1997 American Lake Survey: The Warmwater Fish Community before Stocking Smallmouth Bass

American Lake is the largest (surface area = 446 ha), natural body of freshwater in Pierce County. The lake, which is located 24 km south of the City of Tacoma, consists of two basins separated by a distinct, narrow channel. The southern basin is relatively small (31 ha) and shallow (12 m maximum depth), whereas the northern basin is considerably larger (415 ha) and deeper (27 m maximum depth) (Figure 1). American Lake is primarily fed by groundwater. However, some inflow occurs through Murray Creek from the east, precipitation, and stormwater runoff. Surface water exits the lake mostly through groundwater seepage, some evaporation and, during times of high water (elevation > 71 m), a box culvert overflow channel at the south end of the lake (Bortelson et al. 1976; KCM 1993).

Moderate to steep slopes comprised of gravel characterize the near-shore habitat of American Lake. The aquatic plant community consists of a variety of pondweeds (Potamogeton sp.), muskwort (Chara sp.), common elodea (Elodea canadensis), stonewort (Nitella sp.), common naiad (Najas flexilis), and water celery (Vallisneria americana). However, emergent and submersed aquatic vegetation cover no more than 10% of the littoral zone [Bortelson et al. 1976; KCM 1993; Jenifer Parsons, Washington Department of Ecology (WDE), unpublished data].

Land use around American Lake is mostly urban. Nearly 300 residences are within 100 m of the lake. Furthermore, the Fort Lewis Military Reservation comprises over 30% of the shoreline, Camp Murray, 12%, with the remainder being privately held, including the Tacoma Country and Golf Club along the northwestern shore (KCM 1993).

Surrounding land uses in the American Lake watershed affect its water quality. For example, groundwater studies revealed that the aquifer supplying the lake contains excessive concentrations of nutrients such as phosphorus and nitrate. According to KCM (1993), American Lake is �"a moderately productive lake that is exhibiting tendencies to increased eutrophy. The lake’s progression to a more eutrophic state is characterized by intermittent algal blooms, oxygen-depleted bottom waters (e.g., see Table 1), hypolimnetic buildup of phosphorus, an impoverished benthic invertebrate community, and phosphorus-rich surface sediments. The occurrence of toxic blue-green algal blooms is of particular concern for reasons of both public health and lake ecology.” Furthermore, during 1990 through 1992, over one-third of the swimmers itch (an annoying skin condition caused by a small, free-swimming parasite) reports to the Tacoma-Pierce County Health Department were from American Lake (KCM 1993).

Because of its proximity to the City of Tacoma, Fort Lewis, and McChord Air Force Base, American Lake receives high recreational use. Pierce County Parks and Recreation operates two parks along the northern and eastern shores, while the Washington Department of Fish and Wildlife (WDFW) maintains a public boat launch near the mouth of Murray Creek. Two private marinas rent a variety of watercraft for pleasure, exercise, and fishing. Furthermore, several private swimming areas rim the shoreline, whereas the only seaplane base in Pierce County is located along the northern shore (Bortelson et al. 1976; KCM 1993).

Historically, WDFW managed American Lake as a salmonid-only fishery. To this end, in 1957, WDFW, acting as the Washington Department of Game (WDG), rehabilitated the lake with the natural piscicide, rotenone, in order to eliminate warmwater species, such as largemouth bass (Micropterus salmoides) and yellow perch (Perca flavescens), and roughfish, such as common carp (Cyprinus carpio). However, within a few years of its rehabilitation, American Lake supported a thriving population of rock bass (Ambloplites rupestris). Since the early 1980’s, WDFW has stocked several thousand rainbow trout (Oncorhynchus mykiss), cutthroat trout (O. clarki), and kokanee (O. nerka) annually into the lake to bolster recreational angling opportunities. Nevertheless, a small-scale fisheries survey by KCM (1993) revealed that warmwater species such as rock bass, yellow perch, and pumpkinseed (Lepomis gibbosus) dominated the shallows of American Lake in 1991.

Because of its trophic status, American Lake is well suited for warmwater fishes (KCM 1993; Table 1). Given the relatively steep morphometry of the lake, the ubiquitous gravel substrate, and the abundant forage fish as a possible prey base, the introduction of smallmouth bass (Micropterus dolomieu) into American Lake was proposed in 1997 (Steve Jackson, WDFW, personal communication). Subsequently, on August 19, 1998, several thousand (n = 8,211) juvenile smallmouth bass were released into the lake by WDFW personnel. The approximate total length (TL) and weight of each fish was 102 mm (4”) and 6.5 g (0.2 oz), respectively. Moreover, dozens (n = 179) of adult-size (> 203 mm or 8” TL) smallmouth bass weighing approximately 227 g (8 oz) each were stocked into American Lake on November 2, 1998 (WDFW, management files). Still, no recent information exists concerning the warmwater fish community at the lake. In an effort to assess its warmwater fishery and suitability for smallmouth bass, personnel from WDFW’s Warmwater Enhancement Program conducted a fisheries survey during early fall 1997. Since it was gathered before stocking smallmouth bass, the baseline information presented here will be useful when monitoring the success of the introduction of a new sport fish into American Lake.