Mechanical treatments blamed for raft of health issues
The health status of fish in northern Norway has been noted to be poorer than normal recently – a pattern that has been linked with the increase in mechanical delousing.
So believes veterinarian Kristin Ottesen, who told assembled delegates at the Frisk Fisk conference in Bergen yesterday that: “Fish health in Nordland is not very good and generally lower than normal, largely due to the increased adoption of mechanical delousing techniques.”
Her presentation focused on emerging fish health challenges in Nordland, and she pointed to the increase in indirect health challenges associated with lice.
“New methods of delousing are causing generally impaired fish health and in Nordland fish are now exposed to many harsh treatments,” said Ottesen.
The vet noted the lack of biological expertise employed by the producers and providers of these mechanical treatments.
“The companies that sell these devices often have no biological expertise – one such company told me last week that they cannot afford to hire people with biological expertise, because farmers are pushing to keep price of the machines down…but one has to afford to employ such people when selling a machine that deals with biological issues,” said an upset Ottesen.
Ottesen noted that there has been an upturn in acute injuries – such as bleeding and accumulative damage.
“These accumulative damages are often difficult to detect, but we do see an upwards trend. There are also a lot of stress-related mortalities – treatments are extremely tough and recovery time between each treatment is minimal,” she said.
Ottesen has also seen an upturn in ulcer development following treatments.
“This has a big impact on how well the fish recover afterwards. And we see them lose their appetite, which leads to poorer growth. We should spend a lot of time in 2017 to study these long-term effects,” she urged.
The Norwegian veterinarian also suspects that the recent ISA outbreaks in her region may also be related to mechanical lice treatments.
“We believe the immune system of the fish is lessened by all these treatments and that there is a possibility of spreading infection through the machines. In addition to acute mortality from ISA, we see sub-acute cases with far lower mortality. And it is very difficult to distinguish it from treatment mortality,” she said.
