NO. 3565 POLYCHAETA AND AMPHIPODA—REISH AND BARNARD 3 
ments south of Point Conception that belong with the warm- 
temperate, low-rainfall regime. 
Except where dredging has deepened some channels, Morro Bay is 
exceedingly shallow; much of the bay floor is exposed during minus 
tides. Two streams drain into the bay: Chorro Creek enters the 
Bay through a channel in the marshland (Stations 28 to 25) and 
Los Osos Creek enters near Station 29. The triangular marshland, 
extending from Stations 28 to 25 and then landward to the right 
in figure 1, constitutes the Morro Bay State Park Bird Reserve. 
Changes by man in Morro Bay include the dredging of channels, 
the construction of a small boat harbor at Stations 11 and 12, dock 
facilities along the shore extending from about Stations 3 to 11, 
jetties at the Bay entrance, and fencing for oyster beds. Small 
docks have been built at other localities of the bay. No pollution 
is known to exist (Barrett, 1963). A steam-generating plant near 
Station 3 takes in sea water from this area for use in cooling con- 
densors, but the water is discharged by a channel into the open sea 
north of the Bay. 
Although Morro Bay is important as a port for both commercial 
and sport fisheries, only the oyster, accounting for a value of $24,467 
in 1961, is harvested directly from the bay. The total value of 
commercial landings for 1961 (Anon., 1963) was $632,324, with 
abalone accounting for over one-third of the total. The history of 
oyster farming in Morro Bay has been summarized by Barrett (1963). 
The Pacific oyster, Crassostrea gigas (Thunberg), was first introduced 
from Japan to Morro Bay in 1932. The beds extend throughout 
much of the middle part of the bay from about the region of Station 5 
to Stations 21, 22, and 29 (fig. 1). 
MATERIALS AND METHODS.—Bottom samples, taken on August 25, 
1960, from a small skiff using a size one Hayward orange-peel bucket 
(taking an area of %_ sq. meter), were obtained from all stations indi- 
cated in figure 1 with the exception of Stations 1, 2, 5, and 6 where 
the substrate was a hard-packed sand. The samples were washed 
on shore through a size 24 screen (0.7 mm openings) and preserved 
in formalin diluted with seawater. The polychaetes and amphipods 
were separated from the other organisms by Mr. Harold Pope. 
The polychaetes were identified by Reish and the amphipods by 
Barnard. The dissolved oxygen, salinity, and water temperature 
were determined on August 26, 1960, from 14 representative stations 
at surface and deeper levels; each varied according to depth of water. 
The modified Winkler method was used for dissolved oxygen meas- 
urement (Barnes, 1959), and the chlorinity was determined by the 
Mohr method (Barnes, 1959). Water temperature was measured 
with a thermistor-type thermometer. 
