Waccamaw silverside

Waccamaw silverside
Conservation status
Vulnerable  (IUCN 3.1)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Atheriniformes
Family:	Atherinopsidae
Genus:	Menidia
Species:	M. extensa
Binomial name
Menidia extensa C. L. Hubbs & Raney, 1946

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 and the upper Waccamaw River in Columbus County, North Carolina, 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 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 8,934 acres (36.15 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.

Biology

This species is normally found in large schools close to the surface in open water where the substrate is dark and sandy. The population is able to tolerate heavy predation and they are frequently observed skipping over the water surface, a behavior which is apparently related to predator avoidance.

References

 This article incorporates public domain material from Waccamaw Silverside in North Carolina. United States Fish and Wildlife Service.