2003 Warmwater Fisheries Surveys of Upper and Lower Twin Lakes

Washington Department of Fish and Wildlife biologists surveyed Upper and Lower Twin Lakes (Lincoln County) on June 8â€"12, 2003. Fish were captured using boat electrofishing, gill netting, and fyke netting. Each lake was populated by the same six species; however, relative abundance and indices of population structure differed between the two. The differences observed are most likely due to the cumulative effects of varying mean depth, aquatic vegetation abundance, and top predator densities.

At Upper Twin Lake, largemouth bass (Micropterus salmoides) was the most abundant species by weight (62%) and was second only to pumpkinseed sunfish (Lepomis gibossus) (53% by number) by number, comprising 36% of the sample. Rainbow trout (Oncorhynchus mykiss), brown bullhead (Ameiurus nebulosus), yellow perch (Perca flavescens), and black crappie (Pomoxis nigromaculatus) were also sampled, but at much lower numbers. Largemouth bass are abundant and grow to quality size as evidenced by a high electrofishing catch rate and above average condition. Abundant pumpkinseed sunfish, while likely an important prey species for bass, offer only limited angling opportunity due to their mostly small size. The stocked rainbow trout sampled were of a size typically of interest to anglers and should coexist alongside the warmwater fish species within the lake, which has a high proportion of open water in addition to the shallow, weedy, littoral areas. Managers are encouraged to continue with the current management strategy for Upper Twin Lake.

At Lower Twin Lake, pumpkinseed sunfish was the most abundant species by weight (53%) and number (78%). Largemouth bass were second in abundance and yellow perch, brown bullhead, black crappie and rainbow trout were also sampled. Lower Twin Lake offers anglers only lessthan- quality opportunities. A combination of shallower depth, extensive aquatic vegetation, and a lower density largemouth bass population are likely the key factors influencing the community. Panfish opportunities at Lower Twin Lake are best summarized as abundant, but are composed primarily of small pumpkinseed sunfish, yellow perch, and black crappie. An increase in predator abundance would likely improve the overall quality of the fishery.