Litopenaeus setiferus (Linnaeus, 1767)
Conservation and Management
For decades, White Shrimp and the closely related Brown (Farfantepenaeus aztecus) and pink (F. duorarum) shrimp were thought to be impervious to overfishing due to their high fecundity and annual life cycle. However, recent reports of growth overfishing (i.e., shrimp being caught before reaching a size at which maximum growth and productivity would be obtained from the population) have raised concerns about the health of the populations (Ball and Chapman 2003 and references therein),
White Shrimp eggs hatch within a few hours after spawning and the young emerge as nauplii, the first of 11 larval stages (Perez-Farfante 1969 and references therein).
White Shrimp are found primarily at depths less than about 36 meters, although they may occur to 80 meters (Perez-Farfante 1969 and references therein).
White Shrimp inshore live mostly on muddy or peaty bottoms that have large quantities of decaying organic matter or vegetation for protection. Occasionally they occur on bottoms of sand or clay. Adult White Shrimp are most abundant in offshore waters on soft muddy and silt bottoms. They also live on bottoms of clay or sand with fragments of shells. They burrow in the bottom, but apparently not as regularly as do the Brown (Farfantepenaeus aztecus) or Pink (F. duorarum) Shrimps. The White Shrimp leaves its long antennae lying on the surface of the bottom, whereas the other two shrimps often bury their antennae (which are shorter than those of the white shrimp). (Perez-Farfante 1969 and references therein.)
White Shrimp juveniles require an estuarine environment for development. The adults live and spawn offshore, and their favored habitats include areas with abundant plant life and muddy substrates. (McMillen-Jackson and Bert 2003 and references therein).
The distribution of the White shrimp (Litopenaeus setiferus) appears to be discontinuous. It occurs along the Atlantic Coast of the United States from Fire Island (New York) south to central Florida and along the north coast of the Gulf of Mexico and the northeastern coast of Mexico (with a center of abundance in Louisiana), continuing southward to Campeche, Mexico (with another center of abundance in northeast Tabasco and the adjacent waters of Campeche). In addition to the large distributional discontinuity around southern Florida and the west side of the Florida Peninsula, this species is patchily distributed within its range on a smaller scale, possibly as a result of local variation in salinity, temperature, substrate, food, or cover. (Perez-Farfante 1969)
White shrimp are omnivorous. Their digestive tracts have been found to contain, in addition to inorganic detritus and organic debris, fragments of many different animals, particles of higher plants, and a variety of diatoms and other algae (Perez-Farfante 1969 and references therein).
Reproduction in the White Shrimp and close relatives is facilitated by the transfer of a spermatophore from the male to a modified region of the sternum of the female (the thelycum). The spermatophore consists of a roughly semicylindrical hardened sperm sac enclosing a columnar sperm mass (spermatozoa within a viscous fluid) surrounded by a thick "sheath" of gelatinous substance (Perez Farfante 1975 and references therein). Misamore and Browdy (1996) studied the mating behavior of the White Shrimp. They recognized 4 sequential stages. During the Chase stage, the male closely trails the female, mirroring the female's changes in direction. In the Probe stage, the male approaches the female ventrally and probes the thelycal region of the female with its antennules. The Embrace stage is characterized by the male inverting itself, juxtaposing ventral surfaces with the female, and wrapping its pereiopods around the carapace of the female. In the final stage, the Flex, the male collapses its uropods, hooks its abdomen slightly, and rotates perpendicular to the midline of the female forming a U-shape around the female.
White Shrimp are fed on by a wide variety of fish species and are parasitized by a range of organisms, including trematode and cestode flatworms, nematodes, and others (Perez-Farfante 1969 and references therein).
Evolution and Systematics
Systematics and Taxonomy
Perez-Farfante and Kensley (1997, cited in Maggioni et al. 2001) proposed that the four Penaeus subgenera of Perez-Farfante (1969) be raised to generic status, changing the name of the White Shrimp from Penaeus setiferus to Litopenaeus setiferus. Although Baldwin et al. (1998) questioned this approach based on their molecular data, additional molecular studies by Maggioni et al. (2001) largely supported the recommendations of Perez-Farfante et al. (1997).
The White Shrimp (Litopenaeus setiferus) is an abundant species and important to both commercial and recreational fisheries throughout its range (Ball and Chapman 2003).
Three species of penaeid shrimp (White, Pink, and Brown shrimp) comprise more than 99% of the landings in the Gulf of Mexico shrimp fishery. In recent years, average annual landings of the three species have been approximately 150 million pounds; however, since 2002 landings have declined sharply due to economic conditions in the fishery and hurricane damage, particularly in 2005 when landings dropped to approximately 92 million pounds. (NOAA/NMFS http://www.nmfs.noaa.gov/fishwatch/species/wild_white_shrimp.htm, page updated 1 February 2010)
The White Shrimp was the only shrimp fished in the estuarine waters along the northern coast of the Gulf of Mexico until about 1937-38, when offshore stocks began to be fished. The resource then declined while landings of Brown and Pink Shrimps increased. By the mid-1950, catches of those two species far exceeded catches of White Shrimp. During 1956-59, White Shrimp constituted only 20% of all Gulf shrimp produced by U.S. fishermen, but subsequently landings began to rise again. Annual landings of White Shrimp in the United States during 1965 were nearly 68 million pounds (whole weight), or about 31 percent of all shrimp landed. (Perez-Farfante 1969 and references therein)
Today, White Shrimp are the second most abundant species (after Brown Shrimp), with 1998 and 1999 landings of approximately 55 million pounds and 2000 landings of over 70 million pounds. From 2000 to 2005, landings fluctuated from a low around 80 million pounds to a high of 130 million pounds. Fluctuation in landings is partly the result of the level of effort in the fishery, which in turn is influenced by expected market prices. A total of about 110 million pounds of White Shrimp were landed in U.S. fisheries in 2008, mainly off of Texas and Louisiana. (NOAA/NMFS http://www.nmfs.noaa.gov/fishwatch/species/wild_white_shrimp.htm, page updated 1 February 2010)