Effects of a native rough fish on water quality

Author(s): Goetz, D.; Kröger, R.; Miranda, L.

The smallmouth buffalo (SMB) (Ictiobus bubalus), a large bodied benthivore commonly considered a rough fish, is native to Mississippi. Smallmouth buffalos frequently access floodplain lakes during periods of high water level, and remain isolated within them for extended periods of time after the water recedes. Based on evidence from other benthivore studies we hypothesized that high densities of SMB may contribute to poor water quality conditions. We tested this hypothesis in 0.05 hectare, shallow (<1.5 m) earthen ponds at three stocking densities. Nine ponds were randomly stocked with either a low (15 kg/ha), moderate 85 (kg/ha), and high (315 kg/ha) density and measured for water quality parameters over a ten-week period during the summer of 2012. Results from repeated measures ANOVA suggest SMB at high and moderate densities significantly (p < 0.05) increased chlorophyll, turbidity, total suspended solids, volatile suspended solids, temperature, total inorganic phosphorus, while decreasing dissolved oxygen, and Secchi depth, both through time and across treatments. Several previous studies also attribute high benthivorous fish density to enhanced productivity through feedback mechanisms that keep nutrients and sediments in constant suspension. However, most studies have looked at densities much greater than 315 kg/ha (500 +kg/ha). Our results suggest that effects of SMB even at moderate densities may contribute to degraded water quality conditions in natural habitats such as shallow floodplain lakes.

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