Improving fish habitat can serve several purposes:  assisting reproduction, providing cover for young fish, and concentrating fish to make catching them easier. 

 For example, channel catfish require cavities to protect their eggs.  Stump holes or sunken logs are ideal; however, if your lake does not have any (such as in Lake Joe) reproduction is hampered.  Placing artificial nesting cavities can increase survival hopefully reducing the quantity that must be stocked to maintain the population.  The lakes in the Forest Preserve are generally “bass heavy”, in other words there are a disproportionally high number of bass relative to other types of fish.  Adding brush piles provides cover for young bream (main food source for bass) allowing them to grow and reproduce.