Fish get sick but is it something anglers need to worry about? Fish in the wild definitely DO get sick, but usually escape the notice of fishermen because sick fish are more lethargic and less likely to bite

“Some other clinical signs I would add are lethargy, color change, flashing (where they are scratching themselves), and open wounds,” said Kevin Kwak, veterinarian for the California Department of Fisheries and Wildlife. “Different diseases can manifest differently during an outbreak. There can be other factors that decrease survival. Some of these factors can depend on the type of pathogen/disease infecting the fish, the severity of the infection, where on or in the fish the infection/disease occurs, the age of [the] fish, environmental conditions, the ability in finding shelter, and avoiding predation.”

A disease isn’t always caused by an infectious agent like a pathogen, and a pathogen doesn’t always cause disease. Three main factors usually cause disease by a pathogen. There needs to be a pathogen, the appropriate host, and the right conditions. When all three are present, you typically will see disease.

A lot of times these diseases are not necessarily visible to an angler’s naked eye, but illness often affects spawning and species regeneration. The visible deformities that are actually seen by fishermen (infected eye sockets, gills, fins etc.) are usually part of an otherwise healthy ecosystem (just as terrestrial ecosystems will exhibit some animals with disease).

If a serious enough spread of a disease occurs it can cause problems throughout an ecosystem. A massive die-off can cause a smell that can be a nuisance to the public. A die-off can also draw other animals to the area, which in turn poses a risk of transferring the pathogen to other ecosystems that have yet to be infected.

Humans are also capable of spreading the pathogen to other freshwater ecosystems: gear that hasn’t fully dried and standing water from a boat can carry the disease to other bodies of water.

According to Kwak, sick fish can be a sign that something is wrong in the ecosystem. Water quality issues, water temperature, food availability or the introduction of a new pathogen or predator all need to be considered when investigating disease in fish.

If you are a witness to multiple sightings of diseased fish in an area, take pictures and write a report with a thorough history. Fish investigations are difficult and time-sensitive as fish samples start to deteriorate once the fish dies, while frozen samples limit the examination and exclude some of the diagnostic tests used. 

To prevent yourself from getting sick from an infected fish, remember to thoroughly wash your hands with soap and water before and after handling the fish.

Source: the Log