they only test a percent of fish for ihn so they could actually live spawn more...i think it's either 60 or 120 ovarian samples for testing per species per year...if they find ihn in adult steelhead it's not so bad....eggs are water hardened in iodophor which seems to do the trick preventing vertical transmission to the fry...and if they are being transferred they have to be iodophored again...the harder thing is to get ihn free water to raise the fish in...so places like cowlitz and coleman have ozone treatment plants for their water...other places use well water and try to prevent stray sockeye(big ihn carriers) from getting upstream into their water supply if they use ihn free surface water...trout seem to handle ihn better but not salmon...except coho don't seem to carry it much