Farmed salmon. (Photo:Blue Planet Society)
Three out of four salmon escapes caused by equipment failure
Friday, February 08, 2013, 05:00 (GMT + 9)
Researchers working on the SECURE project (Securing fish – farming technology and operations to reduce escapes) have analysed all escape incidents between 2006-9 in Norwegian fish farms. They discovered that 68 per cent of salmon escapes are caused by equipment failure and 8 per cent by human operational error, and that two out of three escapes are caused by holes in sea cage nets; 11 per cent of escapes occurred from land-based facilities and another 11 per cent due to external factors.
"Common structural failures include problems with mooring lines, collapsed floating collars and holes torn in the netting of a sea cage. Bad weather is another factor contributing to structural failure and escape. We have also documented incidents of automatic feeding devices loosen and causing damage," said Østen Jensen, Research Manager with SINTEF Fisheries and Aquaculture and project manager of the SECURE project.
Still, equipment suppliers and fish farmers have got better at preventing some of the equipment problems, such as mooring or floating collar failure. The greatest challenge at this time for salmon and trout farmers, Jensen told, is how to prevent wear and tear to the netting; holes led to more than 50 per cent of total escapees between 2008-10.
Then, operational error during delousing, maintenance and so on, combined with fish transfer, made up almost 20 per cent of escapes.
"Large-scale escape events in which more than 10,000 fish are involved comprise 19 per cent of the total number of escapes during the period studied. As much as 91 per cent of all fish that escaped can be attributed to large-scale events," states Jensen.
Behavioural differences among the species of farmed fish also play a role: cod are much more likely than salmon or trout to bite the netting and tear the net wall to escape, according to Jensen.
"If the aquaculture industry is ever going to realistically realise its vision of zero escapes from sea-based production facilities, it must solve two big challenges. The first is that weighting systems currently in use to maintain the shape and volume of the net pens lead to wear and tear in the netting. The second is finding ways to decrease the incidence of operational – or human – error," Jensen stated.
He believes that the key to solving these challenges is in the supplier industry, with improved product design and procedures.
"Much of the equipment in use in sea-based facilities should be redesigned and simplified to make it difficult or impossible to use incorrectly. Under the SECURE project we have acquired the knowledge needed to develop better and more secure solutions. The next step is up to the suppliers," Jensen declared.
They have already begun applying the documented findings from the SECURE project to try out new solutions.
Since 1 January, all fish-production facilities must have certification stating that the facility is using compatible components in their systems.
By Natalia Real