Derby-determined vital statistics and trends of the Smallmouth Bass, Micropterus dolomieu, recreational fishery in the middle reaches of the Grand River, Ontario

Abstract

Data from Grand River Bass Derbies (1988-1997) documents trends in relative abundance and provides information on vital statistics of Smallmouth Bass (Micropterus dolomieu) in the recreational fishery on the Grand River, Ontario. The length-weight relationship for all fish entered in the derby was described as weight (g) = (2 x 105) x total length (mm)2.95. A significant declining trend in mean fish length existed for the 10 longest fish entered in the derby each year over the 10 year period (r2= 0.071, p < 0.05). Relative weights observed were consistently below the length specific standard of 100, similar to other riverine Smallmouth Bass populations. Age and growth rates were similar to other northern riverine Smallmouth Bass populations, and the oldest fish observed was 16 + (441 mm TL). Trends in the middle Grand River Catch Per Unit Effort (CPUE) data suggest that the relative abundance of Smallmouth Bass has decreased significantly since 1988 (r2=0.552, p<0.05), although the 10-year derby CPUE (0.36) is similar to CPUE from other nverine populations. The derby data indicates that the population size and structure require further investigations to determine exactly where problems and management opportunities exist.