Norwegian researchers were onboard the Vikingbank during a blue whiting fishing trip in March. Photo: Vikingbank
Researchers are close to finding good solutions to control the catches in the blue whiting fishery. On a fishing trip with the pelagic trawler Vikingbank in March, they got to try out different solutions. And the results are promising, according to the researchers.
The blue whiting fishery takes place with float trawls at great depths, which leads to extra challenges in calculating the size of the catch and preventing the trawl sack from being blown up when it reaches the surface. Now, the researchers in collaboration with the fishing fleet can be closer to good solutions to avoid these problems.
In March, a group of marine scientists were with the pelagic trawler Vikingbank on blue whiting fishing west of Ireland. This is the second fishing trip with Vikingbank after the project started in 2017. In addition, the researchers have traveled with several fishing boats during the period.
“For us, it is important to contribute to this work, and we see that it gives us better solutions. We also have a very good collaboration with the researchers, and are very little at home in the fishery,” says skipper at Vikingbank, Anders Klovning.
The project was started on the initiative of the fishermen and was a collaboration between the Institute of Marine Research (HI), the Fisheries and Aquaculture Research Funding (FHF) and the Directorate of Fisheries.
“The goal is to find methods for calculating and regulating the catch, so that one avoids blasting the bag. It is also a great advantage if you can regulate how much fish is in the tail before you catch it, so that the fishermen become more accurate in the catches and thus can adapt the catches better in relation to what they have room for on board,” says Olafur Arnar Ingolfsson, researcher at HI.
Got good results
All cruises in the project have been on boats that have been in active fishing. In this way, researchers have been able to test their theories under practical conditions. Representatives from the Institute of Marine Research and the Directorate of Fisheries took part in the last cruise with Vikingbank in March, and say they got good results on this trip.
“Yes, we have got good results, but there is much more we want to find out. We have, among other things, tried out a solution with longitudinal slots on the trawl bag. These are three to four metres long, and open when the bag fills up and the pressure increases. This, in addition to a large opening at the bottom of the trawl bag and several slits in the top, means that excess fish comes out,” says Ingolfsson. “It is clear that blue whiting seeks up, but to a small extent goes down. Such information is very useful in order to be able to design a catch emission that does not result in a loss of catch before the bag is filled up.”
A “fish lock” has also been tried out, which acts as a one-way valve, through which the fish can pass. However, this is a solution that needs more testing before it works optimally.
Expands the trawl bag
The researchers have also tried out a “bag trigger”, which is used to determine the volume in the bag as needed. If the trawl bag, for example, holds 800 tonnes, but the remaining load capacity is only 400 tonnes, the bag will be pulled together in the middle so that it can only hold 400 tonnes. This constriction can be achieved automatically when it is at, for example, 150 metres, and there is thus twice as much space in the backpack. This is a simple and good solution and a good measure to prevent it from exploding on the way up, says Ingolfsson. Preliminary results indicate that the ascent is more controlled by using the trigger, which is also noticeable with less resistance on the wire and winch.
Another challenge with the blue whiting fishery is unwanted bycatch. On the March cruise, both tuna and shark came in the trawl bag. Some of these were salvaged and towed out again, but according to Ingolfsson this is a problem that one should try to find better solutions to.
“This can be a red list of species that one should therefore not get in the catch. If one is still unlucky to get large animals in the catch, it can lead to a problem with the equipment on board. Among other things, it is not always as easy to get them out of the bag, and the pumps are not calculated for such catches. So here we have a job to do with trying to find good solutions to handle this,” says Ingolfsson.
According to the plan, the project will be completed during the year, but even though the budget will soon be used up, there are still many challenges that one does not have an answer to.
The skipper of Vikingbank is also happy to see the project expanded.
“Yes, it is to the great advantage of all parties if we get more data and get to try it out on a larger scale. We have now seen that the methods work, so this is probably the way to go,” says Anders Klovning.