Tackling fish farm problems

Profiles of Norwegian Science

Fish farm

Photo: Ilan Kelman
Fish farm in Frøya, near Trondheim.

ILAN KELMAN
Agder, Norway

One icon of Norway is salmon. The country lives up to its fishy reputation by exporting vast quantities of it, much of it from fish farms. A lot of research published this year has looked at how to tackle some of the problems experienced by these farms, including possible impacts on the surrounding environment.

A team led by the Norwegian Institute for Nature Research in Trondheim, and including colleagues from Tromsø and Spain, was concerned about organic matter falling out of the farms where wild fish could reach it. Aside from fish feces, wasted food is a big issue.

The scientists wondered whether the quality of wild fish could be affected when they congregate around the farms to feast on food pellets dropping outside the fish farm’s cages. Odor, color, texture, and a few other factors measured the quality of the wild fish fillets.

They selected sei (pollock), catching some beside two farms—one near Stavanger and one near Trondheim—and some over 3 miles from each farm. To avoid influences from seasons and capture techniques, they fished over spring, summer, and autumn using two fishing means.

Some quality differences appeared between the fish taken near the farms and those caught far from the farms. Many of the sei away from Stavanger’s farm had eaten pellets, demonstrating this farm’s wide range of influence.

Most importantly, the proportion of poor quality fish near the farms measured four to five times as much as the proportion of poor quality fish far from the farms. The scientists flag this as problematic, because any catch would have much less value given the expectation for so many substandard fish.

Sea lice are another threat to fish stocks, both wild and farmed. A trio of researchers from Oslo and Lysaker scrutinized methods for dealing with the parasite. They reviewed medicines, chemicals, and lice-munching critters, along with selective fish breeding for lice resistance and using different cages or other equipment to control the lice.

The scientists underscored two innovations as being of highest appeal. First, cages that are closed to the ocean, meaning that lice and other parasites cannot get in or out. Second, selectively breeding salmon to be much more lice resistant. Both would contribute to reducing lice in wild fish as well.

Care is needed, in that breeding fish means entirely separating them from the wild to avoid contaminating the genetic stock. New breeds always have the potential for outcompeting wild fish for food and breeding sites.

In their paper, the authors highlight how both of their proposed innovations have strong advantages for the public yet are least likely to be supported by or to succeed in the private sector. They conclude that government support to test and implement the proposals would help both industry and the public.

Another concern is chemicals (metals and organic matter) from fish farms fouling the seabed. The pollution comes from nutrients for the fish, cleaners and disinfectants for the cages, and medicines.

Four scientists from the Norwegian University of Science and Technology in Trondheim investigated possible contamination in the sediment on the bottom of the sea near two fish farms around the island of Smøla, near Trondheim. On a single day in March 2017, they collected sediment cores from 24 sites and stored them for lab analysis.

Five dozen organic substances of interest were identified, and 47 elements from aluminum to zinc were measured. Human activities had clearly led to the appearance of many of the chemicals, while local geology was responsible for several other elements. None of them exceeded Norway’s guidelines for chemicals in seafloor sediment, so no concerns were raised about pollution from the farms affecting the local area.

As with all industries, fish farming has environmental impacts, but plenty of ways exist to try to reduce or eliminate them. Science working with industry can help ensure that, rather than assuming a trade-off between a higher product cost and a higher environmental cost, the long-term option of prevention—which is also cheaper—is always chosen.

The papers mentioned in this article, in order, are:

doi.org/10.1111/are.14519

doi.org/10.1016/j.marpol.2020.103942

doi.org/10.1016/j.scitotenv.2020.139130

This article originally appeared in the June 26, 2020, issue of The Norwegian American. To subscribe, visit SUBSCRIBE or call us at (206) 784-4617.

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