“new” species in Illinois. The Redspotted Sunfish

January 2007 OutdoorIllinois / 17

M ost people have neverheard of the redspot-ted sunfish (Lepomisminiatus)—and forgood reason. Until

1992 when researchers at Southern Illi-nois University determined this fish to bea separate species, it was known as thespotted sunfish (Lepomis punctatus).The redspotted sunfish is found as farsouth as Florida and Texas, and Illinoisis at the northern edge of its distribution.

Although never abundant in Illinois,when the first collections of Illinois fishwere made 100 years ago, the redspot-ted sunfish was more widespread than itis today. Historically, the redspotted sun-fish was found along the Illinois and Ohiorivers, and in the Mississippi and the Iro-quois rivers. Currently, this speciesappears to be much less abundant alongthe Illinois and Ohio rivers, and has dis-appeared from the other two rivers.

The habitat of this sunfish is largerriver backwater lakes with aquatic

plants—habitatsthat have been lostthrough draining,filling or construc-tion of extensivelevee systems.While many of thebackwater lakesstill exist, siltationand introducedspecies (grasscarp) have diminished the aquatic vege-tation, leading to the demise of theredspotted sunfish except in small, slow-moving, vegetated streams—habitatsthat are quite vulnerable to disturbance.

With the help of a federal grant, theDepartment of Natural Resources’ Divi-sion of Fisheries has begun a statewidesurvey to determine the population statusof the redspotted sunfish. Small fin-clipsare being taken from fish collected in Illi-nois and neighboring states for use ingenetic studies. Results from these sur-veys and studies will guide efforts to rein-troduce this species into restored habitatsthroughout their historic Illinois range.

Preliminary results of the populationsurveys show the redspotted sunfish isquite rare in Illinois. An adult populationis yet to be found along the Illinois River(a few juvenile fish were found in a sin-gle, small stream in the lower Sanga-mon River basin), which was once theheart of its existence in the state.

The news is better along the OhioRiver as the occasional redspotted sun-fish is found in a few backwater lakesdespite the lack of necessary aquaticvegetation and presence of exotic silvercarp. Several adults have been collect-ed from a remnant population in a smallstream in the lower Saline River basin.

Plans for the Illinois population of thissunfish include continuation of popula-tion surveys and genetic analyses todetermine if genetic variation existsamong the isolated populations, allow-ing for identification of the most appro-priate source of fish for stocking intorestored habitats. Adult redspotted sun-fish will be collected and spawned inrearing ponds, producing the number offish needed for stocking efforts.

—Trent Thomas, Region 3 StreamsBiologist, DNR Division of Fisheries

The RedspottedSunfishPhotos By Trent Thomas

Population studies reveal critically low numbers of this“new” species in Illinois.

Redspotted sunfish habitatRedspotted sunfish habitat