Why do some clupeiform eggs stick to rocks, gravel, or plants?

Some clupeiform fishes, such as those in the genera Clupea and Pomolobus, possess eggs that are coated with an adhesive secretion. This substance allows the eggs to stick to stones, gravel, or plants shortly after they are released into the water.1

While the majority of clupeiform fishes produce pelagic (free-floating) eggs, the use of adhesive eggs is a specific reproductive strategy. These adhesive eggs are typically found in species that spawn in shallow waters where the bottom is clean and hard, often covered with gravel or sand. By sticking to these substrates, the eggs remain in the spawning area rather than drifting away with currents.1