As someone that started as a trout angler and learned the genus and species of the mayflies and a least a bit of the Latin for the other insects, and as a fisheries biologist, I certainly understand the forage fishes. Streamer anglers do not seem to be much into the whole ichthyology thing like trout anglers are into entomology. Maybe they should be? This is the post I wanted to write - I have no idea if it is going to the post you want to read. And it may not be a post to read in a single sitting - it is rather information-dense. But hopefully there is a little something for everyone that is interested in knowing what forage fishes their streamers are, or should be, representing.
This post is mostly a fish-geek look at the fishes you will encounter in Wisconsin and other Midwestern states. I will follow it up with a more fly tying focused post.
I will write about forage fishes including minnows (family Cyprinidae), sculpin (Cottidae), suckers (Catostomidae), Perch and darters (Percidae), shad (Clupeidae), and sunfishes (Centrarchidae) and then a bit about some more minor and specific players like madtoms (catfishes - Ictaluridae), the diverse salmonids (trout, salmon, whitefish/cisco - Salmonidae), and a few other groups.
Diversity as a function of stream size and temperature
As a general rule, the diversity of fishes increases as one moves from the cold headwaters downstream to increasingly larger and warmer streams. This idea is encapsulated by the River Continuum Concept which I have written about previously and is a unifying idea in stream ecology. In trout streams, we expect low diversity of fishes which only trout and maybe sculpin being present. As streams warm up - moving from say a Brook Trout to a stream that holds more Brown Trout - we may pick up a few species of minnows, maybe suckers and darters too. As me move to more transitional areas - streams that are a mix of cold- and warm-water species or only hold trout outside of the summer - will see an increasing diversity of minnows, suckers, and darters and may start seeing sunfishes and shad species and the sculpin are likely missing in the fish assemblage. As we move into larger warmwater rivers - smallmouth and musky rivers - diversity likely peaks and we see more large bodied fishes - sunfishes and suckers in particular.
Then, of course, depending upon where you are, you are likely to see (or not see) some other taxa. Fishes like Round Goby (Gobiidae), Eurasian Ruffe (a perch species - like darters), Alewives (a shad species), and a few other species are associated with the Great Lakes. Fishing streams near lakes or impoundments - "Flowages" in Wisconsin-speak - may bring some additional diversity.
Size, Shape, and Color
In trying to imitate the fishes that larger fishes are eating; size, shape, and color - in that order - are the three most important factors. Size is a rather obvious one - fishes grow larger as they grow but sometimes we overlook that there are changes in size throughout the year. I remember a day fishing early in the Smallmouth Bass season with my friend Ben where all my smallie flies were 2.5 inches and larger but the bass were chasing baitfish that were an inch to an inch and a half and I caught rather few fish on my own flies. I know I am not the only one that has been caught with a box full of flies that were too large for season. Spring and early summer is when most fishes spawn so new young of the year (YOY) fishes are abundant. Slowly throughout the season, these minnows, suckers, darters, and other taxa grow and die becoming larger but less abundant (less abundant is not necessarily a bad thing for the angler!).
While there are a diversity of shapes, in generally we talk about fishes being round (or nearly so) and compressed - either dorso-ventrally (top to bottom like sculpin) or laterally (like sunfishes that are "tall and narrow"). Any of these shapes can be pretty easily mimicked by fly tyers. Lastly, I would say color is the least important factor but the countershading - dark on the top, light on the bottom - is something tyers should try to imitate. Tyers can also imitate the "shininess" of several species - particularly the minnows - with the abundant flash materials available to us.
Minnows (Cyprinidae) - variety of shapes but round and slightly laterally compressed are the most common shapes.
Sculpin (Cottidae) - dorso-ventrally compressed with a hydrodynamic shape where the head is large and the body tapers to the tail.
Suckers (Catostomidae) - mostly round but some are slightly laterally compressed; maximum sizes larger than (most) minnows.
Darters (Percidae) - members of the perch/Walleye family and are round or nearly so like little-tiny Walleye - another member of the same family.
Shad (Clupeidae) - quite laterally compressed - but you know shad...
Sunfishes (Centrarchidae) - most of them being eaten by musky and other large predators are laterally compressed and often quite tall.
Salmonidae (trout, salmon, whitefish/cisco) - Round to somewhat laterally compressed
While "minnow" is what many call any small fish, the cyprinids are the minnows and they range from fishes we call chubs, dace, shiners, and minnows to large fishes like the carps and many Asian and European species that are typically much larger than our minnow species. Minnows are extremely diverse with over 1,250 living species in about 370 different genera. I could write a huge, long post on the different species but let's not (this post will be long enough). Here are a few of the common names and some of the most common representatives. The Wisconsin Sea Grant's Fish ID database is full of information and great pictures of each species but unfortunately, because of its database nature, links to species profiles are not available but you can find them from their main page. But it allows me a chance to use Becker's classic book, Fishes of Wisconsin for the links below.
"Minnow" is a nearly useless common name but then again, most common names are. There are about 8 species of cyprinids in Wisconsin that include minnow in the common name, probably the best known are the fathead minnow (Pimephales promelas) that are the "crappie minnows" we buy. They are round and slightly laterally compressed and easily imitated but few "minnows" are important forage fishes in Wisconsin streams.
There are at least 20 different "Shiners" across 7 different genera - in other words, damn near any shiny minnow is called a shiner and there is a ton of diversity among the "shiners". The "shiner-est" of the shiners are the Notropis spp. shiners such as the emerald (N. athernoides) and river (N. blennius) that are common in larger rivers (Wisconsin, Mississippi, St. Croix). Notropis are elongate (long and not very "tall") and generally very shiny (yeah, common names work, sort of...). Three genera - Luxilus, Cyprinella, and the non-native Lythrurus shiners - are all similar enough that they once were part of the same genus, Luxilus - the "highscaled shiners" (but before that, they were all Notropis - do NOT try to make sense of taxonomic history unless you are ready to go down a rabbit hole). Compared to Notropis, they are all more laterally compressed and "taller" for their length (length:height ratio is greater in Notropis). The Common Shiner (L. cornutus) - genius common name, eh? - are one of the baitfishes you've probably baited a tipup with and maybe have caught a few in warmer trout streams. Lastly, and trust me, I have skipped a bunch here, is the Golden Shiner (Notemigonus crysoleucas) that again, you have probably used as bait. In addition to being more golden in color - the others are silvery - they are yet taller, shorter, and more laterally compressed.
"Dace" is the name universally given to minnows with small scales. We have 7 different species across 5 different genera. Rhinichthys includes the very common Western Blacknose Dace (R. obtusus - formerly R. atratulus) and the riffle-dwelling Longnose Dace (R. cataractae) both of which are found across a range of stream sizes and maximum temperatures. The Northern and Southern Redbelly Dace (Phoxinus eos and P. erythrogaster) are found in a range of cool and warmwaters. Lastly, maybe my favorite scientific name - the Pearl Dace (Margariscus margarita) iis a cool/coldwater omnivore of northern Wisconsin. They're not terribly important in many places but how about that scientific name? Dace are mostly round but the Longnose Dace has a bit of a dorso-ventrally flattening, particularly the head.
"Chubs" are another common name that is made up of five different genera but really the two chubs to know are the Creek Chub (Semotilus atromaculatus) and Hornyhead Chub (Nocomis biguttatus). Both of these are quite common. The Creek Chub tends towards smaller streams including warmer trout streams whereas hornyheads are generally fishes of larger and warmer streams. Chubs are round with a bit of lateral compression.
Lastly (!), there are two species of stonerollers, both in the same genus (Campostoma) and both look relatively and have similar habitats. Central (C. anomalum) and Largescale (C. oligolepis) Stonerollers are fishes of small to relatively large warmwater streams and rivers. They have a unique cartilaginous lower lip that allows them to scrape algae from rocks - which is how they got their common name.
Believe it or not, that was my attempt at being concise about the different minnows to expect in Midwest streams. In my defense, minnows are a hugely diverse group - among the most diverse of the fishes which are a very diverse taxonomic group. There are more species of fishes (about 34,000 known species) than birds (~10,000), mammals (~6,500), amphibians (8,400), and reptiles (~3,500) combined. Thankfully, imitating them with flies is a pretty simple matter. Most have round bodies that are slightly laterally compressed. Some like the Notropis shiners are quite elongate while others are more laterally compressed. Fly tyers probably should not much care as I am fairly confident no Smallmouth Bass has ever turned down a fly because they thought it looked more like a Luxilus than the Cyprinella that they more commonly encounter. Tie your flies roundish, with some flash, and you will cover most of the minnows. There are a few hundred (thousand?) different fly patterns to imitate the minnows.
Sculpin are fishes that are unique in that most species are marine but there are a number of freshwater species as well. Sculpin are diverse - most being marine speices - but there are 4 species in Wisconsin, two of which are found in streams (the others are deepwater, Great Lakes species). Mottled (Cottus bairdii) and Slimy (C. cognatus) Sculpin look quite similar and like most sculpin, they have large heads and pectoral fins and their bodies taper to their tails. Two other species are mostly found in the Great Lakes. There is not a fish alive - other than a Mottled or Slimy Sculpin - that can tell the two species apart.
By Painting by Ellen Edmonson - State of New York. A biological survey of the Oswego River system. Supplemental to Seventeenth annual report, 1927 - plate 7, after page 94, Public Domain, https://commons.wikimedia.org/w/index.php?curid=4964812
Sculpin are evolved to life in cold, rocky streams. Their large pectoral fins and tapered bodies help hold them down against the substrates they live in and upon and their lack of a swim bladder is another adaptation to their benthic lifestyle. Sculpin swim near the bottom in short bursts and can be imitated with heavy flies. I find in the Midwest, sculpin are common but nowhere near as common as I found them to be in the streams we sampled in West Virginia where some streams had densities of one fish per half a square meter.
Suckers are another diverse group of fishes and many trout anglers have spent at least a bit of time over the bridge railing questioning if those fishes were trout or suckers. Suckers are identified by their sucker mouths - see, this ichthyology thing is not that difficult - and for our purposes, there are a couple of smaller cool to warm water species and a number of redhorses (Moxostoma spp.) which tend to be fishes of larger warmwater rivers. There are a number of other sucker species you may have encountered or heard of - buffalo (Ictiobus), quillbacks and carpsuckers (Carproides), the Blue Sucker (Cycleptus elongatus) which is one of the state's rarest fishes, Spotted Sucker (Minytrema melanops) which are probably most common in the Mississippi and Lower Wisconsin Rivers, and chubsuckers (Erimyzon spp.) which are common in many northern lakes and streams.
The suckers that fly anglers are most interested in are the White Sucker (Catostomus commersonii), the Northern Hog Sucker (Hypentelium nigricans), and the redhorses of the genus Moxostoma. While it is less than perfect, in general, as you move from White Suckers to redhorses, stream size increases and the water warms. That said, White Suckers are pretty tolerant, widespread, and not just river species as many musky anglers know.
Tying sucker imitations can be handled all at once. Most suckers are mostly round bodied with a bit of compression - hog suckers are about a close to rectangular as a fish gets. In early summer (June), there is an abundance of small suckers but they fairly quickly grow to 6+ inches by the end of summer. White Suckers and redhorses are generally silvery or gold and redhorses often have red fins which gave them their common name (though this is mostly seen during the spring spawning season). Northern Hog Suckers are identified by the concavity between their eyes on the top of their heads and the four or so dark bars across their backs. Soft-rayed suckers are a favorite of muskies - and this is a point I think is missed by many anglers. Predators like musky, pike, and bass do not want a spiny dorsal fin in the roof of their mouths.
Percids include a host of anglers' favorite fishes and table fare, Walleye (Sander vitreus), Sauger (Sander canadensis), and Yellow Perch (Perca flavescens) but the greatest diversity of percids occurs within the group we call "darters". Percids are cool to warm water species with a few darter species being found in marginally-warm trout streams. Darters tend to be small - ranging from a maximum size of 2 inches to Logperch (Percina caproides) which may top out at 6 inches. The larger percids are often both lotic (stream) and lentic (lake) species whereas most (but not all) darters are stream specialists (lotic).
Percids are a pretty common forage fish in warmwater streams, rivers, and lakes. The ubiquity of the "fire tiger" pattern on lures and flies should provide a clue that everything eats perch. Despite the pissing and moaning of Walleye anglers about how musky are "killing all our Walleye", there is no scientific evidence of that. I write a bit more about it on a post about fisheries management and mortality but the simplest explanations are that Walleye are faster swimmers and have better defenses (spiny dorsal fins) than to suckers, minnows, and other favored musky prey. But darters are a common forage fish for many warmwater fishes like bass and Walleye. There are about 17 different species of darters in four different genera in Wisconsin (Etheostoma, Percina, Ammocryptya, and Crystallaria) but most are in the genus, Etheostoma. For details on the darters of Wisconsin, visit the Wisconsin Sea Grant's Fish ID database. Percids are generally about as round-bodies as fishes get (few fishes are round in cross-section).
For bass anglers, shad refer to the plentiful Gizzard (Dorosoma cepedianum) and Threadfin (D. petensence) shad that are the most abundant forage fishes in many lakes and rivers. Threadfin are unlikely to be found in Wisconsin - they do not do well in coldwater. Eastern fly anglers certainly think of the anadromous shad runs they fish (Alosa spp.) which are in the same genus as Alewives (A. pseudoharengus), a Great Lakes non-native fish and the reason we stocked Pacific salmon into the Great Lakes. The state's other clupeid is the Skipjack Herring (A. chrysochloris) a fish that is a heck of a lot of fun to catch.
I grouped two other large river species with the shad/herring family. Mooneye (Hiodon tergisus) and Goldeye (H. alosoides) are similar in appearance to clupeids though the species in Wisconsin tend grow larger than the state's shad species. All of these species are imitated with white/silver flies that are laterally compressed.
This well known family includes Bluegill (Lepomis macrochirus) along with a number of other Lepomis species, crappie (Pomoxis spp.), Rock Bass (Ambloplites rupestris), and Largemouth (Micropterus salmoides) and Smallmouth (M. dolomieu) Bass. Sunfishes, particularly juvenile fishes, are common forage for other centrarchids (and yes, many are quite cannibalistic) and esocids (pickerel, pike, and musky).
If you are trying to imitate these fishes with flies, they break into two groups based on size and shape. Rock Bass, crappie, and Lepomis are strongly laterally compressed and are typically described as "tall bodied". The basses are more elongate and less laterally compressed. I think for all of these species, smaller imitations are generally better. Bass tend to stop feeding on other bass when what they are trying to eat is too large to easily consume. Same with bass, pike, and musky eating Bluegill and other sunfishes. By 4 or 5 inches in length, they are getting to a size where they are difficult to handle for all but the largest of predators. And that spiny dorsal fin becomes a significant deterrent for most predators.
Other Forage Fishes
I have covered an awful lot of ground above but there are still some pretty important
There are about 30 described species of madtoms (Noturus spp.), all in Eastern North America. Madtoms and Stonecats (N. flavus) are found in warmwater rivers - including the Mississippi River where "willowcats" (there is no such species...) are the "secret" bait of many Walleye anglers on the "Big Muddy". Noturus species look like little catfishes (because they are...) and have large heads, somewhat dorso-ventrally flattned bodies, and bodies that tend to grade from darker on the top to their light bellies. Many madtoms are much more active at night. Give a madom (or sculpin) pattern a run through a riffle at night and see if it works.
Salmonids are more diverse than just the trout and salmon we are familiar with. But before moving to the whitefishes and ciscos, remember that trout are cannibals. In many trout streams, larger trout have few other choices but to eat their own or at least their "cousins". Most all of us have had a larger brown or brookie take a swipe at the small trout we had hooked. We do not see a lot of it in Wisconsin but in some western states, lakes with trout often grow large pike and bass.
In addition to the trout, there are about 9 species of Coregonus and Prosopium - the common names of which are a mess - but most are referred to as ciscos or whitefishes. These are relatives of the Mountain Whitefish (Prosopium williamsoni) that so many western anglers "love". Several species are restricted to the Great Lakes but there are some important coregonids is Midwestern lakes. Several "big fish" musky lakes have ciscos.
There are three different species of sticklebacks - interestingly enough each in a different genus - in Wisconsin. Brook Stickleback (Culaea inconstans) is the species you are most likely to see in cool/coldwater streams and ponds. The other two species are Ninespine Stickleback (Pungitius pungitius) and the Three-spined (Gasterosteus aculeatus) which is a relatively recent non-native introduction to the state.
Central Mudminnows (Umbra limi) are an interesting fish that are closely related to pike (Esocidae) and like pike, they are able to breathe atmospheric air so they often live in low-oxygen ponds. They are probably not a terribly important forage fish but you find them in pike stomachs fairly regularly.
Again, not species that are probably terribly important to imitate but since we have made it this far, there are two more "perches" to include - Trout-perch (Percopsis omiscomaycus) are neither trout nor perch but are one of two species in the family Percopsidae and likewise, the Pirate Perch (Aphredoderus sayanus) is neither pirate nor perch and are the only member of their family. It is one species that is very easy to identify - adult Pirate Perch's anuses are near their mouths and in front of their pelvic fins. That always made remember their scientific name rather easy.
I may not have covered every forage fish in the state but I think that is a pretty comprehensive examination of what fishes your streamers are - or should be imitating. How about something a little lighter for next week?!
A good article on the other species of fish that inhabit the Driftless Area streams. But we all seem to be ignorant of the fact that mammals, birds, turtles, snakes, amphibians, etc. that reside in the watershed also need these fish in their food chains.