Summary
Bluegill (Lepomis macrochirus) and pumpkinseed (L. gibbosus) sunfish are sympatric over most of the Great Lakes basin and various studies have been car- ried out on the habitat and resource partition- ing of the older age classes (Keast, 1978; Werner et al., 1977; Hall and Werner, 1977). Work on the young-of-year age class has been ham- pered by the absence of a reliable method of distinguishing the two species and by the secretive habits of the young fish in the vegetation of the littoral zone (Keast, 1978). However, in 1979 we carried out preliminary observations on bluegill and pumpkinseed young-of-year in the littoral zone of Lake Opinicon. The results indicated that the vertical distribution of the two species was similar to that reported for the older fish (Keast, 1978; Werner et al., 1977). We undertook a study in 1980 to quantify the distribution of young-of-year bluegills and pump- kinseeds and to determine if their inshore vertical distribution is similar to that described for the older age classes.
Methodology
The study took place in the littoral zone of Lake Opinicon, Ontario, 40 km northeast of Kingston on the Rideau Lake system (described in Keast et al., 1978). The method used to distinguish young-of-year blue- gills and pumpkinseeds is based on differences in the lateral body-bar markings of the two species which enable identification of young-of- year fish >24 mm in total body length (Brown and Colgan, 1981). Only fish that could be pos- itively identified were considered. Data were collected at three separate sites categorized as "weedy deep" by Keast et al. (1978). The sites are characterized by large beds of Myriophyllum spicatum, a Eurasian milfoil, which extends 1.5 to 2.5 m from the substrate. The inshore edge of the beds forms a "curtain" which prevents the passage of a SCUBA diver through it. The curtain occurs at depths of between 2 and 3 m and is between 25 and 30 m offshore.