Join the Fight Against Saprolegnia: An Updated Guide for Anglers on the Spey

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Dear River Spey Anglers,

As many of you are aware, Scottish rivers have been dealing with the resurgence of Saprolegnia – a potentially harmful water mould that resembles fungus and poses a serious threat to fish health. In particular, recent updates from Fisheries Management Scotland have indicated the emergence of more aggressive strains of this pathogen in various rivers across Scotland, which are proving to be much more virulent than before and deadly to fish.

Below we have outlined what you can do to help protect our precious Atlantic salmon and stop the spread of this potentially fatal disease.

Understanding Saprolegnia

Saprolegnia often manifests as white, cream, or pale brown cotton wool-like growths on fish skin and fins, causing severe skin damage that could lead to lethargy, debilitation, and in severe cases, mass fish mortality.

An Atlantic salmon infected with Saprolegnia

Your Role in the Fight Against Saprolegnia

As dedicated anglers, you have a crucial role in mitigating this issue. You can significantly help to reduce the spread of Saprolegnia by adopting a rigorous biosecurity protocol, focusing particularly on a detailed disinfection of your angling equipment both before and after use. Here’s a quick guide on how to do this:

  1. Cleaning: Remove visible dirt and debris from your equipment. Warm soapy water can be effective to clean your gear thoroughly, focusing on hard-to-reach areas where pathogens might hide.
  1. Disinfection: After cleaning, you should disinfect your equipment. There are several methods for doing this:
  • Virkon Aquatic: An effective, environmentally friendly, and user-friendly disinfectant. Use a 1% solution (one 10ml scoop or two 5g tablets per litre of water) in a sprayer. Our trial found that about 160ml of Virkon Aquatic can disinfect a pair of boots and breathable waders. Please note that Virkon is effective for about 7 days after being mixed, and while its pink color fades, it should not be relied upon as an indicator of its effectiveness. (Virkon can be purchased from a range of online retailers.)
  • Salt Water Solution: Prepare a salt water solution of at least 15 grams of salt per litre of water and immerse your kit for at least 45 minutes, then rinse in tap water.
  1. Drying: Allow your gear to dry completely. Some pathogens, including strains of Saprolegnia, can survive in damp environments, so this step is crucial.

For your safety, we recommend wearing protective gloves and goggles while handling and mixing Virkon Aquatic. Also, if you have surplus disinfectant, small volumes can be disposed of by pouring or spraying on hard ground.

Stay Alert and Stay Involved

Aside from equipment disinfection, we urge all anglers to avoid transferring water from one site to another to prevent the carriage of microscopic pathogens. 

Also, we cannot stress enough the importance of reporting suspected Saprolegnia infections. 

If you catch a fish showing symptoms of Saprolegnia, report the incident to Fisheries Management Scotland immediately. Please refrain from returning the infected fish to the water or attempting to handle or treat the fish yourself.

Fisheries Management Scotland, Fish disease reporting tool

Lastly, stay informed. Regularly check the Fisheries Management Scotland’s interactive dashboard to keep abreast of any reported instances of fish diseases in our rivers.

Fisheries Management Scotland, Fish Disease Dashboard

For any further queries, feel free to reach out to us or directly to our biologist, Atticus Albright, at

Thank you for your unwavering support and cooperation.

Tight Lines,

The Spey Fishery Board

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