A research project to investigate the effects of fish farming on wild fish is now complete. The project was a collaboration among Nofima, the Norwegian Institute for Nature Research (NINA), the Norwegian Institute of Marine Research, and the University of Alicante, and was financed by the Norwegian Seafood Research Fund (FHF). It started as a result of inquiries from fishermen and fish landing facilities, with respect to the poor quality of wild fish that had eaten salmon fodder near farming facilities.
The project carried out an extensive literature review of research worldwide and summarized it. In addition, scientists carried out field studies where they looked more closely at individual conditions. Initially they investigated the quality of saithe that are caught near fish farms, and compared this with saithe in areas without fish farming facilities. Scientists found a difference, but it was not big.
“The saithe that had eaten fish farm fodder had somewhat softer and more fissured muscle than other saithe, but it was still within the good quality category. Such a change in quality, however, is usual for fish that have good access to food; for example cod, when it preys on capelin,” stated Bjørn-Steinar Sæther at Nofima.
The biggest difference scientists found had to do with “pellet saithe” (wild fish that fed on salmon fodder) that had been caught in nets and had died while in the net. These fish spoil more rapidly than other fish.
“We have found some answers; still, there is more that we wonder about. How could it be that there is such a big gap between our results and what fishermen actually experience? We would like to cooperate with them to understand why we experience the fish so differently,” says Sæther.
But what of the offspring of wild fish that eat salmon fodder? Will the parent’s diet affect the next generation of wild fish? The common diet of wild fish contains marine fat, but there is not enough of this. A large portion of plant fat is therefore used in salmon fodder. The project group wishes to determine whether the wild fish roe could be adversely affected.
To conduct their assessment, the scientists caught saithe and cod, held them captive and alive in cages, and gave them salmon fodder over two spawning seasons.
The cod roe and fry were then analayzed. Both the fish and the roe had an increased content of vegetable fatty acids, but scientists found no essential negative effects on the quality of the roe or fry, which developed normally.
The literature review of the effects shows that aquaculture can affect the biology of a number of marine organisms. But the effects can vary among different species, life stages and other ecological factors. “Different interest groups may experience the effects differently; both in a positive and negative direction, depending on the perspective of the various groups.
“For those making decisions about how the coastal environment will be used, it will be a balancing act between the ecosystem and various stakeholder concerns. It is important that those who consider this take the entirety of ecological and social concerns into account,” concluded Sæther.
Learn more about the NOFIMA study