Investigating Interactions Between Channel Catfish and Other Sport Fishes in Alabama’s State Public Fishing Lakes
Type of DegreeThesis
Fisheries and Allied Aquacultures
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Channel catfish Ictalurus puntatus is a popular sportfish maintained by annual stocking in Alabama's State Public Fishing Lakes. Channel catfish may negatively affect bluegill Lepomis macrochirus and largemouth bass Micropterus salmoides populations in these systems through direct and indirect effects of competition or predation. I sought to determine if channel catfish were becoming overly abundant in Alabama’s State Public Fishing Lakes via stockpiling and if they were negatively affecting other sportfish populations. Using a variety of gears, I sampled channel catfish, largemouth bass, and bluegill in twelve Alabama State Public Fishing Lakes from 2006-2007 that contained variable channel catfish abundances and population size structures. From these data, population statistics were calculated and compared to investigate potential relationships which may be associated with channel catfish negative effects. Four of these lakes (two with high channel catfish abundance and two with low channel catfish abundance) were sampled more intensively, including quarterly samples of diet of each fish species, to determine the potential for competition between species and to quantify channel catfish piscivory. From diet data, bioenergetics models were used to predict total annual consumption of average channel catfish and largemouth bass populations in a typical Alabama State Public Fishing Lakes. Relative weights of channel catfish and bluegill were positively correlated, but channel catfish and largemouth bass relative weights were not related. Growth was not correlated between species, but latitude had an effect on growth of all species. No strong trends were found relating catfish abundances or population structures with any other sportfish population statistics. Channel catfish and bluegill diets were moderately similar, with little seasonal or among lake variability in similarity. Channel catfish and largemouth bass diets were dissimilar across all seasons in all lakes. Within a species, diet similarity was high among lakes. Percent of empty stomachs within a species also did not vary among lakes. From bioenergetics models, a typical channel catfish population was predicted to consume 32 kg/ha of fish (82% Lepomis sp. by number) annually, compared to 241 kg/ha of fish (77% Lepomis sp. by number) by a typical largemouth bass population. I found no evidence to indicate channel catfish were negatively affecting bluegill and largemouth bass populations in most of Alabama’s State Public Fishing Lakes. Because of the moderate similarity in diets between channel catfish and bluegill, the potential exists for competition between these species when prey resources are limiting. However, current stocking and exploitation rates in most lakes appeared to maintain channel catfish abundances below a level at which this may occur. One possible exception was in Marion County Lake, which had low bluegill CPUE, largemouth bass growth and condition, and extremely high channel catfish stocking rates. However, in all other study lakes, channel catfish piscivory appeared low enough to preclude any predatory (on bluegill) or competitive (with largemouth bass) negative effects on other sportfish. Current channel catfish stocking rates could probably be marginally increased to improve angler catch rates without causing any negative effects on other sportfish, although given the recent decline in number of anglers visiting Alabama’s State Public Fishing Lakes, this may not be necessary.