There are several companies that have really streamlined the silent auction process... gone are the days where every item has to have a bid sheet, and a large amount of space that it takes up.
They are now bringing in an ipod with a custom app for each participant for you to borrow for the event to allow you to sign up to follow certain items. If you are outbid on an object, the system will automatically ping your ipod to see if you want to increase your bid. Items usually go on the block and expire on a rolling schedule through the night, to help cut down on being limited on how much you can bid on.
Granted, because of the costs of setting up the infrastructure (they do a fantastic job of making sure every square inch of your venue has a strong wireless signal) this is not a cheep option, but over the past year, I have been seeing more and more events at the hotel I work at start using this process... but these are for fundraisng Galas that easily bring in several hundred thousand dollars in one night just on the silent auctions. Largest auction that I have seen of this type was about 2500 or so participants.
While hiring in one of these companies may not be feasable for a fish auction, maybe there are ideas in their process that can be used on a smaller/less expensive scale?