Ichthyofaunal Utilization of a Man-Made Salt Marsh Creek in Mission Bay, California, 25 Years After Creation

Abstract: Southern California\u27s wetlands are drastically declining due to human activities. Increasingly, marsh restoration and creation are being used to mitigate such losses. This study used minnow traps to resample the ichthyofauna of a created marsh (Crown Point Mitigation Site; CPMS) and an adjacent natural marsh (Kendall Frost) in Mission Bay, California, 26 years following the marsh creation. These data were compared to data collected from 1995-1998, immediately after marsh creation. Fishes trapped included Fundulus parvipinnis, Gillichthys mirabilis, Ctenogobius sagittula, Atherinops affinis, and Mugil cephalus. Species richness and dominance measures were higher in the natural relative to the created marsh. The size-structure of F. parvipinnis in the natural marsh was skewed towards larger sizes relative to those in the created marsh. These size differences are the opposite of those noted in the years immediately following marsh creation and appear to arise from differences in creek morphology between the created and natural systems, with the created marsh having become shallower through time. The differences in size-structure and species richness between the created and natural systems suggest that marsh and creek geomorphology may affect the suitability of habitat for resident fishes, and so should be considered when designing marsh restoration projects

The Role of Resident Fishes in Linking Habitats of a Southern California Salt Marsh

Natural environments are not homogenous, but instead are mosaic landscapes often comprised of quite environmentally distinct habitats. They harbor distinct biological communities which vary across a number of spatial and temporal scales. These habitats are not isolated but are connected through physical and biological linkages which themselves vary through time and across spatial scales. This study addressed the effect of habitat heterogeneity on the resident fish community of a tidal salt marsh in Mission Bay, CA, and examined how fish-utilization patterns mediated linkages between habitats. First, reproductive and habitat utilization data were combined with a comprehensive review of the literature on F. parvipinnis to highlight major gaps in our understanding of this important species. Next, small- (decimeler) and larger-scale (100's of meter) patterns of habitat utilization within the marsh landscape were examined. Physical environments differed among microhabitats (seagrass beds, unvegetated flat, subtidal creeks, intertidal creeks and intertidal pools) and changed over short (tidal) through longer (interannual) time scales. Small resident fishes recognized and responded to these habitats, showing preferences in utilization even at the smallest spatial scales examined. Fundulus panipinnis habitat preferences changed through ontogeny, with small juveniles preferring intertidal pool and shallow creek habitats, while larger juveniles selected deeper habitats. Nighttime foraging of Fundulus parvipinnis, a numerical dominant in the southern California marsh fish community, was also investigated. Fundulus parvipinnis was found to feed nocturnally, but with reduced efficiency, ingesting more detritus at night than during daytime. Further, F. panipinnis was shown to spawn on nighttime spring tides in Mission Bay. Thus, habitat value changes for this species over diel time scales. Finally, the potential consequences of microhabitat availability were explored in a study of ichthyofaunal colonization of a newly-created marsh was examined in Mission Bay, CA. This highly-modified habitat was rapidly colonized by fishes, but in the created marsh size-structure of the fish communities was skewed towards larger individuals. Lack of juveniles was attributed to absence of critical pool and shallow creek (microhabitat) availability. The results of this study indicate that the activities of resident fishes can create likages at multiple scales between habitats within the wetland mosaic

The Role of Resident Fishes in Linking Habitats of a Southern California Salt Marsh

Natural environments are not homogenous, but instead are mosaic landscapes often comprised of quite environmentally distinct habitats. They harbor distinct biological communities which vary across a number of spatial and temporal scales. These habitats are not isolated but are connected through physical and biological linkages which themselves vary through time and across spatial scales. This study addressed the effect of habitat heterogeneity on the resident fish community of a tidal salt marsh in Mission Bay, CA, and examined how fish-utilization patterns mediated linkages between habitats. First, reproductive and habitat utilization data were combined with a comprehensive review of the literature on F. parvipinnis to highlight major gaps in our understanding of this important species. Next, small- (decimeler) and larger-scale (100's of meter) patterns of habitat utilization within the marsh landscape were examined. Physical environments differed among microhabitats (seagrass beds, unvegetated flat, subtidal creeks, intertidal creeks and intertidal pools) and changed over short (tidal) through longer (interannual) time scales. Small resident fishes recognized and responded to these habitats, showing preferences in utilization even at the smallest spatial scales examined. Fundulus panipinnis habitat preferences changed through ontogeny, with small juveniles preferring intertidal pool and shallow creek habitats, while larger juveniles selected deeper habitats. Nighttime foraging of Fundulus parvipinnis, a numerical dominant in the southern California marsh fish community, was also investigated. Fundulus parvipinnis was found to feed nocturnally, but with reduced efficiency, ingesting more detritus at night than during daytime. Further, F. panipinnis was shown to spawn on nighttime spring tides in Mission Bay. Thus, habitat value changes for this species over diel time scales. Finally, the potential consequences of microhabitat availability were explored in a study of ichthyofaunal colonization of a newly-created marsh was examined in Mission Bay, CA. This highly-modified habitat was rapidly colonized by fishes, but in the created marsh size-structure of the fish communities was skewed towards larger individuals. Lack of juveniles was attributed to absence of critical pool and shallow creek (microhabitat) availability. The results of this study indicate that the activities of resident fishes can create likages at multiple scales between habitats within the wetland mosaic

Insights into the establishment of the Manila clam on a tidal flat at the southern end of an introduced range in Southern California, USA.

Coastal ecosystem modifications have contributed to the spread of introduced species through alterations of historic disturbance regimes and resource availability, and increased propagule pressure. Frequency of occurrence of the Manila clam (Venerupis phillipinarum, Veneridae) in Southern California estuaries has increased from absent or sparse to common since the mid-1990s. Potential invasion vectors include seafood sales and aquaculture, and spread from established northern populations over decades. The clam's post-settlement habitat preferences are, however, uncertain in this region. Our project aimed to identify factors associated with established patches of the clam within a bay toward the southern end of this introduced range. During summer 2013, we sampled 10 tidal flat sites in Mission Bay, San Diego; each containing an area with and without hard structure (e.g., riprap, boulders). We measured likely environmental influences (e.g., sediment variables, distance to ocean). Manila clam densities across the bay were most strongly associated with site, where highest densities were located in the northern and/or back halves of the bay; and weakly correlated with lower porewater salinities. Within sites, Manila clam density was enhanced in the presence of hard structure in most sites. Prevailing currents and salinity regimes likely contribute to bay wide distributions, while hard structures may provide suitable microhabitats (refuge from predators and physical stress) and larval entrapment within sites. Results provide insights into decisions about future shoreline management efforts. Finally, we identify directions for future study to better understand and therefore predict patterns of establishment of the Manila clam in the southern portion of its introduced range

Backtransformed average (±SE) density of the Manila clam in benthic cores taken from beside hard substrate (rip rap) and in adjacent areas without significant hard substrate in Mission Bay, San Diego, California, USA.

<p>n = 10 paired sites. * = 0.01</p

Map of intertidal benthic study sites within Mission Bay, San Diego, California, USA.

<p>SM = South Mission Bay, IP = Island Point, NC = North Cove, NSB = North Ski Beach, WFI = Fiesta Island, CP = Crown Point, DAC = D’Anza Cove, CLD = Clairemont Drive, EMB = East Mission Bay Drive, SW = Sea World. The Manila clam was found in all sites except SM and WFI.</p

Results of multiple linear regression testing relationships between densities of all Manila clam individuals (A.), juveniles only (<2 cm diameter) (B.), and adults only (C.); and environmental variables (presence/absence of hard structure, distance from bay mouth, sediment salinity, grain size and organic matter content) in Mission Bay, San Diego, California, USA.

<p>Results of multiple linear regression testing relationships between densities of all Manila clam individuals (A.), juveniles only (<2 cm diameter) (B.), and adults only (C.); and environmental variables (presence/absence of hard structure, distance from bay mouth, sediment salinity, grain size and organic matter content) in Mission Bay, San Diego, California, USA.</p

Results of two-way ANOVA testing differences in sediment variables (A.) and bivalve variables (B.) between areas with and without hard structure) and among sites in Mission Bay.

<p>Structure presence/absence was treated as a fixed variable, while site (block) was designated as a random variable. N = 60 samples (6 each per 10 sites) <i>V</i>.<i>p</i>. = Manila clam (<i>Venerupis philippinarum</i>). Average (±standard error) of raw (untransformed) variables in the presence and absence of hard structure are shown; bold indicates significant difference between the presence and absence of structure. Significance was determined using Bonferroni adjusted alpha value (initial α = 0.05).</p><p>Results of two-way ANOVA testing differences in sediment variables (A.) and bivalve variables (B.) between areas with and without hard structure) and among sites in Mission Bay.</p

Spatial and Temporal Examination of Bivalve Communities in Several Estuaries of Southern California and Northern Baja California, MX.

A combination of historical bivalve surveys spanning 30-50 years and contemporary sampling were used to document the changes in bivalve community structure over time at four southern California and one northern Baja California estuaries. While there are limitations to the interpretation of historic data, we observed generally similar trends of reduced total bivalve species richness, losses of relatively large and/or deeper-dwelling natives, and gains of relatively small, surface dwelling introduced species across the southern California estuaries, despite fairly distinct bivalve communities. A nearly 50-year absence of bivalves from two wetlands surveyed in a Baja California estuary continued. A combination of site history and current characteristics (e.g., location, depth) likely contributes to maintenance of distinct communities, and both episodic and gradual environmental changes likely contribute to within-estuary temporal shifts (or absences). We highlight future research needed to determine mechanisms underlying patterns so that we can better predict responses of bivalve communities to future scenarios, including climate change and restoration