Date of Award

8-2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Wildlife and Fisheries Biology

Advisor

Robert F. Baldwin

Committee Member

Mark C. Scott

Committee Member

Bryan L. Brown

Committee Member

William R. English

Abstract

South Atlantic coastal plain wadeable streams are unique and understudied freshwater environments that provide crucial habitats for a wide range of aquatic taxa. In Chapter 1, we investigated patterns in fish assemblages across South Carolina's coastal plain, and developed statistical models to identify the dominant multi-scale abiotic environmental factors that influence assemblage structure. Our analyses indicated the presence of four predominant fish assemblages that commonly occur in the coastal plain, which we termed the: 1) fluvial, 2) eastern mudminnow, 3) centrarchid, and 4) non-fluvial assemblages. Natural geographic gradients and instream habitat parameters associated with velocity, channel form, stream size, and depth played a greater role in distinguishing fish assemblages than catchment land cover, and these instream habitat parameters showed weak relationships with anthropogenic land cover conditions. This study provides a better understanding how coastal plain fish assemblages respond to multi-scale abiotic factors, and will help improve conservation and management strategies, as well as assist in the development of appropriate indicators for standardized evaluations of ecological integrity. In Chapter 2, we investigated the impacts of channelization on South Atlantic coastal plain fish assemblages using both taxonomic and trait-based analyses. We categorized sampled streams a priori into 4 channel types based on observations of their gross channel morphology: 1) single channel non-channelized streams, 2) maintained channelized streams, 3) unmaintained (>5years) channelized streams, and 4) braided swamp-like non-channelized streams. We found no difference in fish taxonomic diversity metrics among channel types, and taxonomic assemblage-based analyses revealed limited information regarding structural associations. In contrast, our trait-based analysis elucidated species differences among all channelized and non-channelized channel types; principal differences were found in habitat preference, and body size/reproductive ecology. Our study suggests that trait-based analyses may be particularly well suited to elucidating information on ecological response to environmental disturbances in the South Atlantic coastal plain, and their use in conjunction with taxonomic analyses should provide a fruitful avenue for developing and testing ecological theory of fish assemblage organization in this region. In Chapter 3, we examined the effects of two dam removals on instream habitat, fish metrics, and fish assemblage structure of Twelvemile Creek, located in Pickens County, South Carolina. Our results indicated that the bulk of instream habitat changes occurred within 1-year of each dam removal. Previously lentic-dominated fish assemblages at former impounded sites generally shifted to a lotic-dominated structure within 6-months (upper-removed dam), and 1-1.5 years (lower-removed dam) after dam removal. Despite these prominent assemblage shifts, we found impacts on benthic invertivore density at sites flanking the upper-removed dam at 2.5-years post dam removal, and impacts on total density, richness, benthic invertivore density, and native centrarchid density at sites flanking the lower-removed dam at 2-years post dam removal. These findings suggested that multiple dam removals had a cumulative downstream increase in negative impacts on fish assemblages. Although dam removal can have ecological trade-offs and short-term disturbance impacts, we demonstrated that dam removal can also reverse many of the negative impacts dams have on fish assemblages, primarily through the restoration of high-quality lotic habitats required by native riverine species.

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