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

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, Onta rio. The length-weight relationship for all fish entered in the derby was d escribed as weight (g)=(2 x 10(5)) x total length (mm)(2.95). A significant declining trend in mean fish length existed for the 10 longest fish entere d in the derby each year over the 10 year period (r(2) = 0.071, p < 0.05). Relative weights observed were consistently below the length specific stand ard of 100, similar to other riverine Smallmouth Bass populations. Age and growth rates were similar to other northern riverine Smallmouth Bass popula tions, and the oldest fish observed was 16 + (441 mm TL). Trends in the mid dle Grand River Catch Per Unit Effort (CPUE) data suggest that the relative abundance of Smallmouth Bass has decreased significantly since 1988 (r(2) = 0.552, p < 0.05), although the 10-year derby CPUE (0.36) is similar to CP UE from other riverine populations. The derby data indicates that the popul ation size and structure require further investigations to determine exactl y where problems and management opportunities exist.