I grew up summers living on the lake during the summer vacations and weekends during school months. My bed was next to the window 70 ft away from the lake edge. During times when I awoke during the late spring and summer days I would be hit with that particular scent… those same times I would notice bedding gills sometimes many hundreds in numbers spawning in the shallows in front of our sea wall.

The lake was near eutrophic in identity with muck approaching several feet in thickness… our cottage shore line was kept free of muck by constant swimming and boating use as well as maintenance with raking. The bluegills apparently loved it bedding on the firm sand bottom. So through the years I always associated the smell with spawning gills … but never knew the reason.

Through some digging ansd research I learned it is a pheromone released by male and female bluegills to attract other to the colony to spawn.

“ Moreover, large bluegills tend to spawn first, occupying the best areas. ... Because this species nests in colonies, there may also be some involvement of pheromones from males and females that draws more fish to the colony, where over 100 adults may be in various phases of the spawn.” … In-Fisherman Mag

It is the pheromones being released into the water that some of us smell… I believe many of us cant smell the odor released as well as others.

I can smell it and hound down the areas of the spawning gills. If you know your lakes like I know mine… you know where these potential areas are and they vary from season to season. I do perimeter checks often on my BOW during the fishing Lull.Periods during the day… visually as well as side scan imaging. I feel confident in finding the areas that need to be fished.

Having guests in the boat during these times of pheromone release many don’t notice any particular smell at all when asked.
To add I don’t believe in fishing the spawn at all during this time… there is enough knowledge base out there to know that it is bad for the future fishing for all bodies of water period.

I do believe in fishing the deeper areas or the first breaks adjacent to the spawning areas … there are where the females will congregate. Best of advice is to leave the guarding males finish the process so the dominant gene gets passed.

Hope this helps