RNA/DNA ratio and total length of yellow perch (Perca flavescens) in managed and natural wetlands of a large fluvial lake

Abstract

RNA/DNA ratios and total lengths were compared to determine growth patterns of age-0 yellow perch (Perca flavescens) in managed and natural habitats of a large fluvial lake (Lake Saint-Pierre, St. Lawrence River, Quebec, Canada) over seasonal and yearly temporal scales. In 2002, the RNA/DNA ratio responded to degree-days accumulated over periods of 7–8 days before sampling, while in 2003, no relationship with temperature was established. The growth patterns obtained each year probably reflect indices responding to different limiting variables. In 2002, temperature would have been limiting, whereas in 2003, other factors such as prey availability, food quality, and competition may have influenced growth. In addition, the discrepancy between total length and RNA/DNA ratio observed in 2003 may reflect a differential time of response to limiting variables. These results together show that the two indices reflect growth at different time scales and suggest that their combination can help identify shifts between limiting environmental variables. Also, growth in managed wetlands during springtime was systematically superior to that in the natural environment, supporting the contention that managed wetlands are highly productive habitats. In natural habitats, growth rates were higher on the south shore by summer, which is consistent with the established north-south productivity gradient in Lake Saint-Pierre.