Relationships between Environmental Variables and Size-Specific Growth Rates of Illinois Stream Fishes

Abstract

We quantified size-specific growth of small and large rock bass Ambloplites rupestris, bluegill Lepomis macrochirus, largemouth bass Micropterus salmoides, smallmouth bass M. dolomieu, and channel catfish Ictalurus punctatus from Illinois streams. Growth rates for each species fell within ranges previously reported for lakes and rivers in Illinois and adjacent states, although growth rates in our study averaged slightly lower. Intraspecific growth rate comparisons of small and large individuals were not significantly correlated for bluegill and rock bass. This suggests ontogenetic shifts occurred in diet or habitat use of these two species, similar to those reported for lentic populations. Using 12 biological, 22 physical, and 8 chemical variables collected concurrently with the fish, we developed simple- and multiple-regression models of growth for each species and size. Our best multiple-regression models accounted for 67–99% of the growth variation in seven species–size combinations, with substrate variables contributing to models for all species except rock bass. Although these models require testing against independent data for general applicability, they demonstrate the potential for predicting the growth of stream fish from commonly collected, and often readily available, habitat data. These empirical relationships with environmental variables may also enhance the efficiency of stream fisheries management by providing an inexpensive, a priori basis for directing management efforts.