2001 Beaver Lake Survey: The Warmwater Fish Community of a Lake Dominated by Non-game Fish and Aquatic Vegetation

The WDFW Warmwater Fish Enhancement Program conducted a stock assessment survey of the fish community in the littoral zone of Beaver Lake (Skagit County) in fall 2001. Fish were captured using boat electrofishing, gill netting and fyke netting. Of the 817 fish captured, 10 species were identified, including: largescale sucker; largemouth bass; brown bullhead; yellow perch; black crappie; peamouth; pumpkinseed; cutthroat trout; rainbow trout; and, sculpin. Largescale sucker contributed nearly 90% of the fish biomass sampled in the lake during our survey. The ecological significance of such a large population of largescale suckers is unclear, however, it is likely that their benthic feeding habits may, at times, disrupt centrarchid nests, particularly those of the smaller pumpkinseed. While yellow perch densities were relatively high, centrarchid densities were low. Dense beds of floating and submergent aquatic vegetation may have contributed to low catch rates by providing abundant cover during electrofishing. Largemouth bass were represented by individuals ranging in age from young-of-year to nineyears old. Of the stock-size bass sampled (11 fish >200mm), 55% were less than 300 mm (11.8 inches) and 36% were between 380 to 510 mm (15 - 20 inches). Stock density indices for largemouth bass, yellow perch, black crappie and pumpkinseed were similar to populations with predator/prey balance. However the lack of preferred-size prey species suggest more of a �"big bass” scheme. The small population of black crappie surveyed exhibited higher than average catch rates and faster than average growth. Management options include: monitoring water quality; implementing vegetation and nutrient control; selective removal of largescale suckers; improvement of boat ramp and bank access; and conducting a creel survey.