fish community in the river also exists because of the connection between 

 the two systems. This increased community diversity may be restricted to the 

 area of the channel in the immediate vicinity of the pit. 



Pit depths are important to fish utilization. Obstructions to movement 

 are not a factor during open water periods if either an inlet or outlet are 

 available for fish movement between the river and the pit. A potential for 

 fish entrapment exists, however, during winter when ice cover is present on 

 the river, the pit, and the interconnecting channel. In the latter situation 

 the pit must be sufficiently deep so it does not freeze to the bottom and 

 decomposition of aquatic vegetation does not decrease the oxygen content of 

 the water below that necessary for fish survival. 



The creation of a pit in a floodplain constitutes a major change to the 

 local terrestrial environment. Pits are usually situated on vegetated flood- 

 plains, consequently, terrestrial habitat is almost always destroyed. The 

 depth of excavation and the permanent inundation that results also greatly 

 retards or prevents on the long-term, the re-establishment of pred i sturbance 

 conditions. What most frequently occurs, however, is the creation of a more 

 diverse habitat with concomitant changes in faunal communities. 



The creation of a pit in meandering river floodplains, that contain 

 oxbow lakes, merely adds to the habitat diversity in a localized area. Where 

 pits are located in floodplains lacking natural lakes and ponds, the effect 

 is again principally local, but has implications that affect a much larger 

 system. In these cases, the newly formed body of water can attract migrant 

 waterfowl and shorebirds and perhaps even provide habitat suitable for 

 nesting and rearing that did not previously exist. The higher aquatic produc- 

 tivity of many of these ponds could afford a significant food source for 

 those species adapted to feeding in pond and lake environments. 



The effect of creation of a pit, on the scenic quality of an area, 



is totally dependent on the diversity of the floodplain environment. A pit 



will have less effect where lakes and ponds occur naturally than where 



these types of aquatic systems do not occur. Where lakes and ponds do not 



357 



