Thursday, July 7, 2011

Red Alert

Redbreast sunfish (Lepomis auritus) and red shiners (Cyprinella lutrensis) are two common invasive species that inhabit Tennessee waters. However, they have native fishes on “red alert,” threatening them with extinction.

Redbreast sunfish are very common in Tennessee and popular with anglers. They inhabit a wide range of aquatic habitats including small creeks, large rivers, and reservoirs. They are in the same genus as other common sunfish species in the area, like the bluegill sunfish (Lepomis macrochirus), and longear sunfish (Lepomis megalotis). Despite their popularity, redbreast sunfish are are causing ecological damage.

Native to the Atlantic and Gulf slopes, they were introduced into Tennessee and other states in the 1920’s and 1930’s for sports fishing. Now they are established throughout the Tennessee River drainage. They occupy a similar ecological niche as native sunfish species, requiring the same resources and serving the same function in the ecosystem. Because of this, they compete with bluegill sunfish and longear sunfish for food and habitat. In some areas, redbreast sunfish have caused the extinction of longear sunfish becasue of resource competition.

Red ShinersRed Shiner (Cyprinella lutrensis) from

Red shiners are a small minnow species native to rivers and streams in the central United States. Introductions outside the native range occurred due to home aquarium and bait bucket releases. They are native to western portions of Tennessee, but not to central or eastern Tennessee. Currently, there are no established populations outside the native range in the state, but they are established in the Upper Coosa River System in Northern Georgia and are moving quickly. They pose a serious threat to native species in the Coosa River and to the Tennessee River should they establish.

Water quality in many streams of the southeastern U.S. is severely degraded due to urbanization. Red shiners are able to thrive under in these conditions, giving them an advantage over native fishes that cannot adapt to rapid environmental changes. Red shiners also reproduce with native minnow species, resulting in a variety of hybrids. So far, nine different red shiner hybrids have been documented. One of the common combinations is a red shiner-blacktail shiner (Cyprinella venusta) hybrid. Hybridization reduces genetic diversity and fitness of the native species. In some areas, hybridization happens so quickly, that the native parent species goes extinct.