Guest essay by Eric Worrall
According to Professor Karin Limburg, studying the composition of bony growths in fish ears can reveal historical ocean hypoxia and other environmental issues.
How is climate change affecting fishes? There are clues inside their ears
May 14, 2019 8.44pm AEST
Climate change affects all life on Earth, but it poses unique challenges for aquatic species. For example, as water warms it holds less dissolved oxygen than cooler water. As a result, the world’s oceans, coastal seas, estuaries, rivers and lakes are undergoing a process known as “deoxygenation.”
When dissolved oxygen levels fall to about 2 milligrams per liter – compared to a normal range of roughly 5 to 10 mg/L – many aquatic organisms become severely stressed. Scientists call this low oxygen threshold “hypoxia.”
Globally fisheries generate US$362 billion annually. Scientists are already forecasting loss of fish biomass due to warming water. But can we measure effects on fish directly?
For some climate change impacts, the answer is yes. Increasingly, a window on the secret lives of fishes is opening up through study of tiny, calcified formations inside fish skulls called otoliths – literally, “ear-stones.”Read more: https://theconversation.com/how-is-climate-change-affecting-fishes-there-are-clues-inside-their-ears-110249
The description of otoliths is interesting – but why preface it with vague and in my opinion likely misleading warnings about impending climate damage to global fisheries?
If oceans do warm, a very gradual process, in most cases fish distressed by the warmer water will simply migrate North a few miles, until they find cooler water more to their liking. Hinting that gradual ocean warming presents a major threat to global fisheries is pure alarmism.