Here is my commentary on electrofishing and a couple additional things for you to consider and research.
Firstly, get some HANDS ON (not just watching) experience using a fish electroshocker with someone else. I have participated in electroshocking for sampling fish in college and as a helper on numerous fish sampling projects.
Considering the cost & maintenence of all equipment and then amount of effort required each time, and the overall results of the fish produced, and limitations of the technique (only good in shallow water up to 4-6ft & that it is most successful at night, mismatches in power transfer, & better in higher conductivity waters), I am not impressed with the techinque and it is over rated as a tool for the private pond owner. Other disadvantages of fish shockers are: the shock zone is not all that large, often numerous fish sense the encroachment of the boat &/or the electrical current field and avoid the shock zone by moving away or deeper, numerous fish (maybe the larger percentage) are only partially or inadequately stunned and cavort out of the reach of the netters. Some species of fish are more vulnerable to electrofishing than others. Some types of fish due to morphology, physiology, and behavior or habitat preference are poorly sampled by electrofishing. Electrofishing tends to be biased toward sampling the larger fish. Water temperature, water transparency (cloudiness), substrate composition, and habitat/cover all affect the electrofishing efficiency directly and indirectly. Electrofishing units in untrained or unknowledgable hands often results in over stressed and injured fish which later die. Improper electrofishing can cause fish injury such as acidosis & reduced respiratory efficiency which can eventually kill fish. Injuries usually take two forms brusing or hemorrhages and fractures in hard tissues. More study needs to be done on the effects of electroshocking on fish eggs (laid and unlaid). So you could actually be inadvertently killing or permenately damaging some of your better and more prized fish by improperly electrofishing.
As commonly mentioned the technique is extremly dangerous to even trained users. Make sure insurance policies are paid up for all users; accidents very easily happen on rocking boats and with excitable, nonfocused, inexperienced, "helpers".
Secondly, Electrofishing is a good tool for a private or government business where time is money and they need a relatively good AND quick idea of what fishes are present to make mananagement decisions. BUT FOR THE EDUCATED AND INOVATIVE PONDOWNER WHO HAS CONSTANT ACCESS TO THIS POND, THERE ARE JUST AS GOOD, IF NOT BETTER WAYS OF SAMPLING FISH TO DETERMINE THE OVERALL COMPOSITION OF A FISHERY COMMUNITY. Note that almost always a written report is created (or should be created) from each electrofishing sampling trip. This is performed to make an educated, data filled, statistical evaluation of the electrofishing results. If one is not capabale of writing one of those reports, then I my opinion, you have no business with a fish electroshocking unit because you do not know how to make best use of the information gleened from the equipment.
In summary, electrofishing is a glamorous and seemingly impressive way to collect fish from your pond. But due to its inherent danger and several other disadvantages it is a sampling method that is best used by those with some training and experience.
A little research into a good fisheries techniques book will reveal other very good, sometimes better, and definately safer methods FOR PRIVATE PONDOWNERS to themselves sample their fish (as ewest mentions, see the book Fisheries Techniques, 2nd edition, 1996, by Brian Murphy & David Willis (Dr Willis is a PB regular forum contributor; book is available from sellers such as Amazon.com)). Hopefully Pond Boss magazine will in the future, feature some of these fish sampling techniques and how to effectively use the results or data they are capable of producing to help pondowners improve or enhance their fish populations.
