Dead Usually used to refer to dead tissue (cells) Necrotic tissue is often caused as a result of infections or abrasion, and provides an easy entrance for pathogens to enter the body Large areas of necrotic tissue on the skin of the fish can lead to difficulty in osmoregulation Areas of necrotic tissue can grow as the dead areas prevent the flow of blood and nutrients to other healthy cells, causing the gradual increase in the size of the necrotic area