Just an idea, but how about instead resetting the focused fishing because of public events, either completing public events give a boost to focused fishing, have a personal tracker of the progress you add to the meter that stays until you leave the planet, or both?
I have yet to find anyone that likes the current system, and tying it to the amount of fish caught in your bag may cause coding issues, but with the aforementioned ideas, they seem like a good compromise/balance.
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try a two pond approach at first pond don't pick up anything, let the public event happen, then when the second pond shows, fish once then go back and pick up all your fish (yes your fish will stay), hopefully you have some purples and this will spike you're new second pond if by then you have some new friends fishing, and focusing is high, you can either fish out or leave all your purples again to fish a third pond, and so on I want to try this with a fire team, cause you could immediately get to half way right at the beginning and have more time fishing with great focus. Imagine getting two fire teams on one planet and then doing this, almost like the excavation protocol of days past