Redear sunfish (Lepomis microlophus)

Synonyms: Pomotis microlophus, Pomotis notatus, Pomotis speciosus, Xystroplites longimanus

Common Names: Shellcracker, stumpknocker, cherry gill, sun perch, sunny, Georgia bream, chinquapin, rouge ear, mojarra oreja roja

Description:

Redear sunfish (Lepomis microlophus) is a small pan-shaped fish native to the Atlantic and Gulf Slope drainages of the southeastern United States and the lower Mississippi River basin [1][2]. It has been widely stocked outside its native range as a sport fish, and now lives in more than 28 states, including in the Great Lakes basin [2]. MISIN tracks it because introduced populations reduce native pumpkinseed sunfish and the snails both species depend on [1][3][4].

Identification:

Redear sunfish is a small, deep-bodied pan-shaped fish, typical adult size around 8 to 10 inches [1][5]. The body is olive above with darker spots and flecks of red, and sometimes vertical bars along the sides; the belly is yellowish to cream [1].

Two features settle the identification. First, look at the gill flap: on redear the hind end is black with a bright red spot at its tip, and hence the name "redear" [1]. Second, check the mouth: it is small and, when closed, just barely reaches the front margin of the eye ? not past it [1]. Redear also has long, pointed pectoral fins and a first dorsal fin with 10 stiff spines followed by 10 to 12 soft rays [1].

The spring spawning season is when redear are easiest to see. Like other sunfish, they nest in colonies on shallow sandy or muddy bottoms, and the males guard visible saucer-shaped nest depressions [1]. That is also the season anglers most often catch them, since they concentrate near the beds.

At-a-glance cues:

1. A bright red spot on the tip of the black gill flap [1]
2. A small mouth that just reaches the front of the eye when closed ? not past it [1]
3. Deep, pan-shaped body, olive above with red flecks and a yellowish-cream belly [1]
4. Long pointed pectoral fins, more pointed than those of most other sunfish [1]

Habitat:

Redear sunfish is native to Atlantic and Gulf Slope drainages of the southeastern United States, from about the Savannah River in South Carolina south through Florida and west to the Nueces River in Texas, and north in the Mississippi River basin as far as southern Illinois and southern Indiana [1][2]. It is not native to the Great Lakes.

It prefers warm, quiet water. Look for it in the vegetated shallow zones (the littoral zone) of ponds, small to large lakes, marshes, and reservoirs, and in streams or rivers with sluggish to slow flow [1]. It favors clear water with plenty of underwater plants, snags, and cover, over a bottom of mud or sand [1].

Introduced populations are now established in more than 28 states outside the native range, including the Great Lakes basin [2]. NAS's records show it has been documented in the Great Lakes since 1928 [1], with records from Illinois, Indiana, Michigan, Ohio, and Vermont [1]. In southern Michigan, natural reproduction has been documented ? a 1995 survey found it self-sustaining in Clear Lake, Jackson County [1].

Reproduction:

Redear sunfish arrives in a new water body one of two ways: intentional stocking or release from private ponds. Stocking is by far the more common pathway ? state agencies and private landowners plant it as a sport fish and to control snails, and NAS documents that in the Great Lakes, intentional stocking for sportfishing is the recorded means of introduction [1]. The other route is a stocked pond that eventually connects, through flooding or an outlet, to a stream or lake next door. The fish does not walk overland by itself.

Once introduced into warm water with plentiful vegetation, redear reproduces successfully ? a Michigan survey found it self-sustaining and reproducing naturally by 1995 [1]. Redear spawn in spring in colonies of saucer-shaped nests on shallow, sandy or muddy bottoms [1]. Males build and guard the nests.

NAS notes that Michigan DNR has observed hybridization of redear with green sunfish (L. cyanellus) and bluegill (L. macrochirus) in Joslin Lake, Washtenaw County [1]. Hybridization complicates identification and can affect neighboring native populations.

For prevention timing: because the pathway is people, not the fish itself, the entire "life cycle" that matters here is the decision to stock. The most useful action is not stocking redear into a water that does not have it, and not releasing an aquarium or pond fish into public water.

Impact and Damage:

Redear sunfish is safe to handle and is a popular pan-fish for eating [2] ? it is the same fish anglers know as "shellcracker" [1]. It presents no direct hazard to people.

The harm is to native fish, and the mechanism is snail eating. Redear is one of the very few sunfish specialized for crushing hard-shelled prey; in North American waters, only redear and pumpkinseed sunfish (Lepomis gibbosus) are true molluscivores in the family [1]. Where redear is introduced, it competes directly with pumpkinseed for snails ? and redear wins that competition. In laboratory feeding experiments, redear apply greater crushing force and eat more snails than pumpkinseed does [3].

In the field, that competitive advantage translates to measurable losses. In a study across inland Michigan lakes with and without introduced redear, redear introduction was associated with a 56% reduction in pumpkinseed abundance and a 69% reduction in average snail biomass compared with lakes that had no redear [4]. The pumpkinseed that remained in redear-invaded lakes ate fewer snails and had lower body condition [3][4].

Beyond the pumpkinseed?snail relationship, the redear diet can ripple through the ecosystem. Removing snails from a lake means less snail grazing on periphyton (the algae film on plants and rocks), which can shift a lake toward more phytoplankton dominance and away from macrophyte (rooted plant) dominance [1].

The federal assessment is measured. NAS classifies redear's environmental impact in the Great Lakes as moderate [1] ? real, documented, but not catastrophic. Kolar and Lodge (2002) predicted redear would spread slowly through the Great Lakes but achieve "nuisance" species status once established, based on its impact potential [1]. That prediction has not been fully tested.

Note that redear is not effective as a zebra mussel biocontrol, despite eating hard-shelled prey ? experiments show it strongly prefers snails over zebra mussel [1]. Stocking it as a mussel-management tool is unsupported by evidence.

Similar species:

Pumpkinseed sunfish (Lepomis gibbosus) is the native this species most needs to be told apart from ? and it is the very species redear reduces in introduced waters [3][4]. Both are pan-shaped sunfish in the same genus. The gill flap is the fast field mark: pumpkinseed shows an orange-red spot on the tip, but it also carries wavy blue-green lines across its cheek and gill cover, and its body sides are peppered with orange spots that redear does not have. Redear's chest color is yellowish to cream, and its distinctive red gill-flap spot sits on a plain, dark, white-bordered flap [1].

Bluegill (Lepomis macrochirus) is the other very common look-alike in the same waters and one of the species redear hybridizes with [1]. Bluegill's gill flap is entirely black with no red spot at the tip, and it carries a dark spot on the base of the soft dorsal fin that redear lacks. Bluegill also has a chevron-marked yellowish belly rather than redear's plain cream one.

Monitoring and rapid response:

Signs to watch for:

1. Small pan-shaped fish caught in a lake or pond that did not previously have it ? check the gill flap for a bright red spot on the tip [1]
2. Colonies of saucer-shaped nest depressions on shallow sand or mud bottoms in spring [1]
3. Fish showing intermediate features between redear and bluegill or green sunfish ? hybridization is documented in Michigan waters [1]
4. Anyone offering redear ("shellcracker") for sale for stocking a pond that connects to public water

What you can do:

1. Do not stock redear into a water that does not have it. Introduction is by people, not by the fish itself ? every established Great Lakes population traces to a stocking decision [1].
2. Clean, drain, and dry equipment before moving between waters ? boats, trailers, buckets, livewells. Never move live fish or lake water from one lake to another.
3. Never release aquarium or private-pond fish into public waters. This is illegal in most states, and it is one of the two documented Great Lakes introduction pathways for this species.
4. If you catch redear in a lake that did not previously have them, keep the catch (it is good eating), photograph it against something for scale, and report it ? that record is the point of the sighting.
5. For lake associations, fishing clubs, and pond owners: press the "not effective for zebra mussels" point when redear stocking gets pitched as mussel biocontrol. It is not ? experiments show redear strongly prefers snails over zebra mussel [1].

When to call a professional:

1. A new established population in an inland lake ? contact your state fisheries agency. Once a sunfish is reproducing in a lake, removing it is not a volunteer job.
2. Suspected illegal stocking, which is an enforcement matter for the state DNR.
3. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. Fuller P, Neilson M, Procopio J. Lepomis microlophus (Gunther, 1859) ? Species Profile. U.S. Geological Survey Nonindigenous Aquatic Species Database / NOAA Great Lakes Aquatic Nonindigenous Species Information System. nas.er.usgs.gov
2. U.S. Fish and Wildlife Service. Redear Sunfish (Lepomis microlophus) ? species page. fws.gov
3. Huckins CJF (1997). "Functional linkages among morphology, feeding performance, diet, and competitive ability in molluscivorous sunfish." Ecology 78(8):2401?2414. semanticscholar.org
4. Huckins CJF, Osenberg CW, Mittelbach GG (2000). "Species introductions and their ecological consequences: an example with congeneric sunfish." Ecological Applications 10(2):612?625. semanticscholar.org
5. Integrated Taxonomic Information System. Lepomis microlophus (Gunther, 1859), TSN 168154. itis.gov

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