Author: Lance H. Butler
Publisher:
ISBN:
Category : Fish communities
Languages : en
Pages : 234

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Book Description

Author: Kristina Yoshida
Publisher:
ISBN:
Category :
Languages : en
Pages : 108

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Book Description
Freshwaters ecosystems support extraordinary biodiversity relative to their extent and provide important societal benefits. As such, freshwater environments and biota are often heavily impacted by anthropogenic activities. Freshwater fishes in Mediterranean-climate regions are especially impacted because of large human populations in these regions and extensive agricultural production, extensive river modification for flood control and to meet societal demands, and because these systems are heavily invaded by non-native organisms. The distribution and ecology of freshwater fishes in Mediterranean-climate regions are also influenced by the distinct wet and dry periods and the high inter-annual variability in precipitation. Thus, efforts to manage and conserve native fishes in Mediterranean-climate regions require understanding both the effects of human disturbance and the strong seasonality that characterizes these regions. In this dissertation, I examine the relationship between land use and Mediterranean seasonality on freshwater fishes in streams within the greater San Francisco Bay region in California, USA. In my second chapter, I use a multivariate approach to explore variability among fish communities in 25 Bay Area watersheds. I found that a combination of local (water conductivity) and watershed-scale factors (percent forested watershed, watershed area, elevation) were important predictors of fish communities across sites. Furthermore, watershed-scale factors had indirect effects on fish communities through their influence on a local-scale factor, water conductivity. The results of this chapter highlight the importance of considering both the direct and indirect effects of watershed-scale factors on freshwater fish communities. In my third chapter, I continued my analysis of land use and fish communities with a focus on contemporary land change. For this chapter, I performed a resurvey study, surveying the habitat and fish communities in 32 sites in the Alameda Creek Watershed that had been surveyed by Dr. Robert Leidy in the mid-1990s, including sites in the rapidly urbanizing Livermore Valley region. Again using a multivariate approach, I found that the increase in urbanization across an approximately 16-year period was related to change in fish community composition, a decline in native species richness, and a decline in a common native cyprinid - changes that were not observed in another part of the watershed that has experienced little land use change in the last 16 years. The relationship between land use change and fish community change was strongest when considering land use change at a local scale. These results suggest that ongoing land change alters fish communities and that contemporary resurveys are an important tool for examining how freshwater taxa respond to recent and ongoing environmental change. In my final chapter, I assessed how seasonal drought, a characteristic feature of Mediterranean-climate systems, influenced food webs in a small intermittent stream in Marin County, CA that provides rearing habitat for threatened steelhead trout (Oncorhynchus mykiss). I used stable isotopes of carbon and nitrogen to characterize food web structure and the trophic position of a suite of predators in this system, including O. mykiss and several macroinvertebrate predators. I compared food web snapshots across time, as well as between permanent and temporary pools. I found that the intermittent stream food web remained relatively stable across time and did not differ between pool types. However, I also found significant changes in the trophic position, niche width, and mean [delta]13C values for aquatic predators. This study provides an important first look at the trophic ecology of an imperiled fish species in intermittent streams during the summer drought season, and emphasizes that food chain length increases across the drought season, possibly because invertebrate prey are concentrated with declining water levels. In conclusion, my research shows that anthropogenic factors at the watershed scale influence instream conditions and freshwater fish communities, and emphasizes that contemporary changes in land use can have subtle changes on fish community structure, which may be indicative of future declines of extirpations of native fishes. Finally, my research shows that changing conditions across the summer drought season lead to shifts in the trophic ecology of some, but not all, aquatic predators, including threatened steelhead trout. Overall my research contributes to a growing body of research that demonstrates how multi-scale natural and anthropogenic factors influence freshwater fishes in Mediterranean-climate region.

Author: Mark B. Bain
Publisher:
ISBN:
Category : Habitat (Ecology)
Languages : en
Pages : 54

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Book Description

Author: Mark B. Bain
Publisher:
ISBN:
Category : Environmental impact analysis
Languages : en
Pages : 40

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Book Description

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 132

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Book Description

Author:
Publisher:
ISBN:
Category : Boats and boating
Languages : en
Pages : 396

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Book Description

Author: Pennsylvania. Dept. of Fisheries
Publisher:
ISBN:
Category : Fish-culture
Languages : en
Pages : 228

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Book Description

Author: Pennsylvania. Board of Fish Commissioners
Publisher:
ISBN:
Category : Fishes
Languages : en
Pages : 20

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Book Description

Author: Louis Augustus Krumholz
Publisher:
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 440

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Book Description

Author: Justin D. Selden
Publisher:
ISBN:
Category : Dredging
Languages : en
Pages : 110

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Book Description
Agricultural streams provide infrastructure for flood control and are periodically straightened and dredged to maintain their efficiency to drain farm land. These streams also serve as headwaters and may provide important spawning and refuge habitat for native fish. Twenty study sites were selected in Sandusky, Crawford and Seneca counties (Ohio) and sampled for habitat and fish community variables in June and September during each of four years (2008-2011). Sites had to (1) be surrounded by agricultural land, (2) likely hold water in the summer, (3) lack canopy cover, (4) represent varying times since last dip-out, and (5) have landowner permission for access. I included streams from both lake plain and morainal regions. Measures of stream morphology, time-since-last-dredging and selected habitat variables were correlated with fish community metrics such as abundance, richness, Simpson's Index, Shannon Diversity, and Index of Biotic Integrity. Fish communities were assessed using block seines in 50 m stream segments. Captured fish were identified to species, counted, assigned to an age class, inspected for gravidity and DELT, and released outside of the sampling segment downstream to prevent recapture. A total of 38,074 individual fish were sampled belonging to 35 species. Fathead minnow (10,068), creek chub (5,252), bluntnose minnow (4,737), central stoneroller (4,185), blacknose dace (3,942), blackstripe topminnow (3,803) and Johnny darter (1474) were most common and comprised 88% of the total fish catch. Non-native fish (wild goldfish, common carp, and mosquitofish) comprised only 0.1% of the total abundance. Adult fish data were combined into a June and September dataset to produce a more robust dataset and minimize pseudo replication. Channel morphology, expressed per site as the coefficient of variation of 11 wetted-stream width measurements (CoV-H) correlated weakly with year-since-last-dip-out (r=0.35, p=0.11) with a non-linear regression predicting only 14% of the variation. The coefficient of variation of 11 maximum water depth measurements (CoV-V) did not correlate with year-since-last-dip-out. Only IBI was significantly linked with CoV-V for the combined June and the combined September data (r=53, p=0.02; r=0.60, p=0.01, respectively). Using a non-parametric approach (Mann-Whitney), sites in morainal regions displayed a significantly higher CoV-V (z=3.08; p=0.002), whereas the difference in CoV-H approached significance (z=1.79; p=0.074). Lake plain and morainal sample sites did not differ in their year-since-last-dip-out (z=0.80; p=0.424) and IBI was the only fish community variable that was significantly higher in morainal streams than in lake plain sites for June and September (z=2.43; p=0.015 and z=2.28; 0.023, respectively). Cluster analysis did not produce obvious groupings based on physiography, location in the watershed or season of sampling. The fish community composition in each stream, however, is impacted by a multitude of biotic and abiotic factors that are difficult to separate. Agricultural streams provide habitat to a great number of fish and a substantial number of native species. Such environmental considerations should be considered in the management of these man-made streams.