When you think about the words “fish” and “smell” you might think about a fishy odor. One thing you’re probably not thinking of is a fish’s sense of smell. Many people are in fact unaware that fish can smell anything at all; but the fact is, fish do possess scent receptors and they rely on them for a number of things. As if pollution were not causing enough problems for many of the world’s fish species to begin with, scientists have discovered that it hurts in another totally unexpected way.
Fish and Heavy Metals Don’t Mix
You may already know that heavy metals, which are classed as neurotoxins, can have a devastating effect on living things, including plants, animals, humans, and of course, fish. Unfortunately, they’re doing more to fish than accumulating inside tissues and causing reproductive damage – they’re causing fish to lose their sense of smell, too. Along with this comes a loss of an affected fish’s ability to find a mate, a loss of a fish’s ability to find appropriate food, and a loss of ability to effectively navigate through the underwater world, particularly in murky waters.
Perhaps you’re wondering how this works. According to researchers including Keith Tierney of the University of Alberta and Greg Pyle of the University of Lethbridge, when these metals come into contact with a fish’s nostrils, the nostrils cause a certain set of neurons to deactivate. This deactivation protects the brain from further damage that the substances could cause.
Pyle and other researchers studying the effects of heavy metals on fish and other aquatic life are deeply concerned about this problem, because it’s not just affecting a tiny portion of a small population of relatively unknown fish somewhere on a single portion of the planet. Instead, it’s widespread. It is affecting aquatic life of many types, including small creatures like water fleas and leeches, and larger creatures like the yellow perch that are ubiquitous throughout the Great Lakes region where researchers have been focusing their studies.
Throughout Ontario, and in many other lakes, rivers, and streams in North America and the rest of the world, heavy metal pollution is widespread. Our waterways are contaminated with mercury, copper, nickel, manganese, and iron – to name just a few of the substances that we humans have spilled or intentionally released into the environment.
Luckily, there are still plenty of places where pollution isn’t bad enough to cause problems for fish and other animals. As part of their research, Pyle and his team moved fish from Lakes Ramsey and Hannah, which are both contaminated to a much cleaner one called Lake Geneva. After just 24 hours swimming in clean water, the fish involved in the study regained their sense of smell. When fish from Lake Geneva were transferred to one of the dirtier lakes as part of the study, they lost their ability to smell; they regained it when returned to their home.
What can we do to help fish in lakes and streams near us? For one, make decisions about chemicals with an ecological mindset. Many fertilizers, paints, and other common household products contain small amounts of these metals – and if they’re not good for aquatic life, you can bet they’re not good for you either. Second, you can participate in waterway cleanups or even organize cleanups in your community. Third, you can learn more about industries that contribute heavily to pollution, such as factory farms and large-scale non-organic agricultural businesses, and vote for the environment with your pocketbook. Small changes really do make a difference - for fish, and for us.