Thank you for sharing your dream with us. Please take everything that I share to the Holy Spirit as He Alone gives the accurate interpretation.
I believe that I have a partial interpretation to this dream and there are many levels of interpretation. The key message is that you are observing people being focused and staying in their own lane. I think that there is quite a bit of word play going on in your dream. Like lane, race, fish. This dream might suggest groups of souls (fish) and people running their own race and may (fish in a school/group- could represent church) or not (individual swimmers- could represent individual Christ-followers) be aware of others as they go along their life purpose/destiny (lane). You were mostly observing and therefore, I think it is about what you saw, an extrinsic dream and it is about all the other parties in your dream. In addition, a great leader (trunk) may be cut down from their position and you are concerned about the damage it might cause a church (or some other ministry) but God is still in control in overseeing things.
May the Holy Spirit give you clarity in Jesus’s Almighty Name I pray, Amen!