2001 Spencer Lake Survey: Biological Characteristics of a Minimally Exploited, Isolated Fish Community Consisting of Smallmouth Bass, Largemouth Bass, and Prickly Sculpin

Spencer Lake, a remote, isolated body of water located on Blakely Island (San Juan County), was surveyed by members of the Washington Department of Fish and Wildlife Warmwater Fish Enhancement Program and students and faculty from Seattle Pacific University’s Department of Biology during April, August, and November 2001. Smallmouth bass Micropterus dolomieu dominated the catch, followed by largemouth bass M. salmoides and, to a much lesser extent, prickly sculpin Cottus asper. Size structures and catch rates varied with season, and fish were of primarily moderate size relative to those in other Washington lakes. Relative weights of smallmouth bass were low by regional and national standards (75th percentile) and decreased with length. Largemouth bass displayed relative weights that were consistent with the national standard but also decreased with length. The oldest fishes captured were a 13 year-old smallmouth bass and a 10 year-old largemouth bass. The median age of all fish captured was five years for smallmouth bass and four years for largemouth bass. Smallmouth bass growth, expressed as length at age, was lower than in other western Washington lakes available for comparison with this study. Largemouth bass growth was similar to other western Washington lakes for the first five years, then declined markedly. A reduced forage base, low water temperatures, and a lack of fishing pressure may all contribute to the observed bass population characteristics, though their effects are apparently stronger in shaping the smallmouth bass population.