World’s largest population of Atlantic cod is located in Norway and off Iceland. Now the rising climate threat for global warming is also affecting the population of cod which in turn could crash critical fisheries.
With the increase in greenhouse gas emissions, a double whammy is assumed to occur for Atlantic and polar cod populations. There will be a negative impact on reproduction due to acidification and warming of the ocean as the planet warms up. The reproduction could come down to two-thirds. There are also chances of their alteration of habitat.
According to the study of the scientists associated with Alfred Wegener Institute for Polar and Ocean Research, if the temperature rise exceeds 3C above the pre-industrial level, Atlantic cod hatchling numbers will reduce by 60% around Iceland and Norway. This situation may occur after the first half of this century if greenhouse gas emissions do not get controlled significantly.
According to the Flemming Dahlke, lead author of the study, in the journal Science Advances, cod are the primary source of the food for the other species. The decline in the population of cod may have a disastrous effect on the local ecosystem of the ocean. Presently it’s a significant threat for commercial fishing.
The dramatic impact of climate observed on the fish population, and it affects those fast. The changes are already taking place as a result. The shift of population taking place in the Barents Sea and communities of Arctic fish are retreating. In 1940 during the phase of temporary Regional Ocean warming, there was a shift of Atlantic cod populations to the north by 1000km.
The Iceland fishing fleet found no mackerel before 2000, but in 2016 Iceland’s 8% catch was mackerel because of the shifting based on the temperature of ocean water. Other species are also affected by the rapid warming climate, and it can have international implications also.
U.S. National Climate Assessment warns that if the rate of emissions of greenhouse gases continue to be high, then by the middle of this century, 86% of U.S. marine ecosystems and modern species will experience first ever combinations of temperature and acidity.
As per Daniela Storch, co-author of the new cod study, cod are very sensitive to temperature and increase in acidity. As larvae of the cod float near the surface, minimal changes in the combination of temperature and acidity are fatal for their eggs, and severe deformation may occur.
As per the study, the cod embryos have become more sensitive to higher and lower temperatures for increasing acidification. As a result, the optimal range of temperature for reproduction is narrowing down, and there will further decrease in the production of embryos.
2016 study along with the new findings on cod shows that global fishing revenues will reduce by 10 billion dollars by 2050 because of climate change. According to the economic study of Vicky Lam, a scientist in the University of British Columbia fisheries, the impact on the developing countries will be biggest where the primary source of daily food is fishing.
The cod fisheries catch 800,000 tons annually that costs 2 billion Euros in Iceland and Norway. However, in the Gulf of Alaska, a recent heat wave caused cod numbers dropping abnormally in 2016 & 2017 that fisheries managers reduced the quota by 80% in 2018.
National Climate Assessment found ocean heat waves occurred by the human-caused climate change have series of lasting impacts on fisheries. In 2012 lobster prices collapsed in New England. On the West Coast, the Dungeness crab fishery shut down in 2015 due to the outbreak of toxin-producing algae, an outbreak of the disease in shellfish and pelagic fisheries, an increase in “intensity and frequency of toxic algal blooms.” Lisa Kerr of Gulf of Maine Research Institute pointed on the infectious disease and parasites that may occur due to the warming ocean.
To conclude, limiting global warming to 1.5C as per the Paris Agreement is the best possible way to save the cod population from the worst long-term impacts. Reductions in carbon dioxide emissions from burning fossil fuels can only avoid the transformative implications of global warming on ocean ecosystems.