Native and Alien Fishes in a California Estuarine Marsh: Twenty-One Years of Changing Assemblages

Abstract

We used monthly otter trawling and beach seining to sample the fishes of Suisun Marsh in the San Francisco Estuary from 1979 to 1999. We collected nearly 173,000 fish, mostly young of the year, representing 28 native species and 25 alien species. Catch data were related to temperature, salinity, water transparency, and several measures of freshwater inflow into the marsh. Species abundance and distribution within the marsh were the product of several interacting factors:(1) the timing and place of reproduction of the abundant resident species, (2) past reproductive success, (3) habitat differences among sloughs, and (4) physiological tolerance. We did not find consistent groups of potentially interacting species, although some native species showed weak concordance in abundance. The lack of persistent fish assemblages is related to the naturally fluctuating environmental conditions of the estuary, the overall decline in fish abundance through time, and the frequent invasions of alien fishes and invertebrates. Our results suggest that the fish assemblages in Suisun Marsh will continue to be unpredictable until estuarine processes approach their historic range of variability and alien invasions are halted.

The Aquatic Trophic Ecology of Suisun Marsh, San Francisco Estuary, California, During Autumn in a Wet Year

“…However, the communities of this brackish marsh are similar to the communities found in other areas of the estuary, with alien species accounting for the largest portion of the invertebrate and fish catch (Matern et al 2002;Schroeter 2008;O'Rear and Moyle 2010). Alien species are not only numerically dominant in Suisun Marsh but are also very diverse, having at least one abundant representative in nearly all taxonomic groups and being the sole members of the classes Hydrozoa and Cirripedia.…”

“…As freshwater inflow decreases in late spring and early summer, saltier water intrudes and salinity increases, reaching its highest levels in fall before declining after winter rains begin and freshwater inflows from the watershed subsequently increase. These factors strongly influence the diversity of the aquatic community and the abundance of species (Meng and Matern 2001;Matern et al 2002;Schroeter 2008). Suisun Marsh is generally recognized as being an important low-salinity nursery area for numerous fishes and macroinvertebrates (Meng et al 1994;Meng and Matern 2001;Matern et al 2002;Feyrer et al 2003;Moyle et al 2014).…”

“…Sampling locations were in the southwest region of Suisun Marsh and included the lower reaches of Suisun, Cordelia, and Goodyear sloughs ( Figure 1). We selected this area in autumn because of the high taxonomic diversity of fishes and invertebrates that typically reside there (Matern et al 2002). We intentionally chose a limited area within Suisun Marsh to minimize the variability often encountered with stable isotope analyses along a spatial gradient (e.g., Fry 1999).…”

“…The pumped water was pre-filtered through a 100-µm mesh net to remove zooplankton and then further filtered using a low-pressure vacuum pump that pulled the water through an ashed Whatman glass microfiber filter (46-mm diameter) and retained the phytoplankton samples. 4 km hr -1 at three spatially fixed sampling locations (SU3, SU4, and GY3; Figure 1) that are part of a monthly monitoring survey of fish and invertebrates in Suisun Marsh that the University of California, Davis, conducts (Matern et al 2002;Schroeter 2008); a total of six trawls were pulled, three in each month, one per site per month. The trawl mesh was 35-mm fully stretched with a 17-mm rough opening, and the cod-end was lined with a 6-mm fully stretched and 3-mm rough-opening mesh.…”

Maternal transfer of xenobiotics and effects on larval striped bass in the San Francisco Estuary

“…Contaminants from industry, agriculture, urban runoff, and other sources have found their way into these environments, affecting all levels of biological organization, from the individual to the entire ecosystem (1)(2)(3). Consequently, fish species assemblages have shifted (4), and major fish population declines have occurred (5,6). Understanding the role contaminants play in contributing to these declines is essential and will ultimately help elucidate their effects on human populations.…”