Chapter 3 - Natural Resources - Marine Corps Base Camp Pendleton
Chapter 3 - Natural Resources - Marine Corps Base Camp Pendleton
Chapter 3 - Natural Resources - Marine Corps Base Camp Pendleton
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MCB <strong>Camp</strong> <strong>Pendleton</strong>, California<br />
MCBCP<br />
<strong>Camp</strong> <strong>Pendleton</strong> contains three of the remaining 19 drainage basins where arroyo toads are<br />
reasonably believed to be extant: the Santa Margarita, San Onofre, and San Mateo (Figure<br />
3-30). It is likely that some of the largest remaining populations of this species occur on<br />
<strong>Camp</strong> <strong>Pendleton</strong> (Holland & Goodman 1998a). For detailed information on the arroyo toad<br />
and its management on <strong>Base</strong> see Appendix F, Section F.1. Distribution of arroyo toads on<br />
<strong>Camp</strong> <strong>Pendleton</strong> are areas identified as believed to be required by the USFWS for recovery<br />
of the species in the recovery plan (USFWS 1999a).<br />
3.2.4.14. Riverside Fairy Shrimp (Streptocephalus woottoni)<br />
FIGURE 3-32. RIVERSIDE FAIRY SHRIMP<br />
Riverside Fairy Shrimp (Streptocephalus<br />
woottoni) are free-swimming filter feeder<br />
crustaceans, which hatch from dormant cysts<br />
once hydrated under specific environmental<br />
conditions. Mature male Riverside fairy<br />
shrimp are approximately 0.5 to 1.0 inches<br />
long and the females are approximately 0.5<br />
to 0.87 inches in total length (USFWS 2005).<br />
Riverside fairy shrimp generally occur in<br />
groups of vernal pools (aka IEW) referred to<br />
as vernal pool complexes, and are typically<br />
visible from January to March; however, the<br />
hatching period may be extended in years of<br />
late rainfall (USFWS 2008h). Vernal pool<br />
complexes tend to average between 5 and 50<br />
(PHOTO SOURCE: C. BROWN, USGS)<br />
vernal pools, although some contain as few as<br />
two vernal pools and others contain several<br />
hundred vernal pools (complexes containing Riverside fairy shrimp often contain only 1 or<br />
2 pools; however, on MCB <strong>Camp</strong> <strong>Pendleton</strong> and Otay Mesa in San Diego County,<br />
complexes generally contain many pools). Vernal pools within a complex are generally<br />
hydrologically connected, such that water flows over the surface from one pool to another,<br />
and/or water flows and collects belowground such that the soil becomes saturated with<br />
water, thus filling the vernal pool (USFWS 2008h). For this reason, vernal pool complexes<br />
are best described from a watershed perspective (USFWS 2008h). The vernal pool<br />
watershed includes all areas around a vernal pool complex needed to collect rainfall and<br />
adequately fill the vernal pools within the complex. Vernal pools begin to fill following<br />
the onset of fall and winter rains and may remain hydrated until April or May. Some pools<br />
in a complex have substantial watersheds that contribute to filling the vernal pools, while<br />
others fill almost entirely from rainfall (USFWS 2008h). Additionally, subsurface inflows<br />
from surrounding soils may be an important factor in filling some vernal pools (USFWS<br />
2008h). Riverside fairy shrimp are restricted to dilute vernal pools, having relatively low<br />
sodium (Na+) concentrations (below 60 millimoles per liter), low alkalinity (below 1000<br />
milligrams per liter), and neutral pH (near 7) (USFWS 2008h). Riverside fairy shrimp are<br />
unable to regulate their internal ion levels and mortality increases at higher Na+<br />
concentrations and alkalinity (USFWS 2008h).<br />
3-66 <strong>Chapter</strong> 3 – <strong>Natural</strong> <strong>Resources</strong>