Long Term Effects of Jim Chapman Reservoir on Upper Sulphur River Fish Communities

Author

Rahul Rai

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biological and Environmental Sciences

Date of Award

Fall 2024

Abstract

Reservoirs, along with their importance in the modern ecosystem and economic development, bring a serious alteration in the natural habitat of fish communities. Understanding their impact on fish communities can help in supporting fish conservation. However, studies on reservoir impact on fish communities are mostly limited to short time scales and more long-term studies are needed for more comprehensive understanding of impacts. We compared fish communities of upper Sulphur River tributaries in 2024 with pre-impoundment surveys in the same region conducted in 1971. Jim Chapman reservoir was built in 1986 and isolates upstream Middle, and upstream South Sulphur sections from the rest of the system. Twenty-five sites from upstream Middle, upstream South Sulphur, above the lake, and non-fragmented locations (mostly North Sulphur) were sampled using standardized surveys with backpack electrofishing and seine nets from February 2024 to September 2024. Data were analyzed using non-metric dimensional scaling (NMDS), analysis of similarity (ANOSIM), a modified regionally calibrated index of biotic integrity (IBI), analysis of similarity percentage (SIMPER), indicator species analysis, species richness, Shannon diversity index, Jaccard distance of similarity and regional abundance. The analysis showed that two species, Cyprinella lutrensis and Carpiodes carpio, were significantly reduced over the years including likely complete extirpation of Cyprinella lutrensis in the Upstream Middle Sulphur section. Additionally, fish communities seem to have homogenized since 1971 across regions and ~56% of fish species were common in all two or three of the regions. The Sulphur River system had ~36% species richness increase compared with the 1971 study (likely impacted by addition of electrofishing data), but despite this trend, the Upstream Middle Sulphur had a negative community shift with ~29% decline in species richness and lowest regional modified IBI score. Upstream South Sulphur showed relatively high diversity and included the presence of Phenacobius mirabilis, a species of conservation needs in Texas, despite being isolated above the lake, possibly related to it being a larger system than the Middle Sulphur that can better withstand drought. Centrarchidae species like Lepomis aquilensis, Lepomis macrochirus and Lepomis cyanellus and mosquitofish Gambusia affinis were indicator species in the 2024 samples, replacing Carpiodes carpio and Cyprinella lutrensis which were the indicator species of the 1971 samples. These findings suggest that the stream size is significant in shaping fish communities upstream of the impoundments, and indicates a possible relationship between stream size, drought, and available refugia in connected flowing systems as driving ecosystem resilience to declines in species richness. Homogenization across the three regions may have been driven by compounded effects from long-term modifications such as channelization, reservoir construction, agricultural land use, high annual variability in flows, and increasing drought events. Further studies could address patterns and causes for the declines for Cyprinella lutrensis (Middle Sulphur) and Carpiodes carpio (Upper Sulphur River). Finally, the patterns seen in the Upper South Sulphur suggest that it had the capacity to conserve diverse fish communities including species of conservation need like Phenacobius mirabilis, thus, any water projects in that section are not recommended.

Advisor

Bjorn Schmidt

Subject Categories

Biology | Life Sciences

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