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Forage Fishes of Cold and Cool-water Streams

My goal of this post is twofold; first is to provide some information on the forage fishes that occur in trout streams and how to imitate them, and second, to get people to stop calling all small fishes "minnows". I wrote a similar post a while back - this one is more focused on trout stream fishes and will focus in on specific species more than generalities in the from trout to musky forage post.


Probably one of the most significant things to understand about forage fishes in trout streams is that there is a strong relationship between water temperature and species richness (diversity). As trout streams warm, they tend to accumulate a greater number of species and the coldest of streams are likely to hold only trout and maybe sculpin. As seen in the figure from Lyons et al. (1996), as habitat in Timber Coulee Creek was improved and the water temperatures dropped as a result of reducing the amount of shallow, slow moving water; the stream saw a decrease in the number of fish species. And from a stream health (IBI) perspective, lower species richness is an indicator of higher quality for coldwater (trout) streams. This result was expected and fits our expectations of coldwater streams which few fishes are evolved to live under their energetic constraints.

Diversity of small trout stream forage fishes.
A diversity of small forage fishes from a West Virginia trout stream near a larger, warmwater river - a good explaination for the diversity of fishes captured. There are 6 different species in the image.

This is all a round-about way of saying that for the angler looking for fish streamers, they should concentrate on sculpin imitations in the coldest of streams and diversify - particularly to shinier minnow imitations - as you move downstream to warmer trout streams. There is a lot of overlap here with forage fishes for Smallmouth Bass (Micropterus dolomieu) which overlap with trout in those stream reaches which are "marginal" trout waters. Another important consideration is that if you are fishing a trout stream that flows into a large river or lake, the stream will likely have a greater diversity of forage fishes than that same stream without access to the species pool of that larger river or lake.


There are thousands of fly patterns to imitate these different forage fishes. I will try to provide video links to a range of fly patterns; some that are quick and simple ties and others that are significantly more complex. I'll limit myself to a dozen patterns - though there are many, many more options - you have a set a line somewhere. As you will see with most streamers - they tend to have a strongly countershaded body with a ligher belly and a darker top, much like the fishes they are imitating.


Sculpin


Sculpin are probably the non-trout fishes that are most associated with coldwater streams. Sculpin are members of the family Cottidae, the largest family in the order Scorpaeniformes. While there are about 275 species of cottids - most of which are oceanic species - two species are common in Midwest streams, the Mottled Sculpin (Cottus bairdii) and poorly named Slimy Sculpin (C. cognatus). The two species are quite similar to one another and the angler likely cares little which is which. In fact, some historic identifications from biologists in Wisconsin are likely incorrect in places. In practical terms, these sculpins are small, mottled-olive benthic invertivores that lack a swim bladder and rarely stray far from the stream's bottom. Slimy Sculpin are more strongly associated with colder waters whereas Mottled Scuplin will exist in warmer waters.

Top-down view of a Mottled Sculpin showing that distinct body shape and large pectoral fins. Image from the Creative Commons.


These fishes are identified by their unique, kite-like shape with their large, wide head and long, tapering bodies. Sculpins are evolved to a benthic (bottom-dwelling) life with their lack of a swim bladder, their hydrodynamic shape, and their large pectoral fins which they use as hydrofoils to stay on the bottom of the stream. Along with their mottled olive coloration, these are the features that most flies imitate. Probably the most famous of the sculpin imitations is Don Gapen's Muddler Minnow. Today, there are a huge number of sculpin imitations for fly anglers that range from very simple to quite complex ties.

Minnows


Despite many calling all small fishes minnows (or "minners"), minnows belong to the family Cyprinidae and they range from small fishes we know as minnows to the carps, the largest of which are over 100 pounds. It is a diverse group - the most diverse of all the vertebrate families with nearly 1,300 species still existing (less than half the number known to have once existed). There is a good amount of uncertainty in the taxonomy of minnows with a great number of recent changes - but anglers should not lose much sleep over their taxonomy.

  • Campostoma are the stonerollers, a genus with two quite similar species in Wisconsin - the Largescale Stoneroller (C. oligolepis) and the Central Stoneroller (C. anomalum). Stonerollers are algae eaters and have a distinct cartilaginous ridge for a lower lip which allows them to scrape algae (periphyton) from rocks. They tend to be found in stream reaches that produce a lot of algae which tend to be either large enough that the stream can not be shaded or streams with non-woody riparian zones. Stonerollers are mostly found in warmer trout streams and they are quite mobile, moving throughout the season, seeking places with significant periphyton. They have a quite round body and adults are typically 3 to 6 inches in length.

Hornyhead Chub
Hornyhead Chub from the Milwaukee River.
  • Hornyhead Chub (Nocomis biguttatus) are common in larger streams though Becker's Fishes of Wisconsin shows them to be absent from a large part of the Driftless north of Military Ridge. They are superficially similar to Creek Chubs (Semotolis atromaculatus) though they tend to be more olive in color and have a different mouth size and shape. Hornyheads tend to be found in larger, warmer, and less turbid streams compared to Creek Chubs. Adult hornyheads range from about 4 to 8 inches and are a favorite forage fish of Smalmouth Bass and Northern Pike. They get their name from their nuptial tubercles that give them their "horny heads" during their spring spawning season.

  • Creek Chubs (Semotolis atromaculatus) are one of the more common and widespread of the cyprinids. As their name suggests, they are a small stream specialist and both they and hornyheads (above) are ominvorous. They have a distinct black lateral line and are distinguished from most other species by the black dot on the front edge of their dorsal fin. "Semotolis with the spotolis" is how we learned to memorize the species and its scientific name. They grow up to 12 inches but more typically range from 2 to 6 inches. These are probably one of the most common "trout stream" minnows but they typically occur in streams that can get a little warm.

Longnose Dace head - showing its adaptations to life in fast flowing riffles. US Fish and Wildlife Service image - Public Domain.

  • Rhinichthys are daces which is a common name given to a number of species of different genera that have small, nearly indistinguishable scales. Wisconsin is home to a number of daces, two within this genus - Western Blacknose Dace (R. obtusus) and the aptly named Longnose Dace (R. cataractae). Blacknose Dace are often a fish of sluggish, turbid streams and are often an indicator of degradation whereas Longnose Dace are a fish of clear, fast waters. In fact, their species epithet, "cataractae", refers to the fact that they were first captured from Niagara Falls. In streams, they are generally found in the fastest of riffles, a place few other fishes are able to survive, much less thrive. Both species will typically be about 2 to 4 inches in length with longnoses growing larger, generally.

  • Pearl Dace (Margariscus margarita) has one of the great scientific names and is another dace, a small-scaled minnow. These omnivorous fishes are a small, fine-scaled minnow that tend towards cooler streams. In Wisconsin, most of their populations are in the northern part of the state and there are really no populations in the Driftless Area. They are a small fish, generally topping out around 3 to 3.5 inches.

Notropis shiner
A Notropis shiner from the Milwaukee River
  • Shiners - there are a number of species across different genera that are referred to as "shiners" that include the following genera: Cyprinella (satinfin shiner), Luxillus (highscale shiners), Lythrurus (finescale shiners), Notemigonus (golden shiner), and Notropis (Eastern shiners). While all these shiners are, well, shiny, their bodies vary quite a bit. The Notropis shiners tend to be long, slim-bodied fishes and the others are often taller and broader fishes. The more common of these fishes are the Common Shiner (Luxillus cornutus), Golden Shiner (Notemigonus crysoleucas), and Emerald Shiner (Notropis atherinoides). Shiners are found in larger, warmer trout streams and generally range from 2 to 5 or even 6 inches in length.

  • Minnows of the genus Pimephales are what many anglers associate with minnows as they are the Fathead (P. promelas) and Bluntnose Minnows (P. notatus) that are the common bait shop minnows. The Bullhead Minnow (P. vigilax) is another minnow of this genus in Wisconsin streams. Most of these tend to be more common in slightly warmer, more organically enriched and turbid streams. All of these species range from about 1.5 to 3, maybe 4 inches.

  • Brassy Minnow (Hybognatus hankinsoni) is another minnow with a great scientific name. Brassy Minnows are omnivores and are generally found in cooler streams, hence their overlap with trout. They are a handsome little minnow that is generally 1.5 inches up to maybe 3 inches.

  • There are two other groups of dace - again, small-scaled minnows. One species is in the genus Clinostomus and three are in the Chrosomus genus. The Redside Dace (Clinostomus elongatus), and three Chrosomus (formerly Phoxinus) species: Southern Redbelly (Chrosomus erythrogaster), Northern Redbelly (C. eos), and Finescale Dace (C. neogaeus). Like most minnows, they tend to be more common in somewhat warmer trout streams. Redside Dace have largely declined in Wisconsin. The Northern Redbelly is mostly a fish of northern Wisconsin, the Southern Redbelly is more widely distributed, and the Finescale Dace has a limited distribution in Northern Wisconsin. The redbelly dace are red and yellow in spawning colors and are quite lovely little fishes with some of the smallest scales of any fishes. These dace are generally 2 to 3 inches in length.

Knowing the minnows is probably more important for the warmwater angler but some like Longnose Dace, Common Shiner, Creek Chub, and Hornyhead Chub are certainly worth knowing. Anglers that fish larger streams or lower ends of trout streams are more likely to come across minnows than anglers that fish your more typical trout streams. There are, of course, a huge range of patterns to imitate these small fishes. A few videos to fly patterns are below:

Suckers


Suckers are not minnows but rather members of the family, Catostomidae which includes two common trout stream suckers and a large variety of larger river fishes like buffalo and redhorses. The best known of these is the White Sucker (Catostomus commersoni) which is a fish nearly all of us have mistaken for a trout as we are staring at a pod of large fishes in the bridge hole. White Suckers will range up to 20 inches or longer but they are important in trout streams for two reasons; as juveniles, they provide a significant meal for trout and second, their spring spawning migrations provide a ton of eggs for trout to eat. Trout are well known for following spawning suckers and will eat the eggs that get carried downstream. They are easily identified by their mouths and the fact that their scales decrease in size as they move towards the head.

White Sucker
A large White Sucker from the Milwaukee River

The other sucker encountered on larger trout streams / rivers is the Northern Hogsucker (Hypentelium nigricans). Hogsuckers are identified by their 3-5 large saddles and the large concavity at the top of their heads. They generally need cleaner water than do White Suckers and will grow to 12 to 16 inches (or more). Again, their juveniles are more likely to be trout food than are the adults. They generally lack the numbers and large spawning migrations of the White Sucker and are certainly of secondary importance for coldwater anglers. Certainly many of the minnow patterns above will work well to imitate juvenile suckers.

Darters


Darters are relatives of the much larger Yellow Perch, Walleye, and Sauger and are a diverse group of fishes in the family Percidae. The family has over 200 species, most of which are darters, the common name for a wide variety of generally small percids. Like most families I have written about here, they are more diverse in larger, warmer streams.

Fantail Darter
Fantail Darter from the Milwaukee River

Two genera in Wisconsin are found in larger, warmer trout streams - Percina are the logperches (and some that have darter as a common names) and Etheostoma are the generally smaller darters. While there is a wide variety of these "perch-like" fishes in Wisconsin, two species are most important in trout waters - the Johnny Darter (E. nigrum) and Fantail Darter (E. flabellare). Johnny Darters are generally smaller - up to 2 to 3 inches - and are identified by the faint "M's", "W's", and "X's" along their sides. The Fantail Darter obviously has a fan-shaped tail and may grow to 4 or even 5 inches.


Again, many of the patterns above can be tied to imitate darters but here are a few more specific imitations.

Catfishes (Madtoms)


Madtoms are members of the catfish family (Ictaluridae) and are mostly nocturnal. In Wisconsin, the Stonecat (Noturus flavus) is the species of greatest note. Becker (Fishes of Wisconsin) notes that they are common in Lake Superior tributaries. Again, expect these in larger, warmer streams - in this case, they like larger rock substrates.

Stonecat
A Stonecat from the Milwaukee River

There are few stonecat specific flies but sculpin imitations will likely suffice, particularly tied in a yellow-brown color. Harry Murray provides an introduction to madtoms and their imitations.


Sticklebacks


Sticklebacks are a largely marine family of fishes (Gasterosteidae) that are most easily identified by their dorsal spines. We have a one species of interest in Wisconsin - the Brook Stickleback (Culaea inconstans). Brook Sticklebacks tend to like cold, weedy habitats and are often found around springs. They are rarely found in areas with much current.

Brook Stickleback
Brook Stickleback from southeastern Wisconsin

Flies for minnows tied in smaller sizes - a large Brook Stickleback is 3 or 4 inches in length but more are between 2 and 3.5 inches - will work. There are a number of European species so a number of stickleback imitations come from there.

Lamprey


First, yes, lamprey are fishes and no, they are not all parasitic (order Petromyzontiformes). Lamprey are jawless fishes, some of the most primitive of the fishes which some question if they truly belong with the fishes.

American Brook Lamprey ammocete; photo by "Fungus Guy", Creative Commons.


While the Sea Lamprey - a non-native parasitic species - is probably the best known species in Wisconsin; the American Brook Lamprey (Lethenteron appendix) are a native, non-parasitic species of cold streams that anglers should know. Their life history means that most of their lives are spent as filter feeding ammocetes (larvae) buried in riffles. Only during their spawning migrations are they important to imitate. While the window of opportunity is brief, they provide a significant meal for trout which will really let their guards down while chasing spawning brook lamprey.


While a 4 to 6 inch olive rubber worm is probably the perfect imitation, the next best imitations are worm-like flies. Not much more than an olive zonker strip on a hook with a bit of weight is needed.

The Wrap-Up


That is an awful lot of information about fishes that can be found in trout streams and are - at times - likely eaten by trout. Of these groups, the sculpin are the most likely to be important for most trout anglers. Minnows, suckers, and darters become more common in slightly larger and warmer trout streams. All of these species are likely to be important for warmwater anglers. There are tons of different streamers to imitate these fishes, which you choose depends upon your preference and tying style and skill.

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