Dear Colleagues, in order to try to understand triggering factors, I am currently trying to collect information about cases of saprolegniasis outbreaks, observed among mature salmonids (especially brown trout and grayling) and other fish species during and/or following their reproduction period. I know that many outbreaks have been observed, some of which were published or mentioned in scientific papers but many were not.
Thus, if you have knowledge/information related to such noteworthy cases (I mean, with an unusually high prevalence and associated mortality), whether published or not in scientific literature, do not hesitate to get in touch with me.
Saprolegniasis, a disease affecting fish eggs and juvenile fish in hatcheries worldwide, is caused by the pathogenic oomycete Saprolegnia parasitica. This disease presents as greyish-white patches of filamentous mycelium on the body or fins of fish and is associated with tissue damage leading to death of the animal.
Saprolegniosis is a general term referring to a number of species of fungi that occur in water and infect the epithelium and eggs of a variety of fish species including striped bass (Figure 11.9). The principal species are Saprolegnia parasitica, Aphanomyces sp., and Achlya sp.
if you want more information can see the flowing links:
https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/saprolegnia
Article Resistance to Saprolegnia parasitica infection: A heritable ...
Saprolegniasis, also known as "fungus" or "slimy disease," is a common and potentially serious condition that affects fish, particularly during the spawning season. It is caused by the fungus Saprolegnia, which is found naturally in many aquatic environments and can infect fish through open wounds or mucous membranes.
Outbreaks of saprolegniasis are more common in mature wild salmonids and other fish species during the spawning season due to a number of factors. One of the main reasons is that the spawning season is a time of increased stress for fish, which can weaken their immune systems and make them more susceptible to infections. Additionally, the spawning season is often characterized by colder water temperatures and reduced water flow, which can create conditions that are more favorable for the growth and spread of the Saprolegnia fungus.
Symptoms of saprolegniasis can include the presence of white or grayish patches on the skin or fins of the fish, as well as swelling, redness, and lesions on the skin. In severe cases, the fungus can spread to the gills and other internal organs, leading to serious illness and death.
To prevent outbreaks of saprolegniasis in mature wild salmonids and other fish species during the spawning season, it is important to maintain good water quality and to avoid exposing fish to unnecessary stress or injury. Additionally, fish that are already infected with the fungus should be treated promptly to prevent the infection from spreading to other individuals.
After having read the replies I have received, I renew my call for information about cases of epizootic outbreaks of saprolegniasis among WILD mature fish (especially salmonids) during their spawning season in river or lake. I would especially like to collect precise information about the environmental conditions prevailing during the weeks/months before the onset of the outbreaks i.e. : water chemistry, water levels/flow, rainfall regime, composition and thickness of the benthos, etc...
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