Come hell or high water, fish still need to eat. Here’s how to adjust your tactics when the creek starts to rise.
[by Jason Randall]
THUNDERSTORMS TURN MY NORMALLY BRAVE AND FEARLESS DOG into a basket case and send her into hiding until the coast is clear, usually under the bed. I’ve heard of other dogs digging holes through the carpet in closet corners, seeking refuge from a storm. But dogs are not alone in this innate fear of severe weather. In fact, most other animals share the same anxiety.
Trout are no different; when the conditions change abruptly, they usually hole up somewhere safe. But since they must eat to live, they poke their heads out soon after the storm passes. And when they do, they’re often greeted by a world transformed. Dramatically altered conditions created by raging, turbid water may have replaced the previously comfortable flows and high visibility. Old feeding lies are gone, blown out by the high water. Food distribution within the river and even the population of prey species in the drift may have changed.
Fishing after a storm can be just as challenging. Conventional wisdom suggests that you move upriver, closer to the headwaters where the river clears faster, or fish closer to the banks where fish cling to shoreline structure. But beyond that, what else can be done to turn a fishless day into a pretty good day?
The Catastrophic Drift
The ways that trout adjust their feeding under new conditions dictate how anglers have to adjust in order to catch them. As usual, these feeding adjustments are based mostly on the prey species the trout feed on. During periods of high flows, the river transforms: fresh log jams form; new sweepers from deadfall trees appear in the water; and new channels or meanders are carved from erosion. The same erosive hydrodynamic forces also dislodge streambed residents such as insect larvae, nymphs, and crustaceans from the safety of the bottom and into the current, where trout can eat them.
High water from heavy rains or the rapid melt of winter’s snow and ice creates a catastrophic drift, which is the large-scale, unintentional displacement of organisms from the nooks and crannies in the streambed where they normally reside. Once in the current, they are vulnerable to predation. This is opposed to behavioral drift—which is the intentional release of organisms into the current to redistribute the population of their species— and the more or less sporadic but continuous occurrence of organisms in the current, called the constant drift, which predominates most of the time.
The population of organisms in the catastrophic drift is skewed toward those species, such as scuds, that have less reliable “holdfast” mechanisms—such as the flattened bodies and claws of stoneflies, or the premade shelters or even silk threads of some caddisflies—elaborate adaptations to keep them attached to the bottom. As a result, scuds are abundant in the catastrophic drift. They normally favor depositional zones in the stream—current protected areas behind rocks, pocket water, and on the soft-seam side of current—but during high flows, even these depositional areas are subject to strong current and scuds are swept away.
The Gunni Special (Ben Furimsky)
HOOK: 3X-long streamer hook, sizes 2 to 6.
THREAD: Black 3/0.
BEAD: Gold tungsten bead.
BODY: Black chenille.
TAIL: Black over chartreuse marabou.
LEGS: Chartreuse round rubber legs.
BEN’S TIP: Try fishing this fly as a streamer after a short dead drift that allows it to sink and tumble in the current.
The population of insects in the catastrophic drift is also different from that which would be found under normal conditions. Insect hatches that might otherwise occur are often temporarily disrupted. Normally reclusive insect larvae, such as craneflies, that burrow in the soft banks and stream bottom appear in higher proportions in the catastrophic drift. The erosive effect of the high water flow excavates them from their burrows and casts them into the water, where trout can eat them.
Terrestrial worms are also excavated from the soil of the banks and appear in larger numbers in the catastrophic drift. Streams that have erodible banks have the largest increase in worms and burrowing insects.
The most striking change, however, is a bit of a surprise: The catastrophic drift often shows a dramatic increase in the percentage of midges. In researcher T. F. Waters’s study of a Minnesota stream, he found up to a 50-fold increase in midges in the catastrophic drift, compared to normal drift conditions. This marked increase was due to the changes in water flow in the normal habitat of midges, which is the slack water along the river margins and wet edges. Even a moderate rise in water levels was enough to change their habitat, transforming it from slack water to flowing water and sweeping midges into the current.
Fishing the Catastrophic Drift
Conventional wisdom says to tie on a streamer when a stream is blown out, but nymphing and even fishing a dry fly can be productive under the right circumstances. Knowing when, how, and where is the key to success.
Nymphing: As with any nymphing application, there are three factors to consider when you’re fishing the catastrophic drift: fly selection, fly color, and fly depth. Fly selection should be based on the composition of the catastrophic drift, so try a San Juan Worm, a Scud, or even a Cranefly Larva. Make sure to carry some Zebra Midges or other midge patterns, too, even if flow conditions are only moderately higher than normal. It doesn’t take much added water fl ow to wash midges into the drift.