To most fishermen, a day out on the water doesn’t seem like the time nor the place to make a comparison between two very unlike things, but the truth of the matter is this: humans and trout have a lot more in common than we’d like to admit. We both, as species, can be stubborn at times, we’re both attracted to shiny new things, and, let’s face it, we both spend most of our time around bottom feeders. But today’s focus is not so much about what makes us similar, but about identifying and becoming more aware of the differences we have with one another in our animal kingdom. One thing is quite unique about these fish, a biological ability held by their kind that separates us from them: magnetosensitivity.
Magnetosensitivity, for those who are still unaware of what that is, is a truly primal animalistic trait that allows a select few fish species access to underwater navigation through the use of magnetic poles. Certain species of fish have the special, fairly uncommon ability to use magnetic fields as a way of finding food, shelter, identifying other trout and sticking to a set path to avoid becoming lunch for nearby predators. This is an incredible evolutionary trait developed over millions of years, making for a finely-tuned sense of magnetic sensitivity for today’s modern trout populations to use at their own freewill. But does this mean that trout are magnetic? Well, not exactly. Let’s take a closer look.
Rainbow Trout are a notorious fish species amongst river systems and waterways in the American West, and after being introduced to man-made bodies of water over the last 100 years, Rainbows have become a staple species to anglers and the surrounding ecosystem. Thanks to the efforts of conservationists and the National Department of Fish and Wildlife, Rainbow Trout are stocked regularly in our nation’s backyard ponds and streams, as well as in major lakes and important ecological locations. Trout of many different species can be caught in the American Southwest, with states like Utah, Nevada, Idaho, Colorado, Arizona, and California, among others, becoming a haven for the freshwater fish species to call home.
The spread of “stockers,” otherwise referred to as “Stocked trout,” didn’t just happen overnight. While populations of wild Rainbow Trout have existed for millions of years, efforts to avoid overfishing has allowed the DFW to control how many of a species are released into waterways at a time, assuming anglers and other fish species are on the hunt for them. It can take millions of years for a population to spread throughout various waterways, but thanks to the use of the Rainbows’ keen trigeminal cranial nerve, this fish knows how to get around.
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The trigeminal cranial nerve is the fish’s brain is the part of the brain where all of the magnetic sensitivity originates. How it functions and how it is used are mysteries solved by marine biologists at Auckland University in Australia who, in recent studies, conducted tests to observe how the use of magnetic pulses and activity make Trout and their trigeminal cranial nerves react.
Trigeminal Cranial Nerve
The study included the placing of a small trout inside of a container surrounded by a coil, at which point a very fast, split-second magnetic pulse was applied to the coil, and the reaction was observed and recorded. Researchers were able to prove, through the use of these tests, that the Rainbow Trout’s specialized internal navigation system can and will respond to magnetic activity in the water when it is presented to them. Finally understanding the complex makeup of a fish species is one thing, but pinpointing a definite understanding as to the existence of magnetic cells within fish is a major scientific discovery. These are huge feats in the world of marine biology, as it gives us an inside look into how the wildlife of a certain population communicates and navigates with one another at a level much deeper than just the surface.
Having proven the abilities of the Rainbow Trout, researchers and marine analysts around the globe now have important insight into how fish think, how they make decisions, and how their animalistic instincts function. Speaking of instincts, the recent discovery of magnetite, the most abundant of the magnetic iron ores, in a layer beneath the Rainbow Trout’s olfactory tissues (nose tissues) further perpetuates the research that goes into understanding our underwater counterparts.
Magnetite particles in the nose respond to magnet-sensitive nerve fibers to create neurological activity, something scientists have been deciphering for over 20 years but have only recently been able to fully understand. According to the US National Library of Medicine and National Institutes of Health, other Rainbow Trout studies have also been conducted with reference to the use of varying types of light.
“In the present study, we demonstrate the role of the trigeminal system in the perception process of different magnetic field parameters by heartbeat conditioning, i.e. a significantly longer interval between two consecutive heartbeats after magnetic stimulus onset in the salmonid fish Oncorhynchus mykiss,” the research report states. “The electrocardiogram was recorded with subcutaneous silver wire electrodes in freely- swimming fish. Inactivation of the ophthalmic branch of the trigeminal nerve by local anaesthesia revealed its role in the perception of intensity/inclination of the magnetic field by abolishing the conditioned response (CR).
In contrast, experiments with 90° direction shifts clearly showed the normal conditioning effect during trigeminal inactivation. In experiments under red light and in darkness, CR occurred in case of both the intensity/inclination stimulation and 90° direction shifts, respectively. With regard to the data obtained, we propose the trigeminal system to perceive the intensity/inclination of the magnetic field in rainbow trouts and suggest the existence of another light-independent sensory structure that enables fish to detect the magnetic field direction,” the report continued.
Rainbow Trout Navigation
Research as to how Rainbow Trout navigate is of much greater importance along the Pacific coast, where the euryhaline-branch of the species spends much of its life travelling upstream to lay eggs in the warm spring months, only to return to the ocean to the cold, brackish waters of the Pacific Ocean estuaries. Steelhead Trout, also known as simply “steelheads,” are a branch of the Rainbow Trout species that lives its life differently than other “resident” trout of the same species. While Steelhead and Rainbow Trout are the same exact species, Oncorhynchus mykiss, steelhead make the yearly journey back inland for spawning season, a time for Trout and Salmon populations to lay their eggs and complete the life-cycle once again.
Young fry remain in the stream for several years after spawning, where they will grow large enough to one day swim out to sea. During their years out in the ocean, these trout tend to turn from their olive-colored, spotted skin to silvery, much-larger mature fish. After several years spent in the ocean, female Steelhead will use their highly-tuned sense of navigation, thanks to their unique gift, to return to the same streams and redds ( underwater gravel nesting beds) where they spawned years prior, only to lay their eggs and return to the ocean to come back some day and repeat the cycle once again.
The navigation skills of all animals are very important, including humans. As humans have developed our own ways of getting around for thousands of years, so, too, have the abundant life below the surface. These fish travel for thousands of miles during their lifetimes, only to return to the same place that generations before them have always called home. It’s kind of an inspiring feat for fish to take on, but nature never ceases to amaze. The absolutely amazing evolutionary traits we hold close to us are tools designed to guide us through life, and whether that’s an 85-year-old man or a 5-year-old Steelhead Trout, we all have to give it our best fight. After all, when trout aren’t fighting for survival against the elements, they sure can put up quite a fight against an old fisherman. This is just the beginning for animal kingdom exploration, and we as humans have got our work cut out for us.
Humans will never stop learning, but then again, neither will Rainbow Trout. I guess humans and trout have more in common than I’d previously thought. It’s funny, humans have spent years and years studying the complexities and intricacies of the Rainbow Trout’s navigation, and the answer they were searching for was there all along: right beneath their noses.