Saving Seafood

Combination microscopy and DNA analysis reveals new insights into the diet of polar cod

November 1, 2022 — Polar cod is an important part of the food web of the Arctic. Sarah Maes (KU Leuven) and Fokje Schaafsma (Wageningen Marine Research) investigated the diet of polar cod from the Barents Sea, with the help of colleagues from the KU Leuven and the Alfred Wegener Institute. They did this by combining traditional microscopy with DNA analysis. The study resulted in new insights regarding the diet of polar cod which are now published in the journal Marine Ecology Progress Series.

Diet investigations are usually done by opening the stomach and looking what is inside, using a microscope when the investigated animal is small. This way, researchers can see which and how much prey was consumed. However, some  are more easily digested than others, leading to a potential biased view on the importance of certain prey .

Some prey species can even be overlooked altogether. Sarah Maes of the KU Leuven initiated an investigation of the diet of polar cod using DNA analysis to overcome this problem. By combining this method with traditional microscopic analysis results gained from the two different methods could be compared.

Read the full article at phys.org

Acid threatens almighty cod

November 30, 2018 —Climate change could devastate a major northern hemisphere fishing industry, modelling finds.

For cod facing the effects of climate change, it’s not the heat but the acid that threatens.

Ocean acidification – caused by atmospheric carbon dioxide entering the water and lowering its pH value – means there’s a narrower thermal window for the success of two species of northern cod, meaning that one of the world’s largest fisheries will be threatened if global temperature increases are not limited to 1.5 degrees Celsius, a new study finds.

The researchers, led by Flemming Dahlke of the Alfred Wegener Institute in Germany, find that embryos of cod are able to survive only within a limited temperature range, and that the range lessens in more acidic conditions.

The researchers predict that Atlantic cod (Gadus morhuai) would be unable to spawn below the Arctic Circle by 2100 under a “business as usual” emissions scenario. The polar cod (Boreogadus saida) faces an even more perilous future, since it not only needs colder water, but also depends on ocean ice for its habitat.

Read the full story at Cosmos Magazine

Scientists catch billions of juvenile polar cod under arctic sea ice

October 13, 2015 — Polar cod are a vital food source for whales, narwhals, ringed seals and arctic seabirds, but researchers have had a hard time studying these fish and estimating their numbers.

That’s now changing, thanks to new netting technology. Recently, a team of German researchers were able to catch a large number of polar cod living beneath the arctic sea ice. Their findings suggest billions of juvenile cod prefer the shelter of the arctic shelves and drifting sea ice.

The researchers published their findings this week in the journal Polar Biology.

“For the first time, we’ve been able to use a special net directly below the sea ice to catch a large number of polar cod, and therefore to estimate their prevalence over a large area,” Carmen David, a biologist with the Alfred Wegener Institute and first author of the new study, said in a press release.

Read the full story from UPI