ABSTRACT
Buoyancy and the physiology of buoyancy compensation of adult fishes is well studied. Studies of the specific gravity of fish eggs and larvae, and of the development of the mechanisms and structures that effect buoyancy compensation are spread over a wide array of literature, as well as the phylogenetic myriad of fishes. Passive vertical movements owing to buoyancy change can be avoided if an egg or larva is neutrally buoyant and has a specific gravity equal to the surrounding water. Developmental events within the ovary that prepare eggs for release into ambient water influence egg buoyancy. The contribution of oil globules to buoyancy is greater among the few freshwater fishes with pelagic eggs than among many marine fishes with pelagic eggs. The effects on a larva with a swimbladder are that the water density increase with depth owing to the temperature decrease and salinity increase, will result in increased buoyancy as a larva descends.
