Factors Affecting Regional Variation in Growth of Channel Catfish

—We related the length at age of channel catfish Ictalurus punctatus, an indirect measure of growth, to three climatic and five morphoedaphic variables in 144 Texas reservoirs. Growth of channel catfish ages 3 through 6 was negatively related to longitude, a factor that explained as much as 34% of the variation in length at age. Channel catfish length at age was not significantly related to latitude, conductivity, morphoedaphic index, mean depth, and maximum depth in all age-classes. Among age-7 channel catfish, length at age was positively related to reservoir area, which explained 35% of the variation in growth. A quadratic model for growing-season length explained 7–17% of the variation in length at age in all age-classes. Overall, length at age for channel catfish was greatest in reservoirs with intermediate growing seasons (approximately 270 d in length) and was lower when the growing-season length was either longer or shorter. Our results provide the first evidence that the length of growing season on a statewide or regional scale may affect the growth of channel catfish. Native or introduced populations of channel catfish Ictalurus punctatus are present in almost all of the 50 states in the USA (Miller 1966). Nationwide, channel catfish is one of the most frequently targeted freshwater fishes (U.S. Fish and Wildlife Service and Bureau of the Census 2002); consequently, managers in most states recognize the need to actively manage channel catfish fisheries (Vanderford 1984). Despite the popularity of channel catfish among recreational anglers, most studies of the species have been directed towards aquaculture. As a result, factors that influence the population dynamics of wild channel catfish populations targeted by anglers remain unknown. In a recent literature review, Hubert (1999) identified the need for more studies on the factors affecting the growth of channel catfish. Although growth of the species varies substantially across its range, it has never been related to regional variation in climatic factors such as temperature or growingseason length (Hubert 1999). In this study, we sought to determine if growth of age-1 through age-7 channel catfish in 144 Texas reservoirs was related to three climatic and five morphoedaphic variables.