Fly Fishing Techniques for Northern Patagonia

 This small, green worm is seen in great numbers by fishermen during the summer months in the willow trees that line the shores of some rivers in northern Patagonia. They are a major source of nutrition in the summer months, allowing the rainbow trout and brown trout to gain significant weight, strength, and energy.If you learn more about their behavior and the most effective way to imitate these worms, you will have significant advantages in your days spent fly fishing in Patagonia Argentina.

Common Name: Willow Worm
Scientific Name: Nematus desantisi
Family of the Hymenoptera.
Size: 0.5 -1.5 cm Larva - Adult 0.5-1 cm
Color: Green-Yellow fluo
They are commonly found in some of the most famous fly fishing rivers in Argentina, like the Malleo, Chimehuin, Alumine, and Collon Cura among others.

Life Cycle 
The larvae typically begin emerging at 8 days after the eggs have been deposited on the leaves. Immediately after birth, the larvae begin feeding on the same leaves on which they are perched, leaving them reduced to only the veins. Once they have consumed the entire leaf, they move to the next and continue feeding non-stop. This period lasts about 3 weeks, until the larva reaches its maximum size. Before pupation, the larvae will spin a cocoon on the bark, leaf veins and leaves of willow, where it will spend the metamorphosis stage of it’s life cycle (4-8 days). The adult emerges, looking much a like a small wasp; with

brownish-orange wings and a short, green body.

It is worth noting that in the rivers of northern Argentina, an early hatch often begins in late November, but in smaller numbers. Then the second generation is larger and covers a larger territory. In seasons with ideal conditions, we have seen up to 4 different generations of worms in the same section of the river, lasting until the end of March. The hatches may migrate either upstream or downstream, depending on the available foliage; and are not always consistent. (It’s a good idea to communicate with local guides who can share information about sections of the rivers they have fished each day.) 

How to Fly Fish with Worm Imitations

When fly fishing with worms, it’s important to be very observant of the environment, and look for information that may be critical for proper pattern and tippet selection. When conditions become difficult, this will make the difference in your success or failure. 
The worms frequently fall into the water from the leaves of the willow trees in gusts of wind, and when they lack grip because there are few remaining leaves.

This when your sense of observation is really important; here are some things to consider: 
• All the worms when they hit the water make a noise that attracts the attention of the trout, sometimes they will move several feet to take a worm. To imitate the plop, chenille flies make a far more natural sound than foam. Trout frequently selective about the variety of worms they eat in an area! It's good to have different types and colors of worms, some floating a few seconds and then sinking (this is done with chenille worms, using a little float fluid or powder). 
• It is good to have some foam worms in case they prefer high floating imitations. 
• Although not immediately noticeable, the worms change color and size during their transformation process. Pay attention, sometimes a slight change of color in your fly makes a difference. I frequently rub my flies with soil to take off some of the fluorescent shine of synthetic materials. 
• The trout may progress past taking the worms, and you'll notice that they are actually feeding on the flying adults. You should have some imitation of the adult insect. 
•Look closely under willows hanging out over the river, or close to shore; you will often see trout in a feeding line taking worms off the surface.  

I hope this information will help you understand this fascinating food source the trout of Patagonia, and improve your success on the river.                                                                                                                  
Tight lines and, Wet Nets! 

Gabriel Fontanazza 
www.flotadaschimehuin.com.ar 

 

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