By Koaw - 2023

BEST FEATURES FOR ID: (All of these features are discussed below in detail.)

1. Check if the cheek and the operculum are mostly scaled.

2. Check for a short snout (relative to other esocids in Esox.)

3. Compare the end of the maxilla vs. the position of the eye’s pupil.

4. Get a count on the branchiostegal rays.

5. Get a count on the lateral line scales.

Try the Quick Esox ID App that may offer a fast analysis, if needed.

Although color and patterning are very useful to assess when identifying the species within the genus Esox, there are countable (meristic) and measurable (morphometric) features that are more reliable, and as such, are the focus of this guide.

It’s important to examine more than one feature for confident IDs.

INTRO: The redfin pickerel (Esox americanus americanus) is one of two subspecies of the American pickerel (Esox americanus) [1] [2] [3]; the other subspecies being the grass pickerel (Esox americanus vermiculatus). Both subspecies are separated by range, though, a fairly broad intergrade zone exists in the Gulf Slope drainages between the Biloxi River of Mississippi and the St. Johns River in Florida; attempting to identify specimens to the subspecies level in this region is impractical and these specimens should, in most all cases, be regarded only as American pickerel (Esox americanus); [1] (see range maps in “LOCATION” below & “REDFIN VS. GRASS” for comparison features.) Furthermore, intergrades possibly exist in the upper northeast most part of the range.

Although it remains okay to describe a redfin pickerel as an American pickerel, it’s usually always best to be as precise as possible when describing species; if able to confidently designate a subspecies, then do so.

Though this is primarily a freshwater species, the redfin pickerel may be found in brackish waters.

KEY FEATURE #1 - SCALATION ON CHEEK & OPERCULUM: Of the North American esocids in Esox, only the redfin pickerel (E. a. americanus), the grass pickerel (E. a. vermiculatus), and the chain pickerel (E. niger) will have a cheek & an operculum that are both nearly fully scaled. Aside from the youngest of juveniles, these scales should be readily visible to the naked-eye.

These scales are best seen if the specimen’s head can be rotated underneath light, allowing for the shimmering scales to reveal themselves more easily. Aside from the youngest of juveniles, these scales will be readily visible.

If the cheek and operculum are mostly scaled, see Key Feature #2 to further help distinguish between the grass/redfin pickerels and the chain pickerel.

BODY: Like all members of the genus Esox, the redfin pickerel has an elongated body with a single posterior dorsal fin above an anal fin of almost equal size. Also notice the deeply forked caudal fin, the low set pectoral fins, and pelvic fins set fairly far back, all traits of other esocids.

All members of Esox have an elongated ‘duck-bill’-like snout. Though, the snout of the redfin pickerel is often comparably shorter to the snout of the conspecific (within species) grass pickerel and the congeneric (within genus) chain pickerel. The short snout of the American pickerel is a good feature to examine to help distinguish these sympatric species. There are no spines within the fins and only soft rays.

Typically, there are between 16-19 dorsal rays, 14-17 anal rays, and 94-117 lateral line scales. [1] [4] (Lateral line scales discussed further below in comparison to the other pike/pickerel/musky. All rudiments included in ray counts.)

KEY FEATURE #2 – SNOUT LENGTH vs. POSTORBITAL LENGTH OF HEAD: The redfin pickerel will most often express a snout length that will not exceed the length of the postorbital length of the head, true of young and mature specimens. The chain pickerel has a noticeably longer snout length that usually nears or surpasses the postorbital length of the head.

Of the data collected for this guide for redfin pickerel, the snout length (SnL) fit into the postorbital length of the head (PtOL) for a mean of 1.40 times (PtOL/SnL) with a range of (1.15 – 1.53) including juvenile, subadult, and adult specimens. The snout length for chain pickerel fit into the postorbital length 0.94 times on average with a range of (0.78 – 1.13) including juvenile, subadult, adult specimens.

Measurement method displayed in adjacent graphic with point-to-point measurements between most anterior point of upper lip to the most anterior margin of the orbit for snout length (SnL) and postorbital length of the head (PtOL) taken from the most posterior margin of the orbit to the most posterior margin of the bony operculum; measurements taken on same parallel plane. [4]

The morphometric data gathered for this ID guide agrees with the underlying trends of snout length vs. postorbital length of head presented in Crossman (1966) & Casselman et al. (1986).* [1] [5]

PATTERN/COLORATION: Young and adults express very different colors and patterning. Even between mature specimens, coloration and patterning varies. Specimens may also flare-up or flare-down where colorations and patterns change rapidly along the body. Hence why a fish might be caught appearing fully barred along the body, and after one minute, the bars mostly disappear, or vice versa. That’s why meristics (countable features like lateral line scales) and morphometrics (measurable features like snout length) are such valuable features to use when identifying the fishes of Esox.

Mature specimens tend to have darker overall colors. Adults are usually dark brown, to tan, to olive green above with a white or cream-colored belly. A number of irregular wavy-bars exist on the body that may extend onto the underside. A slanted suborbital line, or ‘teardrop’, exists beneath the eye. The teardrop is often more vertical on young specimens, becoming most slanted and curved on adults. The redfin typically has the most slanted and curviest suborbital line within the genus Esox. Adult patterning and colors are typically not fully present until 6 inches (15 cm) in TL, [6] though specimens mature at different sizes.

One of the few consistencies of coloration is the red to orange coloration of the rays within the fins, especially the pectoral and pelvic fins. Specimens from the Carolinas exhibit the most vibrant colors of red within the fins. [1] Mature and subadult specimens will have red to orange in the fins year-round. Juveniles will express red to orange at the base and/or anterior margins of the fins while the youngest specimens will likely express mostly clear fins. The fins will not express spotting like is seen on the fins of muskellunge and northern pike, though young northern pike, even up to ~6 in (15 cm), may not yet express spotting in their fins.

Juvenile redfin pickerel have a radiant dorsal stripe that extends from the tip of the snout to the caudal peduncle. A bright lateral band will also exist on young. At around 2.5 – 4 inches (6 – 10 cm) this stripe begins to disappear, as well as the lateral band, while the barring along the body becomes more conspicuous. [6]

According to Crossman (1966), the red to orange in the fins is a fairly reliable distinguishing trait when comparing the redfin pickerel to the grass pickerel and their intergrades. While the redfin pickerel has orange to red fins, the grass pickerel has dusky, yellow, or amber fins while the intergrades usually express amber fins. [1] Though, it’s often difficult to demonstrate and rely on color differences when identifying specimens because the observer, a human, will most likely see color differently than another human.

Determining sex is very difficult without examining gonads/gametes. Though it is possible, if the trend holds true for redfin pickerel as it does for other esocids, females will have a larger urogenital opening than males. Females typically will attain larger sizes, and, according to Crossman (1966), usually have a much darker suborbital line, though this trait does not have great reliability for sex determination. [1]

KEY FEATURE #3 – MAXILLA VS. POSTION OF EYE’S PUPIL: For mature redfin pickerel (E. a. americanus) the posterior end of the maxilla will almost always extend past the anterior edge of the pupil. This is very useful for distinguishing redfin pickerel from chain pickerel (E. niger), where on the chain pickerel, on both young and mature forms, the end of the maxilla usually will never extend as far as the anterior edge of the pupil, if even extending past the anterior margin of the eye. Juvenile & subadult redfin pickerel will almost always still at least have the maxilla extending past the anterior edge of the eye.

The grass pickerel (E. a. vermiculatus) tends to have less extension of the maxilla compared to redfin pickerel populations where the posterior end of the maxilla does not usually pass the anterior portion of the pupil yet typically passes the anterior margin of the eye, though in some cases, still extending past the anterior margin of the pupil. [4] The morphometric data gathered for this ID guide agrees with the underlying trend of maxilla length presented in Crossman (1966) [1] .**

KEY FEATURE #4 – BRANCHIOSTEGAL RAYS: Though not definitive, getting a count on the branchiostegal rays will also help determine a redfin pickerel from a chain pickerel. Typically, redfin will have 11-14 branchiostegal rays on a single side with a range of at least 10-16. Chain pickerel typically have more rays with 14-17 branchiostegal rays, sometimes as low as 12-13. [5]

Crossman (1966) reported surveyed redfin pickerel mostly showing branchiostegal ray counts of 5+6 (11) and 5+7 (12) [1] while in Crossman (1962) the specimens sampled from North Carolina mostly showed branchiostegal ray counts from 12-14, with only 5 of 64 specimens showing counts of 11, 15, or 16. [6]

SUBMANDIBULAR PORES: A count on the submandibular pores is indeed a reliable feature to examine. Most all specimens of redfin pickerel will show a count of 4/4, where there will be 4 pores on each side. However, this trait is not so handy to use with redfin pickerel because the pores are very small and difficult to see on most specimens. Often there are flecks and other spots on the undersides of the chin that are difficult to distinguish from pores. A magnifying glass is often needed to verify pores on this small species.

Furthermore, like most all the traits of esocids, this feature is not 100% reliable on its own. Small percentages of specimens from a population may show counts including 2,3,5, and, rarely, up to 6 pores on one side. [1]

Same as the redfin pickerel, only the chain pickerel and the grass pickerel will most often show 4/4 counts. The northern pike typically shows 5/5 counts with a common range of (4/5-5/6). Muskellunge typically show counts that almost always are equal to or greater than 6 pores on a single side.

SIZE: : Adults typically will have a total length (TL) between 5.0 to 8.5 in (13 – 22 cm). [6] [7] [8]

Max TL is ~15 in (38 cm). [9] The IGFA All-Tackle world record is 2 lb 4 oz (1.02 kg). [10]

Swift et al. (1977) reported at least one specimen achieving 14.6 in (37.1 cm) TL in Florida, though this specimen was most likely an intergrade (with grass pickerel). [11] For Connecticut, Jacobs & O’Donnell (2009) reported the largest state survey size as 11.4 in (29.0 cm). [8] For Virginia, Jenkins & Burkhead (1993) reported the largest state specimen as 8.3 in (21.2 cm). [7]

KEY FEATURE #5 – LATERAL LINE SCALES: Of the members of Esox in North America, the redfin pickerel shows, on average, the fewest lateral line scales. Though tedious to count on young specimens, this feature may be helpful identifying small specimens and/or further understanding a possible hybrid. For most populations of redfin pickerel, expect the lateral line scales to be below 110, though some populations will show higher counts. [5] Crossman (1966) found a range of 94-117 lateral line scales. The data collected for this guide found a range of 99-113.

Chain pickerel (E. niger), muskellunge (E. masquinongy), and northern pike (E. lucius) all typically have more than 120 lateral line scales.

Of the meristics gathered for this guide, chain pickerel lateral line scales range was 114-138 with only 7% of specimens having fewer than 120 lateral line scales. Casselman et al. (1986) report a chain pickerel lateral line scale range of 114-131.

The main lateral line is very hard to find on redfin pickerel because this species has so many pored scales. It may be more practical to start at the tail side and count backwards; start at the most central scale on the caudal peduncle, then go back a scale or two to approximate where the hypural crease is, then begin your count along that row of scales all the way until reaching the gill plate.

HABITAT: Redfin pickerel almost exclusively inhabit areas with dense vegetation and calm waters. Swamps, backwaters, and quiet streams are preferred. This species may also be found in ponds and lakes, and less so, in rivers within slow waters. This subspecies is known to tolerate a wide range of pH in waters from acidic to neutral to basic but typically is known to inhabit more acidic, stained waters. This species may, at times, be found in brackish waters.

LOCATION: The northernmost part of the redfin pickerel range begins in the southernmost part of Quebec around Lac Saint-Pierre of the Saint Lawrence River system, though redfin pickerel are rare to find in this range. [12] The ranges continues south through the Richelieu River system and into the Champlain system of Vermont and New York, extending into the southern parts of New Hampshire, Massachusetts, Rhode Island, Connecticut, eastern parts of Pennsylvania, and continuing into the Atlantic Coastal Plain into New Jersey, Maryland, and Delaware.

In western Maryland, redfin may have been introduced into the Deep Creek system in the early 1930s [13], though I suspect if this introduction actually occurred then that isolated population has been displaced by chain pickerel (E. niger), a species that is now abundant in these waters and also known to displace redfin pickerel populations.

In Virginia, the redfin pickerel is only found in the easternmost part of the state along the Coastal Plain, primarily in the southern-central part of the state. Jenkins and Burkehead (1993) reported many specimens of redfin pickerel in the upper parts of the Occoquan River drainage in northeast Virginia. Though, after having sampled these waters a few times myself, and without any recent sightings reported on USGS-NAS and iNaturalist, it may be that this population has dwindled significantly and/or is possibly extirpated. [7] [14] [15]

The range continues south along the Coastal Plain into the Carolinas and approximately to the St. Marys River in Georgia where, near this location begins the zone of intergradation with the grass pickerel (E. a. vermiculatus.)

INTERGRADE ZONE - As mentioned in the intro, the redfin pickerel (E. a. americanus) is a subspecies of the American pickerel (E. americanus) while the grass pickerel (E. a. vermiculatus) is the other subspecies. A broad intergrade zone exists, or a zone where genes have been swapped between the subspecies. Specimens within this zone most often show intermediate features between the two subspecies.

This zone extends from the Gulf Slope drainages between the Pearl/Biloxi Rivers of Mississippi to the St. Johns River in Florida into peninsular Florida; attempting to identify specimens to the subspecies level in this region is impractical and these specimens should, in most all cases, be regarded only as American pickerel (Esox americanus). However, it is quite possible that ‘purer’ redfin populations have been expanding their range since the last assessment of this intergrade zone.

There are isolated populations within this intergrade zone, specifically in certain areas of the Yellow and Blackwater Rivers, that show primarily redfin characteristics, [1] though I suspect genetic data would reveal intergrades.

It is suspected by Crossman that intergrades should exist, or at least soon will exist, in the northernmost part of the range. [1] I believe Crossman’s predication has some credibility after I analyzed a specimen observed in 2020 in the Richelieu River, just south of Montreal, that appeared to demonstrate intermediate features between both parent subspecies. [16]

REDFIN PICKEREL VS. GRASS PICKEREL: Determining the location of a captured specimen against the range map for this species will most likely determine the subspecies. Specimens captured in the intergrade zone are “impossible” to identify down to a subspecies level according to Crossman (1966). Ergo, specimens captured in this range should, in most cases, be described at the species level of Esox americanus. For the most part, intergrades show intermediate features between the grass pickerel and redfin pickerel. Color of the fins, # of cardioid scales, snout length, and maxilla extension are all features that will typically be intermediate between the parent subspecies.

A number of attempts have been made to quantify any morphometric and meristic differences between the grass pickerel (Esox a. vermiculatus) and redfin pickerel (Esox a. americanus) subspecies [17] [18] [19]. Utilizing and expanding on these studies, Crossman (1966) found that even in the non-intergrade zone, the two subspecies, upon grouping all uniform subspecies populations, produced almost completely overlapping morphometric characteristics except, to a lesser degree, when examining the postorbital length divided by the snout length and the postorbital length divided by the nostril to tip of snout.

In Crossman’s study, specimens larger than 80 mm were examined from uniform populations of grass pickerel and redfin pickerel, as well as their intergrades. From eight different populations of redfin pickerel the snout length fit into the postorbital length of the head (PoL/SnL) with a mean range of 1.2-1.4x (all data range 1.0-1.4). From seventeen populations of grass pickerel examined, the mean range of PoL/SnL was 0.9-1.1x (all data range 0.9-1.3), demonstrating that grass pickerel generally have a longer snout, but there exists overlap for this feature.*

Furthermore, this guide examined the maxilla extension of grass vs. redfin pickerel as Crossman (1966) suggested there was a slight trend for the grass pickerel’s posterior maxilla extension to be less than what is seen on the redfin. Of 27 grass pickerel examined for this feature, only 3 specimens had a maxilla that extended as far back to be between the anterior edge of the pupil and the middle of the pupil. Every mature redfin pickerel examined for this feature had a maxilla that extended at least past the anterior edge of the pupil, while only 1 juvenile and 1 subadult only had the maxilla extending past the anterior edge of the eye. So, usually the maxilla of the redfin pickerel will pass the anterior edge of the pupil while the maxilla does not extend this far on the grass pickerel.

Another difference between the grass pickerel and redfin pickerel are the number of cardioid scales present on the ventral side of the fish, particularly counted between the pelvic fins. These cardioid scales are scales with notches in the posterior ends, sometimes with more than one notch. This feature was first proposed to distinguish grass pickerel and redfin pickerel by Legendre (1952) in the northernmost part of the ranges of both subspecies, verified again and built upon in Crossman (1966) as a good feature to examine.

Though a magnifying glass is helpful, especially on small specimens, these scales become more easily visible on specimens larger than 4 in (10 cm). Redfin pickerel have more cardioid scales than the grass pickerel. If counting cardioid scales between the triangular area between the pelvic fins of redfin pickerel, this count will be 6 or higher, possibly up to 30 or more. And grass pickerel usually never show more than 3 or 4 cardioid scales, if any at all in this area. [1]

FISHING TIPS: This small species is not often targeted by anglers and is more often caught by accident. Though, nowadays there is a larger community of anglers dedicated to targeting smaller species, many with a goal to notch-off as many species as possible from a ‘life-list’.

What really makes the redfin pickerel difficult to catch are the habitat locations. The prime redfin spots are often in areas that are not easily accessible (or desired to be accessed) by most anglers, habitats like swamps, rough creek edges, and very weedy bays. Furthermore, the redfin pickerel will most often be sitting in dense vegetation, making bait and lure choices more limited.

My preferred bait choices for pickerels are a weighted jig-head with a soft plastic (#10-#6), medium-to-large flies (#14-#8), and safety-pin spinnerbaits (#8-#4, #2-#1 for large specimens).

From my experience catching pickerels, one of the best strategies is to find an accessible spot of shoreline that has a weed edge against a pool or any open water. (Take care to sneak up on locations, as redfin are often sitting shallow and will spook easily.) Start with casting into the open lanes along the weed edges to work the open water. If there are emergent plants (like lily pads), selectively dipping and twitching a bait in the exposed holes will likely produce a fish, possibly a pickerel.

Considering all members of Esox are primarily lie-and-wait predators, it means that these species won’t often be cruising around for meals (like largemouth bass do.) It’s important to work as much water as possible. Though, do have patience to work a single spot for five minutes or so before moving on. With some effort, often a pickerel will eventually shoot out of a hiding spot and snatch a bait.

*Note from KEY FEATURE #2: This feature was selected from Crossman (1966) as well as Casselman et al. (1986) that derived methods from Legendre (1952, 54). Crossman (1966) claimed to use morphometric measuring methods from Hubbs & Lagler (1958), though there seems to be an inconsistency (or at least lack of transparency) with how the suborbital length measurement is taken, specifically in Casselman et al. (1986), be it a direct line measurement from the most posterior edge of the orbit to the most posterior portion of the head or a parallel measurement (along what the standard length would be taken) between the same aforementioned point-to-point locations. Both measurements produce very similar, yet different results. [1] [5] [19] [20] [21]

**Note from KEY FEATURE #3 This feature is suggested as a distinguishable trait in Crossman (1966) and Casselman et al. (1986). Yet, it seems that within these aforementioned sources the supra-maxilla bone may be used synonymously with the maxilla bone. Though, even if the posterior end of supra-maxilla is used rather than the maxilla, the position of supra-maxilla on chain pickerel still does not usually extend to the midpoint of the pupil and in the redfin pickerel this bone only extends farther past the midpoint of the eye. [1] [5] The morphometric data I collected is used to influence my graphics and descriptions on this trend.

REFERENCES:

[1] E. J. Crossman, "A Taxonomic Study of Esox americanus and Its Subspecies in Eastern North America," Copeia, vol. 1, pp. 1-20, 1966
[2] R. Fricke, W. N. Eschmeyer and R. van der Laan, "ESCHMEYER'S CATALOG OF FISHES: GENERA, SPECIES, REFERENCES".
[3] J. F. Gmelin, "Systema naturae by C. Linnaeus pt.3," 13 ed., vol. 1, 1788.
[4] Koaw, "Select Morphometrics and Meristics of Esocids," Koaw LC - KNFS, 2023. http://www.koaw/org/esoxdatakoaw
[5] J. M. Casselman, E. J. Crossman, P. E. Ihssen, J. D. Reist and H. E. Booke, "Identification of Muskellunge, Northern Pike, and their Hybrids," Am. Fish. Soc. Spec. Publ., vol. 15, pp. 14-46, 1986.
[6] E. J. Crossman, "The Redfin Pickerel, Esox a. americanus in North Carolina," Copeia, vol. 1962, no. 1, pp. 114-123, 1962.
[7] R. E. Jenkins and N. M. Burkhead, Freshwater Fishes of Virginia, Bethesda, MD: American Fisheries Society, 1993.
[8] R. P. Jacobs and E. B. O'Donnell, Freshwater Fishes of Connecticut; A Pictorial Guide to, Hartford: Connecticut Dept. of Env. Protection, 2009.
[9] L. M. Page and B. M. Burr, Field Guide to Freshwater Fishes of North America North of Mexico, NY: Houghton Mifflin Harcourt, 2011
[10] IGFA - The International Game Fish Association, "Pickerel, Redin - Esox americanus americanus," IGFA, 2022.  https://igfa.org/
[11] C. C. Swift, R. W. Yerger and P. R. Parrish, Distribution and natural history of the fresh and brackish water fishes of the Ochlockonee River, Florida & Georgia, Vols. Bulletin, no. 20, Talahassee, Fla.: Tall Timbers Research Station.
[12] J. F. Desroches, "Clé d’identification pratique des poissons d’eau douce du Québec.," Cégep de Sherbrooke, 2010.
[13] F. J. Schwartz, "The pickerels.," Maryland Conservationist, vol. 37, no. 4, pp. 23-26, 1960.
[14] USGS-NAS, "Esox americanus americanus Redfin Pickerel Point Map," USGS, 2022. from https://nas.er.usgs.gov/viewer/omap.aspx?SpeciesID=674
[15] iNaturalist.org, "Redfin Pickerel Esox americanus americanus," iNaturalist- Cal. Acad. of Sci - Nat. Geo., 2022.
[16] iNaturalist, "Possible intergrade observation in northernmost part of range," iNaturalist.org / Cal. Acad. of Sci. / Nat Geo, 2020. https://www.inaturalist.org/observations/53421292
[17] A. C. Weed, "Pike, pickerel, and muskaonge.," Field Mus. Nat. Hist. Zool. Leaf, vol. 9, 1927.
[18] W. C. Kendall, "The pikes, their geographic distribution, habits, culture, and commercial importance. Rept. U.S. Comm. Fish.," Bur. Fish. Doc., 1917.
[19] V. Legendre, "Clef des poissons de pêche sportive et commerciale dans la province de Québec.," Soc. Canad. Ecol. Minist. Chasse Pêch., 1952.
[20] V. Legendre, "The pike of Quebec: The ogres of our water. (Unpublished manuscript)," Dept. of Fish and Game, Office of Bio. Prov. of Quebec, Montreal, 1952.
[21] C. L. Hubbs and K. F. Lagler, "Fishes of the Great Lakes Region, Rev. Ed.," vol. Bull. 26, 1958.