Larval Clownfish are able to smell their predators.

The ability to detect and avoid predators is one of the most important mechanisms to ensure survival. Consequently, animals have evolved their senses to detect the presence of predators as a skill to avoiding them.
Just like most marine organisms, Clownfish are most vulnerable at early life stages when they are developing and on the move. On coral reefs, newly hatched clownfish larvae depart from the reef to open water. When fully developed the small adults return to the reef to settle in a new host anemone. While they are on the move they pass a dangerous amount of predators and other dangers.

Researchers have found the clownfish sense of smell essential for its survival in this critical stage of life. The fish are able to smell the presence of predators early and are able to escape before being seen. Additionally, it has also been revealed that clownfish use their sense of smell to orientate their way back to the reef from the open ocean.

Recent discovery of increasing ocean acidification due to global warming has revealed a sincere threat to the future of clownfish and other species with similar vulnerabilities. Researchers believe that the increased acidity of the ocean does not only affect the abundance of coral reefs around the world but affect the clownfish’ sense of smell directly.
In simulated acidic conditions, researchers noted that fish seem to have lost this essential sense completely or even found to be more attracted to the smell of predators. Reasons for this abrupt change in behaviour are not confirmed but theories suggest the C02 could be affecting the fishes’ neurons and confusing how they perceive threats and interpret smells.
Other fish will likely be similarly affected.

Although there are many scenarios that could potentially link ocean acidification to increased mortality of marine species, few direct links have been established. The research on Clownfish has raised a lot of public awareness to the issue.

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