My phone chimed an alert last week while I was on vacation, a text message accompanied by a photo of a prodigious sunfish, brilliantly colored, with a simple question.
What is it?
These are the occupational hazards of a professional fish geek. You will be asked all sorts of questions about fish, particularly identification. Friends, acquaintances and sometimes complete strangers will send photos of catches, bizarre stories, or newspaper clippings to try to get an answer or opinion.
I do my best to provide an answer. After all, I similarly query my friends about their expertise or career field — fishing guides, dog trainers, veterinarians, electricians, builders, writers, attorneys and teachers have all fielded questions from me on various topics, and I expect there will be more.
Minnesota is blessed with a diversity of aquatic habitats and as such, a diversity of fish species. Minnesota’s aquatic ecosystems vary from shallow, prairie lakes in the southwest to deep and cold Canadian Shield lakes in the northeast. Minnesota’s count of fish species sits at 159 from eight major water drainages, a count which fluctuates depending on which invasive species are counted or not.
Alabama takes the United States’ prize for having the most fish diversity with more than 450 different fish species. Alabama’s diversity is due to having a number of largely undisturbed warm-water streams and being completely missed by glaciation. Their fish diversity is buoyed by an amazing proliferation of non-game fishes, in particular minnows and darters.
By and large, anglers and lay people overly rely on color as the means of fish identification. Colors and patterns are usually enough to identify fish, broadly speaking, but often color is very circumstantial.
Fish color varies based on fish age, spawning season and water conditions (turbid vs. clear, warm vs cold, etc.). For these reasons, fish biologists and ichthyologists rely on meristics, which are countable, quantitative features used to identify fish, such as the numbers of scales along a lateral line or the number of rays in a particular fin.
These characters are part of a larger formula to describe families, genus and species, and in some cases, are the only way to tell apart fish species.
Think you know your fish? Here are a few surefire ways to determine fish species that are commonly confused.
Minnesota has both black and white crappies. Black crappies are more widely distributed across the state, while the white crappies are sprinkled across parts of central and southern Minnesota and typically found in lakes with either turbid water quality or a river connection.
The fish are known to hybridize, which further confounds identification. The best way to tell the species apart is to count spines on the dorsal fin. Five or six spines is a white crappie, while seven or eight spines is a black crappie.
Sunfish are a large group in Minnesota, with six different species in the Lepomis genera. Each species has a different combination of characteristics used for differentiation.
One of the meristics used for these species are examining the gill rakers. Fish gills have red gill filaments on the outer gill arch margin, called lamellae, where fish use counter-current ion exchange to pick up oxygen and release carbon dioxide. On the inner gill arch margin, you’ll find the gill rakers.
These are the projections, like teeth on a comb, that are spaced and specialized to how fish feed. Some fish gill rakers are dense and fine, intended for straining plankton and directing it to the gullet opening. Other fish have long, fingerlike rakers for processing plankton and invertebrates. Others yet have sharp inward facing studs, intended to direct prey back to the gullet.
All fish swallow their prey whole, but rather than swallowing all the water that comes into the mouth while feeding, the mouth can shut and the water can be strained out through the gills and gill rakers.
For pumpkinseed sunfish, you’ll find short and stubby gill rakers, used for their crustacean/mollusk-rich diet. For bluegill sunfish, you’ll find long gill rakers suited to sorting plankton and small aquatic insects. Rock bass always have 11 dorsal spines. Green sunfish have the largest mouths of the Lepomis genera, to the point you can usually thumb them while holding the fish.
Warmouth sunfish, orange-spotted sunfish and longear sunfish can be distinguished by lateral scale counts, opercular flap color (tabs on the gill cover), pectoral fin shape (pointed or round) and pigment pattern on sides and on the soft dorsal fin. Hybrids within the sunfish are common and produce larger fish by heterosis (hybrid vigor); often you see characteristics from both species present.
Amongst the Black Bass (Genus Micropterus), largemouth and smallmouth bass occasionally get misidentified. While largemouth are often green and smallmouth are often bronze or brown, they can look strangely similar at times. The giveaway is looking at the upper jaw bone, or maxilla. If it extends beyond the midpoint of the eye, you have a largemouth bass. If it is at or in front of the midpoint of the eye, a smallmouth bass.
The temperate bass (Genus Morone, yellow bass and white bass) are completely different than the black bass, with a different body shape and differing counts of dorsal and anal fin rays and spines.
Northern pike and muskellunge get mixed up by many anglers because both have so much variability in color patterns. Muskies can be clear, spotted or barred color phased. Pike can similarly be “silver” with few spots or numerous markings like an east coast chain or grass pickerel.
Overall, it’s about observing the fish’s contrasting color pattern. Northern pike have light markings on a dark background, while muskies have the inverse. Pike typically have rounded caudal (or tail) fin tips while muskies are pointed. Muskie have six to nine submandibular pores on each underside of the jaw; pike have 5 or fewer.
Hybrids, called tiger muskellunge, have characteristics of both species but typically show a pattern of both bars and spots.
In the catfish family, few confuse the flathead and channel catfish. Flatheads have big, flattened heads and squared caudal (tail) fins, while channel catfish are usually slate gray with forked tails. Bullheads, however, give folks trouble. Yellow bullheads have light-colored barbels, or whiskers, on the underside of the jaw.
Black and brown bullheads have dark-colored barbels. Separating black and brown bullheads falls to finding a bar or crescent shaped mark that isn’t always present on black bullheads near the base of the caudal (tail) fin, and which is never present on brown bullheads, or by feeling the barbs on the pectoral spines. Black bullheads have fine serrations on pectoral spines while brown bullheads have coarser teeth.
Folks fishing northern Minnesota often come across whitefish (Genus Coregonus) species. Most common are ciscoes, also called tullibees or lake herring, and less common are lake whitefish. Among the ciscoes are several different species, particular in Lake Superior.
For simplicity and to focus on the more common species found inland, the easiest way to tell cisco and lake whitefish apart is mouth position. Cisco lower jaws extend up to or beyond the tip of the snout (superior mouth position), while whitefish have a snout that overhangs the lower jaw (subterminal mouth position).
It should probably be a misdemeanor to misidentify our state fish, yet some folks always do. Walleye and their close cousin the sauger get mixed up on occasion. Walleye have a distinct white spot on the tip of their caudal fins, no spots on their anterior dorsal fin and a dark spot on the rear most membranes of the posterior dorsal fin, while sauger have mottled body markings, spots in their anterior dorsal fin, no dark spot in the posterior dorsal fin, and while they can have some white on the lower most ray of the dorsal fin, it’s nowhere near as large as the walleye’s large white tip.
Sauger often have scaled cheeks while walleye cheeks are often naked or sparsely scaled. Crosses between the species, called saugeyes, often have characteristics of both species.
If you fish Lake Superior for Pacific Salmon, King or Chinook, salmon will have an all-black mouth, especially the lower jaw, “gumline”, and vomer (bony patch which holds teeth in salmon). Cohos will have a white base where the teeth emerge from that is surrounded on either side by black.
For stream trout, know that brook trout will have vermiculations, or wormlike markings, on their backs, with black gumlines. Rainbow trout will have black spots, smaller than the pupil of the eye, covering most of their sides, and brown trout will have red and black spots nearly as big as the pupil of the eye, ranging from few to many across the body.
The minutiae of identifying fish is useful for the sport species listed above; it becomes even more tedious for the more numerous families of non-game fish, like suckers and minnows. If you get stumped by a fish, do a fish biologist a favor. Take clear, closeup shots of the whole fish on a side, of the mouth and head, and clear shots of the sides with all fins extended.
The more pictures to examine and compare, the better.
Scott Mackenthun is an outdoors enthusiast who has been writing about hunting and fishing since 2005. He resides in New Prague and may be contacted at scott.mackenthun@gmail.com.
The Link LonkJuly 26, 2020 at 04:30PM
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Mackenthun: From scales to markings, sometimes it's tricky to get fish ID - Mankato Free Press
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