10 Things to Remember While Fishing in Variable Weather

South Island, New Zealand.

The Maruia River is a gorgeous river with beautiful, predictable riffles, runs, and pools. It has great spotting banks and flows through a mix of pasture and beech forest. It doesn’t stand out among southern island rivers but compliments nearby water with a gentler feel than others in the Lewis Pass. On sunny days, the river can be fire.

We haven’t fished New Zealand’s Maruia River the past 5 years because it smacks of all the same things that frustrate us about our home brown trout waters in central Alberta. When a cold front sweeps up the west coast of the South Island, two things occur: heavy rain falls on the west side of the divide, and the air and water temperatures about the divide fall dramatically. The Maruia gets smacked with this double-edged sword every year through early January. It seems the trout have grown to accept the resulting high, cold water conditions and have established where and how to ride them out. From an angler’s perspective, the Browns simply go doggo and wait. A good run of water that should have browns popping or swaying to feed? Nope. Check the very recess of the tail out about a foot off a cut bank or the pillow above a shoreline rock. Doggo. Stoned-cold. Our brown trout here at home do the same because our spring and fall temperatures and barometric pressure gradients can be severe.

Thankfully this condition isn’t hard-set, universally absolute amongst trout species. Rainbows, cutthroat, and whitefish act and feed decidedly different in facing these temperature gradients. For my money, after a steep cold front I’m looking to fish a river with whitefish and cutties first, then targeting riffled up rainbows, with browns and brookies sought last.

There are 10 things I keep in mind after a steep conditions change. These should be learned and applied as they can help set expectations, hopes, and tactics on such days on your home water:

1. If there is too steep a barometric and temperature change, you can forget it.
I can’t begin to describe how many times, particularly in fall and late spring, that a steep temperature and barometric curve kills trout feeding activity. Summer is less impacted because there’s not much chance of the bottom falling out (read: snow). But if a spring or fall day is in the 20s C (70s F) and the next day has snow on the ground and the storm is heavy, chances are that you are in for a rough day of sluggish fish regardless the hatch density. That steep curve has impact and trout usually need a day to adjust.

2. Hatches that do occur aren’t likely until 1 or 2 pm.
Temperature and barometric pressure changes affect the entire ecosystem. It all slows down. There are always exceptions (like tailwaters, lake outflows, and some spring creeks) but if there’s a serious drop in temperature, timing gets pushed way back. If you love hatches and are loathe to fish streamers or nymphs, sleep in and drive slowly through Starbucks.

3. When heavier hatches do come off, trout will likely go nuts under protected cover of dark skies.
The catch? You might not see a single rise because trout may not feel up to the task of rising. Remember, they’re still a little sluggish to rise vertically in the water column but are almost certain to be willing to sway to feed on drift and emerging nymphs at depth. Hatches get going in the afternoon, but the migration, movement, and early insect emergence can occur an hour earlier, so that’s a great time to get the nymph gear going.

4. Straight-line/Czech-nymphing is king in slots and riffles.
Those spring and fall condition gradients are perfect for these water features because of the ever-presence of baetis (olives) and other clinger mayflies that love broken rock and gravel. Some form of straight line, in-line, point-fly nymphing is incredibly effective. If you did nothing but target 2 or 3 prime riffles and troughs in a 4 or 5-hour outing, you’ll likely have a ball. You’re good to go with a 2-foot dropper in shallow riffles, shelves, and troughs also. Amelia & I floated the Clark Fork a couple of days last spring with a friend. He fished straight line nymphing with an orange, in-leader bead indicator system and cleaned house in the deeper riffles. I didn’t want to fish that way, preferring to do a skwala-dropper in case a phantom skwala eat might happen. It didn’t but I fished one side channel slot and pounded away on the dropper. In comparing notes, in the hour or so we fished one of us had landed 15, the other 17 before we moved on.

5. Use small nymphs.
Again, trout are sluggish and so too are the larger stonefly nymphs. Life slows down, so size down. #16 to 20 tungsten bead heads are your strongest ally.

6. Finish ‘em off with a large, shiny nymph.
How counter-intuitive to #5. There are no absolutes in fly fishing but it’s better to vacuum a run using the small stuff, then run a large stonefly or mayfly nymph to entice the stragglers that might have eaten the small stuff but popped off.

7. Flash ‘em
A little flash in dark conditions sometimes gets their attention, so look at some kind of bead, flashback, etc. Brass, copper, gold all work but copper beads work better on some tannic waters while gold does a better job on some deeper, faster, clear-water riffles. Pay attention to what kind of water and what light various bead color has success in.

8. Mornings can be extremely rough with fish glued to the bottom.
The odds of moving anything on nymphs is low, so too dries. Streamers are king mornings and evenings – often just off the first depth step of shallow riffles. Look at thigh depth and work to shoulder depth. Cast and swing, twitch, pause, lift and shoot… repeat the cause. Don’t be afraid to work from head to toe on the swing, then…

9. Dead Drift small streamers by working your way back up a run, like you’re nymphing.
Get your indicator out and hang a #10 tungsten cone streamer under it. Sometimes sluggish trout are waiting for the next dead thing to drift past. Better are things like chamois leeches and chamois worms – these too get sluggish and drift in the cold water. Insta-meal to catch your Insta-fish for the feed.

10. Sight-fishing is sometimes your best bet.
It’s funny I’d leave this to the end because this is the first thing we do, but North Americans have access issues precluding walking along some stream banks and sight-fishing simply isn’t common here – it’s often dismissed as a “New Zealand thing”. But a cloudy day on a bushy stream simply pops feeding fish in the low light ignitors. It’s not always the fish you see, rather, smudges, shapes, colors, and outlines, white fin tips, or just hints of movement. Every fly fisher should learn sight-fishing tactics as a tool. Depending on what water, what features, and what the population structure of the river you fish, sight-fishing and some form of tight line nymphing could be tough to choose from. 

Interested in learning more about how to sight fish big trout? Check out the Jensen’s video series on how to fool even the wariest brown trout, here!

The Jensen’s are Alberta, Canada natives who migrate down to New Zealand every year on the hunt for big trout! Their videos of sight fishing to trout are second to none. Be sure to check them out on Instagram @jensenflyfishing.

Photos courtesy of Dave Jensen.

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