Effects of abiotic and biotic factors on bluegill reproduction and growth in seven unexploited surface coal mine lakes.

摘要

Understanding the density-dependent and density-independent factors that influence bluegill life histories and recruitment processes are necessary for managing quality populations. I evaluated the effects of the size structure of adult bluegill and habitat conditions on their larval production, time of spawning, and survival of seven unexploited populations in small (2.47-8.67ha) surface coal mine lakes near Sparta, IL, during the summer of 2003. Lakes were stratified across categories of adult size structure, the availability of littoral habitat, and other habitat parameters (i.e. mean depth, shoreline development, and chlorophyll a concentrations). Adult fish community characteristics were assessed using three-phase boat electrofishing. Larval tows were conducted weekly in each of the lakes to estimate densities throughout the spawning season. Littoral habitat and lake morphology characteristics were quantified by conducting bathymetric surveys with an echosounder. Age-0 bluegill were sampled in the fall of 2003 to assess survival from the larval stage by estimating swim-up date using otoliths. Peak and total larval sunfish densities increased with adult size structure. A positive relationship occurred between summer chlorophyll a concentrations and larval production. The earliest peak spawning occurred in lakes with large adults. Although lakes ranged from 9% to 40% littoral volume, littoral volume was not correlated with larval sunfish production among lakes. Juvenile bluegill growth differed among lakes and was negatively affected by adult density. Survival of larvae to the juvenile stage differed among lakes and was negatively correlated with larval densities. Densitiy-dependent factors were mostly responsible for the structuring of bluegill populations in these seven unexploited surface coal mine lakes and allowed them to reach equilibrium. Management that encompasses an approach that examines all of these processes will likely be the most successful in increasing adult size in lakes, by improving reproduction, recruitment success, and maintaining quality size structure.