Pink salmon update

September 07, 2017


On 10th July the first pink salmon was captured by an angler on the Dee. Subsequently, a further 12 were caught. In mid-August, a group of around 30 pink salmon were observed, which were starting to cut redds, and it would now appear that they spawned successfully. We obtained an emergency licence to remove these fish by netting and 25 pink salmon were removed over three attempts. 13 of these fish were sampled by the Fish Health Inspectorate for disease; so far, no diseases have been found but full testing is still underway.

Last weekend – 2nd September – a new batch of pink salmon were seen cutting redds on the Dee. We are currently carrying out a full assessment of the amount of spawning that has taken place, and as of today, a total of 218 pink salmon redds have been identified. These have all been in the lower river, spread across five fishing beats. However, we expect the total to reach about 300 redds once surveys are complete.

All spawning redds are being counted, mapped and marked, so that we can identify them even after a spate. We are also attempting to destroy the eggs that have been laid in the gravel. We have found this requires a huge manpower resource: approximately 4-6 man hours is required to remove eggs from one redd.

The eggs that we have dug up are fertile, with some of the eggs already being in the ‘eyed’ stage (i.e. the embryo’s eyes have developed and can be seen through the egg casing).

Photo: Eyed pink salmon eggs dug up on 5th September.


We are hoping that the eggs that were laid at the weekend are still in their vulnerable, ‘non-eyed’ stage. Therefore, instead of removing them, we just need to physically shock them. For the eggs laid in August, however, they need to be removed from the river or else they are likely to hatch.

We do not have enough manpower to remove or destroy 300 redds, and so we have approached Scottish Government to see if their agencies can provide staff to help with this work. We are also planning sessions with groups of volunteers, so if anyone is available for this - admittedly physically demanding - work, please contact the River Office.

Yesterday, an invasive species rapid risk assessment for pink salmon in the UK was released by CEFAS (UK wide government agency to inform on fisheries). It is still considered to be a draft document and will also be updated as new information becomes available. Its message is that pink salmon are ‘very likely’ to establish in the UK, which is an assessment made with a ‘high’ level of confidence. However, the impact these fish will have is a lot less certain. The document considers that the negative impacts that these fish will cause will be moderate, but this conclusion only has a low level of confidence.


What you can do

  • Keep a look out and report any sightings of pink salmon or redds, particularly upstream of the Crathes/Banchory area. Our native Atlantic salmon will not be spawning for another six weeks, so any redds seen before then will be pink salmon redds.
  • Any pink salmon caught by anglers must be killed and not returned to the river. Please also report any catches to the River Office.
  • Volunteer with our egg removal teams. We note that it is physically demanding work, and it would be particularly helpful if you have your own waders or drysuits. We are trialling our first volunteer day this weekend and will develop further work plans after this event.


 Background

We don’t expect that these pink salmon have swum from the Pacific Ocean as they are well established in Russia and northern Norway, having repeatedly been introduced into Russia since the 1950s to establish a commercial fishery. They subsequently established in northern Norway and since then the occasional pink salmon has turned up in UK waters. The first pink salmon was caught in the UK just off our coast, by Altens, in 1960. This is the first year they have been seen in numbers in the UK.

Pink salmon have a rigid 2-year life cycle, with juveniles spending only a month or two in the river, before heading out to sea. They return to spawn as 2-year old adults and then die. Because of this, fish produced in odd years will never overlap with fish produced in even years. Therefore, any offspring produced this year would return to the Dee in 2019.

In 2017 pink salmon have appeared in around 20 Scottish rivers, a situation that is unprecedented. Some of these rivers have also confirmed pink salmon are spawning. They have also appeared in rivers in England, Ireland, Iceland, Finland, Denmark, Germany and France.

The impact that pink salmon will have on our Atlantic salmon is unknown. Their differing life cycles mean that they don’t cross paths for long, however, pink salmon arriving from the sea may bring disease, and we do not know how Atlantic salmon would respond to this. It is also unclear whether there will be competitive interactions amongst juveniles in the river.

 Photo: Searching and marking salmon redds 

Photo: Digging out a pink salmon redd


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