While the majority of species have wide latitudinal ranges, most species 
show differences in abundance among the three ecoregions within the 2003 
EMAP sampling frame. The polychaete Magelona longicornis and bivalve 
Axinopsida serricata are examples of species with maximum densities in the 
northern portion of the sampling frame, the Oregon, Washington, Vancouver 
Shelf & Coast ecoregion (Figs. 3.5.11, 3.5.12). The ophiuroid Amphiodia urtica is 
an example of a species with maximum densities in the SCB ecoregion (Fig. 
3.5.13), while Pinnixa occidentalis has its maximum densities in the middle of the 
coast, in the Northern California ecoregion (Fig. 3.5.14). 
The second question that we address is whether there is a unique shelf 
fauna different from that found in Puget Sound or the coastal estuaries. The 
Puget Sound ecoregion has a high species overlap with the shelf fauna, with 
87% of the abundant species on the shelf also reported from Puget Sound 
(Appendix Table 5). While portions of Puget Sound are estuarine, much of Puget 
Sound resembles the shelf with its greater depth and high salinity, which 
presumably explains much of the species’ overlap. Three of the five species not 
found in Puget Sound were not found along the Oregon-Washington coast, 
suggesting that they are limited to more southern latitudes in general, rather than 
from Puget Sound specifically. The other two abundant species ( Chloeia pinnata 
and Paradiopatra parva) not found in Puget Sound are found in the Oregon, 
Washington, Vancouver Shelf & Coast ecoregion. However, Chloeia pinnata 
was not found north of 44 degrees in the present survey and may not be well 
adapted to the most northern latitudes within the ecoregion. In contrast, 
Paradiopatra parva was found in the present survey up to 48 degrees latitude, 
suggesting that there are specific conditions within Puget Sound that limit its 
distribution or abundance. 
Less expected was the extent of faunal overlap with the coastal estuaries. 
Almost 85% (33) of the most abundant shelf species have been reported at least 
once from the coastal estuaries of California, Oregon, or Washington exclusive of 
Puget Sound. Thus, it appears that the habitat requirements for many of the 
shelf species are sufficiently broad to allow at least colonization in estuarine 
ecosystems, though it is not clear whether they establish self-maintaining 
populations in all cases. Of the habitat requirements likely to limit shelf species 
from estuaries, the lower and variable salinities in estuaries are likely to be 
critical, if not the most critical, factors. Among the species reported from 
estuaries, one possibility is that they are able to colonize only the high-salinity 
Southern California estuaries, such as San Diego, which are euhaline (> 30 psu) 
over most of their area. Of the 33 species found in estuaries, eight ( Prionospio 
jubata, Paradiopatra parva, Monticellina cryptica, Aricidea catherinae, 
Pseudofabriciola californica, Maldane sarsi, Scalibregma californicum, and 
Ampelisca brevisimulata) have been reported only from Southern California 
estuaries. In comparison to the Southern California estuaries, small estuaries in 
the Pacific Northwest undergo large salinity shifts both seasonally and tidally, so 
that species found in small estuaries are likely to have relatively broad salinity 
101 
