The link Bill provided should have most of the info you need.

When I build my next hatchery pond, I'll buy another commercial net that fits my budget first, then build the pond around it. Raising fish is easy, but getting them out in a timely and easily manageable manner often isn't. IF you want to move forage out several times a year, as opposed to long term projects, then I'd always go with a shoe box shaped pond. Most commercial hatchery ponds are shaped that way.

AL