Endangered and Threatened Wildlife and Plants; Revised Critical Habitat for the Riverside Fairy Shrimp, 31686-31747 [2011-12947]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 76, Number 105 (Wednesday, June 1, 2011)]
[Proposed Rules]
[Pages 31686-31747]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2011-12947]



[[Page 31685]]

Vol. 76

Wednesday,

No. 105

June 1, 2011

Part II





Department of the Interior





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Fish and Wildlife Service



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50 CFR Part 17



Endangered and Threatened Wildlife and Plants; Revised Critical Habitat 
for the Riverside Fairy Shrimp; Proposed Rule

Federal Register / Vol. 76 , No. 105 / Wednesday, June 1, 2011 / 
Proposed Rules

[[Page 31686]]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R8-ES-2011-0013; MO 92210-0-009]
RIN 1018-AX15


Endangered and Threatened Wildlife and Plants; Revised Critical 
Habitat for the Riverside Fairy Shrimp

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), propose to 
revise the currently designated critical habitat for the Riverside 
fairy shrimp (Streptocephalus woottoni) under the Endangered Species 
Act of 1973, as amended (Act). The current critical habitat consists of 
306 acres (124 hectares) of land in four units in Ventura, Orange, and 
San Diego Counties, California. We now propose to designate 
approximately 2,984 acres (1,208 hectares) of land in five units in 
Ventura, Orange, Riverside, and San Diego Counties, California, which, 
if finalized as proposed, would result in an increase of approximately 
2,678 acres (1,084 hectares) of critical habitat for this species.

DATES: We will consider comments received or postmarked on or before 
August 1, 2011. We must receive requests for public hearings, in 
writing, at the address shown in the FOR FURTHER INFORMATION CONTACT 
section by July 18, 2011.

ADDRESSES: You may submit comments by one of the following methods:
    (1) Federal eRulemaking Portal: https://www.regulations.gov. Follow 
the instructions for submitting comments to Docket Number FWS-R8-ES-
2011-0013.
    (2) U.S. mail or hand-delivery: Public Comments Processing, Attn: 
FWS-R8-ES-2011-0013; Division of Policy and Directives Management; U.S. 
Fish and Wildlife Service; 4401 N. Fairfax Drive, MS2042; Arlington, VA 
22203.
    We will not accept e-mail or faxes. We will post all comments on 
https://www.regulations.gov. This generally means that we will post any 
personal information you provide us (see the Public Comments section 
below for more information).

FOR FURTHER INFORMATION CONTACT: Jim Bartel, Field Supervisor, U.S. 
Fish and Wildlife Service, Carlsbad Fish and Wildlife Office, 6010 
Hidden Valley Road, Suite 101, Carlsbad, CA 92011; telephone 760-431-
9440; facsimile 760-431-5901. If you use a telecommunications device 
for the deaf (TDD), call the Federal Information Relay Service (FIRS) 
at 800-877-8339.

SUPPLEMENTARY INFORMATION: 

Public Comments

    We intend that any final action resulting from this proposed rule 
will be based on the best scientific and commercial data available and 
be as accurate and as effective as possible. Therefore, we request 
comments or information from other concerned government agencies, the 
scientific community, industry, or other interested party concerning 
this proposed rule. We particularly seek comments concerning:
    (1) The reasons why we should or should not revise the designation 
of habitat as ``critical habitat'' under section 4 of the Act (16 
U.S.C. 1531 et seq.), including whether there are threats to the 
species from human activity, the degree of which can be expected to 
increase due to the designation, and whether that increase in threat 
outweighs the benefit of designation such that the designation of 
critical habitat may not be prudent.
    (2) Specific information on:
    (a) The amount and distribution of Riverside fairy shrimp habitat;
    (b) What areas occupied at the time of listing (or currently 
occupied) and containing features essential to the conservation of the 
species, should be included in the designation and why;
    (c) What areas not occupied at the time of listing are essential 
for the conservation of the species and why;
    (d) Special management considerations or protection that the 
features essential for the conservation of the species may require, 
including management for potential impacts associated with climate 
change; and
    (e) Areas identified in this proposed revised critical habitat rule 
that should not be proposed as critical habitat and why.
    (3) Land-use designations and current or planned activities in the 
subject areas and their possible impacts on proposed revised critical 
habitat.
    (4) Information that may assist us in identifying or clarifying the 
physical and biological features essential to the conservation of 
Riverside fairy shrimp.
    (5) Special management considerations or protection that the 
physical and biological features essential to the conservation of the 
species may require.
    (6) Specific information regarding the occurrence, or non-
occurrence, of Riverside fairy shrimp in the Cruzan Mesa vernal pools 
(in Los Angeles County) and, if the species is present, whether this 
area is essential to the conservation of the species and if so, whether 
the area should be considered for exclusion under section 4(b)(2) of 
the Act and why.
    (7) Specific information on the habitat conditions for Riverside 
fairy shrimp and the presence of physical and biological features 
essential for the conservation of the species in Subunit 1b (South of 
Tierra Rejada Valley, which is in Ventura County), and whether this 
area is essential to the conservation of the species and why.
    (8) Specific information regarding the occurrence of Riverside 
fairy shrimp within proposed Subunit 3h (Santa Rosa Plateau at Mesa de 
Colorado, which is in western Riverside County), whether this area is 
essential to the conservation of the species, and if so, whether the 
area should be considered for exclusion under section 4(b)(2) of the 
Act and why.
    (9) Specific information regarding a potential occurrence of 
Riverside fairy shrimp at Madrona Marsh (Los Angeles County) and, if 
the species is present, whether this area is essential to the 
conservation of the species and why.
    (10) Specific information regarding the presence or absence of the 
physical and biological features essential to the conservation of the 
species within proposed Subunit 5c, and whether this area is essential 
to the conservation of the species and why.
    (11) Information on the projected and reasonably likely impacts 
associated with climate change on Riverside fairy shrimp and the areas 
we are proposing to designate as critical habitat.
    (12) How the proposed revised critical habitat boundaries could be 
refined to more closely circumscribe the landscapes identified as 
containing the physical and biological features essential to the 
conservation of the Riverside fairy shrimp.
    (13) Any probable economic, national security, or other relevant 
impacts of designating any area that may be included in the final 
designation; in particular, any impacts on small entities or families, 
and the benefits of including or excluding areas that exhibit these 
impacts.
    (14) Whether the potential exclusion under section 4(b)(2) of the 
Act of Subunits 2c ((MCAS) El Toro) and 2i (Southern California Edison 
(SCE) Viejo Conservation Bank), which are covered by the Orange County 
Central-Coastal Natural Community Conservation Plan/Habitat 
Conservation Plan (Orange County Central-Coastal NCCP/HCP), from final 
revised critical habitat is or

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is not appropriate, and whether the benefits of excluding any specific 
area outweigh the benefits of including that area as critical habitat 
and why.
    (15) Whether the potential exclusion under section 4(b)(2) of the 
Act of a portion of Subunit 2dA (Saddleback Meadows); portions of 
Subunit 2dB (O'Neill Regional Park--near Trabuco Canyon) and 2e 
(O'Neill Regional Park--near Ca[ntilde]ada Gobernadora/east of Tijeras 
Creek); and Subunits 2f (Chiquita Ridge) and 2g (Radio Tower Road), 
which are covered by the Southern Orange County Natural Community 
Conservation Plan (NCCP)/Master Streambed Alteration Agreement/Habitat 
Conservation Plan (HCP), now known as the Orange County Southern 
Subregion HCP, from final revised critical habitat is or is not 
appropriate, and whether the benefits of excluding any specific area 
outweigh the benefits of including that area as critical habitat and 
why.
    (16) Whether the potential exclusion under section 4(b)(2) of the 
Act of Subunits 3c, 3d, 3e, 3f, 3g, and 3h, which are covered by the 
Western Riverside County Multiple Species Habitat Conservation Plan 
(the Western Riverside County MSHCP) from final revised critical 
habitat is or is not appropriate, and whether the benefits of excluding 
any specific area outweigh the benefits of including that area as 
critical habitat and why.
    (17) Whether the potential exclusion under section 4(b)(2) of the 
Act of Subunit 4c (Poinsettia Lane Commuter Station) as critical 
habitat covered by the Carlsbad Habitat Management Plan (Carlsbad HMP), 
a subarea plan under the Multiple Habitat Conservation Program (MHCP), 
from final revised critical habitat is or is not appropriate, and 
whether the benefits of excluding any specific area outweigh the 
benefits of including that area as critical habitat and why.
    (18) Whether the potential exclusion under section 4(b)(2) of the 
Act--portions of Subunit 5d, which is covered by the County of San 
Diego Subarea Plan under the San Diego Multiple Species Conservation 
Program (MSCP) from final revised critical habitat is or is not 
appropriate, and whether the benefits of excluding any specific area 
outweigh the benefits of including that area as critical habitat and 
why.
    (19) Although we are not proposing areas within tribal lands in 
this proposed rule, we seek specific information regarding the possible 
species occurrence within two vernal pools on or near tribal land of 
the Pechanga Band of Luise[ntilde]o Mission Indians of the Pechanga 
Reservation, California (Pechanga Band of Luise[ntilde]o Mission 
Indians), and, if the species is present, whether this area is 
essential to the conservation of Riverside fairy shrimp and why.
    (20) Although we are not considering for exclusion lands owned by 
the Department of Homeland Security (DHS) along the U.S.-Mexico border 
in this proposed rule (Subunit 5b and a portion of land in 5h), we seek 
comments on whether or not these lands should be considered for 
exclusion under section 4(b)(2) of the Act of Federal land for national 
security reasons, whether such exclusion is or is not appropriate, and 
whether the benefits of excluding any specific area outweigh the 
benefits of including that area as critical habitat and why.
    (21) Whether our exemption, under section 4(a)(3)(B) of the Act, of 
land on Department of Defense property at Marine Corps Base (MCB) Camp 
Pendleton and Marine Corps Air Station (MCAS) Miramar in San Diego 
County is or is not appropriate, and why.
    (22) Whether the benefit of exclusion of any other particular area 
not specifically identified above outweighs the benefit of inclusion 
under section 4(b)(2) of the Act.
    (23) Information on any quantifiable economic costs or benefits of 
the proposed revised designation of critical habitat.
    (24) Whether we could improve or modify our approach to designating 
critical habitat in any way to provide for greater public participation 
and understanding, or to better accommodate concerns and comments.
    Our final determination concerning the revision of Riverside fairy 
shrimp critical habitat will take into consideration all written 
comments and any additional information we receive during all comment 
periods. The comments will be included in the public record for this 
rulemaking, and we will fully consider them in the preparation of our 
final determination. On the basis of public comments, we may, during 
the development of our final determination, find that areas within the 
proposed designation do not meet the definition of critical habitat, 
that some modifications to the described boundaries are appropriate, or 
that areas may or may not be appropriate for exclusion under section 
4(b)(2) of the Act.
    You may submit your comments and materials concerning this proposed 
rule by one of the methods listed in the ADDRESSES section. We will not 
accept comments sent by e-mail or fax or to an address not listed in 
the ADDRESSES section. We will post your entire comment--including your 
personal identifying information--on https://www.regulations.gov. You 
may request at the top of your document that we withhold personal 
information such as your street address, phone number, or e-mail 
address from public review; however, we cannot guarantee that we will 
be able to do so.
    Comments and materials we receive, as well as supporting 
documentation we used in preparing this proposed rule, will be 
available for public inspection on https://www.regulations.gov, or by 
appointment, during normal business hours, at the U.S. Fish and 
Wildlife Service, Carlsbad Fish and Wildlife Office (see FOR FURTHER 
INFORMATION CONTACT).

Background

    It is our intent to discuss only those topics directly relevant to 
the proposed revision of critical habitat for Riverside fairy shrimp. 
This proposed rule incorporates new information specific to Riverside 
fairy shrimp genetics across the species' range that was not available 
when we completed our 2005 final critical habitat designation (70 FR 
19154; April 12, 2005), and new information on the status and 
distribution of Riverside fairy shrimp that became available since the 
2005 final critical habitat designation for this species. A summary of 
topics that are relevant to this proposed revised critical habitat 
designation is provided below. For more information on the taxonomy, 
biology, and ecology of Riverside fairy shrimp, please refer to the 
final listing rule published in the Federal Register on August 3, 1993 
(58 FR 41384); the first and second rules proposing critical habitat 
published in the Federal Register on September 21, 2000 (65 FR 57136), 
and April 27, 2004 (69 FR 23024), respectively; and the subsequent 
final critical habitat designations published in the Federal Register 
on May 30, 2001 (66 FR 29384), and April 12, 2005 (70 FR 19154). 
Additionally, more species information can be found in the 1998 
Recovery Plan for the Vernal Pools of Southern California (1998 
Recovery Plan) finalized on September 3, 1998 (Service 1998a, pp. 1-
113), in the City of San Diego's 2002-2003 Vernal Pool Inventory (City 
of San Diego 2004, pp. 1-125), and in the Riverside fairy shrimp 5-year 
review (Service 2008, pp. 1-57).

Species Description

    The Riverside fairy shrimp is a small (0.56 to 0.92 inch (in)) (14 
to 23 millimeter (mm)) aquatic crustacean in the order Anostraca, 
restricted to

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seasonal (vernal) pools, ponds, swales, and other pool-like, ephemeral 
(lasting a short time) water bodies in southern coastal California, 
United States, and northern Baja California, Mexico (Eng et al. 1990, 
pp. 258-259). Riverside fairy shrimp, like all fairy shrimp in general, 
have stalked compound eyes, no carapace (hard outer shell), and eleven 
pairs of phyllopods (swimming legs that also function as gills). They 
swim or glide upside down by means of complex beating movements of the 
legs that pass, wave-like, in an anterior to posterior direction. Male 
and females have red-colored cercopods (anterior appendages) on all of 
the ninth and 30 to 40 percent of the eighth abdominal segments, which 
helps to distinguish this species from closely related species (Eng et 
al. 1990, p. 259).
    First collected in 1979 and described as a new species by Eng et 
al. (1990, pp. 258-259), based on a type specimen collected from an 
area between Murrieta Golf Course and California Highway 79 in 
Riverside County (71 FR 14538), Riverside fairy shrimp are currently 
presumed to occupy 60 or fewer pool complexes throughout southern 
California (see Spatial Distribution and Historical Range below). At 
the time the species was listed as endangered in 1993, the type 
locality had been lost to development (Eriksen and Belk 1999, p. 104; 
Service 2008, p. 5).

Habitat

    Typical habitat for fairy shrimp in California includes vernal 
pools, seasonally ponded areas within vernal swales, and ephemeral 
freshwater habitats (68 FR 46685). Riverside fairy shrimp are 
considered habitat specialists, found in moderate to deep (generally 
ranging from 10 inches (in) (25.4 centimeters (cm)) to 5 to 10 feet 
(ft) (1.5 to 3 meters (m)) in depth), longer-lived vernal pools and 
ephemeral wetlands (Eng et al. 1990, p. 259; Simovich and Fugate 1992, 
pp. 7-8; Hathaway and Simovich 1996, p. 39) because of specific life-
history traits and habitat needs (see Life History section below).
    Riverside fairy shrimp's known localities are below 2,100 ft (640 
m) elevation and are within 50 miles (mi) (80 kilometers (km)) of the 
Pacific Ocean. Riverside fairy shrimp do not occur in riverine or 
marine waters or other permanent bodies of water. Water chemistry is an 
important factor in determining fairy shrimp distribution (Belk 1977, 
p. 77; Gonzales et al. 1996, p. 319). As previously described in the 
final listing rule (58 FR 41384; August 3, 1993) and the Background 
section of the final revised critical habitat rule (70 FR 19154; April 
12, 2005), vernal pool habitats that support Riverside fairy shrimp 
occur in areas with Mediterranean climates (cool, wet winters and hot, 
dry summers), where shallow depressions become seasonally wet or 
inundated following winter and spring rains (Keeley and Zedler 1998, p. 
2; Smith and Verrill 1998, p. 15). In general, vernal pools occur as 
poorly drained depressions, perched above an impermeable surface or 
very slowly permeable soil horizon or bedrock (Cheatham 1976, p. 88; 
Smith and Verrill 1998, p. 15); restrictive soil layers are typically 
hardpan or claypan, and bedrock types are volcanic mud or lava flows 
(Jones and Stokes 1987, p. 70; Zedler 1987, p. 13; Smith and Verrill 
1998, p. 15). Other kinds of depressions that hold water of a similar 
volume, depth, and area, and for a similar duration and seasonality as 
vernal pools and ponded areas within swales, may also provide potential 
habitat for Riverside fairy shrimp.
    Vernal pools may fill primarily by direct precipitation, or may 
have contributions from subsurface inflows from surrounding soils, 
which may help to minimize water level fluctuations during late winter 
and early spring (Hanes and Stromberg 1998, p. 48; Rains et al. 2006, 
p. 1158). Although vernal pools may typically associate with specific 
types of geological formations, landforms, and soils and within 
different types of ephemeral wetland landscapes (Zedler 1987, p. 13; 
Hanes and Stromberg 1998, p. 48; Smith and Verrill 1998, p.15; Rains et 
al. 2006, p. 1158), the most common unifying feature to fairy shrimp 
habitat, in general, is ephemerally wet, flooded, or ponded area that 
is typically wet during a portion of the year and dry for the remainder 
of the year.
    Throughout this proposed revised critical habitat rule, the term 
``ephemeral wetlands'' refers to vernal pool habitats including vernal 
lakes, ponds, detention basins, and other natural and manmade 
depressions that seasonally hold water. While these ephemeral wetlands 
often occur within landscapes of ``mima-mound'' topography (Cox 1984, 
pp. 1397-1398), that is, they form during winter rains as a natural 
hydrological feature of a gently sloping, undulating landscape, the 
species can also be found in disturbed vernal pool habitats where 
basins have been compacted or artificially deepened and therefore hold 
water for longer periods of time.
    Depending on topography, soils, and geographic location, the period 
of time varies during which these ephemeral wetlands pond (referred to 
as the ``period of inundation''). Basin size and basin shape (Keeley 
and Zedler 1998, p. 5), soil type, soil consistency, depth of soil to 
impervious layer (for example, hardpan or claypan), type and thickness 
of impervious layer, and other local and regional climatic factors (for 
example, rainfall abundance and timing, rainfall regularity, and 
evaporation rates) (Keeley and Zedler 1998, p. 2; Helm 1998, p. 136) 
all are variables that potentially affect the length of ponding in 
vernal pool landscapes. For southern California's ephemeral wetlands, 
the wet phase typically occurs between the months of October to May, 
and the dry phase lasts for a period of time between the months of June 
to September.
    The Riverside fairy shrimp often hatches later in the season than 
other fairy shrimp species because presumably the deeper pools it 
inhabits require sufficient rainfall to fill (Simovich and Fugate 1992, 
p. 8). A minimum period of inundation, or pool duration, that Riverside 
fairy shrimp need in order to hatch and reach sexual maturity is 
approximately 8 weeks (48 to 56 days) based on field observations 
(Hathaway and Simovich 1996, p. 674) (see Life History section below 
for further discussion).
    Mounds of soil (mima) (Scheffer 1947, p. 288), or swales (broad, 
shallow, vegetated, ephemerally wet areas) (Helm 1998, p. 130), that 
are interconnected with level or low point depressional basins and 
which contain appropriate impervious clay soils (providing ponding 
opportunities during winter and spring), are geographically fixed and 
limited in number. Soils and soil series that underlie vernal pool 
habitat that supports Riverside fairy shrimp are generally 
characterized by a high content of coarse sandy grains (marine alluvial 
sediments), loams, or clay inclusions, or a combination of these, with 
a subsurface clay or hardpan layer. These are also limited in number 
and geographically fixed. Riverside fairy shrimp are known to occur in 
both hardpan and claypan vernal pools in Ventura, San Diego, Los 
Angeles (now extirpated), Riverside, and Orange Counties, and in 
addition, in Riverside County on granitic (basaltic) substrate.
    Vernal pools and vernal swales are often clustered into pool 
``complexes'' (Bauder 1986a, Appendix 1, 4; Keeler-Wolf et al. 1998, 
pp. 60-61, 63-64), and may form dense, interconnected mosaics of small 
pools, or a sparse scattering of larger pools. Vernal pool complexes 
that support from one up to many distinct vernal pools are often 
interconnected by a shared watershed. Both the pool basin and the 
surrounding watershed are essential for a functioning vernal pool 
system (Hanes and

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Stromberg 1998, p. 48). Loss of upland vegetation, increased overland 
water flow due to urban runoff, and alteration of the microtopography 
can modify the function of vernal pool systems, and alter the 
physiochemical parameters that the Riverside fairy shrimp requires for 
survival. Because the Riverside fairy shrimp requires ephemerally 
ponded areas for its conservation (Belk 1998, pp. 147-148), vernal 
pools are best described from a watershed perspective (see Physical and 
Biological Features section below, and Recovery Criteria 1 and 2 in the 
1998 Recovery Plan for Vernal Pools of Southern California (Service 
1998a, pp. iv-vi)).
    The size and number of inundated basins and their associated biota 
are directly correlated to the amount and timing of precipitation (City 
of San Diego 2004, p. 6). In southern California, rainfall is erratic 
within and between years as well as strongly seasonal (Zedler 1987, p. 
12). Pool size, location and elevation, upland hydrology, 
physiochemical processes, and unique species assemblages may all factor 
into the distribution of vernal pool species (Eng et al. 1990, p. 273; 
Branchiopod Research Group 1996, pp. 1-2; Gonzalez et al. 1996, p. 
319). Water chemistry (dissolved solutes, alkalinity, salinity, and 
temperature) and length of time vernal pools are inundated with water 
(see Life History section below) are important factors that potentially 
limit and determine the distribution of Riverside fairy shrimp within 
and among pools complexes.
    Water in the pools that typically support Riverside fairy shrimp 
has low total dissolved solids and alkalinity (means of 77 and 65 
milligrams per liter (mg/l) or parts per million (ppm), respectively), 
corroborated by pH at neutral or just below (6.4-7.1) (Eng et al. 1990, 
p. 254; Gonzalez et al. 1996, p. 317; Eriksen and Belk 1999, p. 104). 
Riverside fairy shrimp have been shown to tightly regulate their 
internal body chemistry for pool environments that have low salinity 
and low alkalinity (Gonzalez et al. 1996, pp. 317-318). Pools are 
generally open and unvegetated with turbid water conditions; habitat 
lies within annual grasslands, which may be interspersed through 
chaparral or coastal sage scrub vegetation (Lahti et al. 2010, p. 5). 
Riverside fairy shrimp are typically found in water temperatures 
ranging between 50 and 77 degrees Fahrenheit (10 and 25 degrees 
Celsius) (Hathaway and Simovich 1996, p. 671).

Life History

    As discussed in detail in the Background section of the final 
revised critical habitat rule (70 FR 19154; April 12, 2005), Riverside 
fairy shrimp feed on algae, bacteria, protozoa, rotifers, and bits of 
detritus, and constitute a cornerstone in the food web for a wide array 
of aquatic and terrestrial species.
    Because vernal pool ecosystems are highly variable in the length of 
time pools remain filled, Riverside fairy shrimp have adapted their 
life-history strategies accordingly. Riverside fairy shrimp populations 
withstand a seasonal desiccation of their pools by producing resting 
eggs (herein referred to as reproductive cysts), which when mature can 
survive environmental conditions such as extremes in temperatures, the 
digestive tracts of animals, and years of desiccation before hatching 
under the correct environmental conditions (Pennak 1989, pp. 352-353; 
Eriksen and Belk 1999, p. 22). Because not all reproductive cysts will 
hatch with any given refilling of their pool, these reproductive cysts 
form a ``cyst bank'' in the soil from which new populations of adults 
may develop, even in pools that have not had adults for years (Eriksen 
and Belk 1999, p. 105). Therefore, it is not mandatory for ideal 
conditions to exist every year for this species to persist.
    Adult Riverside fairy shrimp are usually observed from mid-March to 
April (Eng et al. 1990, p. 259); however, the hatching periods may be 
extended in years with early or late rainfall. Unlike San Diego fairy 
shrimp (Branchinecta sandiegonensis), a species that matures quickly (7 
to 14 days), Riverside fairy shrimp hatch and mature within 48 to 56 
days, depending on water temperature (Hathaway and Simovich 1996, p. 
674; Simovich and Hathaway 1997, p. 39; Eriksen and Belk 1999, p. 105). 
Because of its distinctly longer maturation, Riverside fairy shrimp are 
typically restricted to relatively deep (greater than 12 in (30 cm)), 
cool water vernal pools that are inundated for a longer time to 
complete their reproductive life cycle (Hathaway and Simovich 1996, p. 
675) . This longer deve1opment time is thought to account for the 
species' restriction to deep pools, their rarity, and later appearance 
(Simovich and Fugate 1992, p. 8).

Spatial Distribution and Historical Range

    As discussed in detail in the Background section of the final 
revised critical habitat rule (70 FR 19154; April 12, 2005), Riverside 
fairy shrimp are considered to have one of the most restricted 
distributions among fairy shrimps endemic to the West Coast (Eng et al. 
1990; p. 259, Simovich and Fugate 1992, p. 7; Eriksen and Belk 1999, p. 
104). Because the Riverside fairy shrimp has a slower developmental 
rate, the species is limited to fairly deep, and moderate in size, 
pools that support a longer ponding duration. The Riverside fairy 
shrimp is, therefore, restricted to a subset of vernal pools and vernal 
pool complexes in southern California (Ventura, Orange, Riverside, and 
San Diego Counties) and in northern Mexico (Service 1998a, p. 19; 
Eriksen & Belk 1999, p. 104). The Riverside fairy shrimp has likely 
been extirpated from Los Angeles County. With the exception of the 
Riverside County populations, all populations are within approximately 
15 mi (24 km) of the coast. Riverside fairy shrimp range over a north-
south distance of approximately 163 mi (262 km) within southern 
California (excluding Baja, Mexico locations) and occupy pools that 
range in elevation from 46 to 2,076 ft (14 to 633 m).
    For the purposes of this proposed revised critical habitat 
designation, the word occurrence may be a single pool or a pool 
complex. Keeler-Wolf et al. (1998, p. 8) define a vernal pool complex 
as a set of naturally occurring pools in close proximity. A singular 
pool--geographically situated such that the pool basin is isolated from 
adjoining vernal pool topography by distances greater than 10 mi (16 
km)--or a network of one or more vernal pool basins in close proximity, 
that is to say a vernal pool complex, may comprise an occurrence. At 
the time of listing in 1993, nine historical occurrences for Riverside 
fairy shrimp were known: Four occurrences in a 37-square-mile (91-
square-km) area near Temecula, California (western Riverside County); 
one occurrence in Orange County, California; two documented occurrences 
in San Diego County, California; and two occurrences in Baja 
California, Mexico (58 FR 41384; August 3, 1993).
    In our 2008 5-year review of Riverside fairy shrimp, we assembled 
and reassessed occurrence data for the species (Service 2008, pp. 6-8). 
Seven of the nine historical occurrences (five in the United States and 
two in Mexico) were presumed extant at the time Riverside fairy shrimp 
was listed in 1993 (Service 2008, pp. 7-8). The type locality in 
western Riverside County (at Murrieta Golf Course) was already 
extirpated by the time the species was listed, and the single-
referenced occurrence from Orange County has never been confirmed. 
Based on our analysis in the 2008 5-year review for Riverside fairy 
shrimp, with the discovery of additional occurrences, the regrouping of 
vernal pool complexes, and the extirpation of nine known occurrences 
since listing, we concluded

[[Page 31690]]

that there were approximately 45 known extant (or presumed extant) 
occurrences (approximately 200 vernal pools) of Riverside fairy shrimp 
(Service 2008, p. 5). Discovery of additional occurrences since the 
time of the 1998 Recovery Plan, include at least four more occurrences, 
all in western Riverside County: Warm Springs Ranch Pool, Schau Pool, 
Rancho California Road Pools, and an occurrence (two pools, Pool 4 and 
Pool 5 in Selheim and Searcy 2010, p. 98) atop Santa Rosa Plateau along 
Mesa de Colorado. Identification of additional occurrences since 
listing (1993) has resulted from surveys conducted in locations that 
were not surveyed prior to 1993. In sum, Riverside fairy shrimp are 
presently considered to be extant in approximately 49 occurrences 
(vernal pools and vernal pool complexes), four more than we reported in 
the 2008 5-year review (Service 2008, pp. 5, 10).
    Extant occurrences not identified in the 1993 listing rule (but 
presumed extant at the time of listing) are located in the following 
general areas: (1) One occurrence in Ventura County (Tierra Rejada 
Preserve and South of Tierra Rejada Valley); (2) seven occurrences in 
Orange County: (MCAS) El Toro, SCE Viejo Conservation Bank, Saddleback 
Meadows, O'Neill Regional Park--near Trabuco Canyon, O'Neill Regional 
Park--near Ca[ntilde]ada Gobenadora/east of Tijeras Creek, Chiquita 
Ridge, and Radio Tower Road; (3) nine occurrences in Riverside County 
at the Australia Pool, the Scott Road Pool, the Warm Springs Ranch 
Pools, the Schleuniger Pool, the Schau Pool, in the Johnson Ranch area, 
the Field Pool, the Rancho California Road Pool, and a newly documented 
occurrence on the Santa Rosa Plateau along Mesa de Colorado; (4) ten 
occurrences in north San Diego County on MCB Camp Pendleton: San Onofre 
State Beach, State Park-leased lands, near Christianitos Creek 
foothills (along the northwest corner of MCB Camp Pendleton); area 
south of San Onofre State Beach, in Uniform Training Area; Las Pulgas 
North; Las Pulgas East; Las Pulgas West; Cockleburr North; Cockleburr 
South; Stuart Mesa; San Mateo; and Wire Mountain; and (5) seven 
occurrences in central and southern San Diego County, outside of MCB 
Camp Pendleton: on MCAS Miramar (AA1 pool); City of Carlsbad 
(Poinsettia Lane Commuter Train Station); and numerous pools on Otay 
Mesa (southern San Diego County) including what is referred to as the 
``J series'' of vernal pool complexes (J2, J4, J5, J11, J12, J14, J15, 
J16-18, J29-31, J33).
    For the purpose of this proposed revised critical habitat 
designation, we consider areas where Riverside fairy shrimp have been 
documented since listing (since 1993) to be within the geographical 
area occupied by the species at the time of listing (in 1993). As 
discussed in the 5-year review, most of the additional occurrences 
identified since listing fall generally within the range of the 
Riverside fairy shrimp described in the listing rule, although the 
identification of some occurrences (complexes) broadened the specific 
range within Ventura, Orange, Riverside, and San Diego Counties 
(Service 2008, p. 8). As with many species, listing often results in 
greater efforts to conduct surveys, which may reveal a greater number 
of occurrences than was initially known.
    We believe that these additional occurrences were occupied at the 
time of listing but had not been identified due to lack of survey 
effort. We believe occurrences documented since the 1993 listing do not 
represent an expansion of the species' distribution and range into 
previously unoccupied areas (with the exception of Johnson Ranch 
Created Pools), but rather a better understanding of the historical 
distribution and range of the species (Service 2008, p. 9). Because 
occurrences documented since listing are within relative proximity to 
existing, occupied, vernal pool habitat or within similar landscape 
types (e.g., coastal terraces and mesas, inland valleys, inland mesas, 
cismontane depressions) supporting ephemeral wetlands with occurrences 
that were known at the time of listing, it is reasonable to conclude, 
based on several life-history traits, that Riverside fairy shrimp were 
present at the time of listing in these unsurveyed habitats.
    Riverside fairy shrimp are generally sedentary and are adapted to 
survive and persist in seasonally ephemeral habitat. Because they are 
sedentary, possess limited dispersal capabilities (passive dispersal 
mediated by resistant stages), and exhibit specialized habitat 
affinities (specific habitat types with fixed landscape features, see 
Life History and Habitat sections of this document), we believe it is 
unlikely that additional occurrences have become established during the 
relatively short time period since the listing of this species (with 
the exception of Johnson Ranch Created Pools). With the exception of 
the land we are proposing to designate under section 3(5)(A)(ii) of the 
Act--Johnson Ranch Created Pools (in Riverside County), which were 
created after the species was listed--we consider all known occurrences 
to be occupied at the time of listing and within the geographical area 
occupied by the species at the time of listing in this proposed 
critical habitat designation. Therefore, throughout this proposed rule, 
we refer to all occurrences (with the exception of Johnson Ranch 
Created Pools) as being occupied at the time of listing whether the 
areas were documented before or after the species was listed.
    We are designating one area, Johnson Ranch Created Pools, as 
essential under section 3(5)(A)(ii) of the Act. Although this area 
falls within the currently occupied geographic range of the species, at 
the time Riverside fairy shrimp was listed, it was not occupied.
    Each area that we are proposing as revised critical habitat 
contains a currently extant (or in the case of Subunit 1b, considered 
extant) occurrence of Riverside fairy shrimp; however, Riverside fairy 
shrimp do not physically occur throughout the entirety of each area. 
The 2,984 ac (1,208 ha) we are proposing as revised critical habitat 
contains occurrences of Riverside fairy shrimp as well as surrounding 
upland areas (the contributing watershed) that contain the physical and 
biological features essential to support Riverside fairy shrimp where 
they physically occur within the proposed revised critical habitat 
subunits (see Physical and Biological Features below). For specific 
information about how this proposed rule compares to the final critical 
habitat designated for this species in 2005, see the Summary of Changes 
From Previously Designated Critical Habitat section below.

New Information Specific to Riverside Fairy Shrimp

    A study to gather genetic distribution data for Riverside fairy 
shrimp across its range, using mitochondrial DNA (mtDNA) on the 
cytochrome oxidase I (COI) gene, was conducted in 2010 (Lahti et al. 
2010, pp. 1-47). Sequencing of 179 individuals from 32 pools comprising 
20 pool complexes detected low population genetic variability overall 
at the selected locus, and resulted in detection of five unique 
haplotypes (Lahti et al. 2010, p. 17). A haplotype is a combination of 
alleles (the alternative forms of a gene that is located at a specific 
position on a specific chromosome) at a single locus or multiple loci 
that are transmitted together on the same chromosome. This was the 
first study of its kind to look at genetic composition and variation of 
Riverside fairy shrimp across its range and, as such, represents 
preliminary information. Most of the genetic variability was limited to 
San Diego County (Camp Pendleton, San Diego

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north; haplotypes D, E) and Otay Mesa (San Diego south; haplotypes B, 
C), and all pools in Riverside and Orange Counties were fixed for the 
most common haplotype, haplotype A (Lahti et al. 2010, p. 17).
    Although the amount of genetic variation was low, haplotype 
frequencies among complexes varied, showing approximately 60 percent of 
the genetic variability partitioned among pool complexes and 18 percent 
partitioned among regions (Lahti et al. 2010, p. 19). Lahti et al. 
concluded that low variation at the COI gene region does not confer 
definitive evidence that Riverside fairy shrimp populations are 
currently connected by high levels of gene flow rangewide; on the 
contrary in areas where genetic variation was detected, haplotype 
frequencies varied significantly across even geographically proximate 
pools, suggesting low gene flow (Lahti et al. 2010, p. 19). Genetic 
variability and genetic differentiation between and among populations 
(and across the species' distribution) may be important to long-term 
species persistence because it represents the raw material for 
adaptation to differing local conditions and environmental 
stochasticity (Frankham 2005, p. 754). The maintenance of genetic 
variability is crucial to the survival of a species with declining 
populations and a limited range, such as the Riverside fairy shrimp 
(Gilpin and Soul[eacute] 1986, pp. 32-33; Lesica and Allendorf 1995, p. 
756). Loss of genetic connectivity and diversity can hinder a 
population's ability to adapt to ecological perturbations commonly 
associated with urbanization, such as habitat degradation, climatic 
changes, and introduced species (Vandergast et al. 2007, p. 977). 
Vernal pool complexes throughout the range of the Riverside fairy 
shrimp, and within different habitat types, are critical for the 
conservation of this species.

Previous Federal Actions

    The Riverside fairy shrimp was listed as an endangered species on 
August 3, 1993 (58 FR 41384). For a history of Federal actions prior to 
2001, please refer to the September 21, 2000, proposed critical habitat 
rule (65 FR 57136). On May 30, 2001, we published a final rule 
designating critical habitat for the Riverside fairy shrimp (66 FR 
29384). On November 6, 2001, the Building Industry Legal Defense 
Foundation, Foothill/Eastern Transportation Corridor Agency, National 
Association of Home Builders, California Building Industry Association, 
and Building Industry Association of San Diego County filed a lawsuit 
in the United States District Court for the District of Columbia 
challenging the designation of Riverside fairy shrimp critical habitat 
and alleging errors in our promulgation of the May 30, 2001, final 
rule. We requested a voluntary remand, and on October 30, 2002, 
critical habitat for this species was vacated by order of the Federal 
District Court for the District of Columbia and the Service was ordered 
to publish a new final rule with respect to the designation of critical 
habitat for the Riverside fairy shrimp (Building Industry Legal Defense 
Foundation, et al., v. Gale Norton, Secretary of the Interior, et al., 
and Center for Biological Diversity, Inc. and Defenders of Wildlife, 
Inc. Civil Action No. 01-2311 (JDB) (U.S. District Court, District of 
Columbia)).
    On April 27, 2004, we again proposed to designate critical habitat 
for the Riverside fairy shrimp (69 FR 23024). The final critical 
habitat published in the Federal Register on April 12, 2005 (70 FR 
19154). On January 14, 2009, the Center for Biological Diversity filed 
a complaint in the U.S. District Court for the Southern District of 
California challenging our 2005 designation of critical habitat for 
Riverside fairy shrimp (Center for Biological Diversity v. United 
States Fish and Wildlife Service and Dirk Kempthorne, Secretary of the 
Interior, Case No. 3:09-CV-0050-MMA-AJB). A settlement agreement was 
reached with the plaintiffs (Case No. 3:09-cv-00051-JM-JMA; November 
16, 2009) in which we agreed to submit a proposed revised critical 
habitat designation for the Riverside fairy shrimp to the Federal 
Register by May 20, 2011, and submit a final revised critical habitat 
designation to the Federal Register by November 15, 2012.

Critical Habitat

Background

    Critical habitat is defined in section 3 of the Act as:
    (1) The specific areas within the geographical area occupied by the 
species, at the time it is listed in accordance with the Act, on which 
are found those physical or biological features
    (a) Essential to the conservation of the species and
    (b) Which may require special management considerations or 
protection; and
    (2) Specific areas outside the geographical area occupied by a 
species at the time it is listed, upon a determination that such areas 
are essential for the conservation of the species.
    Conservation, as defined under section 3 of the Act, means to use 
and the use of all methods and procedures that are necessary to bring 
any endangered or threatened species to the point at which the measures 
provided pursuant to the Act are no longer necessary. Such methods and 
procedures include, but are not limited to, all activities associated 
with scientific resources management, such as research, census, law 
enforcement, habitat acquisition and maintenance, propagation, live 
trapping, and transplantation, and, in the extraordinary case where 
population pressures within a given ecosystem cannot otherwise be 
relieved, may include regulated taking.
    Critical habitat receives protection under section 7 of the Act 
through the requirement that Federal agencies ensure, in consultation 
with the Service, that any action they authorize, fund, or carry out is 
not likely to result in the destruction or adverse modification of 
critical habitat. The designation of critical habitat does not affect 
land ownership or establish a refuge, wilderness, reserve, preserve, or 
other conservation area. Such designation does not allow the government 
or public to access private lands. Such designation does not require 
implementation of restoration, recovery, or enhancement measures by 
non-Federal landowners. Where a landowner seeks or requests Federal 
agency funding or authorization for an action that may affect a listed 
species or critical habitat, the consultation requirements of section 
7(a)(2) would apply, but even in the event of a destruction or adverse 
modification finding, the obligation of the Federal action agency and 
the landowner is not to restore or recover the species, but to 
implement reasonable and prudent alternatives to avoid destruction or 
adverse modification of critical habitat.
    For inclusion in a critical habitat designation, the habitat within 
the geographical area occupied by the species at the time it was listed 
must contain physical and biological features which are essential to 
the conservation of the species, and it is included only if those 
features may require special management considerations or protection. 
Critical habitat designations identify, to the extent known using the 
best scientific and commercial data available, habitat areas that 
provide essential life-history needs of the species, including but not 
limited to areas which provide for space, food, cover, and protected 
habitat.
    Under the Act, we can designate critical habitat in areas outside 
the

[[Page 31692]]

geographical area occupied by the species at the time it is listed, 
upon a determination that such areas are essential for the conservation 
of the species. We designate critical habitat in areas outside the 
geographical area occupied by a species only when a designation limited 
to its range would be inadequate to ensure the conservation of the 
species. When the best available scientific data do not demonstrate 
that the conservation needs of the species require such additional 
areas, we will not designate critical habitat in areas outside the 
geographical area occupied by the species. An area currently occupied 
by the species but that was not occupied at the time of listing may, 
however, be essential to the conservation of the species and may be 
included in the critical habitat designation.
    Section 4 of the Act requires that we designate critical habitat on 
the basis of the best scientific and commercial data available. 
Further, our Policy on Information Standards Under the Endangered 
Species Act (published in the Federal Register on July 1, 1994 (59 FR 
34271)), the Information Quality Act (section 515 of the Treasury and 
General Government Appropriations Act for Fiscal Year 2001 (Pub. L. 
106-554; H.R. 5658)), and our associated Information Quality Guidelines 
provide criteria, establish procedures, and provide guidance to ensure 
that our decisions are based on the best scientific data available. 
They require our biologists, to the extent consistent with the Act and 
with the use of the best scientific data available, to use primary and 
original sources of information as the basis for recommendations to 
designate critical habitat.
    When we are determining which areas should be designated as revised 
critical habitat, our primary source of information is generally the 
information developed during the listing process for the species. 
Additional information sources include the 1998 Recovery Plan and the 
2008 5-year review for the species, articles in peer-reviewed journals, 
conservation plans developed by States and counties, scientific status 
surveys and studies, biological assessments, or other unpublished 
materials and expert opinion or personal knowledge.
    Habitat and species are often dynamic in that both may shift 
naturally within an area or from one area to another over time. Climate 
change will be a particular challenge for biodiversity because the 
interaction of additional stressors associated with climate change and 
current stressors may push species beyond their ability to survive 
(Lovejoy 2005, pp. 325-326). The synergistic implications of climate 
change and habitat fragmentation are the most threatening facet of 
climate change for biodiversity (Hannah et al. 2005, p. 4). Current 
climate change predictions for terrestrial areas in the Northern 
Hemisphere indicate warmer air temperatures, more intense precipitation 
events, and increased summer continental drying (Field et al. 1999, pp. 
1-3; Hayhoe et al. 2004, p. 12422; Cayan et al. 2005, p. 6; 
Intergovernmental Panel on Climate Change (IPCC) 2007, p. 1181). 
Climate change may lead to increased frequency and duration of severe 
storms and droughts (McLaughlin et al. 2002, p. 6074; Cook et al. 2004, 
p. 1015; Golladay et al. 2004, p. 504). The southwestern region of the 
country is predicted to become drier and hotter overall (Hayhoe et al. 
2004, p. 12424; Seager et al. 2007, p. 1181). Predictions of climatic 
conditions for smaller subregions such as California are less certain.
    Documentation of climate-related changes that have already occurred 
in California (Croke et al. 1998, pp. 2128, 2130; Brashears et al. 
2005, p. 15144), and future drought predictions for California (e.g., 
Field et al. 1999, pp. 8-10; Lenihen et al. 2003, p. 1667; Hayhoe et 
al. 2004, p. 12422; Brashears et al. 2005, p. 15144; Seager et al. 
2007, p. 1181) and North America (IPCC 2007, p. 9), indicate prolonged 
drought and other climate-related changes will continue in the 
foreseeable future. While climate change was not discussed in the 1993 
listing rule, drought was noted in the rule as a stochastic (random or 
unpredictable) event that could have drastic effects on Riverside fairy 
shrimp, given its fragmented and restricted range (58 FR 41384, p. 
41389, August 3, 1993; Service 1998a, p. 34). The magnitude and 
frequency with which local climate-related changes or drought-induced 
impacts may negatively affect limited ephemeral wetland habitats, in 
terms of their seasonal timing, ponding durations, or patterns of 
inundation and dry down, remains untested.
    In southern California, climatic variables affecting vernal pool 
habitats are most influenced by distance from the coast, topography, 
and elevation (Bauder and McMillian 1998, p. 64). As presence and 
persistence of Riverside fairy shrimp appear to be associated with 
precipitation patterns, draw-down factors, and other regional climatic 
factors including aridity (Eriksen and Belk 1999, p. 71), the likely 
impacts of climate change on ecological processes for Riverside fairy 
shrimp are most closely tied to availability and persistence of ponded 
water during the winter and spring. Vernal pools are particularly 
sensitive to slight increases in evaporation or reductions in rainfall 
due to their relative shallowness and seasonality (Field et al. 1999, 
p. 19). Based on existing data, weather conditions in which vernal pool 
flooding promotes hatching, but in which pools become dry (or too warm) 
before embryos are fully developed, are expected to have the greatest 
negative impact on Riverside fairy shrimp resistance and resilience. In 
the 2008 5-year review, we noted that climate change may potentially 
cause changes in vernal pool inundation patterns and pool consistency 
and that drought may decrease or terminate reproductive output if pools 
fail to flood, or if pools dry up before reproduction is complete 
(Service 1998a, p. 34). Long-term or continuing drought conditions may 
deplete cyst banks in affected pools as new reproductive cysts are not 
deposited. Additionally, localized climate-related changes may alter 
the temporal spatial array of occupied habitat patches (across and 
between pool complexes) across the species' geographical range. The 
ability of Riverside fairy shrimp to survive is likely to depend in 
part on their ability to disperse to pools where conditions are 
suitable (Bohonak and Jenkins 2003, p. 786) through passive dispersal 
mechanisms utilizing reproductive cysts (see Life History section 
above).
    The information currently available on the effects of global 
climate change and increasing temperatures does not adequately predict 
the location and magnitude of climate change effects to Riverside fairy 
shrimp; therefore, we are unable to determine if any additional areas 
may be appropriate to include in this proposed revised critical habitat 
designation to address the effects of climate change. We specifically 
request information from the public on the currently predicted effects 
of climate change on Riverside fairy shrimp and its habitat. 
Furthermore, we recognize that designation of critical habitat may not 
include all habitat areas that we may eventually determine are 
necessary for the recovery of the species, based on scientific data not 
now available to the Service. For these reasons, a critical habitat 
designation does not signal that habitat outside the designated area is 
unimportant or may not promote the recovery of the species.
    Areas that support populations of Riverside fairy shrimp, but are 
outside the critical habitat designation, will continue to be subject 
to conservation actions we and other Federal agencies

[[Page 31693]]

implement under section 7(a)(1) of the Act. They are also subject to 
the regulatory protections afforded by the section 7(a)(2) jeopardy 
standard, as determined on the basis of the best available information 
at the time of the agency action. Federally funded or permitted 
projects affecting listed species outside their designated critical 
habitat areas may still result in jeopardy findings in some cases. 
Similarly, critical habitat designations made on the basis of the best 
available information at the time of designation will not control the 
direction and substance of future Recovery Plans, habitat conservation 
plans (HCPs), section 7 consultations, or other species conservation 
planning efforts if new information available to these planning efforts 
calls for a different outcome.

Physical and Biological Features

    In accordance with sections 3(5)(A)(i) and 4(b)(1)(A) of the Act 
and regulations at 50 CFR 424.12, in determining which areas within the 
geographical area occupied at the time of listing to propose as revised 
critical habitat, we consider those physical and biological features 
that are essential to the conservation of the species and which may 
require special management considerations or protection. These include, 
but are not limited to:
    (1) Space for individual and population growth and for normal 
behavior;
    (2) Food, water, air, light, minerals, or other nutritional or 
physiological requirements;
    (3) Cover or shelter;
    (4) Sites for breeding, reproduction, and rearing (or development) 
of offspring; and
    (5) Habitats that are protected from disturbance or are 
representative of the historical, geographical, and ecological 
distributions of a species.
    We derive the specific physical and biological features required 
for Riverside fairy shrimp from studies of this species' habitat, 
ecology, and life history as described below. Additional information 
can be found in the final listing rule published in the Federal 
Register on August 3, 1993 (58 FR 41384), and the 1998 Recovery Plan 
(Service 1998a). We have determined that the Riverside fairy shrimp 
requires physical and biological features described below.
Space for Individual and Population Growth and for Normal Behavior
    Riverside fairy shrimp require vernal pool habitat to grow and 
reproduce. Their life cycle requires periods of inundation as well as 
dry periods (Ripley et al. 2004, pp. 221-223). Habitats (ephemeral 
wetlands) that provide space for growth and persistence of Riverside 
fairy shrimp include areas that generally pond for 2 to 8 months and 
dry down for a period during the late spring to summer months. Habitats 
include natural and manmade pools (usually >12 in (30 cm) deep) which 
support these longer inundation periods; some of these habitats are 
artificial pools (cattle tanks and road embankments) which have been 
modified or deepened with berms (Hathaway and Simovich 1996, p. 670). 
Artificial depressions, often associated with degraded vernal pool 
habitat, are capable of functioning as habitat and can support vernal 
pool species including Riverside fairy shrimp (Moran 1977, p. 155; 
Service 1998a, p. 22). Space for the Riverside fairy shrimp's normal 
growth and behavior requires an underlying soil series (typically clay 
soil inclusions with a subsurface claypan or hardpan component), which 
forms an impermeable layer, that sustains appropriate inundation 
periods (i.e., water only slowly percolates once filled) and provides 
necessary physiological requirements, including but not limited to, 
appropriate water temperature and water chemistry (mineral) regimes, a 
natural prey base, foraging opportunities, and areas for predator 
avoidance.
    Intact vernal pool hydrology (including the seasonal filling and 
drying down of pools) is the essential feature that governs the life 
cycle of the Riverside fairy shrimp. An intact hydrological regime 
includes seasonal hydration (during not all but most years) followed by 
drying out of the substrate to promote overwintering of cysts, and 
provide conditions to support a viable cyst bank for the following 
season. Proper timing of precipitation and the associated hydrological 
and soil processes in the upland watershed contributes to the provision 
of space for growth and normal behavior; seasonal filling and 
persistence of the vernal pool is necessary for cyst hatching and 
successful reproduction of Riverside fairy shrimp (see Sites for 
Breeding, Reproduction, and Rearing (or Development) of Offspring, 
below).
    To maintain high-quality vernal pool ecosystems, the vernal pool 
basin or complex and its upslope vernal pool watershed (adjacent 
vegetation and upland habitat) must be available and functional (Hanes 
and Stromberg 1998, p. 38). Adjacent upland habitat supplies important 
hydrologic inputs to sustain vernal pool ecosystems. Protection of the 
upland habitat between vernal pools within the watershed is essential 
for maintaining space needs for Riverside fairy shrimp (i.e., 
inundation periods of adequate length to support the entire life-
history function and reproductive cycles necessary for Riverside fairy 
shrimp) and to buffer the vernal pools from edge effects.
    Vernal pools generally occur in complexes, which are defined by two 
or more vernal pools in the context of a larger vernal pool watershed. 
The local watershed associated with a vernal pool complex includes all 
surfaces in the surrounding area that flow into the vernal pool 
complex. Within a vernal pool complex, vernal pools are hydrologically 
connected to one another within the local geographical context. These 
vernal pool complexes may connect by either surface, or subsurface, 
flowing water. Pools and complexes are dependent on adjacent 
geomorphology and microtopography for maintenance of their unique 
hydrological conditions (Service 1998a, p. 23). Water may flow over the 
surface from one vernal pool to another (over-fill or ``overbanking''), 
throughout a network of swales, or low-point depressions within a 
watershed. Due to an impervious clay layer or hardpan, water can also 
flow and collect below ground, such that the soil remains saturated 
with water. The result of the movement of the water through vernal pool 
systems is that pools fill and hold water continuously for a number of 
days, to weeks, to months, following the initial rainfall (Hanes et al. 
1990, p. 51). Some hydrologic systems have watersheds that cover a 
large area and that contribute to filling and the hydrological dynamics 
of the system, while other hydrologic systems have very small 
watersheds and fill almost entirely from direct rainfall. It is also 
possible that subsurface inflows from surrounding soils within a 
watershed contribute to filling some vernal pools (Hanes et al. 1990, 
p. 53; Hanes and Stromberg 1998, p. 48).
    Impervious subsurface layers of clay soils or hardpan geology, 
combined with flat to gently sloping topography, serve to inhibit rapid 
infiltration of rainwater, resulting in ponded water in vernal pools 
(Bauder and McMillian 1998, pp. 57-59). These soils also act as a 
buffer to moderate the water chemistry and rate of water loss to 
evaporation (Zedler 1987, pp. 17-30). In Ventura County, soils series 
known to support Riverside fairy shrimp include, but are not limited 
to, the Azule, Calleguas, Cropley, and Linne soil series. In Orange 
County, soils series include the Alo, Balcom, Bosanko, Calleguas, 
Cieneba, Myford, and Soper soil series. In western Riverside County, 
vernal pool habitat known to support Riverside

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fairy shrimp includes the Altamont, Auld, Bosanko, Cajalco, Claypit, 
Murrietta, Porterville, Ramona, Traver, and Willows soil series. In San 
Diego County, vernal pool habitat known to support Riverside fairy 
shrimp includes the Diablo, Huerhuero, Linne, Placentia, Olivenhain, 
Salinas, Stockpen, and Redding soil series. Soil series data are based 
on 2008 Soil Survey Data and are available online at: https://websoilsurvey.nrcs.usda.gov. For additional information on soils, see 
Primary Constituent Elements (PCEs) for Riverside Fairy Shrimp.
Food, Water, Air, Light, Minerals, or Other Nutritional or 
Physiological Requirements
    Riverside fairy shrimp are filter feeders and their diet consists 
mostly of algae, bacteria, and other microorganisms (Parsick 2002, pp. 
37-41, 65-70). In a natural vernal pool setting, these food items are 
readily available. Typically, an undisturbed, intact surface and 
subsurface soil structure (not permanently altered by anthropogenic 
land use activities such as deep, repetitive discing, or grading), and 
the associated hydrogeomorphic processes within the basin and upland 
watershed, are necessary to provide food, water, minerals, and other 
physiological needs for Riverside fairy shrimp. Water temperature, 
water chemistry, and length of time vernal pools are inundated with 
water are the important factors in the hatching and temporal appearance 
of Riverside fairy shrimp (Gonzalez et al. 1996, pp. 315-316; Hathaway 
and Simovich 1996, p. 669). Riverside fairy shrimp hatch and reproduce 
in water at temperatures that range generally from 5 to 20 degrees 
Celsius (C) (41 to 68 degrees Fahrenheit (F)), and typically do not 
hatch at temperatures greater than 25 degrees C (77 degrees F) 
(Hathaway and Simovich 1996, pp. 674-675). Riverside fairy shrimp have 
a wider thermal tolerance than San Diego fairy shrimp (Branchinecta 
sandiegonensis), which allows Riverside fairy shrimp to hatch later in 
the season when deeper vernal pools are still filled with water.
Cover or Shelter
    Ponding of vernal pool habitat (water) also provides cover and 
shelter for Riverside fairy shrimp. During the time these habitats are 
inundated, water plays an important role in providing the necessary 
aquatic environment (shelter) for the fairy shrimp to complete their 
life-history requirements. Without protection from desiccation provided 
by water, fairy shrimp would be unable to hatch, grow, mature, 
reproduce, and disperse within the vernal pool habitat (Helm 1998, p. 
136; Service 1998a, p. 34; Eriksen and Belk 1999, pp. 71, 105). 
Additionally, the wet period (ponding) excludes species that are 
exclusively terrestrial, providing a level of shelter from predation 
and competition for the fairy shrimp that are adapted to short-lived, 
ephemeral wetland habitats.
    The undisturbed soil bank also provides cover and shelter for fairy 
shrimp cysts during the dry-down period of the vernal pool habitat. The 
drying phase allows reproductive cysts to overwinter, as the cysts lay 
dormant in the soil; basin soils provide cover and shelter to Riverside 
fairy shrimp as the vernal pool dries out (Simovich and Hathaway 1997, 
p. 42; Eriksen and Belk 1999, p. 105). By maintaining the population in 
a dormant state, reproductive cysts, and the undisturbed soil in which 
they rest, protect Riverside fairy shrimp from predators and 
competitors during the dry period in vernal pools. Cyst dormancy is an 
importan