Contents xv 



Artificial Fluctuation of Water Levels 155 



EflFects Upon the Exposed Lake Bottom 158 



Effects Upon Rooted Aquatic Vegetation 158 



Effects Upon Invertebrates 159 



Effects Upon Fishes and Other Vertebrates 159 



Types of Drawdowns 161 



Lake Fertilization 162 



Manganese 164 



Lime 164 



Potassium 164 



Phosphorus 165 



Nitrogen 165 



Other Functions of Fertilizers 165 



Dangers From the Use of Fertilizers 166 



Aquatic Vegetation and Control Measures 168 



Types of Aquatic Plants 169 



Algae as a Basic Food 170 



Dangerous Algae 171 



Nuisance Algae 171 



Control of Algae 172 



Loss of Fish Production Through Rooted Vegetation 172 



Sudden Plant Die-Offs 173 



Role of Aquatic Vegetation in Management 176 



Control of Higher Aquatic Vegetation 177 



Literature 177 



Chapter 7. Fishing and Natural Mortality 181 



Population Estimation 181 



Forces Acting Upon a Fish Population 182 



Fishing Mortality 183 



Angling Compared to Natural Predation 183 



Yields and Standing Crop 184 



Maximum Yields and Length of Growing Season 185 



Underfishing 187 



Overfishing 189 



Fishing Pressure vs. Yield 190 



Types of Fishing Pressure 193 



Factors Related to Rate of Catch 195 



Role of Commercial Fishing in Sport-Fish Management 196 



Natural Mortality 199 



Causes of Natural Death 199 



When Do Fish Die? 200 



