Fish Species May Become Smaller Due to Climate Change
Climate change may drive a decrease in body size of fish species by up to 24% according to a new study, BBC News Science and Environment reports.
The study entitled Shrinking of Fishes Exacerbates Impacts of Global Ocean Changes on Marine Ecosystems, was published in Nature Climate Change this September and was led by Dr William Cheung of the University of British Columbia. The new study is the first to employ models to study climate change induced effects on species distribution, population abundance, and fish size in marine ecosystems. Other researches in the past have proposed that warming ocean temperatures would affect fish distribution and reproduction.
According to BBC, the researchers studied the impact of warming ocean temperatures on over 600 species using models with data from the Intergovernmental Panel on Climate Change’s (IPCC) predicted emission scenarios. The study states several factors that strongly affect body size of fish and other aquatic water breathers: temperature, resource availability, and oxygen level among others. The balance between energy demand and supply essentially limits the maximum body weight of invertebrates like fish. Changes in these factors will directly affect marine fish’s ecophysiology.
As the ocean become warmer, oxygen levels go down. Demand for increased oxygen and its reduced supply in marine environments significantly affected fish size as the element is one of the primary ingredients for body growth. Moreover, according to Dr. Cheung, rising temperatures directly increase fish’s metabolic rate of body function.
The study predicts assemblage-averaged maximum body weight shrinkage of 14 to 24% from 2000 to 2050 on a global scale, using a high emissions scenario. Approximately half of this shrinkage rate is due to changes in distribution and abundance, while half is attributed to changes in physiology. Tropical areas are expected to be heavily impacted, as well as those on intermediate latitudes. Research predicts that fish in the Pacific and Southern oceans will have a larger magnitude of reduction in size, followed by fish populations in the Arctic, Atlantic, and Indian oceans.
Moreover, the study predicts a shift in movement of many fish populations towards the North and South poles, at a rate of 27.5 to 36.4 km per decade.
The researchers did not take into consideration the fishes’ capacity for adaptation and cite this factor as well uncertainties associated with climate condition projections as possible sources of doubt. However, even if such factors are considered, marine fishes are hardly expected to completely adapt to global and ocean warming. Continuing trends in greenhouse gases emissions are forecasted to impact marine ecosystems around the world.
While further research is needed in this area, the scientists involved in the study agree that smaller fish size will have no small effects on the organisms’ reproductive potential. Smaller fishes produce fewer and smaller eggs, and possibly weaken the organisms’ resiliency against pollution and fishing pressure. Combined with other factors such as habitat destruction and local extinctions, reduction in fish’ body size due to climate change effects may have a substantial impact on the global health of marine ecosystems.
Photo Credit: Some rights reserved by Raymund Dawang at Rbdawang _615 via Instagram.
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