Factors Affecting Fish Production and Fishing Quality in New Reservoirs, with Guidance on Timber Clearing, Basin Preparation, and Filling.

Fishing pressure on U.S. reservoirs is increasing rapidly and may double in the next 20 years. To meet increasing fishing demands, effective practical plans must be implemented to maximize and prolong the high spot-fish production that characterizes new impoundments. This report reviews literature on fishery resource development and fish production in new reservoirs and provides guidance on filling and site preparation techniques that should enhance fish production and angling quality. During filling, reservoirs are extremely productive because virtually all allochthonous nutrients, detritus, and drowned terrestrial animals, as well as autochthonous production primary and secondary, are retained in the basin. After a new impoundment is filled, fish production and harvest are high for the first 5 to 10 years but progressively decline as the reservoir ages. Strong year classes of fish may be produced in years of increased precipitation which increases inflow of nutrients and detritus from the drainage basin and raises the lake level to inundate woody vegetation, forest litter, andor herbaceous plants. Declines in reservoir fisheries primarily result from the losses of nutrients and detritus to outflow and sediments and from the use of detritus by invertebrates and fish. Concerns during filling include timing of inundation and control of water levels. Concerns for reservoir clearing depend on trade-offs among factors such as mosquito control, water quality, recreation, and fish production. On the basis of biological observations, practical methods of clearing reservoirs are presented, but the effectiveness of various methods has not been evaluated, because of insufficient quantitative data.