Fish embryos and larvae are especially sensitive to environmental impacts, such as habitat loss and chemical contamination. In Puget Sound, many fish species have pelagic eggs that float as part of the zooplankton, or demersal eggs that stick to sand, rocks or seaweed in nearshore areas. These eggs are especially vulnerable to water and sediment contamination from urban and industrial sources, stormwater runoff, and oil spills. Microscopy is just one of many tools used by scientists in the Ecotoxoicology Program to investigate the developmental toxicity of common contaminants.
Herring embryo fourteen days after fertilization
Herring eggs are demersal; they stick to seaweed, rocks, and other hard surfaces in nearshore environments. In Puget Sound, herring eggs and embryos are especially vulnerable to human impacts because they are spawned in shallow waters, often near urban and industrial areas where they may be exposed to a variety of chemicals, including oil spills.
Hatching Surf smelt
Surf smelt (Hypomesus pretiosus) lay sticky eggs on gravel beaches in Puget Sound and other Pacific Coast locations. Just before fish hatch, special cells on the head produce an enzyme that softens the egg shell, making it easier for the fish to break through the chorion. Contaminants in the water, and loss of fine gravel beaches due to construction of bulkheads impact the survival of surf smelt.
Most flatfish have small clear eggs that float as part of the zooplanktion. Eggs from the C-O sole egg (Pleuronectes coenosus) also have elaborate hexagon–shaped structures on the egg surface.