Follow my thinking here.
It has been hot for a long time; it got very hot early and it basically hasn’t let up since. I expect it to be nastyhot up to or through September.
Casual fisherpersons (self included) are doubtless being kept inside due to the heat. That means that less fish are being harvested than normal, during what would be prime fish harvesting season.
I don’t know how quickly fish grow, but will the reduced harvest during the unusually hot summer months mean that fishing will be better this fall, in terms of available fish and size of fish caught?