The Waccamaw silverside (Menidia extensa) is a rare species of fish in the family Atherinopsidae. It is a federally listed threatened species of the United States.

Description

This is a small (growing to about 2.5 inches), slim, almost transparent fish with a silvery stripe along each side. Its body is laterally compressed, the eyes are large, and the jaw is sharply angled upward. This fish spawns from April through June, but spawning reaches its peak when water temperatures are between 68 and 72 Fahrenheit. Fully developed larvae form small isolated schools by early May. No parental care of the young has been noted. The silversides reach sexual maturity by the following spring, spawn, and then shortly thereafter most of the adults die off. A few may survive a second winter.

Range and population level

Known only from Lake Waccamaw

Lake Waccamaw

Lake Waccamaw is a unique fresh water lake located in Columbus County in North Carolina. The lake is oval in shape and measures roughly 5.2 by with an average depth of . It covers 36,170,802 square meters, an average width of 2.32 meters and a shoreline of about 22,852 meters...

 and the upper Waccamaw River

Waccamaw River

The Waccamaw River is a river, approximately 140 miles long, in southeastern North Carolina and eastern South Carolina in the United States. It drains an area of approximately 1110 square miles in the coastal plain along the eastern border between the two states into the Atlantic Ocean...

 in Columbus County, North Carolina

Columbus County, North Carolina

-Demographics:As of the census of 2000, there were 54,749 people, 21,308 households, and 15,043 families residing in the county. The population density was 58/sq mi . As of 2004, there were 24,668 housing units at an average density of 26/sq mi...

, the silverside is found in the upper Waccamaw River only during periods of high water and is not a permanent resident. Lake Waccamaw (not to be confused with the town of Lake Waccamaw) is the property of the State of North Carolina

North Carolina

North Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte...

and is administered by the North Carolina Department of Natural Resources and Community Development's Division of Parks and Recreation. The species' population is estimated to be in the millions.

Habitat

Lake Waccamaw is a natural lake with an approximate surface area of 8934 acres (36.2 km²) and an average depth of 7.5 feet (2.3 m). Although it is fed by acidic swamp streams, the lake has a virtually neutral composition. This neutral condition, unusual among North Carolina's coastal plain lakes, is believed to be caused by the buffering effect of the calcareous Waccamaw Limestone formation, which underlies the lake and is exposed on the north shore. The Waccamaw silverside inhabits open water throughout the lake, where schools are commonly found near the surface over shallow, dark-bottomed areas.