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Effects of conservation practices on fisheries management

Knight, Scott S, Cullum, Robert F.
ARS USDA Submissions 2014 v.3 no.1 pp. 1
agricultural runoff, alluvial plains, animal communities, chlorophyll, clay, conservation practices, fish, fisheries, fisheries management, harvesting, lakes, nitrates, nutrient content, nutrients, phosphorus, pollution control, sediments, soil, sport fishing, total solids, water quality, watersheds
Beasley Lake watershed was subjected to a series of conservation management practices with the goal of reducing sediment and nutrients entering the lake via agricultural runoff. Concurrent with the application of conservation practices, the lake was renovated and restocked to produce a sports fishery. Conservation practices reduced annual mean total solids from 592 mg/L in 1996 to 66.7 mg/L in 2011. This reduction greatly improved water clarity as measured by Secchi visibility which increased from an annual mean of 16 cm to 28 cm for the same time period. Phosphorus, which is typically associated with the high clay content soils of the Mississippi River Alluvial plain where Beasley Lake is located was reduced by 95 % from 1.75 mg/L to 0.08 mg/L while nitrate was reduced by 58% from an average annual high of 0.69 mg/L in 1996 to 0.29 mg/L in 2011. Recovery of the fishery following restocking was slow until after 2000 when water quality improved as reflected in increased Secchi visibility, decreased total solids and increased chlorophyll a concentrations. Numbers of fish per unit of effort peaked at 82 / hr. in 2006 while highest combined catch per unit of effort (9.37 kg/h) was reported in 2009. While clupeids and centrarchids were an important component of the catch by number for the duration of the study, there was a shift from a carp-catfish dominated catch in 1998 – 1999 to one dominated by centrarchids and clupeids by 2004. Catch per effort and numbers per effort over time show a cyclic pattern of highs and lows indicating instability within the fish community. The decision not to harvest fish in favor of catch and release and the reduction of nutrient concentrations within the lake likely contributed to reduced catch per effort in 2011.