Counter to what we’re taught with traditional angling, we don’t run out to buy a vest and a thousand dollar rod simply to fish the vastness that is the murk water.

Rather, we’ll be channeling a lot of Arthur Conan Doyle, and learn the weaknesses of our quarry and his environment, knowing we’re not likely to be holding aces when fishing water with little or no visibility.

“Brown Water” is not brownlining, brown is merely a convenient pseudonym for a body of clay-rich and filthy … the presence of enough suspended sediment to make sight essentially useless.

Our normal fly tying arsenal of eye-searing colors and tinsel Bling is useless when visibility is so scant, as neither the hottest of Oranges nor the flash of iridescence can be seen under any light condition.

Yet those who’ve dipped salted clams for Catfish and other bottom dwelling bewhiskered species can vouch for their being well fed, suggesting fish acclimated to this environment have little issue finding food in opaque water.

It’s plain that something other than visuals draws predators to their prey, and it’s likely that the commotion of a struggling fish might travel further underwater than its visuals. Larger food items are likely to have a signature swimming motion allowing predators to quickly pounce on known items due to their swimming rhythm.

A mud burrowing mayfly may struggle enroute to the surface, but its small size is liable to have a proportional disturbance, which would have an insignificant signature compared to a larger baitfish or swimming frog.

Murk water has plenty of hatching insects, but hatches and surface bugs doesn’t yield the same swarm of opportunistic feeders. The rhythmic dimples we see with clear water species and bug hatches are the result of sight feeding and share no parallels in opaque water.

The science of fish and opaque water (or the impenetrable blackness of low light) is completely fascinating, and suggests that fish have as many as three tools to locate prey without relying on visuals.

First, it may surprise some that fish actually have ears, and their range of hearing (detectable frequencies) varies considerably among species. Scientists classify fish as “hearing specialists” – fish with an ability to hear a greater range of noise frequencies, “hearing generalists” – fish that can hear better than average, and regular fish, like Salmon and Trout with only marginal hearing.

Therefore, for most ?shes that rely on hearing only through particle stimulation mechanism, their hearing ability is limited to a narrow frequency band (less than 1000  H z) with high sound pressure threshold (as high as 120   dB at the best frequency). Such ?shes are hence termed  “ hearing generalist ”  species.

It should be little surprise that many of our dirty water fish like Carp and Catfish are among the hearing specialists.

However, fishes in the superorder Ostariophysi (e.g., cyprinoids, characoids, and siluroids) have a specialized mechanical coupling structure (i.e., the Weberian ossicles) that connect the gas bladder to the inner ear (Furukawa and Ishii 1967 ). Hence, vibrations caused by the passing sound to the gas bladder are transmitted to the ears and hearing abilities are enhanced. Because of their extended hearing frequency range (up to 8000 Hz in certain catfish) and low thresholds (60 dB in goldfish), these fishes are called “ hearing specialist ” species.

In addition to the ears of fish, a fish can also detect vibration in the water around it via its lateral line. It turns out this organ is poorly understood among ichthyologists, and while there is much thought and conjecture, there is a great deal of unknown about its function. What we do know is it is host to numerous types of receptors and its complete range of capabilities is still unknown.

The lateral line has mechanical receptors able to detect vibration in the water around it, akin to a second type of “hearing”. Less well known is the ability of the lateral line to detect electrical fields, the ability to discern the presence of a living organism due the change in their surrounding electrical current.

All organisms produce electrical currents. A variety of aquatic organisms can detect these currents with specialized neurons. Such electrical sense has been found in a number of invertebrates and many aquatic vertebrates including sharks, fish, and even mammals such as the duckbill platypus. Electrical senses are important in turbid waters such as muddy rivers or the vicinity of a bleeding victim after a shark takes its first bite (scarlet billows, through the water ….). Often, the electrical sense neurons are concentrated near the head or in a structure that is placed in contact with a muddy bottom, such as the barbels on the chin of a catfish (which also have chemoreceptors), or the bill of a platypus. Other organisms go so far as to create their own weak electrical currents (modified muscles can do the trick) and actively search out prey.

As turbid water emits “noise” both audible and vibrational, consider your average trout stream to be an exceptionally noisy environment. Water flow around obstacles creates vibration as does current when it scours streambed and propels rocks and debris downstream.

Like light, high pitched noise (high frequency) travels the shortest distance in fluid. So if we’re tiptoeing around the creek and bark our shin on a stone – emitting a girly-nasal-screech will scare less fish than a throaty epithet …

And were we to pull all that murk water auditory science into fly design, we’d want larger beads in the rattle than smaller beads to make the noise as deep (low frequency) as possible, we’d want as many things sticking out of the fly as we could to cause vibrations when yanked through the water, we’d want the thing weedless as we have no idea what peril we’re throwing it at, and we’d want it to throw a dab of static into the water column to alert predators that it has a heartbeat versus some shoddy silicon wiggletail …

… and smell, smell would be nice …