Fishing Terrestrials for Fall Rainbows

The main challenges of fishing small- and medium-sized streams for rainbow trout in early fall have to do with the water conditions of the streams themselves. From a rainbow’s point of view, late September and October conditions are usually in stark contrast to the “best” conditions of the year, which typically occur in spring or early summer.

Over the course of the summer, the water levels in most freestone streams drop and temperatures warm. In dry, hot years, water temperatures in some streams rise outside the range that rainbows prefer, making the fish much less eager to chase food. Warmer water also holds less dissolved oxygen, which can put further pressure on the trout. By September, the variety of large-scale aquatic insect hatches — the main source of food for rainbows in most streams in the spring and summer — are also declining. Rainbows have less food, less cover and less oxygen.

Rainbows react to all these changing conditions by reducing their activity levels and by seeking thermal refuge, either in deeper pools, areas of the stream with good current flow and hence lots of oxygen, parts of the stream with cooler spring seepage or, in some river systems, in cooler spring-fed tributaries.

But by October, overnight temperatures are beginning to drop and the days are shortening. Many streams remain low, especially if it’s a dry fall, but eventually lower water temperatures boost trout activity levels and their willingness to eat.

For fly anglers, low water traditionally means that small flies imitating midges, mosquitoes and the like are top choices. But early fall conditions present a different, and potentially better strategy: Using much larger imitations of terrestrial insects like grasshoppers, crickets, ants and bees.

You might be thinking that because you see fewer of these insects in the fall than you did in the summer, it makes less sense to use them (or flies that imitate them) now. On the contrary, it’s because you see fewer of them that it makes sense to try them now.

Bugs live fast and die young. Female grasshoppers hatch in the spring and start laying eggs in mid-summer and continue to lay pods of 15 to 150 eggs (depending on the species) every four days or so. Each female grasshopper keeps doing this until she’s dead, either because something ate her, or cold weather kills her.

Cooling overnight lows cold-stun terrestrial insects. Cold-stunned grasshoppers, crickets, bees and ants are clumsy bugs, and clumsy bugs fall into water much more often.

By late September, most grasshoppers, worker bees and crickets are already dead. But many of them died and in the process conditioned trout to be on the lookout for big, tasty meals falling out of the sky. Other terrestrials, notably ants, have a higher survival rate, but even ants are born in the thousands to survive in the hundreds.

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Terrestrial insects are prized by trout for another key reason: They are big compared to most aquatic insects. A grasshopper represents orders of magnitude more food than a mayfly for about the same effort to catch — and on a calories-gained-for-the-effort basis, few food sources are better from a rainbow’s point of view.

From the angler’s perspective, just about all terrestrial insects offer another advantage. You don’t have to wait for a hatch to be sure rainbows are keying on them because fish are used to seeing terrestrials come by at widely spaced intervals all day long.

HOW TO FISH TERRESTRIALS FOR TROUT

Traditionally, terrestrials are fished on the surface. Live grasshoppers, crickets and bees that fall into the water are initially quite buoyant, and these flies are typically among the largest dry flies in a fly-angler’s box.

An angler at streamside who sees a grasshopper fall into the stream will see the grasshopper turn toward the bank or the nearest piece of grass and start trying to “hop” its way back to safety. At that point, one of three things happens: The grasshopper will get back to shore (no terrestrial insect really swims well, but grasshoppers are at least able to make some progress), the grasshopper will get eaten by a trout, or the grasshopper will get swept downstream and disappear.

A fly-angler who plops a grasshopper into a stream (a subtle landing isn’t necessary) and twitches the fly feebly back to the nearest shore is doing a pretty good imitation of what real grasshoppers do. A few habitat conditions can make this an especially effective tactic: It works best on streams running through grass pastures or fields. It works even better if the edge of the bank is either undercut or deep enough to hold a fish, and it works best of all if the grass along that bank is tall.

Grasshoppers and bees, unlike most species of crickets, can fly, and that puts them in the position of falling into any part of the stream, even the middle of big rivers, especially on windy days. Thus, they can also be fished along current seams and other mid-stream cover or structure just as any drag-free presentation of a dry fly would be made.

In mid-stream presentations, certain kinds of water put grasshopper flies at a disadvantage. The longer a trout looks at a grasshopper fly, the less likely the trout is to take that fly. Grasshopper flies are large, and if the water flow is slow and a trout gets a long enough look at it, most trout will conclude it is not food. The middle of slow, clear, deep pools is not likely to produce most of your strikes. Water with current, and the head of pools, or the current edges near rock or wood, where the trout has less time to make a decision, tend to be best. If a trout sees a grasshopper fly briefly, he’ll be inclined to take a chance on it before it’s swept away because it is too much food to let go by.

Oddly enough, bait anglers who use live versions of crickets and grasshoppers almost always fish them with weight below the surface. That’s partly a function of practical necessity. Spinning gear doesn’t cast a weightless grasshopper very far.

What’s strange about this is that grasshoppers are an extremely effective live bait fished below the surface. That means that rainbows are not alarmed by seeing a grasshopper below the surface. Why? It’s because the thorax and head of grasshoppers are the most buoyant parts of them, but if those parts are damaged, eventually grasshoppers sink. So, for a trout, it’s not alarmingly unusual to see a grasshopper or other terrestrial insect below the surface.

Fly-anglers should keep this in mind on bright fall days when rainbows are reluctant to rise to the surface. You can add a weight to a terrestrial, especially at the heads of pools and on current seams where there is some depth of water, and fish the fly just as you would a nymph, seeking to reduce drag while maintaining enough contact with the fly to set the hook on a subtle take.

Alternatively, both bee and grasshopper imitations make very good surface flies worked in tandem with a smaller dropper fly. Grasshoppers are big enough to see, and bee imitations, while not as large, are brightly colored.

Of course, the dropper fly can be any contrasting insect imitation, including nymphs of whatever aquatic insects are native to the stream. Ant imitations can also be used as dropper flies, as they can be tied with a bit of red and in small enough sizes that they contrast well with the surface fly.

This fall when you make your last couple of trout fishing trips of the year on fine clear days, don’t be discouraged by a lack of a hatch in the middle of the day. Add terrestrials to your bag of tricks and the fishing could be as good as the weather.

SPINNING GEAR BAIT OPTIONS

In streams where bait is legal, fishing a cricket or grasshopper below a small weight is going to put more rainbow trout on a stringer faster than just about anything else an angler can do. Although many flyfishermen think using live bait is easy, in fact bait-fishing is like any other kind of fishing. Anglers who are good at it catch far more fish than anglers who are not.

There are two main things to help improve catch rates with bait. First is to fish the bait without drag under the surface — exactly as challenging as presenting a nymph because it’s essentially the same process. The second is to efficiently read water, and make casts that present the bait near where the fish are actually holding.

Efficiency is critical because with real bait, trout that see a well-presented bait are either going to hit it or not. Make good casts, show the trout your bait, and if he’s not interested, move to the next hole. It’s faster to find a hungry trout just upstream than it is to wait for a wary or inactive trout to hit a grasshopper he’s already passed up two or three times.