[Federal Register Volume 75, Number 194 (Thursday, October 7, 2010)]
[Proposed Rules]
[Pages 62070-62095]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2010-24871]


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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.

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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

[[Page 62071]]

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).

[[Page 62072]]



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
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                            Recent (Freyer et al.
            River System             Historic (Rutter 1908)    1970s (Cawood 1974)   Mid- 1990s (Sommer et     05) unless noted      Distance to first
                                                                                           al. 1997)              otherwise                dam\a\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Sacramento                           483                     387                     331                    391\b\                 387
--------------------------------------------------------------------------------------------------------------------------------------------------------
Feather                              109                     Present                 94                     94\c\                  109
--------------------------------------------------------------------------------------------------------------------------------------------------------
American                             49                      37                      19                     No new data            37
--------------------------------------------------------------------------------------------------------------------------------------------------------
San Joaquin                          Widespread              Present                 201                    218.5\d\               295
--------------------------------------------------------------------------------------------------------------------------------------------------------
Mokelumne                            NA                      25                      63                     96\e\                  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 non-breeding splittail 
range from 5 to 24[deg] Celsius (C) (75[deg] Fahrenheit (F)) although 
acclimated fish can survive temperatures up to 33[deg]C (91[deg] F) for 
short periods of time (Young and Cech 1996, pp. 667-675). Splittail are 
also tolerant

[[Page 62073]]

of low dissolved oxygen and can be found in water where levels are 
around 1 mg O\2\ 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

[[Page 62074]]

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 well-correlated 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[deg] C, (65.3[deg] 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-bottom-dwelling) 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   1967--present       Catches all         --Targets striped
                                  juvenile striped                         splittail size      bass
                                  bass.                                    classes            --Low adult catch
                                 100 sampling sites:                                           rate
                                 San Pablo Bay in                                             --Sampling does
                                  the west to Rio                                              not cover entire
                                  Vista on the lower                                           range
                                  Sacramento River.                                           --Does not sample
                                 and to Stockton on.                                           benthos or
                                 the San Joaquin                                               shallow channel
                                  River.                                                       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     Samples west of the  1980--present       --Two types of      --Does not cover
 Trawl and Otter Trawl Survey     Delta                                    sampling            entire range
                                 seaward to south                          equipment and      --Non--specific;
                                  San Francisco Bay.                      frequent sampling.   targets entire
                                                                          --Capture all size   pelagic or
                                                                           classes.            benthic community
                                                                                              --Incomplete data
                                                                                               between 1989--
                                                                                               1999
                                                                                              --Splittail only
                                                                                               caught in 5
                                                                                               percent or less
                                                                                               of samples
----------------------------------------------------------------------------------------------------------------

[[Page 62075]]

 
University of California at      Long--term study of  1979--present       Samples all size    --Non--specific;
 Davis (UC Davis) Suisun Marsh    the                                      classes             targets entire
 Otter Trawl                     ecology of the                                               fish community
                                  entire fish                                                 --Geographically
                                  community of the                                             limited
                                  marsh at 21 sites                                           --Larger fish less
                                  and 9 sloughs.                                               vulnerable to
                                                                                               trawls
----------------------------------------------------------------------------------------------------------------
Chipps Island Survey             U.S. Fish and        1976--present       --Samples well      --Designed to
                                  Wildlife Service                         during high flow    sample juvenile
                                  conducts a                               years               salmonids
                                  sampling program                        --Good adult catch  --Geographically
                                  for juvenile                             rates.              limited
                                  salmon in the deep                                          --Samples near--
                                  water channel near                                           surface waters
                                  Chipps                                                       only
                                 Island, midwater                                             --High turbidity
                                  trawl is pulled at                                           in sampling area
                                  the.
                                 surface in 10 20--
                                  minute hauls per
                                  day during May and
                                  June.
----------------------------------------------------------------------------------------------------------------
FWS Beach Seine Survey           Samples 23 stations  1979--present       --Broadest          --Inconsistent
                                  around Delta with                        geographical        from 1983--1992
                                  15--m beach seine                        coverage of all    --Focused on out--
                                  in low velocity                          surveys             migrating
                                  areas near                              --Good adult         juvenile salmon
                                  shoreline                                catches.           ----Low adult
                                                                                               catch
----------------------------------------------------------------------------------------------------------------
Salvage Operations               The Central Valley   1979--present       Highest number of   --Geographically
                                  Project (CVP) and                        splittail caught    localized--mainly
                                  State Water                              out of any survey   reflective of San
                                  Project (SWP)                            for both adult      Joaquin River
                                  operate fish                             and juvenile        production
                                  screening                                catches            --Catches are
                                  facilities to                                                result of
                                  divert fish away                                             entrainment and
                                  from the pump                                                often cause
                                  intakes into                                                 mortality
                                  holding
                                 facilities where
                                  fish are counted,.
                                 measured, and
                                  released..
----------------------------------------------------------------------------------------------------------------

    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 well-known (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

[[Page 62076]]

point to supra-annual patterns of abundance (abundance changes over 
several or many years), but do not appear to support parsing into sub-
annual 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 long-lived (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 year-to-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

[[Page 62077]]

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 multi-purpose (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

[[Page 62078]]

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 early-season 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

[[Page 62079]]

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

[[Page 62080]]

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 
695d-695j) 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

[[Page 62081]]

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 
km\3\ (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 km\3\ (3.81 and 6.81 
maf) averaging 7 km\3\ (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 positive-barrier 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).

[[Page 62082]]

    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 m\3\ 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 m\3\ (81.2 million ft\3\) 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, re-flooding 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

[[Page 62083]]

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/kg-dw 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 EC<INF>10</INF> 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 EC<INF>10</INF> 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/g-dwconcentrations 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 EC<INF>10</INF> 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 EC<INF>10</INF> 
of 0.9 mg/kg-dw derived by Rigby et al. (2010, p.78). However, the 
EC<INF>10</INF> 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 shrimp-dominated 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

[[Page 62084]]

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).

[[Page 62085]]

    Some species of zooplankton are affected by diazinon concentrations 
as low as 0.35 [micro]g/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

[[Page 62086]]

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:
NH<INF>3</INF> + H<INF>2</INF>O [larr][rarr] NH<INF>4</INF>\+\ + OH-
    When 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 Bay-Delta 
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 [deg]C (0.8 [deg]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 [deg]C (0.33 [deg]F) per decade since 
1920 while daytime temperatures have increased 0.05 [deg]C (0.1 [deg]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 [deg]C (3.0 to 5.5 [deg]F) under a low 
emissions scenario and 4.4 to 5.8 [deg]C (8.0 to 10.5[deg]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 [deg]C (91.4 [deg]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

[[Page 62087]]

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

[[Page 62088]]

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 near-shore 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 co-occurrence 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

[[Page 62089]]

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 co-occurrence 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

[[Page 62090]]

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

[[Page 62091]]

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

[[Page 62092]]

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

[[Page 62093]]

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 non-native 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.

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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