Which of the following is a common disease affecting fish in raceways?

Ichthyophthirius, commonly known as ich, is a parasitic disease that poses a significant threat to fish, especially in raceway environments where the conditions can quickly contribute to stress and overcrowding. This disease is caused by a protozoan parasite that infects fish by penetrating their skin and gills. Signs of infection include white cysts on the skin, fins, and gills, which can lead to severe health issues if not treated promptly.

Raceways, which can have high stocking densities and varying water quality, provide an ideal environment for ich to thrive. The stress level in crowded conditions can weaken fish immune systems, making them more susceptible to outbreaks of this parasite. Effective management of water quality, appropriate treatment protocols, and quarantine measures for new stock are vital steps in controlling ich outbreaks in raceway systems.

While other conditions like fin rot, swim bladder disease, and yellowfin disease do affect fish, they might not be as commonly encountered or as critical in fish raised in raceways compared to ich. Each of those diseases has distinct causes and treatment protocols; however, ich remains one of the most widely recognized and problematic parasitic infections impacting fish health in aquaculture settings.