FISH PRODUCTION IN FRESH-WATERS - ARE RIVERS MORE PRODUCTIVE THAN LAKES

Community fish production data were summarized from the literature to test the hypothesis that production is higher in rivers than in lakes. Average community production at 55 river sites was three times greate r (273 kg . ha(-1). year(-1)) than at 22 lakes (82 kg . ha(-1). year(- 1)). Higher production (P) in rivers resulted from much higher densiti es of fish (14 times) and greater biomass (B) (about 2 times). Average fish weight and PIE ratios were inversely correlated. Average fish we ight was 7 times less, and P/B ratios were 1.5 times higher (after cor rection for fish size), in rivers than in lakes. Thus, rivers not only had higher average biomasses of fish but also the turnover rate of th e biomass was greater. Fish production was positively correlated with phosphorus in both lakes and rivers. Information on community fish pro duction supported the hypothesis that the productivity of river habita t is, on average, higher than the productivity of lake habitat. The pr oductive capacity of freshwater habitats can be predicted using a mult iple regression model developed by Boudreau and Dickie (Can. J. Fish. Aquat. Sci. 46: 614. 1989), where fish production is calculated from a verage fish biomass and body mass.