1997 Mason Lake Survey: The Warmwater Fish Community of a Lake Dominated by Non-Game Fish

Mason Lake is a moderate size (surface area = 417 hectares) body of water [mean depth = 14.6 meters (m); max. depth = 27.4 m] located near the base of the Olympic Peninsula in Mason County. Schumacher Creek, a perennial stream, feeds the lake at the south end, whereas water flows out Sherwood Creek at the north end and eventually discharges into Case Inlet. The watershed supports the modest spawning activities of two anadromous fishes.

During fall, adult coho salmon (Oncorhyncus kisutch) pass through Mason Lake on their way to spawning grounds in Schumacher Creek. The Washington Department of Fish and Wildlife (WDFW) conducts annual spawner surveys along a 322 m stretch of the creek, from the mouth to the first county road above the lake. Coho salmon spawning activity, as indicated by the number of ‘fishdays’ within the index area, has been variable over the years. Peak activity occurred during 1981, 1985, and 1987. However, since 1989, coho salmon spawning activity has been nominal in Schumacher Creek.

For the past 30 years, summer-run chum salmon (Oncorhynchus keta) have displayed fairly regular even- and odd-year variations in abundance upon returning to Sherwood Creek spawning grounds below Mason Lake. This is not unusual for chum salmon (Salo 1991). Summer chum spawning activity peaked during the 1970's but declined during the 1980's; however, in recent years, summer chum spawning activity appears to be rising again. Peak spawning activity for fall chum salmon occurred during 1972, 1984, 1990, and 1994.

Mason Lake supports a diverse aquatic plant community as well, including several varieties of floating leaf pondweed (Potamogeton sp.) and the rare, native water gladiole (Lobelia dortmanna; Jenifer Parsons, Washington Department of Ecology, personal communication). Submersed vegetation includes common elodea (Elodea canadensis), water nymph (Najas flexilis), and bladderwort (Utricularia sp.). Emergent vegetation includes horsetail (Equisetum sp.), rushes (family Juncaceae), and sedges (family Cyperaceae).

Although the spawning activities of the watershed’s anadromous fishes have been monitored for decades, no recent information exists regarding the resident fish community of Mason Lake. Therefore, in an effort to assess the warmwater fishery, especially given the potential recreational opportunities at the lake (Dan Collins, WDFW, personal communication), personnel from WDFW’s Warmwater Enhancement Program conducted a fisheries survey at Mason Lake in fall 1997.