The fish are safe to eat and the only way it will have any impact on the fishing is if they kill too much vegetation at one time which is rare as there is a formula used to calculate the amount of acreage safe to treat. Typically an area will be treated once a week to allow time for the treated area to die out then is evaluated the following week and treated again as needed. When the treated vegetation starts to die it pulls oxygen from the water and if too much is treated at a given time thats when the fishing may be affected...and if a newbie nukes the lake then a fish kill may occur due to extremely low oxygen levels.