The Upper Delaware River has become synonymous with the phrase “wild trout,” a term that may seem unimportant to the general public, but is of vital consequence to trout fishermen. Not only is a river filled with only wild trout in the northeastern United States a rarity; it is a major draw as well. But what is it that makes such a fishery superior to another? What is the allure of these wild fish?

The first thing to understand is what makes a wild trout wild. Simply put, it is a fish that started life as an egg in a stream, hatched and grew without any outside interference from man. There is an alternative to this path—that of the stocked fish. Stocked trout are those raised in fish hatcheries then released or “stocked” into rivers, streams, lakes and ponds.

The majority of streams and rivers in the Northeast warm dramatically in the summer and can only offer a viable habitat for trout for a short period of time, and therefore cannot sustain a wild population. Thanks to robust stocking programs instituted by state fisheries over a century ago, these typically barren bodies of water can (albeit briefly) yield fishing opportunities not normally present.

Contrary to this, wild fish populations are found in those rare rivers that remain cold throughout the year. Because of this, they live their entire lives in the same waters with the same chemistry and topography. They come to know the currents, rocks, pools and riffles in which they were born, allowing them to fully adapt and become one with their environment. Wild fish also have a stronger, more diverse genetic stock that allows them to adapt to local changes in the environment, whereas the stocked fish tend to have a very homogenous genetic makeup, which does not allow for the kind of adaptability required to thrive. Wild trout are typically healthier as well, and are much more beautiful in appearance when compared with stocked fish.

Wild fish will have much more vibrant colorations, as well as larger, fully-formed fins and tails. Stocked fish will take on more color the longer they remain in the wild, but typically they will never reach the bright pigment levels seen in native fish, which have been adapting since birth to the specific hues present in their environment.

Visual differentiation between the two is quite simple at times, with stocked fish being very pale, and exhibiting fins with injuries or deformities brought on as a result of constantly colliding with the walls and floors of their cement home.

Why cement? Because stocked fish are born and raised in cement troughs on a diet of Purina Trout Chow (yes, it is a thing) among dozens if not hundreds of their brood-mates. The proximity to their brethren works contrary to nature where adult wild trout are solitary, claiming and defending the best feeding lanes in a given stretch of water. Instead, once these fish are released they tend to group up as they had been at the hatchery, creating pockets and pools filled with very confused fish.

These muddled fish are also unaccustomed to the varied and different type of water they find themselves in, having been in a static environment for years. They also lack the muscle tone and innate knowledge of currents that wild fish do. This leads to one of the biggest differences between the two—the fight. Anglers are always looking to challenge themselves and land the strongest, hardest fighting opponent that they can. A wild trout fits this bill perfectly, while the stocked fish many times just gives up and rolls over, coming right to hand. While this may be less work-intensive, it is definitely not desirable to most fishermen.

Stocked fish are also not selective in their feeding habits, meaning that any fly or other imitation will likely fool them. This is again a result of their diet and previous life in the tank. They are unaware of what item floating on the surface may or may not be food, and therefore have to attack every piece of detritus that floats over their heads, including sticks, seeds, etc. This is also the reason that a cigarette-butt fly was developed (only half in jest) as these fish are known to take them.

Wild fish tend to become highly selective in their feeding habits, and this makes them exponentially more difficult to fool with an imitation. While this may sound counterintuitive (i.e. why would one want the fish to be more difficult to catch?), the truth is that fly fishermen in particular take a queer joy in targeting extremely wary and difficult fish, takingpleasure in fooling such difficult quarry.

Despite their hard fighting nature, beautiful coloration and challenging nature, there is something that draws fishermen to these wild fish that runs even deeper. It is an existential desire, a primal feeling that comes from challenging oneself against a native adversary that has the true home-field advantage and that can trace their genetic line in that body of water for generations. This is a desire that one can fortunately fulfill nearby, in the beautiful, cold waters of the Delaware River.

[Bart Larmouth is a Delaware River fishing guide.]