Fish Eggs, Embryos and Larvae
Marine fish have a planktonic larva. Either the eggs will be sticky and laid on the shore, e.g. sand eels, or for those living further out at sea 1000s of transparent eggs will be released into the water. The latter are the ones seen here. They tend to float to the surface in samples and can vary from just a few to many dozens. May is a good to to find them but any time through to the autumn is possible. The developing embryo can be seen around the yolk and each egg has a strong outer chorion coat, around 1 mm in diameter. Distinct in the photo is the presence of a drop of oil on the developing egg. Along with the yolk within the chorion the oil will also be consumed as food although it helps with buoyancy.
A well developed fish embryo, possibly a Sand eel.
Fish Larvae
Fish larvae are not common in the Dale shore samples. They can be abundant in the water off Skomer in spring and autumn. The white ones are possibly Sand Eel larvae, especially the yolk-sac larva at the bottom.
A Yolk-sac Fish Larva
Upon hatching from the chorion coat the remaining yolk stays with the larva as an important food source until it begins to feed on plankton. Identifying species is difficult until the yolk-sac disappears as at this time the pigment cells migrate around the body to create colour.