Effectiveness of Electro Fishing?

Does anyone have any first hand knowledge of just how efficient or effective electro fishing is? What sort of range does it work over? Are all species stunned? Do lots of fish miss or escape being zapped and therefore evade the electro fishing.

A couple of my club lakes (1 acre and 7 acres) have recently been electro fished, could this give a reasonable idea fish stocks with any degree of accuracy (assuming it has been done properly)?

Here's an extract from With a View to Fisheries - electrofishing

Factors affecting efficiency

Even with the correct electrofishing set up the efficiency of capture will be influenced by certain physical and biological factors. Firstly, the total fishing efficiency increases exponentially with the fish length. This makes electrofishing a size selective method, if the capture of smaller fish is a requirement then an increase in the field strength will decrease selectivity, but in turn this will increase mortality due to the higher voltage gradient. The second factor affecting the fishing efficiency is the specific conductivity of the water. For example, freshwater has a low conductivity, therefore a high field strength (volts per cm) can be achieved due to the reduction created in current flow (amps) caused by the increased resistance (ohms). Conversely, saline water is a better conductor of electricity, it has a lower resistance hence a better current flow. With everything staying equal, more power is required in saltwater to achieve the same voltage as in freshwater. Another important parameter is the temperature. There is a 40% reduction in conductivity when the water temperature is reduced from 20oc to 0oc therefore colder water will increase the fishing efficiency.