Theses and Dissertations


Title: EFFECTS OF THREADFIN SHAD (DOROSOMA PETENENSE) ON WATER QUALITY AND PHYTOPLANKTON IN CHANNEL CATFISH PRODUCTION PONDS

Name: Lo Giudice, Gina Maria

Degree: MS

Chair: David R. Bayne

Resides:

University: Auburn University

Location: Auburn, Alabama

Date: 2002

Pages: 84

Keywords: Channel catfish,threadfin shad,water quality,phytoplankton

Abstract:

Threadfin shad (Dorosoma petenense) have the ability to alter aquatic communities. These fish are particle and filter feeders on larger phytoplankton, zooplankton, and organic detritus. The purpose of this study was to investigate the potential of threadfin shad as a biological control agent to alter the phytoplankton community, improve water quality, and enhance channel catfish production. The year one (1999) study was conducted in experimental earthen ponds near Auburn, Alabama. Ten, 0.04 ha ponds were stocked with 600 fingerling channel catfish (13,200/ha) and five randomly chosen ponds were stocked with 70 threadfin shad (1,750/ha) weighing a total of 3.3 kg (16.5 kg/ha). At harvest, an average of 1,284 threadfin shad (32,100/ha), weighing a total of 55kg (1,375 kg/ha) were collected from each pond. Water quality was improved with the addition of threadfin shad to channel catfish ponds. Mean total ammonia nitrogen was significantly lower and less variable within the shad treatment. Nitrite and total organic carbon were lower with the shad treatment. Threadfin shad filtered out larger, colonial algae and zooplankton, which resulted in significantly higher phytoplankton density (org/mL) and number of algal taxa. In the shad treatment, the phytoplankton community was more diverse and composed of significantly smaller organisms. Channel catfish had significantly higher survival in the shad treatment, fish production was higher and feed conversion ratio was lower than in the no-shad treatment. Ponds in the shad treatment had higher projected dissolved oxygen levels requiring less aeration. Year two (2000) of the study was conducted in eight commercial ponds located on three catfish farms in west Alabama. All ponds were under farmer management so I had no control of stocking, partial harvests, use of algaecide, feed, or aeration. Under these circumstances, any effects that threadfin shad may have had on water quality and phytoplankton were obscured by other variables and could not be explained by the shad treatment alone.

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