Carp (Cyprinus carpio) are alien freshwater fish that are globally widespread and often associated with highly degraded freshwater ecosystems. This study explored carphabitat interactions that could contribute to the worldwide distribution of, and consequent ecological impacts by, carp. Particular emphasis was placed on the role of carp size in these interactions. One component of this study involved a field experiment that was used to quantify the effects of carp biomass density and size-structure on freshwater invertebrate communities and water quality. The treatments in this field experiment comprised different combinations of large (2 kg) and small (0.7 kg) carp, and low (330 kg.ha-1), intermediate (570 kg.ha-1) and high (650 kg.ha-1) biomass densities. Carp impacts were more carp size-dependent than described in previous studies. In particular, carp size was more important than carp biomass density in determining the concentration of total phosphorus and algal biomass. On the other hand, a more even mix of carp sizes increased total nitrogen. The zooplankton and macroinvertebrate taxa that were more abundant in the presence of carp were the taxa most able to avoid carp predation and tolerate habitat changes caused by carp benthivory. To complement the small-spatial scale field experiment, large-scale patterns of carp distribution, biomass density and recruitment were explored among the rivers of New South Wales (Australia) in relation to their physical habitat. In contrast to expectations, and although most recruitment probably occurred at lower-altitudes, the populations with a size structure and biomass density most likely to cause ecological degradation occurred at intermediate altitudes. Furthermore, the distribution of smaller carp (less than or equal to 100 mm, and less than or equal to 300 mm) indicated that the regulation of river flows does not always favour carp populations, particularly during drought conditions. Nevertheless, it was concluded in a review of the carp literature, which incorporated the findings of this study, that invasion by alien carp is most successful in streams with formerly highly variable flows that are now subject to flow regulation. Moreover, carp are likely to enhance their advantage in these waters through habitat modification.

Stream-restoration projects are usually designed to improve habitat quality for fishes. These projects manipulate flow patterns, substrate distribution, and amount and placement of large woody debris. Consequently, they also affect the size and composition of the aquatic macroinvertebrate community. This research evaluates two types of fish habitat restoration: off-channel structures (alcoves) and in-channel structures (log weirs). I compared macroinvertebrate habitats and communities in natural and artificial alcoves in Upper and South Fork Lobster Creeks, Lane Co., and examined the effects of log weirs on in-channel habitat diversity, community composition, drift patterns, and fish consumption of macroinvertebrates. Macroinvertebrate samples were collected from artificial and natural alcoves using hand pumps and D-nets. Within the channel, macroinvertebrates were collected from restored and unrestored reaches with a Hess sampler and using a stratified random sampling scheme. Forty-eight hour invertebrate drift samples were obtained at outlets of log-weir pools. Stomach contents were obtained from coho salmon (Oncorhynchus kisutch) and cutthroat trout (O. clarki) in restored reaches. Although natural alcoves differed from artificial in location within the floodplain, morphology, permanence, and degree of interaction with the stream channel, both alcovetypes provided similar habitats and contained similar macroinvertebrate communities. Average densities and diversity within the alcoves depended on habitat and time of year. Average densities were higher in artificial than in natural. Alcoves contained 29% of species richness within Upper Lobster Creek. Within the stream channel, the diversity of macroinvertebrate habitat was lower in restored than in unrestored sections. Log weirs were associated with reduced taxonomic and functional feeding-group diversity. Composition of drift was not significantly different in restored and unrestored areas; however, drift densities were significantly lower in restored reaches. Diets of fishes in restored areas were composed primarily of organisms produced from outside restored areas. Although in-channel structures may enhance physical habitat for fishes, they may alter or reduce the availability of food for fishes feeding on drifting invertebrates. Recommendations are given for improving the design of stream restoration projects with respect to macroinvertebrates; however stream restoration should focus on restoring whole-system integrity and function, instead of targeting just one or two types of organisms. / Graduation date: 1996

Thesis (doctoral)--Swedish University of Agricultural Sciences, 2005. / Thesis documentation sheet inserted. Appendix reproduces four papers and manuscripts co-authored with R.K. Johnson. Issued also electronically via World Wide Web in PDF format; online version lacks appendix.

Thesis (M.S.)--Washington State University, 2003. / Title from PDF title page (viewed on May 22, 2005). Includes bibliographical references (p. 52-56).

No description available.

The effect of lake acidification was evaluated, in the field, in terms of its impact on both the structural and functional composition of the macrozoobenthic community. The littoral macrozoobenthic community and water chemistry of 45 Canadian Shield lakes was sampled. The water chemistry variables sampled included pH, total dissolved calcium, conductivity, and dissolved organic acid (measured as colour). Partial canonical correlation analysis and partial regression analysis were used to identify those components of the macrozoobenthic community that most directly reflected pH variability. This was done by first removing from the data that portion of the variability attributable to total dissolved calcium, conductivity, and dissolved organic acids. In addition, the spatial structure in the data was removed by identifying the geographic coordinates of the sampling sites. / In general, the results presented here are not consistent with previous studies where the response of the macrozoobenthic community was related to pH without consideration of confounding covariables. Snails, leeches, mayflies and crayfish have all been cited for their sensitivity to acidification. The present study found these taxa to reflect, not pH variability, but rather attributes of water hardness. Similar results were found for both total zoobenthic biomass and functional feeding group abundance.

Thesis (Ph. D.)--George Mason University, 2004. / Includes bibliographical references (leaves 197-207).

Thesis (M. Sc. (Environmental Science))--Rhodes University, 2005.

Thesis (M.A.)--State University of New York College at Oneonta, 2005. / Typescript. Includes bibliographical references (leaves 46-49).

Recent evidence strongly suggests that aluminum toxicity is important in determining the structural and functional characteristics of freshwater communities affected by acid precipitation. To determine the effect dissolved aluminum has on lotic invertebrates previously unexposed to anthropogenic acidification, experiments were carried out in a second-order headwater stream 50 km east of Vancouver, British Columbia during August 1982. In three separate experiments, HC1 and/or A1C1₃ were added to Mayfly Creek during daylight hours, increasing acidity from pH 6.9 - 7.0 to pH 5.8 - 6.0 and total aluminum from < 0.1 mg/L to > 1.0 mg/L. Biological response was monitored by sampling invertebrate drift with 86 Mm nets. Relative to an unmanipulated, upstream control site, drift density doubled in response to added H⁺ alone (pH 5.9). When Al₃⁺ was added (pH 5.9) drift density increased fourfold. Following 48 h continuous dosing with HC1 (pH 5.9) there was an even greater response to added Al₃⁺. Ephemeroptera were able to detect dissolved aluminum and responded almost immediately (within 45 min). Similarly, Trichoptera and Chironomidae detected increased H⁺ concentrations and responded immediately. Response to augmented Al₃⁺ by Trichoptera, Hydracarina, and Chironomidae was delayed 6 h. However, pre-exposing animals to 48 h HC1 resulted in enhanced aluminum sensitivity for Chironomidae and for Simulium and Plecoptera, which had not responded within 10 h to H⁺ or Al₃⁺ alone. It is proposed that rapid increases in drift density are due to behavioral escape responses, while delayed responses are probably associated with physiological impairment. Evidence was also obtained suggesting that during early stages of morphological development Ephemeroptera and Chironomidae are more sensitive to increased Al₃⁺ and H⁺ concentrations than during later developmental stages. In laboratory experiments using artificial stream channels, Chironomidae larvae and Ephemeroptera nymphs were exposed to CI⁻ and H⁺ concentrations, equal to those during field experiments. Results showed that drift behavior in these animals is not stimulated by mildly elevated chloride concentrations. These studies demonstrate that increased dissolved aluminum concentrations intensify biological response to acidification, and confirm acid sensitivity patterns for Ephemeroptera and Chironomidae reported by others. The observed acid insensitivity of Plecoptera, simuliids, and Trichoptera also conforms to previously described patterns. Experimentally manipulating this community produced results closely resembling those obtained in similar studies for areas currently affected by acid precipitation. The major difference in results between studies is that invertebrate communities previously unexposed to acidification contain more species sensitive to mild acidification. These latter animals are particularly sensitive to the presence of elevated dissolved aluminum concentrations. / Science, Faculty of / Zoology, Department of / Graduate