Shrimp anatomy for the fly tyer

Glassy

Michael Jensen

For many salt water anglers, shrimp imitations are a very important part of their fly selection, and whether you fish for seatrout or bonefish, a good shrimp fly should probably always be a part of your fly arsenal.

But having seen and fished shrimp for so many years, I feel a need to do a little lecture on the appearance of shrimp, because the different interpretations of this small but important food item, brings us all the way from huge things that look like paint brushes on steroids to small things that look more like colorful earrings than a natural animal.
I know that many of these flies work just fine, and that there are no set rules that say that flies have to be perfect imitations. But just to set the record straight and to inspire fly tyers, here's a small lecture on shrimp anatomy.

My local shrimp

I will not venture into a lot of Latin names or discuss variations of the local species in detail or spend lots of time on differences between cold and warm water and many other aspects of the world of shrimp.
My lecture is very general, and deals with the average, small shrimp. There are local variations regarding color and other things, but in general the shrimp that I cover are quite alike apart from some color differences.

Shrimp

Michael Jensen - Henning Eskol - Chris Edghill

My aim is to cover some important traits in common shrimps with emphasis on what we can focus on as fly tyers when we want to imitate one.
The observations below are made on the basis of my local Baltic shrimp. I am fully aware that there is a colossal variation in shrimps if you traverse the world, but this is primarily about the kind of shrimp that I need to imitate to fish for my local seatrout. This will also cover shrimp in many tropical flats as well as shrimp found in colder waters on Pacific and Atlantic coasts.

Size

The shrimp I'm covering are small animals, typically in the 2-5 centimeter range or about an inch or two. Shrimp can grow up to 30 centimeters or 12 inches or so, but such monsters are hardly interesting to imitate with a fly.
They are in general quite uniform in size, and although there are smaller and larger specimens, even of the same species, there are no "baby shrimp" or gigantic individuals. Like most crustaceans, fully grown shrimp do not grow from small ones, but they come from larvae that molt and grow in steps until they reach a certain size. They cannot grow continuously due to their exoskeleton.
Look in your local water to assess the average size of shrimp, and use that as a measure for your imitations.

Color

Lonnie Huffman/WikiMedia - Michael Jensen - Haplochromis/WikiMedia

Translucency

Once you start looking closer at shrimp, you will notice one thing: many are translucent! Most shrimp are actually very clear, and some are almost as glass with very few solidly colored features.
These are very delicate animals with slim bodies, thin legs and antennae and just a few bright and obvious features like egg sacks, internal organs, colored bands, segmentation on the shell and oftentimes very visible eyes.
But as a whole the animal is very glassy and almost transparent.

Color

Color varies tremendously, but in keeping with the above, isn't very dense or dominant. Some tropical species are very brightly colored with orange, pink and other "non-earth" colors. If you look at cleaner shrimps you will find really bright neon colors. Their aim is to be seen!
The bright colors and obvious patterns are more common in warmer waters, while cold water shrimp are less visible.
But our local cold water shrimp and many tropical shrimp living on sand and silt flats have colors that come from the earth-tone specter like dull brown, gray, olive and the like maybe with a bit of brighter green, blue, red or orange mixed in.

Shape

Andrew c/WikiMedia - Hans Hillewaert/WikiMedia

Body shape

The shape is very much the same no matter where we look at shrimp. Leg and antenna length can vary - and quite a lot - and body shape can vary, but basically all shrimp are built alike with the exact same body parts.

From the back we have a flat fan-shaped tail, a tapered and very clearly segmented abdomen often with a "hump" in the center and a row of smaller swimming legs underneath, a thorax with some visible internal structures and front walking legs as well as some mouth parts attached underneath and a tapered head with a rostrum (thorn), obvious eyes and the antennae. Some shrimp also have a predominant egg sack underneath.

The basic shape is that of a very elongated and very flat N. Some are flatter, and some have an obvious hump and a very bent shape.

Imitating a shrimp

As fly tyers we can choose to worry about various parts of the shrimp anatomy. I see a number of significant characteristics that I think define shrimp to the predator:

1. Color and transparency
2. Overall size and body shape
3. Legs and antennae
4. Eyes and other "dark structures"
5. Movement

Schematic

Martin Joergensen

1) Color and transparency

A shrimp imitation has to be transparent! At least if it's going to look the least like one of the shrimp that I see almost every time I fish.
The glassy appearance of the animals is the first thing to notice, and an obvious trait to imitate. The best looking shrimp patterns do exactly that, and you see a couple of examples on the adjacent pictures. A shrimp body like that is an obvious part to build with epoxy, hot melt glue or light cured resins - LCR's. All of these allow for shaping the body and all end up translucent like the natural animal.

Legs and antennae galore

Martin Joergensen

2) Overall size and body shape

Size isn't that big a deal. A shrimp tied on a hook in the range 6-4-2 will become the right size. Shrimp that are up towards 10 centimeters or 4 inches in length cannot be called imitations. They may work for other reasons, becoming a huge tempting morsel for the fish, but they do not look like the real thing.
Shape is hardly as critical, but the hump on the abdomen of our local shrimp is a very important feature and all shrimp also have a thorn on the forehead, a rostrum, which is very characteristic. Select a curved shank hook, and the body shape is helped on the way.
Many shrimp patterns feature a loose shell on the top of the animal. On the real shrimp it wraps around the whole body and completely encloses it, looking as one, smooth unbroken piece. The segmentation is also more obvious in color than it is in shape, with no clear dents or creases in the outer shell. So segments should be visible, but the outside of our fly should be smooth.

3) Legs and antennae

A shrimp sometimes seem to be all legs and antennae. On most animals these features are very distinct and very visible and both antennae and legs are often very shiny and with colored bands that make them quite visible. Placement and orientation of these appendices is also important.
The shrimp also has different mouth appendages as well as claws, but for the sake of imitating these limbs, we don't need to worry much since they look like and are positioned much like the walking legs, and hard to tell apart from these.
Feather barbs are an obvious choice for the small swimming legs while rubber legs are the right choice for the walking legs.
Antennae can be made from stripped feathers, rubber, flash straw or other similar thin, almost clear materials. On most of our local shrimp, the antennae are in fact not that long or visibly dominant.

4) Eyes and other "dark structures"

Most shrimp have some obvious "dark structures": eyes, intestines and an egg sack.
The eyes on the side of the head are mostly black and pretty visible. They vary in size, but are quite large on many species. On some species the eyes are flush with the body on others they stand on "stalks". Black monofilament eyes are the perfect imitation in both cases.
Inside the thorax we see some internal organs and many shrimp have an egg sack underneath between the swimming legs, oftentimes colorful and at least very visible. Both these features can be imitated with dubbing, but some tyers actually make small balls to imitate the eggs.

5) Movement

The movement can be hard to imitate, but is never the less an important part of the animal. The swimming legs oscillate in rhythmic and wave-like motions, the front legs and antennae work in more erratic patterns.
The animal as a whole has a slow forward swimming or walking motion and a very quick and sudden backwards escape motion.
Regarding movement, we have to induce this by stripping in the fly in a pattern that mimics the natural. Slow, even strips interchanging with sudden jerks will make the shrimp fly act more shrimpy. You can also let the fly dive to the bottom and rest there before stripping. Shrimp will spend most of their time moving on the bottom, on rocks, on weed or on some other structure.

Creating an imitation

With outset in the above you can start making an imitation. There's a whole bunch of these already, but only few that really imitate (like in look like) a real shrimp. I know very well that the fish don't care much about the precision in our imitative flies. After all they do take Glitter Shrimps and Pink Pigs, which only with a wild stretch of imagination look like a shrimp. But if you want to fish with something that you say look like a shrimp, you need a correct size, proper translucency, fairly short legs and antennae and eyes that sit close to the body.

Should we imitate?

Now, I have said it before, and I'll gladly say it again: I'm much more for the suggestive than the imitative. 95% of my flies look very little like any natural. Magnus, Red Tag, Klympen, CDC&Elk and all the flies that I like, suggest more than they imitate. Still they are definitely perceived as something edible by the fish, but definitely not because they perfectly imitate anything the fish eat.

And that's fine with me. I'm very pragmatic. When it works, I'm happy.

I'm much more for the suggestive than the imitative

But if you want to imitate, and find that it's important to do so, please make your flies look like the real thing - just a little. Look at tyers like Oliver Edwards or our own Radoslav Kiskinov whose flies are very good imitations, tied to look like the real thing and still be useful in practical fishing.

Shrimp flies that look only remotely like shrimp

Henning Eskol - Martin Joergensen

Shrimp flies that look somewhat like shrimp

Kasper Mühlbach - Nils Folmer Jørgensen - Rune Westphal - Martin Joergensen

Shrimp flies that look more like shrimp

flueopskrifter.dk - Martin Joergensen - Chris Edghill

Thanks to Thomas Madsen from flueopskrifter.dk, Rune Westphal from Seatrout flyfisher, and photographer and author Michael Jensen for use of their pictures and thanks to Kern Lund, Kasper Mühlbach, Henning Eskol, Ken Bonde Larsen, Jesper Malmberg and many more for use of flies and/or pics.

What shrimp can produce

Rune Westphal