2008 Annual Monitoring Report (pdf 10.9MB) - Bolsa Chica ...

Bolsa Chica Lowlands Restoration Monitoring
2008 Annual Report
Discussion
The 2008 monitoring year included the period of 17 to 25 months post-opening to the ocean. During
the first survey in October 2007 (13 months post-opening), a total of 17 species were observed in the
FTB (Merkel & Associates 2008). By October 2008, the cumulative total had increased to 38 species
after 5 surveys (though only 15 species were captured in the October 2008 survey itself). The only
species captured in the FTB in 2007 but not 2008 were snubnose pipefish, California tonguefish, and
striped mullet. The pipefish and tonguefish may still be present but undetected and striped mullet were
frequently seen, just not captured due to the difficulty of catching them without a gill net.
The species joining the fish community in the FTB are increasingly associated with structured habitats,
which is most likely due to the spread of eelgrass habitat, particularly in the southern half of the basin.
Structure-associated fish such as blennies, surfperch, and kelpfish will likely increase in abundance as
eelgrass continues to spread in the coming years. The eelgrass also provides nursery habitat for
species such as topsmelt, which lay eggs on the eelgrass in estuaries and bays (Emmett et al. 1991).
The creation of the FTB has increased the availability of important bay habitat, provided nursery
functions for many species of marine fish, and thereby improved southern California fisheries
resources. Nearly every fish species captured during the 2007 and 2008 monitoring was represented
by juvenile size classes, demonstrating the linkages between the basin and coastal fisheries, and the
role of the basin as nursery habitat for spawning or post-larval dispersal. CDFG staff have also
reported spawning by California grunion on the high sand beach on the north side of the channel
entrance (K. O’Reilly pers. comm.). The creation of shallow-water habitat rich with primary
production supplies detritus-based and grazing-based food webs with energy. Ultimately, this energy
is transferred to fish and used to support increased biomass and numbers. Additionally, this increased
production is transferred offshore with individuals that leave the basin, or it supports other ecological
communities through consumption by avian and mammalian consumers.
The fish community of the MTBs was in its early stages in 2008, with only the western basin open to
tidal influence and manual adjustments still being made to its tidal range throughout the year. The
presence of high numbers of topsmelt and California killifish are reflected in the usage of these basins
by terns and wading marsh birds for foraging. The large numbers of post-larval atherinids captured in
July suggests the basin is being used for spawning.
Although the west MTB showed relatively stable water quality, the central and east will continue to
experience fluctuations in temperature, salinity, and dissolved oxygen that will limit the diversity of
fish that can persist there. It is anticipated that diversity and distribution of fish will increase once all
three basins are opened directly to the FTB through their tide gates, allowing for more stable water
quality, regular tidal flushing, and exchange of fish between the basins.
The Muted Pocket Marsh continued to provide an abundant food source of small fish for the many
piscivorous birds that use the marsh. It is key to note that the MPM is not hydrologically connected to
the FTB of Bolsa Chica, rather it receives muted tidal influence through a water control structure from
outer Bolsa Bay, through Huntington Harbour, which ultimately opens to the ocean over 6.5 km (4
miles) to the northwest. It is anticipated that future sampling events may reveal a few more species
tolerant of lower salinities and limited tidal flushing, however the muted tidal conditions, the water
control structure, and the distance from the ocean will likely limit the diversity and size of fish that
ultimately make up the community of the marsh.
Merkel & Associates, Inc. 54