Scottish veterinarians share fish health expertise to Iceland
by Sara Pflaum MRCVS DipRCPath
DNV is strengthening fish health services in Iceland by collaborating with experienced colleagues in Scotland. This cross-regional partnership enables valuable knowledge exchange, helping both regions benefit from decades of practical expertise. Salmon farming in Scotland began in the 1970s and has grown steadily since then. Our Scottish veterinarians bring a wealth of fish health and operational experience to complement local expertise in supporting Iceland’s rapidly growing aquaculture industry.
Gill health: a major issue
One of the most significant fish health challenges has been gill disease, particularly in the last 15 years. Sharing experiences from Scotland can be extremely valuable in helping Icelandic producers prepare for similar challenges.
Amoebic gill disease (AGD) first became a widespread problem in Scotland in 2011, causing high mortality in some cases. AGD can be treated, ideally with freshwater baths, although hydrogen peroxide is also sometimes used. However, gill disease is often complex and may involve multiple factors beyond amoebae, including bacteria, harmful algae, and jellyfish. Determining the initial cause can therefore be difficult.
In response to these challenges, most Scottish farms have established regular gill health monitoring to detect problems early and monitor their progression. This is especially important in summer and autumn when higher sea temperatures accelerate diseases development. Lice treatments are also common during this period, adding extra stress to populations with already compromised gills. These insights are critical when planning operations and assessing the risks associated with handling events.
Monitoring methods
Gill health monitoring involves a variety of approaches, many of which can be performed non-lethally. At farm visits, veterinarians examine live, anaesthetized fish and apply a standardized visual gill-scoring system. Gill mucus samples can be collected and used for PCR testing to identify pathogens. Microscopy of freshly gill mucus allows on-site detection of parasites such as amoebae, while histopathology provides more detailed insights into gill structure and function. Together, these methods give operators a clearer picture of fish health and potential risk factors.
Warmer seas, new risks
While Iceland does not currently experience the same gill disease patterns as Scotland, climate trends suggest increasing risks. Typical Scottish seawater temperatures peak around 15°C in autumn, significantly higher than Iceland. However, global seawater temperatures are rising, with marine heatwaves recorded in Northern Norway in recent years. These events, with 2-4°C above normal, have contributed to accelerated sea lice development and lower dissolved oxygen levels.
In 2025, many Icelandic sea sites recorded sustained temperatures above 11°C, raising the possibility that diseases historically confined to warmer waters could emerge locally. When lice development is rapid and treatment becomes necessary, gill health plays a critical role in determining the success and safety of interventions.
Preparing for the future
Our Scottish colleagues’ experience of managing gill health under higher sea temperatures provides valuable lessons for Iceland. By combining this expertise with the knowledge of local veterinarians, DNV is helping customers anticipate emerging risks, strengthen fish health management, and make informed decisions that support sustainable growth in Iceland’s aquaculture industry.
ENDS
Sara Pflaum MRCVS DipRCPath is an Aquaculture Veterinarian with Ocean Ecology – a DNV company – and is based in Oban in Scotland.
She has worked in Scottish aquaculture since 2012, advising on all aspects of fish health including gill health challenges.She is a Diplomate of the Royal College of Pathologists specialising in veterinary clinical pathology, focusing on haematology and biochemistry of salmonids.
9/29/2025 3:24:00 PM
