Ok, is it just me or is this thread already confusing? The other "pay it forward" type of threads on other forums deal ONLY with the trading at hand and no idle chit chat taking space and distracting from the thread. Also, the others only deal with one trade at a time - which would be a LOT simpler.
The way it's done elsewhere: Person 1 offers the fish he/she is "giving" away for the cost of shipping, Person 2 is interested in that deal (no other deals are on the table at the time), so person 2 says "I would like that fish/those fish and here's what I'm offering". Shipping costs can either be charged by the person doing the trade, or if they don't have much to offer, they could throw in the shipping instead or more/better fish. Then Person 3 likes Person 2's deal and takes it and offers something in return.
Hope that will make things flow smoother on this thread. If it's going too slow, free (or reduced) shipping could be offered to speed things up, or another person can toss something into the current offer (separate shipping of course), but more fish would be added to the current offer and usually gets things moving faster. Constant bumping just makes the thread a zillion pages long with few offers and annoys folks who get email alerts each time something is posted to the thread. If it looks like it's going to go well, then the mods might want to make it a sticky if we don't fill it with useless chatter or bickering (the downfall and eventual shut down by the mods of most of the other forums attempts at this kind of thing).
Side note to MODS - IF there's a way to add the rating system that many other threads have for buying/selling, that would help keep folks honest so their feedback stays good. No need for comments IMHO, it can either be done or not...