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Open Access Publications from the University of California

Scholarly Works (3 results)

  • Article
  • Peer Reviewed
Research Theses and Dissertations (2000)

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.

    Cover page: The Role of Resident Fishes in Linking Habitats of a Southern California Salt Marsh
    • Article
    • Peer Reviewed
    UC San Diego Previously Published Works (2013)
    The Colorado River Delta is one of the most impacted wetland systems in the world and has experienced massive habitat loss owing to severe restrictions in freshwater inflow as a result of dam construction and diversion of water for irrigation. However, the delta still offers nesting and foraging habitats for waterbirds, although the habitats available are highly fragmented and limited. Stable isotope ratio (SIR) analysis was used to assess quantitatively isotopic niche width of gull-billed terns (Gelochelidon nilotica), laughing gulls (Leucophaeus atricilla) and snowy egrets (Egreta thula) that nest at an inland and coastal location. The variance in carbon and nitrogen SIR of egg albumen indicated that inland colonies have a much broader isotope niche width (range 2.9 to 23.9) than coastal colonies (<0.1 to 1.4).Species-specific mean albumen δ13C values from inland nests were significantly more depleted in 13C than coastal colonies (-19.5 to -23.1‰ and -10.4 to -14.9‰, respectively). Comparison of albumen δ13C values corrected for trophic fractionation with those of potential prey and primary producers collected at 10 potential foraging grounds indicates that females of the three species that nest in inland colonies did not feed in habitats located in the vicinity of their nesting site, while coastal colonies had distinct isotopic signatures reflecting marine primary production. Inland colonies probably forage in a variety of habitats and for different prey, relying on food webs based mostly on C3 terrestrial plants. Differences in the isotopic composition of eggs from species nesting in the same area and between conspecifics nesting in different habitats indicate that foraging habitats vary substantially, suggesting that feeding varies as a function of local resource availability. These results suggest that a variety of habitat types fulfill the foraging needs of this suite of nesting waterbird species, especially in inland colonies. Since the specific feeding areas of nesting females from the inland colonies have not been identified, protection of the remaining wetlands within the Colorado River Delta is warranted. © 2013 John Wiley & Sons, Ltd.
      Cover page: Stable isotope ratios of egg albumen of three waterbird species nesting in the Colorado River Delta indicate differences in foraging ground and isotopic niche breadth
      • Article
      • Peer Reviewed
      Extension Publications (2016)
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