Species and Community Profiles - San Francisco Estuary ...

Fish
Amphibians &
Reptiles
numerically dominant fish species of Morro Bay lower
intertidal mudflats. The bay goby inhabits burrows of
the blue mud shrimp (Upogebia pugettensis) and the innkeeper
worm (Urechis caupo) and siphon holes of the
geoduck clam (Panope generosa) in Morro Bay (Grossman
1979a). As for several other species of gobies common
to San Francisco Bay, including arrow goby and longjaw
mudsucker, the bay goby probably utilizes burrows as a
refuge from predators and to avoid desiccation at low
tides.
Few bay gobies have been collected in San Francisco
Bay tidal marshes. One bay goby was reported from
Gallinas Marsh and one from Corte Madera Marsh
(CH 2 M Hill 1982). Both fish were collected by gill nets,
which were used to sample the larger channels. In contrast,
the bay goby was the most common species collected
in otter trawl samples from Corte Madera Creek
channel, adjacent to Corte Madera Marsh. No bay gobies
have been collected by other San Francisco Bay tidal
marsh studies (Wild 1969; Woods 1981; ANATEC
Laboratories1981; CH 2 MHill 1996; CDFG, unpub.
data) or by a study of fishes of Elkhorn Slough tidal
marshes (Barry 1983).
Bay goby YOY are most abundant in otter trawl
samples from February through June, which is a one or
two months after peak abundance period for smaller juveniles
from the ichthyoplankton net (CDFG 1987 and
unpub. data). In several years, multiple cohorts of YOY
fish have been collected; this was especially noticeable
in four of the six years of the 1987-1992 drought
(CDFG, unpub. data). Peak abundance of older fish is
usually from May through September, which corresponds
with the peak period of larval abundance in San
Francisco Bay.
The bay goby has been collected primarily from
polyhaline salinities in San Francisco Bay, with YOY fish
collected at lower salinities than older fish (Table 2.6).
YOY were also collected at slightly lower temperatures
than older fish (Table 2.6). These differences in salinity
and temperature by age class are reflected by the dis-
Table 2.6 Bay Goby Salinity and Temperature
Statistics: 1980-92 (CDFG unpublished data)
Age Class Mean 5 th Median 95 th
percentile percentile
Salinity (ppt):
YOY 27.3 14.9 29.2 31.7
1+ and older 28.1 17.1 29.7 32.4
Temperature (°C):
YOY 15.4 11.3 15.2 18.8
1+ and older 16.0 12.4 16.3 18.9
140 Baylands Ecosystem Species and Community Profiles
tribution of YOY somewhat further upstream than older
fish and by the peak abundance of YOY in the winter
and spring and older fish in summer and fall.
Population Status and Influencing Factors
Although trawls are usually considered ineffective for gobies,
the bay goby is a very common fish in San Francisco
Bay otter trawl surveys. As such, the abundance
indices derived from trawl data may be good indicators
of population trends. California Department of Fish and
Game otter trawl data from 1980-1998 is the longest
data set available for the Bay. The indices from 1988 to
1997 were generally higher than the pre-1988 indices
(Figure 2.9). The relatively stable salinities year-round
during the 1987-92 drought may have resulted in increased
nursery habitat for this species (Hieb and Baxter
1993). The multiple cohorts of YOY collected these
years, which indicate successful recruitment over a period
of several months, in part support this hypothesis.
Additionally, high winter outflow events may carry larvae
or pelagic juveniles from the Bay.
Abundance of predators, as California halibut and
Pacific staghorn sculpin, could influence the bay goby
population. Additionally, factors controlling the abundance
of the commensal burrowing invertebrate hosts
may effect the bay goby population. This would include
the abundance and distribution of intertidal and subtidal
mudflat invertebrate predators, such as the bat ray and
leopard shark.
Trophic Level
Secondary consumer.
Proximal Species
Predators: California halibut, Pacific staghorn sculpin.
Prey: Polychaetes, gammarid amphipods, harpacticoid
copepods, bivalves.
Figure 2.9 Annual Abundance Indices of All Sizes of
Bay Goby, Otter Trawl (CDFG unpublished data)
Plants