Theses and Dissertations


Title: Effects of channel catfish farming on water quality in Big Prairie Creek, west-central Alabama

Name: Silapajarn, Orawan

Degree: PhD

Chair: Claude E. Boyd

Resides:

University: Auburn University

Location: Auburn, Alabama

Date: 2004

Pages: 121

Keywords: channel catfish, Big Prairie Creek, west-central Alabama, water quality, United States Environmental Protection gency, catfish farming, aquaculture

Abstract:

The United States Environmental Protection Agency is making a rule to be finalized 30 June 2004 for regulation of aquaculture effluents. However, there have been few studies to evaluate the effects of aquaculture on stream water quality. The greatest density of channel catfish farms in Alabama is located on the Big Prairie Creek watershed in Hale, Marengo, and Perry Counties. This watershed appears to be ideal to conduct a study to determine the effect of catfish farming on stream water quality. A water quality monitoring effort was initiated with the following objectives: (1) evaluate water quality at a station above the location of catfish farms, in tributaries receiving direct discharge from catfish ponds, and in the downstream reach of Big Prairie Creek: (2) compare water quality in Big Prairie Creek with that of control streams without catfish farms on watersheds: (3) determine if Big Prairie Creek influences water quality in the Black Warrior River. The study was conducted between 17 May 2001 and 10 August 2002. The uppermost sampling station on Big Prairie Creek is located in the Fall Lines Hill ecoregion rather than in the Blackland Prairie ecoregion like all other stations. Thus, the lower pH and specific conductance, and lower concentrations of total alkalinity and total hardness at the upstream station relative to the downstream stations are related to geologic factors. Soils of the Fall Line Hills are highly acidic, while those of the Blackland Prairie usually are alkaline and deposits of limestone are common. Other water quality variables, dissolved oxygen, turbidity, total suspended solids, chloride, total ammonia nitrogen, nitrate nitrogen, soluble reactive phosphorus, total nitrogen, total phosphorus, and 5-day biochemical oxygen demand (BODs), tended to increase in downstream reaches of Big Prairie Creek. The 66,396-ha watershed of this stream contains an estimated 5,001 ha of catfish ponds (7.5% of watershed surface), but there are other land uses which include row crops (9.8%), pasture (53.5%), woodland (23.3%), urban areas (4.7%), and ponds and lakes other than catfish ponds (1.2%). These others land uses, in addition to catfish farming, have influenced water quality of stream in the Big Prairie Creek watershed. Reaches of tributaries and control streams upstream of sampling stations were situated entirely in the Blackland Prairie. Proportions of land used for cropland, pasture, woodland, and urban area were similar among the Big Prairie Creek watershed in which the tributaries occurred and the watersheds of control streams. Thus, comparison of water quality in tributaries of Big Prairie Creek with that of control streams affords the best evidence of the influence of catfish farms on stream water quality. The tributaries had higher specific conductance values and greater concentrations of chloride, total ammonia nitrogen, nitrate nitrogen, and biochemical oxygen demand than control streams. Catfish ponds are treated annually with 50 to 100 mg/L sodium chloride. Large amounts of nitrogen and phosphorus enter catfish ponds in fertilizers and feeds, and dense phytoplankton blooms develop. Thus, catfish pond effluents had elevated concentrations of nutrients, chloride, and organic matter, and this caused specific conductance and concentrations of chloride and combined nitrogen to increase in tributaries. Soluble reactive and total phosphorus concentrations were numerically greater in tributaries than in control streams, but because of high variation, differences were not significant at the 5% probability level. Although copper sulfate often is applied to catfish ponds to control blue-green algae, tributaries did not have elevated copper concentrations relative to control streams. Also, the higher biological oxygen demand of tributaries did not result in them having less dissolved oxygen than control streams. This suggests that the increase in biochemical oxygen demand in streams is probably the result of living plankton entering in pond effluent. Although catfish farming has increased the concentrations of some potential pollutants in Big Prairie Creek and its tributaries, there were no differences in concentrations of water quality variables upstream and downstream from the confluence of the creek with the Black Warrior River. Also, catfish farming did not cause concentrations of water quality variables in downstream Big Prairie Creek to exceed water quality limits of its stream classification standard. Finally, the discharge of Big Prairie Creek measured at the Highway 68 bridge near Gallion, Alabama, was nearly the same as predicted from rainfall data for 2001-2002 and also predicted by an equation developed from stream flow and rainfall for the period 1941 to 1951. Thus, the installation of channel catfish farms on the watershed has not affected stream flow by a measurable amount. In summary, channel catfish farming on its watershed has not caused serious water quality or hydrological changes in Big Prairie Creek. Implementation of best management practices (BMPs) by catfish producers is the best way to avoid adverse effects of channel catfish farming on this and other streams in Alabama in the future.

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