisum Marsh 

suggest they are more dependent upon 

detritus food sources which would 

likely expose them to lower 

concentrations compared of selenium to 

bivalve and amphipod diet sources. 

Moyle et al. (2004, p. 17) 

hypothesized that success of juvenile 

downstream migration is strongly linked 

to the size that juvenile splittail achieve 

prior to exiting the spawning areas. It 

was suggested that a minimum size of 

25 mm (1 in) greatly enhances success 

of downstream migration. Moyle 

presented data demonstrating 

statistically-significant declining growth 

rates. The apparent declines in growth 

rates observed in Suisun Marsh splittail 

between 1980 and 1995 by Moyle et al. 

(2004, p. 14) were correlated to the 

invasion of the Estuary by the overbite 

clam, and the subsequent shift of 

splittail to an overbite clam-dominated 

diet. Moyle et al. (2004, pp. 14-15) 

suggested that this trend might reflect 

cachexia (contaminant-induced weight 

loss despite calorically sufficient dietary 

intake) which is a classic symptom of 

non-lethal selenium poisoning. 

However, Moyle et al. (2004, p. 30) also 

suggested this decline in growth rates 

may reflect poorer energetics from 

shifting to a non-mysid shrimpdominated diet. 

Steps have been taken to reduce the 

input of selenium into the Estuary (see 

discussion under Factor D) and 

selenium loads discharged from the San 


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Joaquin drainage have been reduced 

over the last decade. In addition, the 

predominant source of selenium in the 

Delta (i.e., irrigation drainage from the 

San Joaquin River watershed) is 

somewhat removed from areas 

containing important spawning habitat 

for the species (Sacramento River 

watershed). Furthermore, studies on the 

effects of the overbite clam on splittail 

abundance have been inconclusive. 

Feyrer et al. found that changes in the 

food web have had effects on the diets 

of older splittail (2003, pp. 278-285), but 

Kimmerer found no evidence that the 

splittail decline was directly related to 

the decline in opossum shrimp (2002, 

pp. 51-52). Therefore, we have no 

conclusive scientific data finding that 

the splittail growth rates are the result 

of any selenium induced 

bioaccumulation mechanism. While 

there is scientific information that 

indicates overbite clams do accumulate 

selenium, there is no indication that the 

bioaccumulation of selenium in splittail 

as the result of eating these bivalves has 

resulted in a population decline of the 

species. Therefore, we conclude that 

selenium does not constitute an 

immediate threat to the splittail through 

all or a part of its range at this time or 

in the foreseeable future. However, the 

potential long-term chronic threat that 

selenium may present to splittail 

condition and health cannot be 

discounted when combined with other 

potential water quality stressors and 

should be examined in more detail in 

the future. 

Mercury 

The Sacramento River watershed was 

the site of significant mining activity 

during the 19th century, including hard 

rock and hydraulic gold mining 

(primarily in the Sierra Nevada), 

mercury mining in the Coast Range 

(primarily to support gold mining), and 

hard rock mining for copper, silver, and 

other metals in portions of the Sierras 

and northern Coast Range. California’s 

Coast Range represents one of the 

world’s five major mercury mining areas 

(Jasinski 1995, p. 151). Historic 

hydraulic gold mining and gold 

dredging beginning in the 1850’s in 

mountains upstream of the Delta set in 

motion a continual stream of mercury 

flowing into the Estuary from the 

Sacramento watershed that is still 

having residual effects today (Healy 

2008, p. 23). 

Analytical data indicate that mercury 

concentrations in aquatic biota in the 

San Joaquin River are exceeding 

screening thresholds and may pose 

ecological and human health risks 

(Davis et al. 2000, pp. 9-16). Laboratory 

studies by Deng et al. (2008, p. 200-202) 

found dietary mercury and a 

combination of mercury and selenium 

caused damage to liver, kidney and gill 

tissue of splittail after four weeks of 

exposure. Although liver glycogen 

depletion and kidney tubular dilation 

were observed by the Deng et al. study, 

these lesions did not seem to pose a 

direct threat to the survival of the 

splittail larvae (2008, p. 202). Because 

splittail require floodplain inundation 

to reproduce, they need habitats like the 

Yolo Bypass and the Cosumnes River 

floodplain. The reliance on these 

regions for reproduction creates a 

potential risk for eggs and juveniles to 

be exposed to mercury contamination. 

However, field studies regarding 

mercury toxicity to splittail eggs and 

juveniles are lacking. 

Regarding risks from bioaccumulation 

of mercury via the food chain pathway, 

several research groups are currently 

addressing mercury accumulation in the 

Delta food web. However, no systematic 

study exists of mercury distributions in 

the food web of the Bay. 

Bioaccumulation processes depend on 

the amount of mercury in surficial 

sediments, the water quality at the 

sediment/water interface, and local food 

web dynamics. 

Methylmercury is the most important 

form of mercury in the aquatic 

environment with regard to 

accumulation by biota and transfer 

through the food web. Methylmercury is 

produced through addition of a methyl 

group to Hg2+, a process referred to as 

methylation. The precise mechanism for 

entry of methylmercury to the food 

chain is unknown. However, this initial 

step is critical, because concentrations 

of mercury in plankton can be about 

10,000-fold higher than in water 

(Krabbenhoft 1996, p. 2). After this 

initial step, methylmercury 

concentrations increase approximately 

0.5 log units per trophic level (Watras 

and Bloom 1992, p.1316), suggesting 

that each successive trophic level 

derives methyl-Hg from a progressively 

more concentrated source (i.e. the 

previous trophic level), in a process 

known as biomagnification. In this 

process consumers retain and further 

concentrate much of the methylmercury 

of their prey and subsequently pass this 

on to the next trophic level. Species at 

high trophic positions in the aquatic 

food web, such as predatory fish, attain 

concentrations that are approximately a 

million times higher than 

concentrations in water. Because 

methylmercury biomagnifies, trophic 

position is one of the primary factors 

influencing observed tissue 

concentrations. 

Given that splittail are fairly low in 

trophic status and feeding guilds in the 

Estuary, the likelihood of accumulating 

and biomagnifying mercury from the 

food web is low. One study has linked 

elevated mercury to the Cosumnes River 

floodplain and the Yolo Bypass (Slotten 

et al. 2000, p. 44), which are both 

primary spawning grounds for splittail. 

However, this study found no increased 

levels of mercury in lower trophic level 

biota that occurred in these floodplains 

(Slotten et al. 2000, p. 44). Although 

laboratory studies have shown mercury 

to have adverse effects to splittail 

individuals and there are increased risks 

of mercury exposures in splittail 

spawning grounds, the Slotten study did 

not find that these mercury levels 

transferred into the food web and 

additional field studies regarding 

mercury toxicity to splittail are lacking. 

We have considered mercury as a 

possible threat to the splittail, but there 

is limited information on the effects of 

mercury on splittail population 

dynamics. Therefore we have 

determined that mercury and its 

potential for bioaccumulation and/or 

biomagnifications does not constitute a 

significant threat to splittail now or in 

the foreseeable future. 

Organophosphates 

Organophosphate pesticides such as 

diazinon, chlorpyrifos, and malathion 

are toxic at low concentrations to some 

aquatic organisms. Several areas of the 

Delta, particularly the San Joaquin River 

and its tributaries, are listed as impaired 

under the Clean Water Act due to 

elevated levels of diazinon, 

chlorpyrifos, and other pesticides. 

Organophoshates enter agricultural 

drainage mainly in stormwater runoff 

because it is sprayed on orchards during 

the rainy winter season. The 

environmental fate of chlorpyrifos and 

diazinon are not well understood. 

Previous work shows that chlorpyrifos 

is adsorbed strongly onto sediment 

particles, reducing the aqueous 

concentration (Karen et al. 1998, 

p.1584). The fate of adsorbed 

chlorpyrifos is not known. For 

chlorpyrifos dissolved in water, 

volatilization, photolysis, and 

hydrolysis are major removal 

mechanisms (Howard, 1999; Racke, 

1993). The role of biodegradation in 

chlorpyrifos removal is not well 

understood. Giddings et al. (1997) did 

find that the degradation of chlorpyrifos 

in water followed a first-order decay 

model (p. 2360). The environmental fate 

of diazinon is less known, but it is more 

soluble than chlorpyrifos and undergoes 

pH-dependent decomposition in water 

(Drufovka et al. 2008, p. 295). 


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Some species of zooplankton are 

affected by diazinon concentrations as 

low as 0.35 μg/L (Amato et al, 1992, p. 

214). From 1988 to 1990, the Central 

Valley Regional Water Quality Control 

Board conducted an aquatic toxicity 

survey in the San Joaquin Valley. 

Surface water samples collected from 

certain reaches of the San Joaquin River 

watershed during this survey were 

acutely toxic to the water flea, 

Ceriodaphnia dubia (Foe and Connor 

1991). The cause of toxicity was not 

determined but was attributed to 

pesticides in general. Further study was 

conducted in the Valley during the 

winter of 1991–92, and the resultant 

toxicity was attributed to the presence 

of chlorpyrifos and diazinon (Foe and 

Sheipline, 1993; Foe, 1995; Kuivila and 

Foe, 1995, p. 1149). Recognizing toxic 

concentrations of organophosphates can 

occur in tributaries to the San Joaquin 

and Sacramento River when agricultural 

areas contribute storm runoff, toxic 

concentrations rarely occur in the 

Sacramento River itself (MacCoy et. al 

1995). 

Although organophosphate pesticides 

commonly used in agricultural areas 

have been shown to be present in Delta 

waters and their tributaries at 

concentrations toxic to aquatic 

organisms (Werner et al. 2000, p. 226), 

little is known about the sensitivity of 

Sacramento splittail to these chemicals. 

Previous investigations of larval striped 

bass (Morone saxatilis) in the Delta 

indicated many larvae had been 

exposed to toxic compounds, 

potentially leading to slower growth and 

increased mortality rates (Bennett et al. 

1995). It is possible that these 

contaminants also contribute to 

mortality and potentially affect juvenile 

splittail recruitment. Teh et al. (2005) 

conducted 96–hour acute toxicity tests 

on 7–day-old splittail larvae to 

determine the level of toxicity of 

orchard runoff water containing 

organophosphorus pesticides and 

observe potential biological effects. 

Spliital larvae were then transferred to 

clean water for three months to assess 

the survival, growth, histopathological 

abnormalities, and heat stress proteins. 

The results of although splittail larvae 

survived the 96 h exposure, Teh et al. 

(2005) observed exhibited reduced 

survival and growth and showed signs 

of cellular stress even after a three 

month recovery period. 

Sublethal effects may play a more 

important role than acute mortality, but 

there is a lack of studies to identify and 

quantify sublethal responses to 

pesticides in splittail. In addition, 

although several studies have 

demonstrated the acute and chronic 

toxicity of two common dormant spray 

insecticides, diazinon and esfenvalerate, 

in other fish species (Barry et al. 1995, 

Goodman et al. 1979, Holdway et al. 

1994, Scholz et al. 2000, Tanner and 

Knuth 1996), little work has been done 

integrating acute toxicity with 

biomarkers of exposure. Sublethal 

exposure to insecticides is expected to 

cause a wide range of responses 

(biomarkers) in individuals ranging 

from genetic to reproductive anomalies. 

The addition of sublethal responses to 

routine acute toxicity testing may 

provide advanced warning of 

potentially significant environmental 

impacts and risks associated with 

organophosphate pesticides and prevent 

underestimation of effects on splittail 

populations. However, based upon the 

limited data available, we do not 

consider organophosphates to be a 

significant threat to the splittail 

population at this time. Although 

residual organophosphates will 

continue to be present in the ecosystem 

and site specific exposures will occur in 

localized areas that may affect 

individuals, the reduction of 

organophosphates discharged into the 

Delta due to EPA restrictions in recent 

years has greatly reduced the potential 

threat that organophosphates may have 

posed in the past (Luoma 2008, p. 64). 

Pyrethroids 

Pyrethroid use in the Central Valley 

has steadily increased since 1991 and 

reached an annual use of 80, 740 

kilograms (kg) (178,000 pounds (lbs)) in 

2003 (Oros and Werner 2005, p 11). 

Many farmers have switched from 

organophosphate-based insecticides to 

pyrethroid-based insecticides (which 

adhere to soil more strongly) due to a 

decision by the EPA to phase out 

organophosphates due to their toxicity 

to humans (Luoma 2008, p. 64). 

Pyrethroids have a high absorption rate, 

andlow water solubility; they rapidly 

absorb to soil and organic matter 

(Werner 2004, p. 2719). Although 

pyrethroids bioaccumulate, food web 

exposure is not considered a significant 

route of exposure to fish (Hill 1985). 

The primary mode of transport for 

pyrethroids in aquatic systems is the 

adsorption of pyrethroids to surfaces of 

clay and soil particles that are 

suspended in the water column (Oros 

and Werner 2005, p 24). This 

combination of properties lends itself to 

accumulation of this substance in areas 

such as the Yolo Bypass. 

All synthetic pyrethroids are potent 

neurotoxins that interfere with nerve 

cell function by interacting with 

voltage-dependent sodium channels as 

well as other ion channels, resulting in 

repetitive firing of neurons and 

eventually causing paralysis (Bradbury 

and Coats 1989, pp. 377-378; Shafer and 

Meyer, 2004). Pyrethroids are toxic to 

most aquatic invertebrates and fish, in 

many cases more toxic than the 

organophosphates they are replacing 

with LD50 values for aquatic organisms 

below 1 ppb (Smith and Stratton, 1986). 

The LD50 is the dose required to kill 

half the members of a tested population 

after a specified test duration. Aquatic 

insects are more sensitive to pyrethroids 

than fish, however, mollusks are 

relatively insensitive (Clark et al., 1989). 

Acute effects of pyrethroids on aquatic 

insects could reduce available food 

resources for splittail. However, the 

magnitude of this potential effect is 

unknown and has not been studied. 

Chronic exposures to pyrethroids can 

have significant impacts for immune 

function, reproductive success and 

survival for fish and their food 

organisms. Histopathological lesions in 

the liver were observed in splittail 

shortly (1 week) after 96–hour exposure 

to sublethal concentrations of 

organophosphate and pyrethroid 

insecticides. Fish recovered from these 

lesions, but showed high (delayed) 

mortality rates, grew slower and showed 

signs of cellular stress even after a 3 

month recovery period (Teh et al. 

2004b, p. 246). 

Sub-lethal toxicity studies specific to 

splittail are limited but data exists for 

other fish species. One pyrethroid, 

esfenvalerate, exhibited both larval 

survival and immune effects in two fish 

species. Delayed spawning and reduced 

larval survival of bluegill sunfish 

(Lepomis macrochrius) were observed 

following two applications of 1 ppb of 

esfenvalerate (Tanner and Knuth 1996, 

pp. 246-250). Exposures of 0.08 ppb 

esfenvalerate dramatically increased the 

susceptibility of juvenile Chinook 

salmon (Oncorhynchus tshawytscha) to 

Infectious Hematopoietic Virus (Clifford 

et al. 2005, pp. 1770-1771). 

We conclude that although 

pyrethroids have been shown to have 

potential chronic to sub-lethal effects on 

individuals, there is no evidence to 

suggest that splittail exposures to 

pyrethroids in the Estuary are having a 

significant effect at the population level. 

Therefore we have determined that 

pyrethroids do not represent a 

substantial threat to splittail now or in 

the foreseeable future. 

Ammonium 

The effect of ammonia on aquatic 

organisms depends on its form. 

Ammonia is un-ionized, and has the 

formula NH3. Ammonium is ionized, 

and has the formula NH4+. The major 


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factors determining the proportion of 

ammonia or ammonium in water are 

water pH and temperature. This is 

important as the unionized NH3 is the 

form that can be toxic to aquatic 

organisms while NH4 is the form 

documented to interfere with uptake of 

nitrates (NO3) by phytoplankton 

(Dugdale et al. 2007, Jassby 2008). The 

chemical equation that drives the 

relationship between ammonia and 

ammonium is: 

NH3 + H2O ←→ NH4

+ + OHWhen the pH is low, the reaction is 

driven to the right, and when the pH is 

high, the reaction is driven to the left. 

When temperature is high, the reaction 

is driven to the left and when 

temperature is low the reaction is driven 

to the right. Ammonia enters the Delta 

ecosystem through discharge from 

wastewater treatment plants, 

nitrogenous fertilizers, and atmospheric 

deposition. The largest source of 

ammonia entering the Delta ecosystem 

is the Sacramento Regional Wastewater 

Treatment Plant (SRWTP), which 

accounts for 90 percent of the total 

ammonia load released into the Delta. 

Monthly loads of ammonium from the 

SRWTP released into the river have 

doubled from 1985 to 2005 resulting in 

598 million liters (158 million gallons) 

per day discharged from the SRWTP 

during 2001–2005 (Jasby et al. 2008, p. 

15). 

Ammonia can be toxic to aquatic 

organisms and its acute and chronic 

effects are dependent on both pH and 

temperature. Ammonia is an oxygen 

demanding substance requiring oxygen 

for nitrification and could contribute to 

dissolved oxygen depletion in receiving 

waters. Effects of elevated ammonia 

levels on fish range from irritation of 

skin, gills, and eyes to reduced 

swimming ability and mortality (Wicks 

et al. 2002, p. 67). In addition to direct 

effects on fish, ammonia in the form of 

ammonium may alter the food web by 

adversely impacting phytoplankton and 

zooplankton dynamics in the Estuary 

ecosystem. Ammonia can be toxic to 

several species of copepods important to 

larval and juvenile fishes; ammonium 

may impair primary productivity by 

reducing nitrate uptake in 

phytoplankton (Dugdale et al. 2007, pp. 

27-28). 

A conceptual research framework has 

been prepared to improve 

understanding of the role of 

anthropogenic ammonia in the BayDelta ecosystem (Meyer et al. 2009, pp. 

3-14). No studies to date address the 

effects of ammonia on splittail 

specifically. However, concerns related 

to synergistic effects from ammonia and 

other contaminants on splittail and 

other fish species in the Sacramento 

River have been raised. One study 

conducted at the University of 

California Davis Toxicology Laboratory 

did not observe levels toxic to delta 

smelt, or two of its food organisms, in 

the Sacramento River downstream of 

SRWTP. However, treated effluent was 

found to be more chronically toxic than 

Sacramento River water seeded with 

ammonium chloride to equal 

concentrations, suggesting that 

additional toxicants are present in 

SRWTP effluent (Werner 2009, p. 21). 

EPA is currently updating freshwater 

ammonia criteria that will include new 

discharge limits on ammonia (EPA 

2009, pp. 1-46). There is no projected 

date for its adoption but a National 

Pollution Discharge Elimination System 

(NPDES) permit for the SRWTP is being 

prepared by the California Central 

Valley Regional Water Quality Control 

Board for public notice in the fall of 

2010. The NPDES permit is expected to 

include new ammonia limitations 

which will reduce loadings to the Delta. 

Although ammonia/ammonium is 

identified as a contaminant that is likely 

having a negative impact on the Estuary 

and may chronically or sub-lethally 

affect individual splittail within the 

population, there is no evidence that 

ammonia is having a population level 

effect on the species or will in the 

foreseeable future. 

Summary of Contaminants 

Most fish including splittail can be 

especially sensitive to adverse effects in 

their larval or juvenile stages when 

exposed to contaminants. Given splittail 

biology, adverse effects would be more 

likely to occur where sources of 

contaminants occur in close proximity 

to spawning and /or rearing habitats 

(i.e., floodplains, rivers and tributaries). 

Splittail are benthic feeders (feed on the 

bottom of water column) and are more 

susceptible than other fish to sediment 

contamination. They also face greater 

exposure to urban and agricultural 

runoff which tends to be concentrated 

in shoals where splittail reside (Moyle 

et al. 2004, p. 23). 

Laboratory studies have shown 

certain contaminants to potentially have 

adverse effects on individual splittail. 

Field studies have shown that the 

contaminants of concern are elevated in 

the Delta and co-occur in areas 

important for splittail conservation. 

Although negative impacts to individual 

splittail from contaminants are 

suspected and have been shown on a 

limited basis, the overall extent of these 

impacts to the population remains 

largely unknown without further study 

and investigation. No information to 

date has conclusively shown that each 

of the contaminants identified above 

have a significant effect on splittail at 

the population level. In addition, 

several efforts are being undertaken to 

improve estuarine habitat and reduce 

the amount of contaminants discharged 

into the system. Therefore, we do not 

consider the contaminants of concern, 

as described above, to constitute an 

immediate threat to the species at this 

time or in the foreseeable future. 

Climate Change 

The Intergovernmental Panel on 

Climate Change (IPCC) has concluded 

that warming of the climate is 

unequivocal (2007, p. 5), and that 

temperature increase is widespread over 

the globe and is greater at northern 

latitudes (Soloman et al. 2007, p. 37). 

However, future changes in temperature 

and precipitation will vary regionally 

and locally, with some areas remaining 

unaffected or even decreasing in 

temperature. 

Between 1995 and 2006, 11 of the 12 

years have been the warmest on record 

(Soloman et al. 2007, p. 36). Over the 

next 20 years, climate models estimate 

that the Earth’s average surface 

temperature will increase about 1.4 °C 

(0.8 °F). During the past decade, the 

average temperature in California, like 

that of much of the globe, was higher 

than observed during any comparable 

period of the past century (Soloman et 

al. 2007, pp. 31-32). Nighttime air 

temperatures in California have 

increased 0.18 °C (0.33 °F) per decade 

since 1920 while daytime temperatures 

have increased 0.05 °C (0.1 °F) per 

decade since 1920 (CEC 2009, p. 10). 

By IPCC estimates for 2070-2099, 

California temperatures are expected to 

rise 1.6 to 2.7 °C (3.0 to 5.5 °F) under 

a low emissions scenario and 4.4 to 5.8 

°C (8.0 to 10.5°F) under a high 

emissions scenario. However, recent 

studies have revealed that emissions are 

rising faster than even the most 

aggressive high emission scenarios used 

by IPCC in these calculations (CEC 2009 

p. 41). Thus temperatures in the State 

are expected to rise faster than predicted 

unless global actions are taken to reduce 

emissions (CEC 2009 p. 41). 

Similar to other California cyprinids, 

the splittail exhibits a high thermal 

tolerance. Acclimated fish can survive 

temperatures up to 33 °C (91.4 °F) for 

short periods of time (Young and Cech 

1996, p. 670). Temperatures resulting 

from climate change in the next 50 years 

are not expected to stress splittail 

beyond their temperature range. 

Splittail have historically adapted to 

changes in the Delta system through 


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migratory behavior and it is likely that 

they will continue to adapt and adjust 

their spawning and rearing grounds to 

areas with optimal temperature 

conditions (Moyle et al. 2004, p. 38). 

Changes in precipitation are less 

certain than temperature; climate 

models project more frequent heavy 

precipitation events, separated by longer 

dry spells, especially in the western 

United States (IPCC 2007, p. 15). In 

California, snowfall in higher elevations 

has been increasing while snowfall in 

lower elevations has been decreasing 

(CEC2009, p. 16). This has led to an 

overall decrease in run-off of 19 percent 

in the San Joaquin Basin and 23 percent 

in the Sacramento Basin between the 

months of April to July over the last 100 

years, meaning more runoff is coming in 

earlier months (CEC 2009, p. 17). 

Overall, California snowpack is 

predicted to decrease by 20 to 40 

percent by the end of the century (CEC 

2009, p. 44). However, due to the 

unpredictable nature of climate change, 

we are uncertain how the amount of 

run-off may vary over time and therefore 

we have no scientific evidence that 

potential drought conditions resulting 

from climate change pose a threat to the 

splittail. 

Global sea level has risen at an 

average rate of 1.8mm (.07 inches) per 

year from 1961 to 2003, and an average 

rate of 3.1 mm (.12 in) year from 1993 

to 2003 (IPCC 2007, p. 49). In California, 

sea level has risen about 18 cm (7 in) in 

the last century (CEC 2009, p. 24), 

which is similar to global sea level rise. 

The 2007 IPCC report modestly 

estimates that sea levels could rise by 

0.18 to .58 m (0.6 to 1.9 feet) by 2100, 

but Rahmstorf (2007, p. 369) suggests 

that depending on the warming scenario 

employed, global sea level rise could 

increase by over 1.2 m (4 ft) in that time 

period (CEC 2009, p. 49). Even if 

emissions were halted today, oceans 

would continue to rise and expand for 

centuries because of their efficient heat 

storing abilities (CEC 2009, pp. 49-50). 

Current estimates put sea level rise at 20 

to 50 cm (8 to 19 in) by 2050, which is 

likely to contribute to the flooding of at 

least some Delta islands (Knowles 2010, 

pers. comm.). 

The San Francisco estuary will be 

more susceptible to sea-level rise due to 

its narrow bays and channels and 

because it already lies below or at sea 

level (Moyle et al. 2004, p. 38). Many of 

the Delta islands used for agriculture 

have been drained and armored with 

levees for flood protection and 

groundwater level maintenance. These 

reclamation and agricultural activities 

have caused island surface levels to 

subside due to rapid decomposition of 

their water logged peat soils. Many of 

the central and western Delta islands 

have experienced the most subsidence, 

now lying at 3 to 7.6 m (10 to 25 ft) 

below sea level (Ingebritsen et al. 2000, 

p. 2). These islands are at a high level 

risk from sea level rise because, as 

islands subside and water levels rise, 

levee banks are experiencing greater 

hydrostatic force, thereby increasing the 

risk of their failure. 

Earthquake fault models also show a 

high degree of risk of a significant 

seismic event that could affect the 

islands in the central and western Delta 

(Mount et al. 2005, p. 13). Failure of the 

levees on some or all of these islands, 

as a result of liquefaction of the unstable 

soils that make up the levees’ 

foundations during an earthquake, 

could turn part or the entire Delta into 

a brackish bay in the future. The 

encroaching ocean would increase 

salinity levels in the central and western 

Delta, with the result that the range of 

splittail would likely be curtailed to 

some location upstream of the 

confluence of the Sacramento and San 

Joaquin rivers. 

Due to the divergence of two splittail 

population segments, one population is 

exposed to higher salinities in the Napa 

and Petaluma river systems for at least 

part of its life cycle (Feyrer et al. 2010, 

p. 12). This population may be better 

able to adapt to increased salinity levels 

that sea level rise may bring. Splittail 

have an unusually high salinity 

tolerance and populations have shown 

great resilience in waters with variable 

salinities (Moyle et al. 2004, p. 38; 

Young and Chech 1996, p. 673). 

Abundance indices soared in 1995 and 

1998, in response to wet hydrological 

years following a decade of 

predominantly dry conditions, showing 

the resilience of this species. One 

problem climate change may pose to 

splittail is the reduced spawning habitat 

due to deeper water (Moyle et al. 2007, 

p. 38). However, new spawning habitat 

that may be created as a result of 

flooding will help to accommodate 

splittail spawning in the event of rising 

ocean levels. Liberty Island (discussed 

under Factor A) is one example of the 

benefits that island flooding could have 

on splittail if correctly managed. Under 

predicted future flooding conditions, 

splittail could spawn in the Sutter 

Bypass and rear in the Delta. Splittail 

have adapted to changes in the 

ecosystem through their migratory 

behavior (Moyle 2004, p. 38) and may 

continue to do so in the future. 

Introduced Species 

Copepods (E. affinis, 

Pseudodiaptomus forbesi), a major prey 

item for splittail, have declined in 

abundance in the Delta since the 1970s 

(Kimmerer and Orsi 1996, p. 409). 

Starting in about 1987, declines were 

observed in the abundance of 

phytoplankton (Alpine and Cloern 1992, 

p. 951). These declines have been 

partially attributed to grazing by the 

overbite clam (Corbula amurensis) 

(Kimmerer et al. 1994, p. 86) which 

became abundant in the Delta in the late 

1980s. Asiatic clams (Corbicula 

fluminea) can exceed 200,000 per 

square meter (m2) and overbite clam 

abundance can exceed 10,000 per m2 

(Kimmerer et al. 2008, p. 82). Because 

the overbite clam consumes copepod 

larvae as it feeds, it not only reduces 

phytoplankton biomass but also 

competes directly with splittail for food 

(Kimmerer et al. 1994, p. 87). It is 

believed that these changes in the 

estuarine food web negatively influence 

pelagic fish abundance, including 

splittail abundance. In the Delta, 

phytoplankton production has declined 

43 percent between 1975 and 1995 

(Jasby et al. 2002, p. 703). The 

correlation of phytoplankton decline 

with the appearance of the overbite 

clam leads us to believe that the 

overbite clam is overgrazing the system. 

Three non-native species of copepods 

(Sinocalanus doerrii, Pseudodiaptomus 

forbesi, and Pseudodiaptomus marinus) 

became established in the Delta between 

1978 and 1987 (Carlton et al. 1990, pp. 

81-94), while native Eurytemora affinis 

populations have declined since 1980. It 

is not known whether these non-native 

species have displaced E. affinis or 

whether changes in the estuarine 

ecosystem now favor S. doerrii and the 

two Pseudodiaptomus species. Meng 

and Orsi (1991) reported that S. doerrii 

is more difficult for larval striped bass 

to catch than native copepods because 

S. doerrii is fast swimming and has an 

effective escape response. It is not 

known whether this difference in 

copepod swimming and escape behavior 

has affected the feeding success of 

young splittail. 

Limnoithona tetraspina (no common 

name) is a nonnative copepod that 

began increasing in numbers in the delta 

in the mid 1990s, about the same time 

that P. forbesi began declining (Bennett 

et al. 2005, p. 18). L. tetraspina is now 

the most abundant copepod species in 

the low salinity zone (Bouley and 

Kimmerer 2006, p. 219), and is likely an 

inferior prey species for splittail because 

of its smaller size and superior predator 

avoidance abilities when compared to P. 

forbesi (Bennett et al. 2005, p. 18; Baxter 

et al. 2008, p. 22). 

Splittail have shifted their diet to 

utilize non-native species. Although the 


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non-native copepods and bivalves 

discussed above have altered the food 

web in the Delta ecosystem, we have no 

compelling evidence to suggest that this 

has led to a decline in the splittail 

population. Please refer to the 

bioaccumulation section for a full 

analysis of the effects on splittail due to 

a shift in prey base from native species 

to the overbite clam. 

Chinese mitten crabs (Eriocheir 

sinensis) could reach concentrations 

sufficient to intermittently impede the 

operation of fish screens and salvage 

facilities, thus reducing the 

effectiveness of splittail salvage and 

repatriation efforts. The US Bureau of 

Reclamation has installed a device, 

known as ‘‘Crabzilla’’ to remove Chinese 

mitten crab from their CVP fish salvage 

facility. However, Chinese mitten crabs 

have not appeared in large numbers at 

either of the fish salvage facilities in 

recent years. As a result of the apparent 

decline of this nonnative species 

subsequent to their initial appearance in 

the Delta, along with the measures taken 

at the CVP fish salvage facility, the 

existence of the Chinese mitten crab in 

the Delta is not a current threat to 

splittail. 

Of some concern is the presence of 

Brazilian pondweed (Egeria densa) and 

water hyacinth (Eichhornia crassipes), 

both of which tend to form dense nearshore and slough-wide mats of 

vegetation that serve as retreat, foraging, 

and ambush sites for splittail predators. 

These vegetation mats also may divert 

upstream- and downstream-migrating 

splittail into channels rather than the 

more-productive bankside habitat by 

creating an obstacle (Moyle et al. 2004, 

p. 29). 

Summary of Factor E 

In summary, splittail are not 

significantly threatened by water export 

facilities, agricultural and power plant 

diversions, poor water quality, 

environmental contaminants, climate 

change, or introduced species. 

Operation of the CVP and SWP water 

export facilities directly affects fish by 

entrainment into their diversion 

facilities. CVP and SWP dams and 

diversions changed the historical 

hydrological features of the watershed 

systems, have altered and eliminated 

habitat for splittail, and may have 

reduced the distribution of the splittail 

by restricting movement to potential 

spawning grounds and creating 

migration obstacles. Entrainment at 

SWP and CVP pumps has not been 

demonstrated to affect splittail at the 

population level because loss of 

substantial numbers of fish tends to 

occur during wet years in which the 

species is experiencing a high 

reproductive output. CALFED’s 

Ecosystem Restoration Program 

(discussed under Factors A and E, 

above) has been successful in restoring 

habitat for the splittail and reducing 

threats from entrainment at water 

diversion sites. 

Splittail can become entrained in 

agricultural water diversions resulting 

in injury or mortality. Under both the 

CALFED Bay-Delta Program and the 

Central Valley Project Improvement Act, 

there have been significant efforts to 

screen agricultural diversions in the 

Central Valley and the Sacramento-San 

Joaquin Delta, and studies have found 

splittail entrainment to be exceptionally 

low. We do not consider entrainment by 

agricultural diversions to be a 

significant threat to splittail. 

Two power plants located near the 

confluence of the Sacramento and San 

Joaquin rivers pose an entrainment risk 

to splittail. The intakes for the cooling 

water pumps of these power plants are 

located in close proximity to splittail 

rearing habitat (Moyle et al. 2004, p. 20). 

Thermal and chemical pollution may 

also have a detrimental effect on 

splittail (USFWS 2008, pp. 173-174). 

However, due largely to the reduction in 

the operation of the power plants and 

their associated pumping for cool water, 

we do not consider the operation of 

these power plants to constitute a 

significant threat to the splittail 

population. We have no indications of 

future plans to use these pumps more 

frequently and therefore do not consider 

these operations to be a threat in the 

future. 

Laboratory studies have shown 

certain contaminants to be detrimental 

to individual splittail and the cooccurrence of splittail with 

contaminants has been documented. 

Although negative impacts to individual 

splittail from contaminants have been 

shown, the overall extent of such cases, 

and impacts to the population as a 

whole, remain largely undocumented. 

No studies to date have shown 

contaminants to have a significant effect 

on splittail at the population level. 

Bioaccumulation of selenium and 

mercury in the overbite clam is 

occurring and the overbite clam is a 

substantial prey item for splittail. 

However, we have no evidence that the 

bioaccumulation of selenium or 

mercury is having a detrimental effect 

on splittail at the population level or 

will in the foreseeable future. 

Climate change in California is 

expected to bring increased 

temperatures, changes in precipitation 

and run-off, and increased salinity 

levels associated with sea level rise. 

These changes may restrict splittail 

range or reduce spawning habitat. 

However, splittail exhibit high thermal 

salinity tolerances and are known to 

adapt to changes in the Delta through 

migratory behavior. In addition, new 

spawning habitat may be created as a 

result of flooding. We have no scientific 

evidence that potential drought 

conditions resulting from climate 

change pose a threat to the splittail. 

Introduced species are having an 

effect on the food web and ecology of 

the Estuary. Bivalves such as the 

overbite clam have displaced native 

food sources of the splittail. However, 

splittail have shifted their diets to 

utilize non-native food sources. 

Although the non-native copepods and 

bivalves discussed above have altered 

the food web in the Delta ecosystem, we 

have no compelling evidence to suggest 

that this has led to a decline in the 

splittail population. 

We conclude that the best scientific 

and commercial information available 

indicates that the Sacramento splittail is 

not now, or in the foreseeable future, 

threatened by other natural or manmade 

factors affecting its continued existence. 

Finding 

As required by the Act, we considered 

the five factors in assessing whether the 

Sacramento splittail is endangered or 

threatened throughout all or a 

significant portion of its range. We have 

carefully examined the best scientific 

and commercial information available 

regarding the past, present, and future 

threats faced by the Sacramento 

splittail. We reviewed the petition 

information available in our files, 

reviewed other available published and 

unpublished information, and consulted 

with recognized Sacramento splittail 

experts and other Federal, State, and 

tribal agencies, including the California 

Department of Fish and Game and the 

U.S. Bureau of Reclamation. 

We identified and evaluated the risks 

of the present or threatened destruction, 

modification, or curtailment of the 

habitat or range of the Sacramento 

splittail. The rate of habitat loss in the 

Estuary that occurred the 1900’s is no 

longer occurring today and efforts 

undertaken in the past decade have 

benefited the species by restoring its 

habitat. There is presently sufficient 

habitat to maintain the species; 

inundation frequency and duration in 

key areas is sufficient to provide 

spawning to maintain the species. The 

implementation and magnitude of the 

CALFED, CVPIA (discussed under 

Factor D) and other habitat restoration 

activities, which focus on the 

restoration of habitats that directly and 


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indirectly benefit splittail are greater 

than any foreseeable future habitat 

losses. The overall effect of habitat 

restoration activities is also expected to 

continue to be beneficial for splittail 

into the foreseeable future. Based on a 

review of the best scientific information 

available, we find that the present or 

threatened destruction, modification, or 

curtailment of Sacramento splittail 

habitat or range (Factor A) is not a 

significant threat to the splittail now or 

in the foreseeable future. 

The new CDFG regulation enacted in 

March 2010 limiting take of splittail to 

two individuals per day has eliminated 

any potential threat that fisheries may 

have posed. There is no indication that 

the current level of scientific take 

adversely affects the splittail 

population, and there is no indication 

that the level of mortality will increase 

in the future. Based on a review of the 

best scientific information available, we 

find that overutilization for commercial, 

recreational, scientific, or educational 

purposes (Factor B) is not a significant 

threat to the Sacramento splittail. We 

found disease occurs at low levels in the 

population, but does not constitute a 

significant threat to the species (Factor 

C). Predation by striped bass appears to 

be unchanged from past levels, is 

currently not a significant threat to 

splittail populations, and is not 

expected to increase in the future. 

Largemouth bass populations have 

increased in the Estuary in the past 

three decades, but populations of 

largemouth bass in critical rearing areas 

are low, therefore predation levels 

appear to be minor. Based on a review 

of the best scientific information 

available, we find that disease and 

predation (Factor C) are not significant 

threats to the Sacramento splittail, now 

or in the foreseeable future. 

Federal and State regulations provide 

protection for the splittail and its habitat 

by limiting adverse effects from new 

projects, restoring habitat and limiting 

contaminants discharged into the 

Estuary. Based on a review of the best 

scientific information, we find that a 

lack of regulatory mechanisms (Factor 

D) does not constitute a significant 

threat to the Sacramento splittail 

population now or in the foreseeable 

future. 

Based on the best available science, 

we find that other natural or manmade 

factors affecting the continued existence 

of the splittail (as described under 

Factor E) have not been shown to be 

significant threats to the splittail at this 

time. Furthermore, there is no evidence 

to suggest that these factors will 

increase and become threats to the 

splittail in the foreseeable future. 

Splittail are not threatened by water 

export facilities, agricultural and power 

plant diversions, poor water quality, 

environmental contaminants, climate 

change, or introduced species (Factor 

E). Entrainment at SWP and CVP pumps 

has not been demonstrated to affect 

splittail at the population level. 

CALFED’s Ecosystem Restoration 

Program (discussed under Factors A and 

E above), the CVPIA, and the provisions 

of the OCAP BOs, have been successful 

in reducing threats from entrainment at 

water diversion sites. Under both the 

CALFED Bay-Delta Program and the 

Central Valley Project Improvement Act, 

there have been significant efforts to 

screen agricultural diversions in the 

Central Valley and the Sacramento-San 

Joaquin Delta, and studies have found 

splittail entrainment to be exceptionally 

low. Therefore, we do not consider 

entrainment by agricultural diversions 

to be a significant threat to splittail. Due 

to reduction in the operation of two 

power plants and their associated 

pumping for cool water, we do not 

consider the operation of these power 

plants to constitute a significant threat 

to the splittail population. We have no 

indications of future plans to use these 

pumps more frequently and therefore do 

not consider these operations to be a 

threat in the future. 

Laboratory studies have shown 

certain contaminants to be detrimental 

to individual splittail and the cooccurrence of splittail with 

contaminants has been documented. 

Although negative impacts to individual 

splittail from contaminants have been 

shown, the overall extent of such cases, 

and impacts to the population as a 

whole, remain largely undocumented. 

No studies to date have shown 

contaminants to have a significant effect 

on splittail at the population level. 

Bioaccumulation of selenium and 

mercury in the overbite clam is 

occurring and the overbite clam is a 

substantial prey item for splittail. 

However, we have no evidence that the 

bioaccumulation of selenium or 

mercury is having a detrimental effect 

on splittail at the population level or 

will in the foreseeable future. 

The existing data fails to show a 

significant long term decline of the 

species. Natural fluctuations of 

population levels do not constitute an 

overall decline in the species, but rather 

show a pattern of successful spawning 

during wet years followed by reduced 

spawning during dry years. The model 

deployed in this finding simulates the 

species fluctuations and is compatible 

with known life history traits of the 

species. Population levels are directly 

correlated with inundation of 

floodplains and simulation models 

predict that these habitats must flood at 

a minimum of every 7 years for the 

species to persist in sufficient numbers 

to maintain a robust population level 

(Moyle et al. 2004, p. 38). We have no 

evidence to show that the frequency of 

inundation events on floodplains will 

decrease to the point that these events 

will not be sufficient to maintain robust 

population levels. Therefore, based on 

the best available data, we do not find 

an overall declining trend in the 

species’ population. 

Although global warming will change 

hydrography in the Delta, predictions 

do not foresee an imminent reduction in 

flooding of the Yolo Bypass. Splittail 

have continually adapted to changes in 

the ecosystem including salinity 

variation and we have no evidence to 

show that this will not continue to be 

the case. The Yolo and Sutter Bypasses 

and the Cosumnes River floodplain are 

serving as refuge for the species and 

there is no evidence that these areas will 

not continue to do so in the future. 

These floodplains are currently being 

expanded through public and private 

partnerships including CALFED ERP, 

CVPIA, Cosumnes River Preserve 

restoration efforts, and the acquisition 

and restoration of Liberty Island. 

Our review of the best available 

scientific and commercial information 

pertaining to the five threat factors, does 

not support a conclusion that there are 

independent or cumulative threats of 

sufficient imminence, intensity, or 

magnitude to indicate that the 

Sacramento splittail is in danger of 

extinction (endangered), or likely to 

become endangered within the 

foreseeable future (threatened), 

throughout its range. Therefore, listing 

the Sacramento splittail as endangered 

or threatened is not warranted at this 

time. 

Distinct Vertebrate Population 

Segments 

After assessing whether the species is 

endangered or threatened throughout its 

range, we next consider whether a 

distinct vertebrate population segment 

(DPS) exists and meets the definition of 

endangered or is likely to become 

endangered in the foreseeable future 

(threatened). 

Under the Service’s DPS Policy 

Regarding the Recognition of Distinct 

Vertebrate Population Segments Under 

the Endangered Species Act (61 FR 

4722; February 7, 1996), three elements 

are considered in the decision 

concerning the establishment and 

classification of a possible DPS. These 

are applied similarly for additions to or 

removal from the Federal List of 


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Endangered and Threatened Wildlife. 

These elements include: 

(1) The discreteness of a population in 

relation to the remainder of the taxon to 

which it belongs; 

(2) The significance of the population 

segment to the taxon to which it 

belongs; and 

(3) The population segment’s 

conservation status in relation to the 

Act’s standards for listing, delisting, or 

reclassification (i.e., is the population 

segment endangered or threatened). 

In this analysis, we will evaluate 

whether the San Pablo population of 

splittail is a DPS. This analysis is being 

conducted because recent studies by 

Baerwald et al. (2007) have revealed 

genetic variation between the San Pablo 

and Delta populations of splittail. The 

San Pablo population of splittail 

represents a fraction of the overall 

splittail population. For the purposes of 

this analysis, splittail individuals that 

spawn in the Napa and Petaluma rivers 

will be referred to as the San Pablo 

population and individuals that spawn 

in other rivers including the 

Sacramento, San Joaquin and Cosumnes 

rivers will be referred to as the Delta 

population. 

Discreteness 

Under the DPS policy, a population 

segment of a vertebrate taxon may be 

considered discrete if it satisfies either 

one of the following conditions: 

(1) It is markedly separated from other 

populations of the same taxon as a 

consequence of physical, physiological, 

ecological, or behavioral factors. 

Quantitative measures of genetic or 

morphological discontinuity may 

provide evidence of this separation. 

(2) It is delimited by international 

governmental boundaries within which 

differences in control of exploitation, 

management of habitat, conservation 

status, or regulatory mechanisms exist 

that are significant in light of section 

4(a)(1)(D) of the Act. 

The data used to determine genetic 

differences between two splittail 

populations were collected in 2002 and 

2003 and first published in (Feyrer et al. 

2005, pp. 164-167) to show upstream 

distribution limits of splittail. Young of 

the year splittail individuals were 

collected from the Napa, Petaluma, 

Cosumnes, Sacramento and San Joaquin 

rivers and salinities were recorded at 

these sites. Individuals collected from 

the farthest upstream locations on the 

rivers were chosen for genetic analysis 

in an attempt to ensure that they were 

collected in the natal rivers in which 

they were spawned (Baerwald et al. 

2007, p. 160). 

Baerwald et al. (2007) used 13 

microsatellite markers to genetically 

distinguish 489 young-of-the-year 

splittail collected from these five 

drainage areas (2007, pp. 160-161). Two 

genetically distinct populations were 

found, one in the Napa/Petaluma (San 

Pablo population) drainages and one in 

the greater Central Valley drainages 

(Delta population) (Baerwald et al. 2007, 

p 162). Microsatellite markers are 

neutrally inherited. Neutrally inherited 

genes come from the mother and are 

always passed on to the next mother, 

where as the fathers genes may or may 

not be passed on. The most likely reason 

for finding a statistical difference in 

gene frequencies is isolation of 

spawning populations (Israel and 

Baerwarld et al., 2010, pers. comm.). 

Both splittail populations use Suisun 

Bay as rearing habitat in the 

nonspawning season; however Suisun 

Marsh was used as foraging ground 

almost exclusively by the Delta 

population (Baerwald et al. 2008, p. 

1341). The majority (88 percent) of 

individuals collected foraging in Suisun 

Marsh assigned to the Delta population; 

however, less association was seen in 

individuals in the Ryer and Chipps 

Islands with 54 to 74 percent assigning 

to the Delta population (Baerwald et al. 

2008, p. 1341). Although some overlap 

in foraging grounds was observed, these 

populations largely maintain themselves 

in different habitats and possess 

different genetic make-ups. 

Thus, these studies demonstrate that 

the San Pablo population segment, 

composed of individuals from the Napa 

and Petaluma rivers, is markedly 

separate from the Delta population 

segment composed of individuals from 

the Sutter Bypass and Sacramento, 

Cosumnes and San Joaquin rivers as a 

consequence of genetic variation 

(Baerwald et al. 2007, pp. 164-165). 

Baerwald et al. noted that their results 

appear to be correlated with differences 

in salinities between spawning grounds 

and migration routes. Our analysis of 

the peer reviewed work done by 

Baerwald et al. (2007 and 2008) leads us 

to conclude that the San Pablo 

population is discrete under the 

Service’s DPS policy. 

Significance 

If a population segment is considered 

discrete under one or more of the 

conditions described in the Service’s 

DPS policy, its biological and ecological 

significance will be considered in light 

of Congressional guidance that the 

authority to list DPSes be used 

‘‘sparingly’’ while encouraging the 

conservation of genetic diversity. In 

making this determination, we consider 

available scientific evidence of the 

discrete population segment’s 

importance to the taxon to which it 

belongs. Since precise circumstances are 

likely to vary considerably from case to 

case, the DPS policy does not describe 

all the classes of information that might 

be used in determining the biological 

and ecological importance of a discrete 

population. However, the DPS policy 

describes four possible classes of 

information that provide evidence of a 

population segment’s biological and 

ecological importance to the taxon to 

which it belongs. As specified in the 

DPS policy (61 FR 4722), this 

consideration of the population 

segment’s significance may include, but 

is not limited to, the following: 

(1) Persistence of the discrete 

population segment in an ecological 

setting unusual or unique to the taxon; 

(2) Evidence that loss of the discrete 

population segment would result in a 

significant gap in the range of a taxon; 

(3) Evidence that the discrete 

population segment represents the only 

surviving natural occurrence of a taxon 

that may be more abundant elsewhere as 

an introduced population outside its 

historic range; or 

(4) Evidence that the discrete 

population segment differs markedly 

from other populations of the species in 

its genetic characteristics. 

A population segment needs to satisfy 

only one of these conditions to be 

considered significant. Furthermore, 

other information may be used as 

appropriate to provide evidence for 

significance. 

(1) Persistence of the discrete 

population segment in an ecological 

setting unusual or unique to the taxon. 

Salinity concentrations were recorded 

between April and July in 2002 and 

2003 on the Sacramento, San Joaquin, 

Napa, and Petaluma rivers at various 

locations where splittail were collected. 

Salinity concentrations on the Petaluma 

River averaged 13.0 ppt in 2002 and 6.0 

ppt in 2003. Napa River salinity 

concentrations averaged 5.0 ppt in 2002 

and 0.0 ppt in 2003. The San Joaquin 

and Sacramento rivers averaged 0.0 ppt 

for both years (Baerwald et al. 2008, p. 

165). Sacramento and San Joaquin rivers 

never contained salinity concentrations 

higher than 1.0 ppt. Salinity 

concentrations on the Napa River 

ranged between 0.0–8.5 ppt while 

Petaluma River salinity concentrations 

ranged between 5.5–14.1 ppt (Feyrer et 

al. 2010, p. 8). It is speculated that high 

salinities are creating a barrier between 

these populations that is only broken 

during high outflow years (Feyrer et al. 

2010, p. 11). This barrier likely occurs 


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in the area of Carquinez Straight 

between Suisun Bay and San Pablo Bay. 

Napa River populations mostly 

associate with the San Pablo population 

although a small number of individuals 

caught in 2003 when the salinity was 

0.0 ppt on the Napa River associated 

with the Delta population. The presence 

of the Delta population in the Napa 

River in 2003, when the salinity was 0.0 

ppt and absence in 2002 when salinities 

were higher may reflect the Delta 

population’s limited ability to tolerate 

high salinities for spawning. 

The data we have clearly shows that 

the Napa and Petaluma rivers had 

higher salinities than other areas of the 

Delta where the splittail persists for the 

2 years that surveys were conducted. 

However, we feel that 2 years of data are 

not sufficient to conclude that this 

constitutes a unique ecological setting 

that is persistent over time. A larger data 

set covering more years is needed to 

assess the salinities of these rivers 

particularly at splittail spawning 

grounds before we can conclude the 

range of the San Pablo population 

constitutes a unique ecological 

environment. Therefore, we are lacking 

convincing evidence that shows the San 

Pablo population persists in an unusual 

or unique ecological setting that 

contributes significantly to the taxon at 

this time. 

(2) Evidence that loss of the discrete 

population segment would result in a 

significant gap in the range of a taxon; 

The San Pablo population segment is 

on the western edge of the species range 

and only constitutes a small portion of 

the species range. Loss of this 

population would not create a gap in the 

remainder of the species range because 

the San Pablo population does not 

provide for connectivity with other 

portions of the range. Therefore, we 

conclude that loss of this population 

would not represent a significant gap in 

the range of the species. 

(3) Evidence that the discrete 

population segment represents the only 

surviving natural occurrence of a taxon 

that may be more abundant elsewhere 

as an introduced population outside its 

historic range. 

This criterion does not apply to the 

San Pablo splittail population because it 

is not a population segment 

representing the only surviving natural 

occurrence of the taxon that may be 

more abundant elsewhere as an 

introduced population outside its 

historical range. 

(4) Evidence that the discrete 

population segment differs markedly 

from other populations of the species in 

its genetic characteristics. 

Under the DPS policy we measure the 

evidence for potential biological and 

ecological significance to the species as 

a whole, as reflected by marked 

differences in its genetic characteristics. 

Evidence that the discrete population 

segment differs markedly from other 

populations of the species in its genetic 

characteristics is provided in the 

Baerwald et al study. (2007, p. 166). 

These genetically distinct populations 

may be driven by the strong selective 

pressure separating out species that are 

salinity tolerant from those that are 

susceptible to salinity effects (Baerwald 

et al. 2007, p. 165). We conclude that 

the San Pablo population of splittail 

meets this criterion of the DPS policy 

because it differs markedly from other 

populations in its genetic 

characteristics. 

Determination of Distinct Population 

Segment 

Based on the best scientific and 

commercial information available, as 

described above, we find that under the 

Service’s DPS policy, the San Pablo 

population segment is discrete and is 

significant to the taxon to which it 

belongs. Evidence that the San Pablo 

splittail is biologically and ecologically 

significant from other populations of 

splittail is based on the evidence that 

the discrete population segment differs 

markedly from other populations of the 

species in its genetic characteristics. 

Because the San Pablo population 

segment is both discrete and significant, 

it qualifies as a DPS under the Act. 

Distinct Population Segment Five-Factor 

Analysis 

Since the San Pablo population 

segment qualifies as a DPS, we will now 

evaluate its status with regard to its 

potential for listing as endangered or 

threatened under the five factors listed 

in section 4(a) of the Act. The majority 

of the factors affecting the species 

throughout its range also affect the San 

Pablo DPS of splittail. These factors can 

be found in the five factor analysis 

conducted for the entire range of the 

splittail found above. Our evaluation of 

the San Pablo DPS follows. 

Factor A. The present or threatened 

destruction, modification, or 

curtailment of its habitat or range 

Habitat Loss 

Rapid development within the San 

Pablo DPS’ range began with the 

discovery of gold in the Sierra Nevada 

foothills in the 1850s. Hydraulic mining 

operations contributed huge amounts of 

sediment to San Pablo Bay. For the next 

hundred years, the marshes were filled, 

diked, or drained to support the bay’s 

development as a major center of 

commerce. About 85 percent of the 

historic tidal marshes of San Pablo Bay 

have been altered, negatively affecting 

the ability of the remaining tidal 

marshes to accept winter rainfall and 

purify water in the bay. 

Beneficial Actions Offsetting Adverse 

Effects 

Since the 1960s, State and 

government agencies, non-profit 

organizations, and local grassroots 

organizations have made efforts to 

protect and restore San Pablo Bay. The 

San Pablo Bay National Wildlife Refuge 

was established in 1974 and currently 

protects over 13, 000 acres of wildlife 

habitat. Largely comprised of thousands 

of acres of tidelands leased from the 

California State Lands Commission, the 

refuge’s ultimate plans include 

protection and conservation of more 

than 8,094 ha (20,000 ac) of critical 

wildlife in northern San Pablo Bay 

(FWS Brochure 2001, pp. 1-6). 

Additional efforts are underway to 

protect and restore the bay. The San 

Pablo Bay Preservation Society is 

currently working to acquire land on 

San Pablo point (http:// 

www.pointsanpablo.org/) and the 

friends of San Pablo Bay NWR have 

helped to establish a nursery that is 

being used to re-vegetate tidal wetlands. 

Although the historic loss of 

floodplains has detrimentally affected 

the species in the past, current laws and 

protections including the creation of the 

San Pablo Bay National Wildlife Refuge 

have largely eliminated future losses of 

floodplain to the splittail. Many of the 

natural floodplains in the Napa and 

Petaluma rivers are still intact and 

provide optimal spawning grounds to 

splittail. The San Pablo DPS is much 

closer to the ocean than the Delta DPS 

and is largely influenced by a tidal 

system. Fresh water input into the 

system is essential to provide proper 

salinity levels. Over the past 100 years, 

fresh water input has been reduced by 

diversions and water barriers. Although, 

this reduction in fresh water flow has 

changed salinity concentrations in the 

Napa and Petaluma rivers, we have no 

evidence to suggest that it has had a 

significant effect on the population level 

of the species. 

Recent Abundance Data Trends 

On June 1, 2010, splittail individuals 

encompassing both young-of-the-year 

(less than 1 year in age) and age one 


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were captured in the Petaluma River 

(Sommer et al. unpublished, pp. 1-3). 

The presence of splittail from two 

different age classes makes it likely that 

splittail successfully spawned in the 

Petaluma River in 2010 (a relatively wet 

year) and 2009 (a critically dry year). 

This shows that splittail are persisting 

in the Petaluma River. In addition, all 

10 of the fish captured in the survey 

belonged to the San Pablo population of 

splittail. During this survey, fish were 

collected at two out of three survey 

sites. During previous surveys in the 

Petaluma River, splittail were captured 

at one out of three sites (Feyrer et al. 

2005, p. 162). 

We have no evidence at this time to 

suggest that the San Pablo population of 

splittail is in decline. The accepted 

range of the species in the Napa and 

Petaluma rivers has increased as new 

surveys have found presence of splittail 

in areas where they were previously not 

believed to be in the mid-1990’s 

(Sommer et al. 2007, p. 28). 

Summary of Factor A 

Although there has been substantial 

loss of habitat historically, present and 

future loss of habitat is expected to be 

minimal due to current land protections 

including the San Pablo Bay National 

Wildlife Refuge. Efforts undertaken in 

the past decade have benefited the 

species by restoring its habitat. There is 

presently sufficient habitat to maintain 

the species, inundation frequency and 

duration in key areas is sufficient to 

provide spawning to maintain the 

species. We conclude that the best 

scientific and commercial information 

available indicates that the San Pablo 

DPS of Sacramento splittail is not now, 

or in the foreseeable future, threatened 

by the present or threatened destruction, 

modification, or curtailment of its 

habitat or range. 

Factor B. Overutilization for 

commercial, recreational, scientific, or 

educational purposes 

Recreational Fishing 

Take of splittail due to fisheries is a 

potential threat rangewide to the species 

and this threat is not expected to be any 

different for the San Pablo DPS. Please 

refer to Factor B in the rangewide 

analysis for a full discussion of take due 

to recreational fishing. Take due to 

recreational fishing is not considered to 

be a substantial threat to the San Pablo 

DPS of splittail at this time. 

Scientific Collection 

Take and fatalities attributed to 

scientific sampling in areas occupied by 

the San Pablo population of splittail are 

far less than the rangewide take of the 

species. There have only been 10 known 

surveys of the San Pablo DPS splittail in 

the last 10 years. These include five U.S. 

Army Corp of Engineers’ surveys (2001 

and 2002), three surveys conducted by 

Feyrer et al.(2002, 2003 and 2010) and 

one study by the Napa Creek Floodplain 

Project (2007). There were a total of 4 

splittail captured in 2001 (USACE 

2002), 79 captured in 2002 (USACE 

2002), 48 captured in 2003 (USACE 

2004), 326 captured in 2004 (USACE 

2004), and 305 captured in 2005 

(USACE 2006) by the Army Core of 

Engineers. None of the fish captured by 

the Corps were kept. The amounts of 

Yyung-of-the-year captured in the 

Feyrer et al. studies were: 112 in the 

Napa River and 45 in the Petaluma 

River in 2002, and 62 in the Napa River 

and 171 in the Petaluma River in 2003 

(Feyrer 2010, pers. comm.). During a 

short gill net study in 2003, Feyrer et. 

al. collected 108 adult splittail (Feyrer 

2010, pers. comm.). A total of 13 

splittail were captured in 2010. All of 

the splittail taken in the Feyrer et al. 

studies were preserved for genetic 

analyisis. There were seven splittail 

caught in the Napa Creek Floodplain 

Project study in June of 2007 (Turner 

2007). Female splittail can lay up to 

100, 000 eggs in a single spawning event 

and the take of several hundred 

individuals is not expected to effect the 

population at the species level. 

Therefore, scientific take is not 

considered to be a significant threat to 

splittail at this time, however, scientific 

studies regarding the San Pablo 

population of splittail have been kept to 

a minimum to be sure not to threaten 

the limited number of individuals 

present in this population (Feyrer et al. 

2010, pers. comm.) 

Summary of Factor B 

The new CDFG regulation enacted in 

March 2010 limiting take of splittail to 

two individuals per day has eliminated 

any potential threat that fisheries may 

have posed. There is no indication that 

the current level of scientific take 

adversely affects the splittail 

population, and there is no indication 

that the level of mortality will increase 

in the future. We conclude that the best 

scientific and commercial information 

available indicates that the San Pablo 

DPS of the Sacramento splittail is not 

now, or in the foreseeable future, 

threatened by overutilization for 

commercial, recreational, scientific or 

educational purposes. 

Factor C. Disease or predation 

Disease 

Disease is a potential threat to splittail 

rangewide including in the San Pablo 

Bay and the potential threat of disease 

is expected to be the same in scope and 

intensity as it is in the overall range of 

the population. Please refer to Factor C 

in the range wide analysis for a full 

discussion of the effects of disease on 

splittail. Based on a review of the best 

scientific information available, we find 

that disease is not a significant threat to 

the San Pablo Bay population of splittail 

now or in the foreseeable future. 

Predation 

The salinity level in San Pablo Bay 

and the Napa and Petaluma rivers serves 

as a barrier to potential predators of the 

San Pablo DPS of splittail. Predators 

such as largemouth bass and catfish are 

not able to tolerate the high salinity 

environment present in the area of the 

San Pablo Bay population. The only 

substantial predator of splittail that is 

able to reside in this environment is the 

striped bass (Nobriga 2010, pers. 

comm.). 

Based on a review of the best 

scientific information available, we find 

that predation is not a significant threat 

to the San Pablo Bay population of 

splittail now or in the foreseeable 

future. 

Summary of Factor C 

We found disease occurs at low levels 

in the population, but does not 

constitute a significant threat to the 

species. Because the potential threat of 

predation on the San Pablo DPS of 

splittail is expected to be less than the 

potential threat on the overall 

population due to a salinity barrier, we 

conclude that predation is not a 

significant threat to the San Pablo 

population now or in the foreseeable 

future. We conclude that the best 

scientific and commercial information 

available indicates that the San Pablo 

Bay DPS of the Sacramento splittail is 

not now, or in the foreseeable future, 

threatened by disease or predation. 

Factor D. The inadequacy of existing 

regulatory mechanisms 

State Laws 

State laws acting as existing 

regulatory mechanisms are expected to 

provide the same protections to the San 

Pablo Bay DPS of splittail as they do to 

the entire range of the species because 

the laws are uniform throughout the 

State of California. Please refer to Factor 

D in the rangewide analysis for a full 

discussion of the State laws acting as 


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existing regulatory mechanisms to 

provide protections to the splittail. 

Federal Laws 

Federal laws acting as existing 

regulatory mechanisms are expected to 

provide the same protections to the San 

Pablo Bay DPS of splittail as they do to 

the entire range of the species because 

the laws are uniform throughout the 

United States. Please refer to Factor D in 

the rangewide analysis for a full 

discussion of the Federal laws acting as 

existing regulatory mechanisms to 

provide protections to the splittail. 

Summary of Factor D 

Federal and State regulations 

described in the analysis of the entire 

species range provide protection for the 

splittail and its habitat by limiting 

adverse affects from new projects, 

restoring habitat and limiting 

contaminants discharged into the 

Estuary. Although the Act does not 

directly regulate actions in splittail 

habitat, the provisions in the Act that 

apply to other listed species benefit the 

splittail. We conclude that the best 

scientific and commercial information 

available indicates that the San Pablo 

DPS of the Sacramento splittail is not 

now, nor in the foreseeable future, 

threatened by inadequate regulatory 

mechanisms. 

Factor E. Other natural or manmade 

factors affecting its continued existence 

We have identified the risk of water 

export facilities, agricultural and power 

plant diversions, poor water quality, 

environmental contaminants, climate 

change, or introduced species as 

potential threats to the San Pablo DPS 

of splittail. 

Water export facilities 

Water export facilities (CVP and SWP 

pumps) and power plant diversions 

which were analyzed in the range wide 

splittail finding are not located within 

the range of the San Pablo DPS and 

therefore do not represent potential 

threats to the San Pablo DPS. Water 

export facilities do not exist in the area 

of the San Pablo DPs and therefore are 

not considered to be a substantial threat 

to splittail now or in the foreseeable 

future. 

Agricultural Diversions for Irrigation 

Agricultural diversions are a potential 

threat range wide to splittail including 

in the area occupied by the San Pablo 

DPS. The majority of agricultural 

diversions in the Napa River are utilized 

by wineries for the production of grapes. 

Wine production in the Napa Valley is 

a multimillion dollar industry. There 

are a total of 1200 agricultural 

diversions in Napa County. Of these, 

there are 99 active diversions in the 

Napa River itself and they are primarily 

attributed to wine production 

(California integrated water quality 

systems 2010, p. 1). Splittail 

populations are persisting in the Napa 

and Petaluma Rivers and we have no 

data to show that agricultural diversions 

are a significant threat to the continued 

existence of the species at the 

population level now or in the 

foreseeable future. 

Power Plant Diversions 

There are no power plant diversions 

within the range of the San Pablo DPS 

of splittail. The Contra Costa Power 

Plant and the Pittsburg Power Plant 

(discussed in the rangewide analysis) 

are not a factor because they are located 

outside of the range of the San Pablo 

DPS of splittail. Power plant diversions 

are not expected to be a threat to the San 

Pablo population of splittail now or in 

the foreseeable future. 

Water Quality and Environmental 

Contaminants 

The Napa River exhibits a high 

eutrophication rate and has been placed 

on California List of Impaired Water 

Bodies (303(d) list) because nutrients, 

pathogens and sedimentation. The 

Petaluma River is on the California List 

of Impaired Water Bodies (303(d) list) 

for possessing high elevations of 

diazinon, nutrients, and sedimentation. 

The primary symptom of excessive 

nutrient loading in this watershed is 

dense algae growth. Eutrophication 

occurs when high nutrient levels 

increase growth of plant and algal 

matter resulting in dissolved oxygen 

removal from the system when the 

plants die and begin to decompose 

(Wang et al. 2004, p. 10). 

Efforts are underway by State water 

resource staff to address many nutrient 

sources including faulty septic systems, 

agricultural and urban runoff, and 

livestock through regulatory programs. 

These programs will address multiple 

pollutants, including pathogens, 

nutrients, and sediment. The Napa 

County resource conservation district 

has ongoing restoration efforts including 

native plant re-vegetation, road 

improvements, fish barrier removal, 

upland habitat improvements, and 

stream and wetland restoration. A Napa 

sustainable winegrowing group is active 

in educating wine growers on the 

benefits of reducing pesticide use and 

promoting soil health through erosion 

control. 

Although the Napa and Petaluma 

rivers do exhibit a high amount of 

nutrients, we have no evidence at this 

time to suggest that nutrient loading is 

causing a decline in the San Pablo DPS 

of splittail at the population level now 

or that it will in the foreseeable future. 

The known range of the species in the 

Napa and Petaluma rivers has increased 

as new surveys have found presence of 

splittail in areas where they were 

previously not believed to be found in 

the mid 1990’s (Sommer et al. 2007, p. 

28). 

Effects from selenium, mercury, 

organophosphates, pyrethroids and 

bioaccumulation on the San Pablo DPS 

are expected to be comparable to the 

effects that these potential threats are 

having on the overall population of 

splittail. These contaminants are 

dispersed throughout the estuary and 

we have no evidence to suggest that 

there is a higher concentration of these 

contaminants in the range of the San 

Pablo DPS than in the entire range of the 

species. Please refer to Factor E in the 

range wide analysis for a full discussion 

of the effects of contaminants on 

splittail. Based on a review of the best 

available scientific and commercial 

data, we conclude that contaminants are 

not a significant threat to splittail at the 

population level now or in the 

foreseeable future. 

Climate Change 

Climate change is a potential threat to 

splittail range wide including in the San 

Pablo Bay and the potential threat of 

climate change is expected to be the 

same in scope and intensity as it is in 

the overall range of the species. Please 

refer to Factor E in the range wide 

analysis for a full discussion of the 

effects of climate change on splittail. 

Based on a review of the best scientific 

information available, we find that 

climate change is not a significant threat 

to the San Pablo Bay population of 

splittail now or in the foreseeable 

future. 

Introduced Species 

Introduced species are a potential 

threat to the splittail rangewide and the 

effects of introduced species on the San 

Pablo DPS are expected to be similar to 

the effects on the species range-wide. 

However, several introduced species 

mentioned in the range-wide analysis 

will not be present in the San Pablo Bay. 

The invasive Corbula amurensis has 

become established in San Pablo Bay 

(USGS 2010); no records exist for 

Corbicula fluminea, which is 

physiologically capable of becoming 

established in the freshwater portions of 

the Petaluma and Napa rivers. Corbicula 

fluminea is not expected to be present 

in the San Pablo Bay because it is a 


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freshwater clam. Largemouth bass are 

not expected to be present in San Pablo 

Bay because they are a freshwater 

species. 

Brazilian pondweed and water 

hyacinth are also not expected to be 

present in this brackish environment 

because they are freshwater plants. We 

are lacking any studies on introduced 

species present in the Napa and 

Petaluma rivers. Although the nonnative copepods and bivalves discussed 

in the rangewide analysis have altered 

the food web in the Delta ecosystem, we 

have no compelling evidence to suggest 

that this has led to a decline in the 

splittail population. Therefore, we do 

not consider introduced species to be a 

significant threat to splittail now or in 

the foreseeable future. 

We conclude that the best scientific 

and commercial information available 

indicates that the San Pablo DPS of the 

Sacramento splittail is not now, nor in 

the foreseeable future, threatened by 

other natural or manmade factors 

affecting its continued existence. 

Finding 

As required by the Act, we considered 

the five factors in assessing whether the 

San Pablo DPS of Sacramento splittail is 

endangered or threatened. We examined 

the best scientific and commercial 

information available regarding the past, 

present, and future threats faced by the 

San Pablo DPS. 

The rate of habitat loss in San Pablo 

Bay that occurred the 1900’s is no 

longer occurring today and efforts 

undertaken in the past decade have 

benefited the species by restoring its 

habitat. There is presently sufficient 

habitat to maintain the species: 

inundation frequency and duration in 

key areas is sufficient to provide 

spawning to maintain the species. Based 

on a review of the best scientific 

information available, we find that the 

present or threatened destruction, 

modification, or curtailment of splittail 

habitat or range (Factor A) is not a 

significant threat to the San Pablo DPS 

throughout all or a part of its range. 

The new CDFG regulation enacted in 

March 2010 limiting take of splittail to 

two individuals per day has eliminated 

any potential threat that fisheries may 

have posed. There is no indication that 

the current level of scientific take 

adversely affects the San Pablo DPS, and 

there is no indication that the level of 

mortality will increase in the future. 

Based on a review of the best scientific 

information available, we find that 

overutilization for commercial, 

recreational, scientific, or educational 

purposes (Factor B) is not a significant 

threat to the San Pablo DPS now or in 

the foreseeable future. 

We found disease occurs at low levels 

in the population, but does not 

constitute a significant threat to the 

species (Factor C). Predation by striped 

bass appears to be unchanged from past 

levels and is currently not a significant 

threat to the San Pablo DPS. Other 

freshwater predators are absent from the 

San Pablo Bay due to elevated salinity 

levels. Based on a review of the best 

scientific information available, we find 

that disease and predation (Factor C) are 

not significant threats to the San Pablo 

DPS in all or a significant portion of its 

range, now or in the foreseeable future. 

Federal and State regulations provide 

protection for the San Pablo DPS and its 

habitat by limiting adverse effects from 

new projects, restoring habitat and 

limiting contaminants discharged into 

the Estuary. Based on a review of the 

best scientific information, we find that 

a lack of regulatory mechanisms (Factor 

D) does not constitute a significant 

threat to the San Pablo DPS. 

Based on the best available science, 

we find that other natural or manmade 

factors affecting the continued existence 

of the San Pablo DPS described in 

Factor E have not been shown to be 

significant threats to the San Pablo DPS 

at this time. Furthermore, there is no 

compelling evidence to suggest that 

these factors will increase and become 

threats to the San Pablo DPS in the 

foreseeable future. The San Pablo DPS is 

not threatened by water export facilities, 

agricultural and power plant diversions, 

poor water quality, environmental 

contaminants, climate change, or 

introduced species (Factor E). 

The existing data fails to show a 

significant long-term decline of the San 

Pablo DPS. The accepted range of the 

species in the Napa and Petaluma rivers 

has increased as new surveys have 

found presence of splittail in areas 

where they were previously not 

believed to be in the mid-1990’s 

(Sommer et al. 2007, p. 28).Therefore, 

based on the best available data, we do 

not find an overall declining trend in 

the species’ population. 

Based on our review of the best 

available scientific and commercial 

information pertaining to the five 

factors, we find that the threats are not 

of sufficient imminence, intensity, or 

magnitude to indicate that the San Pablo 

DPS is in danger of extinction 

(endangered), or likely to become 

endangered within the foreseeable 

future (threatened). Therefore, we find 

that listing the San Pablo DPS as an 

endangered or threatened species is not 

warranted at this time. 

Significant Portion of the Range 

Analysis 

Having determined that the splittail 

does not meet the definition of an 

endangered or threatened species, we 

must next consider whether there are 

any significant portions of the range 

where the splittail is in danger of 

extinction or is likely to become 

endangered in the foreseeable future. 

We have analyzed the potential for 

the San Pablo DPS to make up a 

significant portion of the species range 

by looking at areas where there may be 

a significant concentration of threats. 

We evaluated the San Pablo DPS in the 

context of whether any potential threats 

are concentrated in one or more areas of 

the projected range, such that if there 

were concentrated impacts, those 

splittail populations might be 

threatened, and further, whether any 

such population or complex might 

constitute a significant portion of the 

species range. In the case of the San 

Pablo DPS, we conclude that the 

potential threats to the species are 

uniform throughout the DPS. After 

reviewing the range of the species, we 

find that no areas have a significant 

concentration of threats such that a 

significant portion of the range analysis 

on them would be necessary. 

We do not find that the Sacramento 

splittail is in danger of extinction now, 

or is it likely to become endangered 

within the foreseeable future throughout 

all or a significant portion of its range. 

Therefore, listing the Sacramento 

splittail as endangered or threatened 

under the Act is not warranted at this 

time. 

We request that you submit any new 

information concerning the status of, or 

threats to, the Sacramento splittail or 

the markedly separate San Pablo DPS to 

our San Francisco Bay Delta Fish and 

Wildlife Office (see ADDRESSES) 

whenever it becomes available. New 

information will help us monitor the 

Sacramento splittail and encourage its 

conservation. If an emergency situation 

develops for the splittail or any other 

species, we will act to provide 

immediate protection. 

References Cited 

A complete list of references cited in 

this finding is available on the Internet 

at http://www.regulations.gov and upon 

request from the San Francisco Bay 

Delta Fish and Wildlife Office (see 

ADDRESSES). 

Author(s) 

The primary authors of this notice are 

the staff members of the San Francisco 

Bay Delta Fish and Wildlife Office, 

Sacramento, California. 


jdjones on DSK8KYBLC1PROD with PROPOSALS-1
Federal Register / Vol. 75, No. 194 / Thursday, October 7, 2010 / Proposed Rules 62095 

Authority 

The authority for this section is 

section 4 of the Endangered Species Act 

of 1973, as amended (16 U.S.C. 1531 et 

seq.). 

Dated: September 24, 2010 

Daniel M. Ashe, 

Acting Director, Fish and Wildlife Service. 

[FR Doc. 2010–24871 Filed 10–6–10; 8:45 am] 

BILLING CODE 4310–55–S 


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